\input texinfo @c -*-texinfo-*- @c %**start of header @documentencoding UTF-8 @include macros.texinfo @copying @c -------------------------------------------------------------------------------- Copyright @copyright{} 2014, 2015, 2016, 2017 @w{Mattias Andrée @e{m@@maandree.se}} @quotation Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version@tie{}1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being the ``GNU General Public License'', the ``GNU Free Documentation License'', with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''. @end quotation @c THIS WAS LAST CHANGED 2017-NOVEMBER-05 @c -------------------------------------------------------------------------------- @end copying @setfilename mds.info @settitle mds -- The avant-garde micro-display server @documentlanguage en_GB @finalout @iftex @c @set USLETTER @c @set AFOURPAPER @c @set AFIVEPAPER @c @set SMALLBOOK @c @set HARDCOPY @c @set CROPMARKS @c @set SKIPCHAPTERNEWPAGE @c @set SKIPFONTTEXTSIZE @end iftex @c @set LOGO @c @set DOUBLE_HEADINGS @c @set SINGLE_HEADINGS @c @set AMERICANSPACING @ignore This document does not look too good on A5-paper. This document looks best on A4-paper, but smallbook format and US Letter is acceptable. CROPMARKS has no effect unless HARDCOPY is set. CROPMARKS and AFIVEPAPER (or actually @cropmarks and @afivepaper) does not play well together. You can configure how TeX output files should look by uncommenting @set commands above. Do not uncomment more than one of the paper sizes (USLETTER, AFOURPAPER, AFIVEPAPER and SMALLBOOK); if none is uncomment AFOURPAPER will be set unless HARDCOPY is set, in which case SMALLBOOK will be set. However, if you do not want to modify this source file, you can run `make` with for example `TEXIFLAGS='--texinfo="@set HARDCOPY"'`. Finally, you can include, on the front page, the version of mds that the manual is up to date with, by setting the value of VERSION to the version of mds, as well as date of the last update by setting DATE, and edition by setting EDITION. This is intended for printed manuals. The date is recommended to not be more accurate, or less accurate, than to the month. The edition should be formatted as, for example, "1@sup{st}". @end ignore @ifset HARDCOPY @ifclear USLETTER @ifclear AFOURPAPER @ifclear AFIVEPAPER @ifclear SMALLBOOK @set SMALLBOOK @end ifclear @end ifclear @end ifclear @end ifclear @end ifset @ifclear SINGLE_HEADINGS @ifclear DOUBLE_HEADINGS @ifclear HARDCOPY @set SINGLE_HEADINGS @end ifclear @ifset HARDCOPY @set DOUBLE_HEADINGS @end ifset @end ifclear @end ifclear @ifset AFIVEPAPER @afivepaper @end ifset @ifset SMALLBOOK @smallbook @end ifset @ifclear AFIVEPAPER @ifclear SMALLBOOK @ifclear USLETTER @afourpaper @set AFOURPAPER @end ifclear @end ifclear @end ifclear @ifset HARDCOPY @ifset CROPMARKS @cropmarks @end ifset @ifclear SKIPCHAPTERNEWPAGE @setchapternewpage odd @end ifclear @end ifset @ifclear SKIPFONTTEXTSIZE @ifset SMALLBOOK @set SMALLFONT @end ifset @ifset AFIVEPAPER @set SMALLFONT @end ifset @end ifclear @ifset SMALLFONT @fonttextsize 10 @end ifset @ifclear SMALLFONT @fonttextsize 11 @end ifclear @ifclear AMERICANSPACING @frenchspacing on @end ifclear @c @paragraphindent asis @c @firstparagraphindent none @c @exampleindent asis @c @kbdinputstyle distinct @dircategory Graphics environment @direntry * mds: (mds). The avant-garde micro-display server. @end direntry @documentdescription User and developer manual for mds, the avant-garde micro-display server, and servers, protocols, libraries and concepts. @end documentdescription @c %**end of header @ifset AFIVEPAPER @set AFIVEPAPER_OR_USLETTER @set SMALLBOOK_OR_AFIVEPAPER @set AFOURPAPER_OR_AFIVEPAPER @end ifset @ifset USLETTER @set AFIVEPAPER_OR_USLETTER @set AFOURPAPER_OR_USLETTER @end ifset @ifset AFOURPAPER @set AFOURPAPER_OR_USLETTER @set AFOURPAPER_OR_AFIVEPAPER @end ifset @ifset SMALLBOOK @set SMALLBOOK_OR_AFIVEPAPER @end ifset @ifset SMALLFONT @set AFOURPAPER_OR_USLETTER_OR_SMALLFONT @ifset SMALLBOOK @set SMALLBOOK_WITH_SMALLFONT @set AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @set AFIVEPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @end ifset @ifset AFIVEPAPER @set AFIVEPAPER_WITH_SMALLFONT @end ifset @ifset AFOURPAPER @set AFOURPAPER_WITH_SMALLFONT @set AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @end ifset @ifset USLETTER @set USLETTER_WITH_SMALLFONT @end ifset @end ifset @ifset AFOURPAPER_OR_USLETTER @set AFOURPAPER_OR_USLETTER_OR_SMALLFONT @set AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @end ifset @ifset AFIVEPAPER_OR_USLETTER @set AFIVEPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @set AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @end ifset @defindex op @defindex sg @defindex ub @defcodeindex pr @ifset HARDCOPY @include hardcopy-copying.texinfo @end ifset @ifnottex @node Top @top mds -- The avant-garde micro-display server @insertcopying @end ifnottex @titlepage @title The @code{mds} Reference Manual @subtitle The avant-garde micro-display server @ifset DATE @ifset VERSION @ifset EDITION @subtitle @value{DATE}, mds version@tie{}@value{VERSION}, @value{EDITION} edition @end ifset @ifclear EDITION @subtitle @value{DATE}, mds version@tie{}@value{VERSION} @end ifclear @end ifset @ifclear VERSION @ifset EDITION @subtitle @value{DATE}, @value{EDITION} edition @end ifset @ifclear EDITION @subtitle @value{DATE} @end ifclear @end ifclear @end ifset @ifclear DATE @ifset VERSION @ifset EDITION @subtitle mds version@tie{}@value{VERSION}, @value{EDITION} edition @end ifset @ifclear EDITION @subtitle mds version@tie{}@value{VERSION} @end ifclear @end ifset @ifclear VERSION @ifset EDITION @subtitle @value{EDITION} edition @end ifset @end ifclear @end ifclear @ifset LOGO @vskip 0pt plus 1filll @comment this way, it is centered exactly in pdf and approximently in dvi and ps @comment @center does not work for @image in dvi and ps @multitable @columnfractions 0.15 0.7 @item @tab @center @image{../logo,250px} @end multitable @vskip 0pt plus 2filll @end ifset @author by Mattias Andrée (maandree) @page @ifset HARDCOPY @vskip 0pt plus 1filll @insertcopying @page @end ifset @center `To me, writing a monolithic system in 1991 is a truly poor idea.' @c Well, here we are 23 years later, and we are still @c doing it, but where it is even easier not to. @ifclear HARDCOPY @vskip 0pt plus 1filll @c If you prefer a dead tree edition, you can order one from @c ... @c @* @insertcopying @end ifclear @end titlepage @ifset DOUBLE_HEADINGS @headings double @end ifset @ifset SINGLE_HEADINGS @headings single @end ifset @shortcontents @contents @menu * Overview:: Brief overview of @command{mds}. * Features:: Reasons to install and use @command{mds}. * Architecture:: Architectural overview of @command{mds}. * Application Design:: Guildlines for your applications. * Protocol:: The @command{mds} procotol. * Utilities:: About @command{mds} utilities. * Servers:: About @command{mds} servers. * Protocols:: @command{mds} procotols. * libmdsserver:: Overview of @command{libmdsserver}, the server library. * mds-base.o:: Overview of @file{mds-base.o}, the common server base. * libmdsclient:: Overview of @command{libmdsclient}, the client library. * libmdslltk:: Overview of @command{libmdslltk}, the toolkit library. * Keyboard Codes:: Scancodes and keycodes. * Keyboard Layouts:: Writing and compiling keyboard layouts. * Default Keyboard Layouts:: The keyboard layouts installed with @command{mds}. * Accessibility:: Dealing with disabilities. * Specifications:: Specifications. * New Concepts:: Discussion of new display server concepts. * Discussion:: Discussion on display server-architecture and decision. * GNU General Public License:: Copying and sharing @command{mds}. * GNU Free Documentation License:: Copying and sharing this manual. * Concept index:: Index of concepts. * Data type index:: Index of data types. * Function index:: Index of functions. * Option index:: Index of command line options. * Program index:: Index of servers, clients and utilities. * Protocol index:: Index of @command{mds} protocols. * Signal index:: Index of signals. * Unicode block index:: Index of Unicode block. * Variable index:: Index of variables and environment variables. @end menu @c TODO @detailmenu (`C-c C-u m`) @node Overview @chapter Overview @command{mds}@footnote{mds stands for micro-display server.} is a display server protocol and an implementation of said protocol. What makes @command{mds} stand out is its core design choice: it is designed just like a microkernel. Rather than one, possibly modular, process --- a monolithic process --- @command{mds} is comprised of many small servers, each exchangable and responsible for one thing. @cpindex Goals of @command{mds} @command{mds}'s goal is neither security, performance nor a perfect graphical experience. @command{mds} is all about flexibility and freedom 0@footnote{The freedom to run the program as you wish, for any purpose.}. The reason for having a display server architectured as a microkernel is so that components can be added, removed, updated and replaced online. Additionally, the message passing between the servers makes it easy to design a system that lets you make clients that can listen on messages between the servers and perhaps modify them. This enables you to do so much more with your display server. Moreover, if a single part of the system crashes it does not bring down the whole system, and the crashed server can be respawned with minor side-effects. @command{mds} is architectured in three layers: a microkernel, a master server and a collection of servers. And clients are actually located on the same layer as the servers, because there is no actual difference, the only thing that separates a server from a client is for what purpose you run it. @command{mds}'s kernel is a minimal program that do initialisation of the display, such as giving it an index and create runtime files and directories for servers and other programs to use. Then the kernel creates a domain socket for the master server and spawns the master server and respawns it if it crashes. Because of this, if the master server crashes it will not lose its socket when it is respawned. The master server then, on its initial spawn, starts the all servers and other programs that the user have choosen and then starts accepting connections to it and coordinates messages between servers and clients. Further, separating all components into separate processes enables us to only give the servers the privileges they actually need, rather than having one program with root privileges that takes care of everything even things that do not do require any privileges. All @command{mds}'s servers, that is all running parts of @command{mds} except the kernel, are designed so that they can re-execute themself so that they can be updated online without any side-effects. Servers serialises their state, saves it to RAM (in a directory created by the kernel), re-execute themself and loads their serialised state. The kernel cannot do this because when it has spawned the master server it has no reason to re-execute, its only mission is to respawn the master server it if would happen to crash. It would technically be possible to enable the kernel to re-execute but it is not worth it as there is no reason to re-execute, and doing so puts the display server at risk of crashing. @node Features @chapter Features @command{mds} is not the most shiny display server known to the planet (yet), but it does have a number of enticing features: @table @asis @item it is free software Anybody can use, modify, and redistribute it under the terms of the GNU General Public License version 3 (@pxref{GNU General Public License}). Unlike some other display server that are license under the MIT license, @command{mds} is licensed under a copyleft license. Not only that, it is a strong copyleft license too. @item is is open source As an unintended side-effect of @command{mds} being licensed udner the GNU General Public License, @command{mds} is also open source. The principal author of @command{mds} do not value open source, however some people do. @item it will be compatible @command{mds}'s design makes it easy to make it compatile with any display server using a compatibility server. When @command{mds} matures, compatibility servers for X, Wayland and Mir will we written, both for using those display server's client programs in @command{mds} and @command{mds} client programs in those display servers. @item it is built to survive Unlike other dispaly servers, @command{mds} has an object-oriented structure that allows it to evolve without compromising its design. This structure will help the @command{mds} undergo major redesign and modifications without having to be entirely rewritten. @item it is scalable @command{mds}'s design makes it inherently aggressively multithreaded and easy to strip down on features, so that it runs efficiently on any system. @command{mds} can also be distributed on multiple computers in a network, although the servers for this has not yet been implemented. @item it is extensible @command{mds} is designed to modified and extended. Every part of @command{mds} is separated into distinct servers that can easily be modified or replaced, but it is also easy to create servers to modifies or otherwise uses the communication between other servers and clients. @command{mds} is a perfect place for developing new display server technology or just learn about display server technology. @item it is stable It is possible to develop and test new @command{mds} servers without restarting the display server. Servers can be updated to newer versions of themself without losing their state. This means to you never have to restart your display server to update it. Additionally servers that crash can be startared automatically and their state can for the most part be restored. @end table @node Architecture @chapter Architecture @menu * Layers:: The layers of the display server. * Interprocess Communication:: How servers and clients communicate. @end menu @node Layers @section Layers @cpindex Layers, architecture @cpindex Architectural layers @cpindex Kernel @cpindex Display server kernel @pgindex @command{mds} @cpindex Master server @pgindex @command{mds-server} The @command{mds} display server in architectured in three layers. The first layer is called the kernel. The kernel is responsible for acquiring a display server index@footnote{As with any display server, the system can have multiple instances of @command{mds} running at the same time.}, set up environment variables to indicate which display server and display server instance is being used, create a domain socket for the display server and start the master server and restart it if it crashes, and then clean up the system when the display server closes. The kernel only responsible for creating the domain socket for communication with the display server, it is not responsible for using it, that mission falls to the master server. @cpindex Master server @cpindex Message passing, coordination @cpindex Communication, coordination @cpindex Interprocess communication, coordination @pgindex @command{mds-server} The second layer is the master server. The master server has two responsibilities: coordinating message passing between other servers and clients @footnote{In @command{mds} there is no functional distinction between servers and clients, the distinction is purely semantic.} and starting other servers. @cpindex Starting of servers @cpindex Servers, starting @pgindex @file{mdsinitrc} The third layer is the other servers and clients. protocolwise there is no specification on how they are started. But in the reference implementation of the master server, this is done by starting a shell script with the pathname @file{$@{XDG_CONFIG_HOME@}/mdsinitrc} and the user is responsible for providing the logic in that shell script.@footnote{Moonstruck users are allowed to implement this in C or any other language of their choosing.} @c Which is better: cray-cray users, lunatic users, @c moonstruck users, insane users, ballers, madmen, @c loony tunes, systemd-lovers? These servers implements the actual functionality of the display server. @node Interprocess Communication @section Interprocess Communication @cpindex Message passing, mechanism @cpindex Communication, mechanism @cpindex Interprocess communication, mechanism @cpindex Master server @pgindex @command{mds-server} Intrinsic to @command{mds} is a powerful interprocess communication mechanism. Servers and clients connect to the display server by connecting to a domain socket served by the master server. A server or client that has connected to the display server can do three things: @itemize @item Request assignment of a unique ID@. @item Multicast a message. @item Join or leave a multicast group. @end itemize @cpindex Multicast groups @cpindex Client ID assignment @cpindex ID assignment @cpindex Assignment of ID @cpindex Disconnection @cpindex Master server @pgindex @command{mds-server} Upon assignment of an ID the master server will automatically place the client in a multicast group for that specific client. This automatically multicast group assignment is done by the master server simply so you as a debugger do not forget to do so. When a client is disconnected it will send out a message to a specific multicast group that the client, refered to by it's ID, have closed. @cpindex Message passing, message structure @cpindex Communication, message structure @cpindex Interprocess communication, message structure @cpindex Message structure, message passing @cpindex Master server @pgindex @command{mds-server} A message in the @command{mds} protocol is comprised of two parts: headers and a payload. When a client joins a multicast group it is actually saying that it is interested in receiving broadcasts containing a specific header or a specific header--value pair, or that it is interesting in all messages @footnote{This could be used for logging, possibly spying and networking.}. Thus a message is automatically multicasted to groups indicated by its headers. @cpindex Interceptions, message passing @cpindex Message passing, message modification @cpindex Communication, message modification @cpindex Interprocess communication, message modification @cpindex Message modification, message passing @cpindex Master server @pgindex @command{mds-server} @cpindex Multicast groups The multicast groups and receiving of message is called interceptions. The interesting property of interceptions is that they may be modifying. When a server registers for message interception it can say that it wants to be able to modify messages. If this is done and the server receives a message for which it has said it want to be able to modify it, the master server will wait for that server to respond before it send the message to the next server in the interception list. The server can choose to do three things with a message that it has opted in for modification of: leave the message as-is, modify the message, or consume the message. A message consumption is done by modify the message to make it empty. A consumed message will not be send to any further clients or servers in the interception list. @cpindex Interception priority, message passing @cpindex Priority, interception, message passing @cpindex Message consumption, message passing @cpindex Consumption, interception, message passing To make this mechanism sensible, a server or client can set a priority when it registers for interception (does not need to be modifying.) When a message is broadcasted it will be received by all servers in the interception except the original sender, unless it gets consumes. The order in which the master server sends the message to the recipients is determined by priority the servers registed with. The message first sent to the recipients with highest priority and last to the recipients with lowest priority, and ordered by the priority between those priorities. Of two or more servers have the same priority the order in which they will receive the message, of those recipients, is arbitrary. @pgindex @command{mds-vt} @cpindex Virtual terminal, switching @cpindex Switching virtual terminal @cpindex Dual-connection, message passing @cpindex Message passing, dual-connection @cpindex Communication, dual-connection @cpindex Interprocess communication, dual-connection @cpindex Reflexive connection, message passing An interesting property of this mechanism is demonstrated in the @command{mds-vt} server. Unlike most servers @command{mds-vt} maintains two concurrent connections to the display. Once @command{mds-vt} receives a signal from the OS kernel requesting to switch virtual terminal, @command{mds-vt} will from one of its connections send out a message and wait for it to be received in its other connection and the let the OS kernel switch virtual terminal. The secondary connection to the display has registered interception with lower priority of the message than the primary connection broadcasts. This message will be received by other servers that will let the message continue to the next server in the interception list once that server is ready for the OS kernel to switch virtual terminal. All of these servers have registered modifying interception of the message but none of them will actually modify or consume the message; it is only used a mechanism for letting @command{mds-vt} know when all servers are ready for the switch without having to know how many they are and wait for a reply from all of them. @node Application Design @chapter Application Design @cpindex Application design @cpindex Client design @cpindex Guildlines, applications @cpindex Toolkit guildlines When creating graphical @command{mds} applications, there are some guildlines you should follow. @itemize @bullet @item @cpindex Client-side decoration @cpindex Server-side decoration @cpindex Decoration, guildlines @b{Do not create client-side decoration}. Some users do not want decorations or wants minimal decorations. Windows should look similar, server-side decoration helps ensure this. Your client-side decorations may not meet the requirements the users have. For example, your client-side decoration may only support minimise, maximise and close, whilst the user may also want, as provided by her decoration server, stick, shade and always on top. And it should be sufficient to configure your decorations once rather once for every toolkit. Additionally, because of oversight from developers, client-side decoration tends to work poorly with tiling window managers. @item @cpindex Memorisation of size and position @cpindex Position, memorisation @cpindex Size, memorisation @pgindex @command{mds-posmem} @b{Do not remember size and position}. Some users do not want their programs to remember their size and position. There is also a risk that your mechanism for implementing this does not account for the possibility that outputs may have been removed, resized or relocated. @command{mds-posmem} can be used if the user wants programs to start where they were closed the last time they were closed. @end itemize @node Protocol @chapter Protocol @menu * Environment Variables:: Identifying the active display server. * Signals:: Signalling individual servers. * Filesystem:: The display server's footprint on the filesystem. * Message Passing:: Sending messages between servers and clients. * Interception:: Implementing protocols and writing unanticipated clients. * Responses:: How responses to queries and commands are structured. * Portability:: Restrictions for portability on protocols. @end menu @node Environment Variables @section Environment Variables @cpindex Environment variables @vrindex @env{DISPLAY} @vrindex @env{MDS_DISPLAY} @cpindex Display server identification @cpindex Identification, display server A crucial task of any display server is letting child processes know which display server they should connect to. @command{X.org} does this by setting the environment variable @env{DISPLAY} to @code{:}, where @code{} is empty if the display is one the local machine. In this tradition, @command{mds} does the same thing with the environment variable @env{MDS_DISPLAY}@. The display index is the TCP-port if the host is non-empty. @cpindex Networking @pgindex @command{mds-remote} Servers (and clients) that depend the display being local, should reject any value on @env{MDS_DISPLAY} that does not start with a colon. They should instead utilise @command{mds-remote}. @c TODO More on MDS_DISPLAY for remote access, see libmdsclient/address.c @cpindex Environment variables @vrindex @env{MDS_PGROUP} @cpindex Display server process group @cpindex Process group, display server @command{mds} also creates a new process group and export the new process group ID to the environment variable @command{MDS_PGROUP}@. This process group can be used to send signals to all @command{mds} servers collectively. @node Signals @section Signals @cpindex Signals @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} @command{mds} servers can re-execute into an updated version of their binary. This can be used to update display server online after a new version has been installed. To do this send the signal @code{SIGUSR1} to the server you want update. If a server does not support online updating it will ignore this signal. If the operating system defines a signal named @code{SIGUPDATE}, this signal is used instead of @code{SIGUSR1}. @cpindex Signals @cpindex Memory release, automatic @cpindex Memory release, forced @cpindex Automated memory release @cpindex Forcing memory release @cpindex Releasing memory @sgindex @code{SIGDANGER} @sgindex @code{SIGRTMIN + 1} If you need servers to free up allocated memory that they do not use, send the signal @code{SIGDANGER}, or if not defined @code{SIGRTMIN + 1}. Unimportant servers may choose to die on @code{SIGDANGER}@. @sgindex @code{SIGINFO} @sgindex @code{SIGRTMIN + 2} @cpindex State dump @cpindex Statistics dump Server may also choose to support the signal @code{SIGINFO}, or if not defined @code{SIGRTMIN + 2}. It is not expected that server do support this signal, but thay must not die when received. @code{SIGINFO} is send by a user to the server, if she wants the server to dump information about the server's state or statistics to the TTY@. @sgindex @code{SIGRTMIN} @cpindex No-operation signal All servers configured to be interrupted when the signal @code{SIGRTMIN} is received. No further action is taked. This may be used by the user to test that the program supports being interrupted. It can also be used by the server to interrupt itself from another thread. @pgindex @command{valgrind} @sgindex @code{SIGRTMAX} @command{valgrind} uses @code{SIGRTMAX} for its own internal stuff. Therefore servers must not use @code{SIGRTMAX} as it is hence unavailable when running under @command{valgrind}. @node Filesystem @section Filesystem @cpindex Interprocess communication, filesystem @cpindex Filesystem @cpindex Kernel @cpindex Display server kernel @pgindex @command{mds} The @command{mds} kernel creates two directories for the @command{mds} servers to use: one for runtime data and one for temporary data. These directories are named by @code{MDS_RUNTIME_ROOT_DIRECTORY} and @code{MDS_STORAGE_ROOT_DIRECTORY}, respectively, by the header file @file{}. If the systems runtime data directory is @file{/run} and transient temporary data directory is @file{/tmp}, and the package name of @command{mds} is @command{mds}, these directories will be @file{/run/mds} and @file{/tmp/.@{system-directory@}.mds}, respectively. In @file{/tmp/.@{system-directory@}.mds} the kernel will create a directory for the display server instance named @file{.data} prefixed by the display server index. For example if the display server index is zero, temporary data may be stored in @file{/tmp/.@{system-directory@}.mds/0.data} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update As defined by @code{SHM_PATH_PATTERN} in @file{}, when a server re-executes itself it will marshal its state to the POSIX shared memory unit named @file{/.proc-pid-%ji}, where @file{%ji} @footnote{@code{%ji} is the pattern in @code{*printf} functions for the data type @code{intmax_t}.} is replaced with the process ID of the server. This file will be bound to the pathname @file{/dev/shm/.proc-pid-%ji} if POSIX shared memory is stored in @file{/dev/shm} by the operating system. In @code{MDS_RUNTIME_ROOT_DIRECTORY} the kernel will create two files. @file{.pid} and @file{.socket}, both prefixed with the display server index @footnote{@file{0.pid} and @file{0.socket} if the display server index is 0.}. The @file{.pid} file contains the process ID of the display server and is used by the kernel to figure out whether an display server index is still in use or just not properly cleaned up. Of course it can be used by any program to find the process ID of the kernel process of a display server instance. The @file{.socket} is the domain socket used for communication with the display server and its servers and clients. @node Message Passing @section Message Passing @cpindex Message passing, display @cpindex Communication, display @cpindex Interprocess communication, display @cpindex Kernel @cpindex Display server kernel @pgindex @command{mds} Message passing over domain sockets is the underlaying technique for communicating with the display server. To communicate with the display server in the local machine a process must connect to the domain socket created by the display server kernel as named in @ref{Filesystem}. @cpindex Connecting to the display @cpindex Client ID assignment @cpindex ID assignment @cpindex Assignment of ID Clients should request a unique ID when it connects to the display server.@footnote{There is seldom a reason for servers to do this.} To do this the client sends @example @group Command: assign-id\n Message ID: 0\n \n @end group @end example @cpindex Message ID @cpindex Message corruption @cpindex Corrupt messages where @code{\n} is an LF-line break. The value on the @code{Message ID}-line does not need to be 0, but servers and clients often start with 0 and count upwards. The value is however bound to an unsigned 32-bit integer. All message must contain this @code{Message ID}-header, otherwise the message is considered corrupt and is ignored. @cpindex Message structure @cpindex Message passing, message structure @cpindex Communication, message structure @cpindex Interprocess communication, message structure The empty line signifies the end of the header list, and in this case the end of the message. But a message may contain payload beneath this empty line. To include a payload, add the header @code{Length} that says how many bytes the payload is comprised. A header must contain a header name and header value without any trailing or leading spaces, and @w{`: '} (colon, one regular blank space) exactly delimits the name and the value. @cpindex Master server @pgindex @command{mds-server} @cpindex Client ID assignment @cpindex ID assignment @cpindex Assignment of ID When the master server receives this @code{Command: assign-id}-message it will assign the client a unique ID and send it to the client. @footnote{The master server is the only server than can address the client uniquely before it has an ID, so this part can only be implement in the master server.} If the client already has an ID, it will send back that ID to the client. This response consists of two headers @code{ID assignment} and @code{In response to}, containing the client's new (or possibly already assigned) ID and the value that was in the @code{Message ID}-header, respectively. For example: @example @group ID assignment: 0:1\n In response to: 0\n \n @end group @end example @cpindex Message ID Notice that the master server never includes @code{Message ID} in message originating from it. As seen in this example, the client ID consists of two integers delimited by a colon@tie{}(`:'). Both of these integers are unsigned 32-bit integers. This is done this way because unsigned 64-bit integers are forbidden because it is not supported natively be some programming languages. Before a client has gotten a unique client ID assigned to it, it will be `0:0'. @cpindex Disconnection If a client gets disconnected from the master server, the master server will sends out a signal header message. This header will be @code{Client closed} and contain ID of the client that closed. For example: @example @group Client closed: 0:1\n \n @end group @end example Be aware that if a server or client closes and does not have a unique client ID, this message will be: @example @group Client closed: 0:0\n \n @end group @end example @cpindex Addressing message @cpindex Message passing, addressing @cpindex Communication, addressing @cpindex Interprocess communication, addressing Once a client has an unique client ID assigned to it, it should always include the header @code{Client ID} in its messages. The value of @code{Client ID} should be the client's ID@. If a server wants to address this client, it should include the header @code{To} with the value set to the recipient's client ID@. Be aware that such message may not be sent to that recipient uniquely, any server or client is free to sign up for receive of such message, any messages or message contain any other header or header--value pair that may also be included in the header. @node Interception @section Interception @cpindex Interceptions, message passing @cpindex Message passing, message modification @cpindex Communication, message modification @cpindex Interprocess communication, message modification @cpindex Message modification, message passing @cpindex Interceptions, eavesdropping @cpindex Message passing, eavesdropping @cpindex Communication, eavesdropping @cpindex Interprocess communication, eavesdropping @cpindex Eavesdropping, message passing As discussed in @ref{Interprocess Communication}, interception in the primary feature of @command{mds}'s message passing system. Not only does it enable servers to select which message it wants to receive in order to provide it's service. It also enables clients to do anything, things that was never anticipated. As an example of its power, @command{mds} does not provide any protocol for taking screenshots or recording a session. Instead, a screenshot application signs up for messages passed between the compositor and presentation servers, and simply requests that the compositor resends the screen, a feature intended for the presentation servers. A screen recoding application would do the same and just hang on and record all message passed between the servers. If you want your server or client to receive all messages passed around in the display server, simply sign up for all messages: @example @group Command: intercept\n Message ID: 0\n \n @end group @end example But if you only want messages contain the header @code{Command}, include that header in the payload of the message: @example Command: intercept\n Message ID: 0\n Length: 8\n \n Command\n @end example It is allowed to include multiple headers. You can also be more strict, and require a specific value for a header, for example: @example Command: intercept\n Message ID: 0\n Length: 16\n \n Command: get-vt\n @end example You may mix these two types of requirements freely. Your client will receive any message that satisfies at least one of the requirements, these requirements may be split into multiple message or coalesced into one message; but you cannot request to include receive a message if multiple requirements are satisfied. Alternatively you can choose to stop receiving message that satisfies requirements. For example: @example Command: intercept\n Stop: yes\n Message ID: 1\n Length: 16\n \n Command: get-vt\n @end example Or stop receiving all messages: @example Command: intercept\n Stop: yes\n Message ID: 1\n \n @end example Note that this will stop you from receiving messages contain the @code{To}-header addressed to you until you request to receiving such messages again. When you sign up for message you may request to be able to modify them before that are send to the next client in the list of client that should receive them. To do this include the header--value pair @code{Modifying: yes}: @example Command: intercept\n Modifying: yes\n Message ID: 0\n Length: 30\n \n Command: keyboard-enumeration\n @end example It is up to the client to keep track of which message that it may modify. When you receive a message that you can modify you must respond when you are done with the message. For example, if you have signed up for @code{Command: keyboard-enumeration} with the ability to modify such messages and the message @example Command: keyboard-enumeration\n To: 0:1\n In response to: 2\n Message ID: 1\n Length: 7\n \n kernel\n @end example is send from a server, you may receive it as @example Command: keyboard-enumeration\n To: 0:1\n In response to: 2\n Message ID: 1\n Length: 7\n Modify ID: 4\n \n kernel\n @end example Be aware that the @code{Modify ID} may be included even if you have not signed up to be able to modify the message, it is enough that one client before you has or it was originally included @footnote{You may however not include this header when you send out an orginal message.}. If you receive the message as such and want to add the line @code{on-screen-keyboard-20376} to the payload should send out: @footnote{The first line containing starting with @code{Message ID} is an example, it should be whatever is appropriate for your client.} @example Modify ID: 4\n Message ID: 2\n Modify: yes\n Length: 127\n \n Command: keyboard-enumeration\n To: 0:1\n In response to: 2\n Message ID: 1\n Length: 32\n Modify ID: 4\n \n kernel\n on-screen-keyboard-20376\n @end example If you however decide not to modify the message send out @example Modify ID: 4\n Message ID: 2\n Modify: no\n \n @end example @cpindex Message consumption, message passing @cpindex Consumption, interception, message passing There is also a third option: to consume to the message. This stops any further clients from receiving the message. This is done by modifying the message into an empty message: @example Modify ID: 4\n Message ID: 2\n Modify: yes\n \n @end example You may choose to include the header--value pair @code{Length: 0}, it is however redundant and discouraged. @cpindex Interception priority, message passing @cpindex Priority, interception, message passing This mechanism of being able to modify message does not make much sense unless you can control in the order the clients receive messages. This is done with what is called priority. The higher priority you have, the earlier you will receive the message. The default priority is zero, and the priority is bound to a signed 64-bit integer. If you want to be able to list yourself in @code{Command: keyboard-enumeration} message, you should sign up with a positive priority since the final recipient or requested the enumeration will receive it with priority zero. Therefore you should sign up for such message with a message like: @footnote{4611686018427387904 is halfway to the maximium value.} @example Command: intercept\n Modifying: yes\n Priority: 4611686018427387904\n Message ID: 0\n Length: 30\n \n Command: keyboard-enumeration\n @end example @node Responses @section Responses @cpindex Responses @cpindex Error management Many commands are met with no response. The client, can however sometimes infer when the commands has been processed by listening for events that are triggered when some commands have been process. Other times, commands are responded to with an error message either indicating success or failure. @footnote{See @ref{error}}. Queries are always met with a response unless the an involved server failed or the queries was malformated or included invalid parameters and therefore silently@footnote{Although in these cases most servers will print an error to their stderr} ignored. The response will either be an error message indicating failure (or success in very special cases,) or an especially formatted message that includes describes the requested data. Responses will always include at least four headers: @table @code @item To Will include the client's, who made the request, client ID. This will be the value of the header @code{Client ID} in the message that triggered the response. @item In response to Will include the message ID of the message that triggered the response. The value of the @code{Message ID}-header of the received message. @item Message ID The ID of the response message. You will probably not find any use of this. But it is required by the message passing protocol. @item Origin command The value of this header will be the value of the @code{Command}-header in the received message. This can be used if you want to listen for responses, and perhaps modify them, between other servers and clients. @end table The message @code{Command: assign-id} is except from this sections. In particular it will not include the headers @code{To}, @code{Message ID} and @code{Origin command}. See @ref{Message Passing}. @node Portability @section Portability @cpindex Portability For optimal portability, there are some restrictions on protocols. @itemize @bullet{} @item Integers that are not especially encoded must not be larger than 64-bits if they use fixed bit-size. If, for example, @code{size_t} is 128-bits on your platform but you are using a language that only have native integers up to 64-bits you must use arbitrary size integers or otherwise make sure that the value can be properly stored and used. @item @tpindex @code{uint64_t} @cpindex Integers, unsigned, restriction @cpindex Unsigned integer, restriction @cpindex Restrictions on unsigned integers Integer 64-bits that are not especially encoded must not be unsigned if the bit-size is fixed. This is because some programming languages primitive integers are limited to 64-bits and are signed; a large enough unsigned 64-bit integer would overflow. @item @cpindex Endianness, portability Native endianness when a endianness is choosen. Do not assume big endianness, but the same endianness that appear on the same machine when using C@. @item @cpindex UTF-8, portability @cpindex Strings, portibility All strings musts be encoded in UTF-8 without any NUL-character unless express permission is given. NUL-character may be encoded either using a zero byte or using Modified UTF-8, where it is encoded using two bytes. Which is used is selected in the protocol, however headers and their values must not include NUL-characters. No character may be encoded with more bytes than necessary. Encoding a character in extra long form is a security issue, and is prune to bugs, and is hence disallowed by newer specifications of UTF-8. @item @cpindex New line, portability @cpindex Strings, portibility The new line-character is always LF@tie{}(@code{'\n'}, 10, line feed) and never a combination of LF and any other character, or multiple LF:s. @end itemize @node Utilities @chapter Utilities @menu * mds-respawn:: The server immortality protocol. * mds-reg:: The registry control command. * mds-clip:: The clipboard control command. * mds-screenshot:: The screenshot utility. * mds-slay:: The process killing utility. * mds-chvt:: Utility for switching virtual terminal. * mds-kbdc:: The keyboard layout compiler. * External Utilities:: Suggestion on utilities you can utilise. @end menu @node mds-respawn @section @command{mds-respawn} @pgindex @command{mds-respawn} @cpindex Respawning servers, automatic @cpindex Crash resilience @cpindex Hyposerver @command{mds-respawn} is a hyposerver, that is, a utility beneath servers, and intended to be used in @file{$@{XDG_CONFIG_HOME@}/mdsinitrc}. It will spawn a selected set of servers. If a server it spawns exits with a bad status, @command{mds-respawn} will respawn it. @command{mds-respawn} supports two options in the command line: @table @option @item --alarm=SECONDS @opindex @option{--alarm} Schedule @command{mds-respawn} to die in @var{SECONDS} seconds. At most 1 minute. @item --interval=SECONDS @opindex @option{--interval} @sgindex @code{SIGUSR2} Spawned servers that die twice within @var{SECONDS} seconds should stop respawning until the signal @code{SIGUSR2} is send to @command{mds-respawn}. At most 1 minute. @end table Commands for servers to spawn are specified within curly braces. Each of the braces must be alone its its own argument. For example: @opindex @option{--initial-spawn} @example @group mds-respawn --interval=5 \ @{ mds-foo --initial-spawn @} \ @{ mds-bar --initial-spawn @} & @end group @end example @cpindex Server supervision @cpindex Supervision of servers @opindex @option{--initial-spawn} @opindex @option{--respawn} will spawn and supervise the servers @command{mds-foo} and @command{mds-bar}. Both spawned with the argument @option{--initial-spawn}. When a server is respawed by @command{mds-respawn}, @option{--initial-spawn} in its argument list will be replaced by @option{--respawn} to let the server know it is being respawned. @sgindex @code{SIGTERM} A server is considered to exit with a failure status unless it exits with the return value 0 or is terminated by the signal @code{SIGTERM}@. @node mds-reg @section @command{mds-reg} @pgindex @command{mds-reg} @cpindex List protocols @cpindex Protocols, listing @cpindex Protocol registry @cpindex Registry of protocols @opindex @option{--list} @opindex @option{--wait} @command{mds-reg} is a utility that can be used to list available protocols provided by running servers. It can also wait for a set of protocols to become available. To list all available protocols run @command{mds-reg --list}. And to wait for the protocol @code{foo} run @command{mds-reg --wait=foo}. To also wait for the protocol @code{bar} run @command{mds-reg --wait=foo,bar} or @command{mds-reg --wait=foo --wait=bar}. Both of thesestyles can be mixed if you want to wait for even more protocols. @node mds-clip @section @command{mds-clip} @pgindex @command{mds-clip} @cpindex Clipboard @command{mds-clip} is a utility that can be used to review the clipboards on the display and manipulate them. @command{mds-clip} recognises the following options: @table @option @item --push @opindex @option{--push} Push non-option arguments from the command line into the clipboard. @item --expire=SECONDS @opindex @option{--expire} @opindex @option{--push} Can be used with @option{--push}. The clip will not removed after @var{SECONDS} seconds. @item --pop @opindex @option{--pop} Pop items from the clipboard whose indices are listed in the command line as non-option arguments. The first index is 1. @item --clear @opindex @option{--clear} Pop all items in the clipboard. @item --list @opindex @option{--list} List items in the clipboard whose indices are listed in the command line as non-option arguments. The first index is 1. If no indicies are specified, all clips will be listed. @item --size @opindex @option{--size} Print the size of the clipboard, the number of clips in the clipboard. @item --capacity @opindex @option{--capacity} Print the capacity of the clipboard, the number of clips the clipboard can hold. If both @option{--size} and @option{--capacity} is used, the size will be printed on the first line and the capacity will be printed on the second line. @item --resize=CAPACITY @opindex @option{--resize} Change the capaciy of the clipboard to @var{CAPACITY} clips. @item --stdin @opindex @option{--stdin} @opindex @option{--push} Can be used with @option{--push}. If used, the clip that should be placed on the top of the clipboard stack should be read from stdin. @item --delimiter=DELIMITER @opindex @option{--delimiter} @opindex @option{--list} @opindex @option{--stdin} Can be used with @option{--stdin} or @option{--list}. If used with @option{--stdin}, an line containing only @var{DELIMITER} will delimit two values that should be placed in the clipboard. If used with @option{--list}, a line containing only @var{DELIMITER} will delimit two values in the output. The default delimiter for @option{--list} is an empty line. @item -1 @opindex @option{-1} Use the primary clipboard, that is, the text copy clipboard. This is the default clipboard. @item -2 @opindex @option{-2} Use the secondary clipboard, that is, the text selection clipboard. @item -3 @opindex @option{-3} Use the tertiary clipboard, that is, the non-text copy clipboard. @end table @node mds-screenshot @section @command{mds-screenshot} @pgindex @command{mds-screenshot} @cpindex Screenshooting @command{mds-screenshot} is a simple utility, and reference implementation thereof, that can take a screeenshot of either the display, a monitor, or a window with or without its decorating window. It can also include or exclude the rat cursor or gamma ramps. @command{mds-screenshot} recognises the following options: @table @option @item --monitor @opindex @option{--monitor} Take screenshot of the monitor. The rat will be used to select monitor. @item --monitor=WINDOW_ID @opindex @option{--monitor} Take screenshot of the monitor whose root window's window ID is @var{WINDOW_ID} or has another window in it whose window ID is @var{WINDOW_ID}@. @item --embed @opindex @option{--embed} Take a screenshot of an embedded window. The rat will be used to select window. @item --embed=WINDOW_ID @opindex @option{--monitor} Take a screenshot of an embedded window whose window ID is @var{WINDOW_ID}@. @item --window @opindex @option{--window} Take a screenshot a window. The rat will be used to select window. @item --window=WINDOW_ID @opindex @option{--window} Take a screenshot of a window whose window ID is @var{WINDOW_ID}@. @item --decoration @opindex @option{--decoration} Include the window's decoration, if used together with @option{--window}. Ignored if used without @option{--window}. @item --cursor @opindex @option{--cursor} Include the rat cursor in the screenshot. @item --gamma @opindex @option{--gamma} Include the effects of gamma ramps in the screenshot. @item --low-gamma=LOW_PRIORITY @opindex @option{--low-gamma} Include the effects of gamma ramps with a priority above @var{LOW_PRIORITY} in the screenshot. @item --high-gamma=HIGH_PRIORITY @opindex @option{--high-gamma} @opindex @option{--low-gamma} Include the effects of gamma ramps with a priority below @var{HIGH_PRIORITY} in the screenshot. If used together with @option{--low-gamma=LOW_PRIORITY}, the range [@var{LOW_PRIORITY}, @var{HIGH_PRIORITY}] will be used. @end table Optionally, you can add a non-option argument that specifies the pathname of the saved file. @opindex @option{--window} @opindex @option{--monitor} @opindex @option{--embed} If neither @option{--monitor}, @option{--embed} or @option{--window} is used, a screenshot will be taked of the display. That is, all monitors. @opindex @option{--gamma} @opindex @option{--low-gamma} @opindex @option{--high-gamma} In case of mirrored outputs, one of the potential outputs will be selected arbitrarily if @option{--gamma}, @option{--low-gamma} or @option{--high-gamma} is used. If neither is used, the screenshot will be identical for all mirrored outputs. @node mds-slay @section @command{mds-slay} @pgindex @command{mds-slay} @cpindex Process killing @cpindex Killing processes @command{mds-slay} a utility that can be used to kill a process by it window or identify the window ID of a window. @command{mds-slay} recognises the following options: @table @option @item --embed @opindex @option{--embed} Kill an embedded window. The rat will be used to select window. @item --embed=WINDOW_ID @opindex @option{--embed} Kill an embedded window whose window ID is @var{WINDOW_ID}@. @item --window @opindex @option{--window} Kill a window. The rat will be used to select window. @item --window=WINDOW_ID @opindex @option{--window} Kill a window whose window ID is @var{WINDOW_ID}@. @item --signal=SIGNAL @opindex @option{--signal} Send the signal @var{SIGNAL} to the process owning the selected window. @item --no-signal @opindex @option{--no-signal} Do not send a signal; only identify the window. @item --keep-cursor @opindex @option{--keep-cursor} Do not change the cursor to a kill cursor. @item --print @opindex @option{--print} Print the ID of the selected window. @end table @node mds-chvt @section @command{mds-chvt} @pgindex @command{mds-chvt} @pgindex @command{chvt} @cpindex Virtual terminal, switching @cpindex Switching virtual terminal @command{mds-chvt} is a utility similar to the command @command{chvt} from the @command{kbd} project. However, @command{mds-chvt} has setuid and therefore does not require root permissions, but it will only request a virtual terminal switch if the display server's virtual terminal is in the foreground. @command{mds-chvt} recognises the following options: @table @option @item --switch=VT @opindex @option{--switch} Switch to the virtual terminal with the index @var{VT}@. @end table @node mds-kbdc @section @command{mds-kbdc} @pgindex @command{mds-kbdc} @cpindex Keyboard layouts, compile @cpindex Compile keyboard layouts @cpindex Compose tables, compile @cpindex Compile compose tables @command{mds-kbdc} is the program used to compile keyboard layouts and compose tables. TODO how to use mds-kbdc @node External Utilities @section External Utilities @cpindex Background processes @opindex @option{--on-init-fork} @pgindex @file{mdsinitrc} Servers let you use the option @option{--on-init-fork} to put the process in the background when it has been initialised. This can used to spawn that depend on each other in linear order. For example, if @command{mds-bar} requires that @command{mds-foo} is initialised before it can be initialised, you can in @file{$@{XDG_CONFIG_HOME@}/mdsinitrc} write: @example @group mds-foo --on-init-fork mds-bar & @end group @end example @opindex @option{--on-init-fork} @opindex @option{--on-init-sh} @pgindex @command{mds-respawn} @pgindex @command{cmdipc} @pgindex @command{ipcmd} This will start @command{mds-bar} when @command{mds-foo} has been initialised. However if one of them crashes, that server will not respawn; to fix this @command{mds-respawn} can be used, but use of @command{mds-respawn} hinders the use of @option{--on-init-fork}. Instead you can use @option{--on-init-sh} and global semaphores. The packages, and commands, @command{cmdipc} and @command{ipcmd} can be used for this purpose. We will use @command{cmdipc} in an example: @ifset AFOURPAPER @example S=$(cmdipc -Scx set 1 | cut -d ' ' -f 2) # Create a System V semaphore with the value 1. mds-respawn @{ mds-foo --on-init-sh="cmdipc -Sk $S p" @} & # Spawn `mds-foo` and decrease the semaphore with 1 when initialised. cmdipc -Sk $S z # Wait for the semaphore's value to become 0. cmdipc -Srk $S # Remove the semaphore. mds-respawn @{ mds-bar @} & # Spawn `mds-bar`. @end example @end ifset @ifclear AFOURPAPER @ifset USLETTER @example S=$(cmdipc -Scx set 1 | cut -d ' ' -f 2) # Create a System V semaphore with the value 1. mds-respawn @{ mds-foo --on-init-sh="cmdipc -Sk $S p" @} & # Spawn `mds-foo` and decrease the semaphore with 1 when initialised. cmdipc -Sk $S z # Wait for the semaphore's # value to become 0. cmdipc -Srk $S # Remove the semaphore. mds-respawn @{ mds-bar @} & # Spawn `mds-bar`. @end example @end ifset @ifclear USLETTER @example S=$(cmdipc -Scx set 1 | cut -d ' ' -f 2) # Create a System V semaphore with the value 1. mds-respawn @{ mds-foo --on-init-sh="cmdipc -Sk $S p" @} & # Spawn `mds-foo` and decrease the semaphore with # 1 when initialised. cmdipc -Sk $S z # Wait for the semaphore's # value to become 0. cmdipc -Srk $S # Remove the semaphore. mds-respawn @{ mds-bar @} & # Spawn `mds-bar`. @end example @end ifclear @end ifclear @pgindex @command{mds-reg} This is however seldom necessary as @command{mds-reg} can often be used instead, with more abstraction as you would only need to specify what servers need to wait for, not what they provide. @pgindex @command{setpgrp} @cpindex Display server process group @cpindex Process group, display server Another useful command (and package) is @command{setpgrp}. @command{mds} puts itself an all its children in a new process group. However you may want to put processes that are not @command{mds} servers or @command{mds} utilities in a separate process group. @command{setpgrp} can be used to start a process in a new process group. @node Servers @chapter Servers @pgindex @command{mds} @pgindex @command{mds-server} @cpindex Kernel @cpindex Display server kernel @cpindex Master server An @command{mds} display server instance is comprised of multiple small servers that each implements a small part of the display server's functionallity. This chapter will include all servers but the master server, @command{mds-server} and the kernel, @command{mds}, the latter of which is not actually a server. @menu * mds-echo:: The @command{mds-echo} server. * mds-registry:: The @command{mds-registry} server. * mds-vt:: The @command{mds-vt} server. * mds-clipboard:: The @command{mds-clipboard} server. * mds-drag:: The @command{mds-drag} server. * mds-kkbd:: The @command{mds-kkbd} server. * mds-kkbdrate:: The @command{mds-kkbdrate} server. * mds-kbd:: The @command{mds-kbd} server. * mds-keytrans:: The @command{mds-keytrans} server. * mds-keystick:: The @command{mds-keystick} server. * mds-keybounce:: The @command{mds-keybounce} server. * mds-slowkey:: The @command{mds-slowkey} server. * mds-keycue:: The @command{mds-keycue} server. * mds-kbdbind:: The @command{mds-kbdbind} server. * mds-multikey:: The @command{mds-multikey} server. * mds-rat:: The @command{mds-rat} server. * mds-ratbarrier:: The @command{mds-ratbarrier} server. * mds-ratbind:: The @command{mds-ratbind} server. * mds-gestures:: The @command{mds-gestures} server. * mds-kbd2rat:: The @command{mds-kbd2rat} server. * mds-hwcursor:: The @command{mds-hwcursor} server. * mds-swcursor:: The @command{mds-swcursor} server. * mds-cursorshadow:: The @command{mds-cursorshadow} server. * mds-cursorgamma:: The @command{mds-cursorgamma} server. * mds-hwgamma:: The @command{mds-hwgamma} server. * mds-swgamma:: The @command{mds-swgamma} server. * mds-coopgamma:: The @command{mds-coopgamma} server. * mds-dcvs:: The @command{mds-dcvs} server. * mds-colour:: The @command{mds-colour} server. * mds-dither:: The @command{mds-dither} server. * mds-retro-crt:: The @command{mds-retro-crt} server. * mds-state:: The @command{mds-state} server. * mds-focus:: The @command{mds-focus} server. * mds-kill:: The @command{mds-kill} server. * mds-screensaver:: The @command{mds-screensaver} server. * mds-compositor:: The @command{mds-compositor} server. * mds-crtc:: The @command{mds-crtc} server. * mds-dri:: The @command{mds-dri} server. * mds-fb:: The @command{mds-fb} server. * mds-endomon:: The @command{mds-endomon} server. * mds-mds:: The @command{mds-mds} server. * mds-meta:: The @command{mds-meta} server. * mds-seat:: The @command{mds-seat} server. * mds-nest:: The @command{mds-nest} server. * mds-host:: The @command{mds-host} server. * mds-remote:: The @command{mds-remote} server. * mds-xmds:: The @command{mds-xmds} server. * mds-wmds:: The @command{mds-wmds} server. * mds-mmds:: The @command{mds-mmds} server. * mds-mdsx:: The @command{mds-mdsx} server. * mds-mdsw:: The @command{mds-mdsw} server. * mds-mdsm:: The @command{mds-mdsm} server. * mds-posmem:: The @command{mds-posmem} server. * mds-decorator:: The @command{mds-decorator} server. * mds-tile:: The @command{mds-tile} server. * mds-stack:: The @command{mds-stack} server. * mds-desktop:: The @command{mds-desktop} server. * mds-workspace:: The @command{mds-workspace} server. * mds-tray:: The @command{mds-tray} server. @end menu @node mds-echo @section @command{mds-echo} @pgindex @command{mds-echo} @cpindex Ping @cpindex Debugging @cpindex Heartbeat @cpindex Network heartbeat @command{mds-echo} is a server that echos message that contain the header--value pair @code{Command: echo}. This server can be used for debugging and testing as well as to enable network heartbeats. @node mds-registry @section @command{mds-registry} @pgindex @command{mds-registry} @cpindex List protocols @cpindex Protocols, listing @cpindex Protocol registry @cpindex Registry of protocols @command{mds-registry} is a server that keeps a registry of all protocols that are supported they the sum of all active servers. It can also be used by other servers to wait until a protocol has become available. @node mds-vt @section @command{mds-vt} @pgindex @command{mds-vt} @cpindex Virtual terminal, switching @cpindex Virtual terminal, mode switching @cpindex Switching virtual terminal @cpindex Switching virtual terminal mode @cpindex TTY @cpindex Graphical mode @cpindex Text mode @cpindex Mode, virtual terminal, switching @command{mds-vt} is the server that acquires a virtual terminal for the display, manages virtual terminal switches and enables other servers to get access to the virtual terminal's TTY and informs them of which virtual terminal the display is located on. It also enables other servers to switch the virtual terminals mode to graphical mode or text mode. @vrindex @env{XDG_VTNR} @pgindex @command{mds-vt} @pgindex @file{mdsinitrc} By default @command{mds-vt} will select the next available virtual terminal for the display server. You can override this behaviour by exporting a value to the environment variable @env{XDG_VTNR}@. The value must be a decimal integer of a valid virtual terminal index@footnote{Which is the same thing as a valid TTY index.}. To select the virtual terminal the display was started from you can use the following code in your @file{~/.mdsinitrc}: @pgindex @command{fgconsole} @example export XDG_VTNR="$(fgconsole)" @end example @pgindex @command{kbd} @command{fgconsole} is a part of the @command{kbd} package. @node mds-clipboard @section @command{mds-clipboard} @pgindex @command{mds-clipboard} @cpindex Clipboard @command{mds} has three clipboards, one for copied text, one for selected text, and one for non-textual data. Each of these clipboards are stacks, just like in GNU Emacs. @command{mds-clipboard} implements these clipboards and automatic removal of outdated clips. Clips can be configured to expire based on time or when its originator closes. @node mds-drag @section @command{mds-drag} @pgindex @command{mds-drag} @cpindex Drag-and-drop @command{mds-drag} is the server that implements drag-and-drop support. @node mds-kkbd @section @command{mds-kkbd} @pgindex @command{mds-kkbd} @cpindex Keyboard @cpindex Keyboard, kernel-based @cpindex Scancodes @cpindex Keycodes @cpindex Keycodes, remapping @cpindex Keyboard, remapping @cpindex Remapping keycodes @cpindex Keys, swap @cpindex Swap keys @command{mds-kkbd} implements access to the kernel-based keyboard. It does not however implement delay and rate configurations for the kernel-based keyboard as that requires root privileges. The kernel-based keyboard is a keyboard that can be accessed by reconfiguring stdin in a TTY using @code{ioctl} and then read from stdin. @command{mds-kkbd} does not implement any keyboard layout, rather it broadcasts scancodes and keycodes. However it can remap keycodes, but not scancodes. @cpindex Keyboard LED:s @cpindex LED:s, keyboard @cpindex Keyboard LED:s, remap @cpindex LED:s, keyboard, remap @cpindex Remap keyboard LED:s @cpindex Remap LED:s, keyboard @opindex @option{--led} @command{mds-kkbd} implements control over keyboard LED:s, the indicators for locked keys. The user can remap the LED:s both while the server is running, and at launch via the command line arguments. The option @option{--led} is used to remap the LED:s. The valid LED names are @code{num}, @code{caps} and @code{scrl}, and also @code{compose} and SPARC machines. The swap, for example @key{Caps Lock}'s LED and @key{Num Lock}'s LED, start @command{mds-kkbd} with @option{--led=caps=num} and @option{--led=num=caps}. You can also use an index instead of a name, for example @option{--led=caps=0}, but not @option{--led=0=caps}. The index must be a non-negative integer. The server's behaviour is undefined if the used value does not map to a real LED. @node mds-kkbdrate @section @command{mds-kkbdrate} @pgindex @command{mds-kkbdrate} @pgindex @command{mds-kkbd} @cpindex Keyboard @cpindex Keyboard, kernel-based @cpindex Keyboard repeat rate @cpindex Keyboard repeat delay @command{mds-kkbdrate} is a complemental server to @command{mds-kkbd}, it implements rate and delay control for the kernel-based keyboard. @node mds-kbd @section @command{mds-kbd} @pgindex @command{mds-kbd} @cpindex Keyboard @cpindex Keyboard repeat rate @cpindex Keyboard repeat delay @cpindex Scancodes @cpindex Keycodes @cpindex Keycodes, remapping @cpindex Keyboard, remapping @command{mds-kbd} is an alternative to @command{mds-kkbd} and @command{mds-kkbdrate}. In contrast to @command{mds-kkbd}, @command{mds-kbd} implements control over individual keybroads rather than utilising the kernels keyboard drivers to treats all keyboards a one keyboard. This server is only useful for multiseat sessions and if you otherwise actually want to handle the keyboards individually. @node mds-keytrans @section @command{mds-keytrans} @pgindex @command{mds-keytrans} @pgindex @command{mds-kbd} @pgindex @command{mds-kkbd} @cpindex Keyboard layout @cpindex Layout, keyboard @cpindex Dead keys @cpindex Compose key @cpindex Modifier keys @cpindex Keys, mapping, layout @cpindex Keys, dead @cpindex Keys, compose @cpindex Keys, modifiers @command{mds-keytrans} is the server than translates keycodes from @command{mds-kkbd} and @command{mds-kbd}, and third-party alternatives, to characters and other attributes. It implements the keyboard's layouts including modifiers, letters, other symbols, dead keys and compose. @node mds-keystick @section @command{mds-keystick} @pgindex @command{mds-keystick} @cpindex Sticky keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard @command{mds-keystick} is a server that can be used to enable sticky keys. See @ref{Sticky Keys} for more information. @node mds-keybounce @section @command{mds-keybounce} @pgindex @command{mds-keybounce} @cpindex Bounce keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard @command{mds-keybounce} is a server that can be used to enable bounce keys. See @ref{Bounce Keys} for more information. @node mds-slowkey @section @command{mds-slowkey} @pgindex @command{mds-slowkey} @cpindex Slow keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard @command{mds-slowkey} is a server that can be used to enable slow keys. See @ref{Slow Keys} for more information. @node mds-keycue @section @command{mds-keycue} @pgindex @command{mds-keycue} @cpindex Loud keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard @command{mds-keycue} is a server that can be used to enable loud keys. See @ref{Loud Keys} for more information. @node mds-kbdbind @section @command{mds-kbdbind} @pgindex @command{mds-kbdbind} @pgindex @command{xbindkeys} @pgindex @command{dmenu} @cpindex Hotkeys @cpindex Keyboard bindings @cpindex Bindings, keyboard @cpindex Layout, keyboard, switching @cpindex Keyboard layout, switching @cpindex Switching keyboard layout @command{mds-kbdbind} is a server similar to @command{xbindkeys}. It can be used to run commands upon selected key combinations, for example starting @command{dmenu} or change keyboard layout. @command{mds-kbdbind} can distinguish keyboards from each other. @node mds-multikey @section @command{mds-multikey} @pgindex @command{mds-multikey} @pgindex @command{mds-kbdbind} @cpindex Keyboard bindings @cpindex Bindings, keyboard @command{mds-multikey} is a server that can bind a key, key combination, or sequence their of to a sequence of keys or key combinations. For example, you could bind @kbd{x, y} to simulate that a key @key{Faux1} is pressed, a key that does not exist, this key press could be picked up by @command{mds-kbdbind} to enable @command{mds-kbdbind} to respond to squences rather than single keys and single key combinations. alternatively you could bind @kbd{x} to press @key{x} a selected number of times with a short selectable delay between them; or @kbd{x, 5} to press @key{x} five times. @node mds-rat @section @command{mds-rat} @pgindex @command{mds-rat} @cpindex Rat device @cpindex Mouse device @cpindex Pointing device @command{mds-rat} is a server that implements support of rat (also known as mouse) devices. @node mds-ratbarrier @section @command{mds-ratbarrier} @pgindex @command{mds-ratbarrier} @cpindex Cursor barriers @cpindex Rat pointer barriers @cpindex Mouse pointer barriers @cpindex Pointer barriers @cpindex Screen edges, barriers @cpindex Barriers, rat @command{mds-ratbarrier} is a server that lets you set up barriers for the rat pointer, for example at the screen edges. A barrier requires that the rat be moved a bit extra move it can move on to the next pixel. A barrier can be directional. A barrier can also be infinite, which blocks the rat pointer fully and it cannot pass through at all. @node mds-ratbind @section @command{mds-ratbind} @pgindex @command{mds-ratbind} @cpindex Bindings, rat @cpindex Rat bindings @cpindex Mouse bindings @cpindex Pointer bindings @cpindex Hotcorners @command{mds-ratbind} is a server similar to @command{mds-kbdbind}. However, @command{mds-ratbind} respons to rat and rat cursor actions rather than keyboard actions. It can for example be used to implement hotcorners. @node mds-gestures @section @command{mds-gestures} @pgindex @command{mds-gestures} @cpindex Bindings, gestures @cpindex Gestures bindings @cpindex Rat gestures bindings @cpindex Mouse gestures bindings @cpindex Pointer gestures bindings @command{mds-gestures} is a server similar to @command{mds-ratbind}. However it is specialised to respond to gestures. @node mds-kbd2rat @section @command{mds-kbd2rat} @pgindex @command{mds-kbd2rat} @cpindex Keyboard to rat bindings @cpindex Rat keys @cpindex Mouse keys If you do not have a rat or rather use your keyboard, the server @command{mds-kbd2rat} can be used to bind keyboard actions to simulate rat actions. This server is a specialisation of @code{mds-kbdbind}, rather than spawning generic commands it broadcasts messages within the display server to move the rat cursor and click on rat buttons. @code{mds-kbdbind} could be used to do this, but @command{mds-kbd2rat} will not spawn a new process for each action. For more information see @ref{Mouse Keys}. @node mds-hwcursor @section @command{mds-hwcursor} @pgindex @command{mds-hwcursor} @cpindex Cursor, hardware @cpindex Rat cursor, hardware @cpindex Mouse cursor, hardware @cpindex Hardware cursor @command{mds-hwcursor} is a server that draws the rat cursor to the monitor on a plane separate from all other content on the display. In less esoteric terms, it implements a hardware cursor. @node mds-swcursor @section @command{mds-swcursor} @pgindex @command{mds-swcursor} @cpindex Cursor, software @cpindex Rat cursor, software @cpindex Mouse cursor, software @cpindex Software cursor @command{mds-swcursor} is a server that draws the rat cursor to the monitor on the same plane as all other content on the display. In less esoteric terms, it implements a software cursor. @node mds-cursorshadow @section @command{mds-cursorshadow} @pgindex @command{mds-cursorshadow} @cpindex Cursor shadow @cpindex Rat cursor shadow @cpindex Mouse cursor shadow @cpindex Shadow, cursor @command{mds-cursorshadow} is a server that can be used to decorate the rat cursor with a configurable shadow. @node mds-cursorgamma @section @command{mds-cursorgamma} @pgindex @command{mds-cursorgamma} @pgindex @command{mds-hwcursor} @cpindex Gamma correction, hardware cursor @cpindex Cursor, hardware, gamma correction @cpindex Rat cursor, hardware, gamma correction @cpindex Mouse cursor, hardware, gamma correction @cpindex Hardware cursor, gamma correction @cpindex Graphics drivers @command{mds-cursorgamma} is a server you can use if you use @command{mds-hwcursor} to, if not done by the graphics driver, correct the gamma correction on the hardware cursor using software gamma ramps. This of courses works whether you are using hardware or software gamma ramps for your monitor's gamma correction. If can even be used if you do not use gamma correction, in such case, only the cursor will have its gamma corrected. @node mds-hwgamma @section @command{mds-hwgamma} @pgindex @command{mds-hwgamma} @cpindex Gamma correction, hardware @cpindex Hardware gamma correction To enable gamma correction, use the server @command{mds-hwgamma}. It implements hardware gamma ramps, that is, gamma ramps assisted by hardware acceleration. @node mds-swgamma @section @command{mds-swgamma} @pgindex @command{mds-swgamma} @cpindex Gamma correction, software @cpindex Software gamma correction @cpindex Graphics drivers If your graphics driver does not support @command{mds-hwgamma}, you can instead use @command{mds-swgamma}. It implements software gamma ramps, that is, it will modify each pixel according to the selected gamma correction before it is send to the presentation sever. To accelerate this process, @command{mds-swgamma} can tell programs how to modify its colours before sending it; the programs can then tell @command{mds-swgamma} not to apply its correction. Programs such as video players can also use this to tell the server not to apply gamma correction as that may cause the video to be played back to slowly. @node mds-coopgamma @section @command{mds-coopgamma} @pgindex @command{mds-coopgamma} @cpindex Gamma correction, cooperative @cpindex Gamma correction, chain @cpindex Gamma correction, filters @cpindex Cooperative gamma correction @command{mds-coopgamma} is a server that can be used to enable multiple clients to manipulate the gamma ramps without stepping on each others toes. It does this by letting clients tell which priority their corrections has and use this data to chain their modifications together. For example if one program wants to apply a red filter to the display and another program wants to correct the monitors' gamma, the red filter program will send lookup tables for the gamma with high priority and the correction program will send its lookup tables with low priority. @command{mds-coopgamma} will then apply the latter lookup tables on top of the red filter. The clients can tell @command{mds-coopgamma} whether it should remove their changes when they close, or even keep them and wait for the client to restart. @node mds-dcvs @section @command{mds-dcvs} @pgindex @command{mds-dcvs} @cpindex Defective colour vision, simulation @cpindex Simulateion of defective colour vision @cpindex Colour blindness, simulation @cpindex Simulateion of colour blindnes @command{mds-dcvs} is a server than can be used to simulate defective colour vision. That is, it can for example turn the display greyscale (colour blindness) or add a filter the simulates deuteranopia or deuteranomaly. This server is intended for testing that interfaces are suitable for people with defective colour vision. @node mds-colour @section @command{mds-colour} @pgindex @command{mds-colour} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @sgindex @code{SIGUSR2} @command{mds-colour} is a server that implements colour names, such as system colours and generic names, for example `red', whose exact colour can be configured by the user. A terminal written for @command{mds} would look up colours such as `red' and `light-red' and get the colours the terminal should use by default. Nothing is to be assumed for such colours, not even that `light-red' is in fact lighter than `dark red', or that `red' is in fact `red', only that it is the colour the user wants to see when a colour is supposed to be `red'. @command{mds-colour} will notify clients when a colour has been reconfigured, added or removed. @command{mds-colour} can be notified to reload its settings by sending @code{SIGUSR2} to the server. @node mds-dither @section @command{mds-dither} @pgindex @command{mds-dither} @cpindex Colour dithering @cpindex Dithering of colours @command{mds-dither} is a server responsible for informing clients on which two colours clients should use and how to dither them (by percent, not by pattern.) This is useful if only 16-bit colours can be used, or if only 24-colour can used but gradients between for example sRGB(255, 255, 255) and sRGB(254, 254, 254) is to be drawn. @cpindex Gamma correction, dithering @command{mds-dither} is gamma ramp-aware. For example, if for the red channel, 0 is mapped to 0, 1 is mapped to 3, 2 is mapped 2 and 3 is mapped to 1, but 1 and 3 requires dithering, then if 3 is requested, @command{mds-dither} will tell the client to dither 0 and 2 with 50 %, which should generate 1, but 1 and 3 has been swapped. @command{mds-dither} holds a cache of the outputs gamma ramps to optimise performance. It will also inform clients when it is time to redither colours. This happens the gamma ramps change substantially, small changes should not trigger redithering, make it a waste of CPU time if all clients using dithering would spend time figuring out whether redithering is required. @node mds-retro-crt @section @command{mds-retro-crt} @pgindex @command{mds-retro-crt} @pgindex @command{cool-retro-crt} @command{mds-retro-crt} is a server that applies filters used in the terminal emulator @command{cool-retro-term} to the whole display. @node mds-state @section @command{mds-state} @pgindex @command{mds-state} @cpindex State, windows @cpindex Windows states @command{mds-state} is the server that keeps tracks of the windows' state. @node mds-focus @section @command{mds-focus} @pgindex @command{mds-focus} @cpindex Window focus @cpindex Focus of windows and components @command{mds-focus} is the server focuses windows and windows' components. @node mds-kill @section @command{mds-kill} @pgindex @command{mds-kill} @cpindex Signals, sending @cpindex Process identification @cpindex Identification of processes @command{mds-kill} is a server that can be used to send signals to processes by identifying them by their windows. This server can also be used to simply identify the process that owns a window. @node mds-screensaver @section @command{mds-screensaver} @pgindex @command{mds-screensaver} @cpindex Screensaver @cpindex Monitor deactivation @cpindex Deactive monitors @command{mds-screensaver} is a server that can be used to start a screensaver or deactive monitors when the input devices has not be used for a period of time provided that no client has disabled this. It is capable of deactiving single monitors or start a screensaver on single monitors rather than all monitors. @node mds-compositor @section @command{mds-compositor} @pgindex @command{mds-compositor} @pgindex @command{mds-dri} @pgindex @command{mds-fb} @cpindex Compositor @cpindex Presentation @command{mds-compositor} is the server that composes the output. It takes output of all windows and arranges it to one image per monitor and sends it to the presentation servers, such as @command{mds-dri} and @command{mds-fb}. @node mds-crtc @section @command{mds-crtc} @pgindex @command{mds-crtc} @cpindex CRTC @cpindex Cathode ray tube controller @command{mds-crtc} is the server that identifies CRTC:s and provide access to them. @node mds-dri @section @command{mds-dri} @pgindex @command{mds-dri} @cpindex Direct Rendering Infrastructure @cpindex Presentation @cpindex Display of content @cpindex Content, display @command{mds-dri} is a server that displays content using the Direct Rendering Infrastructure. @node mds-fb @section @command{mds-fb} @pgindex @command{mds-fb} @cpindex Framebuffer @cpindex Presentation @cpindex Display of content @cpindex Content, display @command{mds-fb} is a server that displays content using framebuffers. @node mds-endomon @section @command{mds-endomon} @pgindex @command{mds-endomon} @cpindex CRTC @cpindex Cathode ray tube controller @cpindex Presentation @cpindex Display of content @cpindex Content, display @cpindex Endomonitor @cpindex Monitor, endo- @cpindex Cinerama @pgindex @command{mds-cinerama} @command{mds-endomon} is a server that provides a logical monitor inside another monitor or cinerama, an endomonitor. This lets you for example start a single-monitor full screen game but keep a part, for example the status bar with the clock, visible. For more information, see @ref{Endomonitor}. @node mds-mds @section @command{mds-mds} @pgindex @command{mds-mds} @cpindex Monitor emulation @cpindex Emulation, monitor @command{mds-mds} is a server that displays content using another @command{mds} window. It creates a window that emulates a monitor. @node mds-meta @section @command{mds-meta} @pgindex @command{mds-meta} @cpindex Metadisplay server @vrindex @env{MDS_DISPLAY} @cpindex Server sharing @cpindex Sharing, servers @command{mds-meta} is a metadisplay server. It creates or joins a named metadisplay server, and creates an alternative value for @env{MDS_DISPLAY}@. Any server connecting to this alternative @env{MDS_DISPLAY} connects to this metadisplay server. This can be used to make servers shared between display server instances. @command{mds-meta} uses the environment variable @env{MDS_METADISPLAY} to acquire the name of the metadisplay server instance it should join or create. If @env{MDS_METADISPLAY} has not been set it is treated as having an empty string for its value which is a valid metadisplay server instance name. @command{mds-meta} works by connecting to the running display server instance, the display, and create a new display server instance, the metadisplay. Messages passed via the metadisplay's socket is forward to the display, and messages passed to via the display to @command{mds-meta} is send to the appropriate server. @command{mds-meta} manages interception in the same way as @command{mds-server} and @command{mds-remote}. @pgindex @file{mdsmetainitrc} If @command{mds-meta} creates a new metadisplay, rather than joining an existing metadisplay, it will spawn @file{~/.mdsmetainitrc} to let you start the shared servers. @pgindex @command{mds-host} @pgindex @command{mds-clipboard} @pgindex @command{mds-remot} @cpindex Networking An interesting property of @command{mds-meta} is that it can be used to share servers across display servers on multiple computers. For example, if you start @command{mds-host} and @command{mds-clipboard} inside the metadisplay on your central computer, displays started on other servers can run @command{mds-remote} to connect to the metadisplay so that all computers share the same clipboard. However, this network will be centralised and not distributed, so it is not perfect. For more information, see @ref{Metadisplay Server}. @node mds-seat @section @command{mds-seat} @pgindex @command{mds-seat} @cpindex Sandboxing, seats @cpindex Seats @command{mds-seat} is a server that enables seat-sandboxing. It can be used to place two users on the same machine without them interfering with each others monitors and input devices. Servers started below @command{mds-seat} become shared and servers started above @command{mds-seat} become seat-private. @command{mds-seat} can filter messages from shared servers so only the appropriate seat receives them. @node mds-nest @section @command{mds-nest} @pgindex @command{mds-nest} @cpindex Display server, nesting @cpindex Nested display server @command{mds-nest} is a server that creates a new @command{mds} instance inside another @command{mds} instance. A display server inside another display server. @node mds-host @section @command{mds-host} @pgindex @command{mds-host} @pgindex @command{mds-remote} @cpindex Networking @command{mds-host} is a server that enables servers like @command{mds-remote} running on remote machines to connect to the local machine and its display server. @node mds-remote @section @command{mds-remote} @pgindex @command{mds-remote} @cpindex Networking @command{mds-remote} is a server that enables you to connect extend a remote @command{mds} with your local machine. This can be used to make a display server instance span multiple computers including its monitors and input devices. @node mds-xmds @section @command{mds-xmds} @pgindex @command{mds-xmds} @cpindex Compatibility layer, X.org @cpindex X.org compatibility layer @command{mds-xmds} is a server that translates X.org calls to @command{mds} calls. It can be used to run X.org-only programs inside @command{mds}. @node mds-wmds @section @command{mds-wmds} @pgindex @command{mds-wmds} @cpindex Compatibility layer, Wayland @cpindex Wayland compatibility layer @command{mds-wmds} is a server that translates Wayland calls to @command{mds} calls. It can be used to run Wayland-only programs inside @command{mds}. @node mds-mmds @section @command{mds-mmds} @pgindex @command{mds-mmds} @cpindex Compatibility layer, Mir @cpindex Mir compatibility layer @command{mds-mmds} is a server that translates Mir calls to @command{mds} calls. It can be used to run Mir-only programs inside @command{mds}. @node mds-mdsx @section @command{mds-mdsx} @pgindex @command{mds-mdsx} @cpindex Reverse compatibility layer, X.org @cpindex X.org reverse compatibility layer @command{mds-mdsx} is a server that translates @command{mds} calls to X.org calls. It can be used to enable @command{mds} specific programs to run inside the X.org display servers. @node mds-mdsw @section @command{mds-mdsw} @pgindex @command{mds-mdsw} @cpindex Reverse compatibility layer, Wayland @cpindex Wayland reverse compatibility layer @command{mds-mdsw} is a server that translates @command{mds} calls to Wayland calls. It can be used to enable @command{mds} specific programs to run inside the Wayland display servers. @node mds-mdsm @section @command{mds-mdsm} @pgindex @command{mds-mdsm} @cpindex Reverse compatibility layer, Mir @cpindex Mir reverse compatibility layer @command{mds-mdsm} is a server that translates @command{mds} calls to Mir calls. It can be used to enable @command{mds} specific programs to run inside the display server Mir. @node mds-posmem @section @command{mds-posmem} @cpindex Memorisation of size and position @cpindex Position, memorisation @cpindex Size, memorisation @pgindex @command{mds-posmem} @command{mds-posmem} is a server that remembers where window's were positioned and their size, and moves and resizes them accordingly when they are created. @node mds-decorator @section @command{mds-decorator} @pgindex @command{mds-decorator} @cpindex Client-side decoration @cpindex Decoration @command{mds-decorator} is a server that provides a simple, reference implementation of a, window decorator. This window decorator should implement snappy and sticky edges and stacking (the title bars is split into tabs with different windows that have been stacked togather.) @node mds-tile @section @command{mds-tile} @pgindex @command{mds-tile} @cpindex Tiling window manager @cpindex Window manager, tiling @command{mds-tile} is a server that provides a simple, reference implementation of a, tiling window manager. @node mds-stack @section @command{mds-stack} @pgindex @command{mds-stack} @cpindex Stacking window manager @cpindex Window manager, stacking @command{mds-stack} is a server that provides a simple, reference implementation of a, stacking window manager. @node mds-desktop @section @command{mds-desktop} @pgindex @command{mds-desktop} @cpindex Desktop @command{mds-desktop} is a server that provides a simple, reference implementation of a, desktop. @node mds-workspace @section @command{mds-workspace} @pgindex @command{mds-workspace} @cpindex Workspaces @command{mds-workspace} is a server that provides simple, reference implementation of, workspaces. @node mds-tray @section @command{mds-tray} @pgindex @command{mds-tray} @cpindex Status icon tray @cpindex System tray @cpindex Tray, status icons @cpindex Icon, status, tray @command{mds-tray} is a server that provides a simple, reference implementation of a, status icon tray. @node Protocols @chapter Protocols @menu * Infrastructure Protocols:: Infrastructure protocols. * Virtual Terminal Protocols:: Virtual terminal protocols. * Keyboard Protocols:: Keyboard protocols. * Clipboard Protocols:: Clipboard protocols. * Status Icon Protocols:: Status icon protocols. * Colour Protocols:: Colour protocols. * Screensaver Protocols:: Screensaver protocols. * Miscellaneous Protocols:: Miscellaneous protocols. @end menu @node Infrastructure Protocols @section Infrastructure Protocols @menu * assign-id:: Assign new ID to client, or fetch current ID@. * intercept:: Sign up for reception of message. * register:: Register availability of a command for which you implement a service. * reregister:: Request for reregistration for available commands. * error:: Notify a client about a request failure. @end menu @node assign-id @subsection @code{assign-id} @prindex @code{assign-id} @cpindex Client ID assignment @cpindex ID assignment @cpindex Assignment of ID @cpindex Client ID fetching @cpindex ID fetching @cpindex Fetching of ID @table @asis @item Identifying header: @code{Command: assign-id} @item Action: Assign new ID to client, or fetch current ID@. @item Purpose: Assigning ID to clients so server can respond to that client. @item Compulsivity: Manditory, part of the core infrastructure. @item Reference implementation: @pgindex @command{mds-server} @command{mds-server} @end table @node intercept @subsection @code{intercept} @prindex @code{intercept} @cpindex Interceptions, message passing @cpindex Message modification, message passing @table @asis @item Identifying header: @code{Command: intercept} @item Action: Sign up for reception of message. @item Optional header: @code{Stop} Stop reception of messages if the value for the header @code{Stop} is @code{yes}. @item Optional header: @code{Priority} Signed 64-bit integer of reception priority (reversed of order.) @item Optional header: @code{Modifying} Send message asynchronously and await modification if the value for the header @code{Modifying} is @code{yes}. @item Optional header: @code{Length} Length of the message. @item Message: List of headers and header--value-pairs that qualifies a message for reception, all messages qualifies if this list is empty. @item Purpose: Filter received message for clients and servers. @item Purpose: Assigned interception order for modification of messages. @item Compulsivity: Manditory, part of the core infrastructure. @item Reference implementation: @pgindex @command{mds-server} @command{mds-server} @end table @node register @subsection @code{register} @prindex @code{register} @cpindex Protocol registry @cpindex Registry of protocols @table @asis @item Identifying header: @code{Command: register} @item Action: Register availability of a command for which you implement a service. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Conditionally required header: @code{Length} Length of the message. Required if @code{Action: list} is included in the headers. @item Optional header: @code{Action} @table @code @item remove Remove availability from registry if the value of the header @code{Action} is @code{remove}. @item wait Wait until listed commands are available if the value of the header @code{Action} is @code{wait}. However if a protocol becomes unavailable during this wait period it will still be counted as available for this wait action. @item list @cpindex List protocols @cpindex Protocols, listing Send a list of availability commands if the value of the header @code{Action} is @code{list}. @end table @item Conditionally optional header: @code{Time to live} The maximum number of seconds to wait. Available and optional if @code{Action: wait} is included in the headers. @item Message: List of values for the header @code{Command} that you implement. @item Purpose: Identify supported display server operations. @item Purpose: @cpindex Initialisation synchronisation Initialisation process synchronisation. @item Compulsivity: Highly recommended, programs may stall a bit from time to time without it, or at initialisation depending on the program's implementation. @item Reference implementation: @pgindex @command{mds-registry} @command{mds-registry} @end table @node reregister @subsection @code{reregister} @prindex @code{reregister} @cpindex Protocol registry @cpindex Registry of protocols @table @asis @item Identifying header: @code{Command: reregister} @item Action: @prindex @code{register} Request that all servers resends @code{Command: register} with either @code{Action: add} or without the @code{Action}-header (does the same thing.) @item Purpose: @prindex @code{register} Rebuild registry created with @code{Command: register} if the registry server crashes. @item Compulsivity: Highly recommended, programs may think a protocol is not supported of the registry server crashes if you do not implement this in your server. @item Reference implementation: @pgindex @command{mds-registry} @command{mds-registry} @end table @node error @subsection @code{error} @prindex @code{error} @cpindex Error management @cpindex Responses @table @asis @item Identifying header: @code{Command: error} @item Action: Notify a client about a request failure. @item Required header: @code{To} The ID of the client that send a request that failed. @item Required header: @code{In response to} The ID of the message whose request failed. @item Required header: @code{Error} The errno number of the error, 0 on success if the message was not an information query. The string ``custom'' can be used if there is not errno number, optionally followed by a blank space and a number that identifies the error, this number must be positive (not zero). @item Conditionally optional header: @code{Length} The length of the message. Available and optional if ``custom'' is used in the header @code{Error}. @item Message: Description of the error, single line, mid-sentence case, no punctuation in the end, must not be a question but rather it must be a statement. The message shall end with a line feed. @item Purpose: Let clients know whether a command is successful or failed, and why it failed. @item Compulsivity: Optional. @end table @node Virtual Terminal Protocols @section Virtual Terminal Protocols @cpindex Virtual terminal @menu * get-vt:: Get the index of the virtual terminal the server is display on. * configure-vt:: Reconfigure the virtual terminal the server is display on. * switching-vt:: Notify servers about an ongoing virtual terminal switch. @end menu @node get-vt @subsection @code{get-vt} @prindex @code{get-vt} @table @asis @item Identifying header: @code{Command: get-vt} @item Action: Get the index of the virtual terminal the server is display on. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Response: The server will response with the header @code{VT index} and the index of the virtual terminal the server is display on in decimal format. Additionally the server will respond with the header @code{Active} with the value @code{yes} if the VT is in the foreground or the value @code{no} if the VT is in the background. @item Purpose: Allow programs to be aware of whether the display is in the foreground or the background. @item Purpose: Allow programs to be aware of which VT the server is running on. @item Purpose: Allow programs to gain access of the TTY associated with the VT such that they can use @code{ioctl} and similar calls on that TTY@. @item Compulsivity: Required. @item Reference implementation: @pgindex @command{mds-vt} @command{mds-vt} @end table @node configure-vt @subsection @code{configure-vt} @prindex @code{configure-vt} @table @asis @item Identifying header: @code{configure-vt} @item Action: Reconfigure the virtual terminal the server is display on. @cpindex Virtual terminal, mode switching @cpindex Switching virtual terminal mode @cpindex Graphical mode @cpindex Text mode @cpindex Mode, virtual terminal, switching @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Optional header: @code{Graphical} @table @code @item yes Set the TTY graphical mode if the value of the header @code{Graphical} is @code{yes}. @item no Set the TTY text mode if the value of the header @code{Graphical} is @code{no}. @end table The server implementing this protocol should not set the TTY to text mode temporarily when switching TTY@. It is up to the server that set the request for graphical mode to temporarily switch to text mode when switching TTY@. @cpindex Virtual terminal, exclusive mode @cpindex Exclusive mode, virtual terminal @item Optional header: @code{Exclusive} @table @code @item yes The server may block other process from opening the TTY if the value of the header @code{Exclusive} is @code{yes}. @item no The server may not block other process from opening the TTY if the value of the header @code{Exclusive} is @code{no}. @end table The server implementing this protocol should keep a counter for how many servers have requested non-exclusive mode and only switch back to exclusive mode when that counter reaches zero @item Response: The server will response with a @code{Command: error}. @item Purpose: Allow presentation servers to enter and leave graphical mode. @item Purpose: @cpindex TTY Allow programs to gain access of the TTY associated with the VT such that they can use @code{ioctl} and similar calls on that TTY@. @item Compulsivity: Required. @item Reference implementation: @pgindex @command{mds-vt} @command{mds-vt} @end table @node switching-vt @subsection @code{switching-vt} @prindex @code{switching-vt} @cpindex Virtual terminal, switching @cpindex Switching virtual terminal @table @asis @item Identifying header: @code{Command: switching-vt} @item Action: Notify servers about an ongoing virtual terminal switch. @item Required header: @code{Status} @table @code @item deactivating The kernel wants to place the display in the background if the value of the header @code{Status} is @code{deactivating}. @item activating The kernel wants to place the display in the foreground if the value of the header @code{Status} is @code{activating}. @end table @item Instructions: When a virtual terminal switch is requested the server implementing control VT switching involving the display's virtual terminal will get signaled by the kernel. Upon this signal the server should broadcast this command. All servers that need to release or acquire resouces should intercept this message with the possibility of modifying it. Once a server is ready for the VT to switch it should let the message pass to the next server by telling the master server that it is no modification to do. Once all servers are read for the switch the server that emitted this message should signal the kernel that it may switch VT@. The server should detect this by setting up secondary contection to the display that intercepts this message. This connection should intercept this message with priority @math{-2^{62}}, all servers that need to perform actions before the switch takes place must have a priority higher than @math{-2^{62}}, preferably 0. @item Purpose: Allow servers to release resources when the user switch virtual terminal before the terminal actually changes and to reacquire resources when the virtual terminal become active again. @item Compulsivity: Required. @item Reference implementation: @pgindex @command{mds-vt} @command{mds-vt} @end table @node Keyboard Protocols @section Keyboard Protocols @menu * key-sent:: Announce a keyboard input event. * enumerate-keyboards:: List available keyboards. * keyboard-enumeration:: Response to @code{Command: enumerate-keyboards}. * set-keyboard-leds:: Activate and deactivate LED:s on a keyboard. * get-keyboard-leds:: List exisiting LED:s on a keyboard and their state. * map-keyboard-leds:: Remap LED:s on a keyboard. * set-keyboard-rate:: Set the repeat rate and repeat delay on a keyboard. * get-keyboard-rate:: Get the repeat rate and repeat delay on a keyboard. * keycode-map:: Remap keyboard keycodes and query current mapping. * new-keyboard:: Announce the existance of a new keyboard. * old-keyboard:: Announce the removal of an old keyboard. @end menu @node key-sent @subsection @code{key-sent} @prindex @code{key-sent} @table @asis @item Identifying header: @code{Command: key-sent} @item Action: @cpindex Keyboard input events @cpindex Input events, keyboard Announce a keyboard input event. @item Required header: @code{Keyboard} @cpindex Keyboard ID @cpindex ID of keyboard Any string that uniquely identifies the keyboard. @table @asis @item Purpose: Enable multi-keyboard aware programs and give at least one keyboard per seat in a multi-seat environment. @item Note: @pgindex @command{mds-kkbd} @command{mds-kkbd} uses @code{kernel} to indicate that it uses the kernel and thus lumps together all keyboards. @end table @item Required header: @code{Released} @table @code @item yes The value of the header @code{Released} will be @code{yes} if the key was released. @item no The value of the header @code{Released} will be @code{no} otherwise, that is, held down or pressed. @end table Note: @key{Pause}/@key{Break} is automatically released directly after it has been pressed. This is feature built into most keyboards and servers should not try to circumvent this. @item Required header: @code{Keycode} @cpindex Keycodes An unsigned 14-bit integer identifying the key, may be remapped. @item Optional header: @code{Scancode} @cpindex Scancodes Either an unsigned 7-bit integer or a single blank space separated trio of unsigned 7-bit integers, identifying the key. This is the scancode sent from the keyboard and optionally unified by the keyboard driver, however with the typed/released bit zeroed out. This may not be remapped. @item Optional header: @code{Modifiers} @cpindex Modifier keys @cpindex Keys, modifiers Single blank space separated list of active modifiers: @table @code @item shift @key{Shift} (level 2) @item ctrl @key{Control} @item alt @key{Alternative}/@key{Option} @item altgr @key{Alternative Graphic} (level 3) @item lvl* @code{*} may be any @math{2^n + 1} integer with @math{1 < n < 20}. @item super @key{Super} @item hyper @key{Hyper} @item ultra @key{Ultra} @item caps @key{Caps} (usually a lock key) @item num @key{Num} (usually a lock key) @item scrl @key{Scroll} (usually a lock key) @item top @key{Top} (historical) @item front @key{Front} (historical) @item greek @key{Greek} (historical) @item compose @key{Compose} (rare, it is usually a dead key) @end table @cpindex Lock keys @cpindex Keys, lock Any key that has been locked should be prefix with @code{+}, if the key has been locked by nullified with non-lock modifier it should be prefixed with a @code{-}. If no modifier is active or has been nullified, @code{none} should be used. @item Optional header: @code{Key} A textual representation of the key that has been typed or released, as mapped by the keyboard layout. @table @code @item esc @key{Escape} @item f* @key{F*} where @code{*} is any integer. @item sysrq @key{System Request}/@key{Print Screen} @item scrl @key{Scroll} (lock) @item break @key{Break}/@key{Pause} @item backspace @key{Backspace} @item tab @key{Tab} @item return @key{Return}/@key{Enter} @item space @key{Blank Space} @item menu @key{Application Menu} @item ins @key{Insert} @item home @key{Home} @item pgup @key{Page Up} @item del @key{Delete} @item end @key{End} @item pgdown @key{Page Down} @item up @key{Up} arrow @item left @key{Left} arrow @item down @key{Down} arrow @item right @key{Right} arrow @item shift @key{Shift} (level 2) @item begin @key{Begin} (keypad @key{5} in nagivation mode) @item ctrl @key{Control} @item alt @key{Alternative}/@key{Option} @item altgr @key{Alternative Graphic} (level 3) @item lvl* @code{*} may be any @math{2^n + 1} integer with @math{1 < n < 20}. @item super @key{Super} @item hyper @key{Hyper} @item ultra @key{Ultra} @item caps @key{Caps} (usually a lock key) @item num @key{Num} (usually a lock key) @item scrl @key{Scroll} (usually a lock key) @item top @key{Top} (historical) @item front @key{Front} (historical) @item greek @key{Greek} (historical) @item compose @key{Compose} (usually a dead key) @item hexcompose @key{Hex-Compose} (usually a dead key) (Used to create aribitrary characters.) @item longhexcompose @key{Long Hex-Compose} (usually a dead key) (Variant of @code{hexcompose} for longer codepoints.) @item modelock @key{Mode Lock} @item letter * @code{*} may be any UTF-8 encoded letter. @end table Keys that lock/unlock a modifer should be suffixed with a blank space and a @code{lock}. If the key is a dead key (even the @key{Compose} key) should use @code{dead} instead. A position, either @code{left}, @code{right}, @code{keypad} or an index, followed by a blank space, should prefix any key that occurs on multiple position on the keyboard, unless it only appears on the keypad once and once not on the keypad. Keys without any meaning should be identified as @code{unknown}. Modifiers and dead keys should not affect the value. @item Optional header: @code{Characters} UTF-8 encoded string that has been written. @item Purpose: @cpindex On-screen keyboards @cpindex Keyboards, on-screen Enable the user to use a keyboard, physical or on-screen. @item Purpose: Enable programs to send keys as part of a script or a reply of a recorded session. @item Compulsivity: Highly-recommended, a computer is as good as useless without a keyboard. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @pgindex @command{mds-keytrans} @command{mds-kkbd}, @command{mds-kbd} and @command{mds-keytrans} @end table @node enumerate-keyboards @subsection @code{enumerate-keyboards} @prindex @code{enumerate-keyboards} @cpindex Keyboard listing @cpindex List keyboards @table @asis @item Identifying header: @code{Command: enumerate-keyboards} @item Action: List available keyboards. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Instructions: @prindex @code{keyboard-enumeration} @prindex @code{key-sent} This message must be consumed by the first server that receives it and implements support for it, and then send out a @code{Command: keyboard-enumeration} populated with the keyboard it provide as named in the @code{Keyboard}-header for protocols such as @code{Command: key-sent}. @item Purpose: Make it possible for clients to list all available keyboards so that can be configured individually. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @command{mds-kkbd} and @command{mds-kbd} @end table @node keyboard-enumeration @subsection @code{keyboard-enumeration} @prindex @code{keyboard-enumeration} @cpindex Keyboard listing @cpindex List keyboards @table @asis @item Identifying header: @code{Command: keyboard-enumeration} @item Action: @prindex @code{enumerate-keyboards} Response to @code{Command: enumerate-keyboards}. @item Required header: @code{To} @prindex @code{enumerate-keyboards} The ID received under @code{Client ID}-header in the @code{Command: enumerate-keyboards}-message that triggered this message to be broadcasted @item Required header: @code{In response to} @prindex @code{enumerate-keyboards} The ID received under the @code{Message ID}-header in the @code{Command: enumerate-keyboards}-message that triggered this message to be broadcasted. @item Required header: @code{Length} Length of the message. @item Message: New line separated list of available keyboards. @item Instructions: All keyboard servers should listen for this message and append all keyboards it implement to the message once recieved. @item Purpose: Make it possible for clients to list all available keyboards so that can be configured individually. @item Compulsivity: @prindex @code{enumerate-keyboards} Required if you implement @code{Command: enumerate-keyboards}. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @command{mds-kkbd} and @command{mds-kbd} @end table @node set-keyboard-leds @subsection @code{set-keyboard-leds} @prindex @code{set-keyboard-leds} @cpindex Keyboard LED:s @cpindex LED:s, keyboard @table @asis @item Identifying header: @code{Command: set-keyboard-leds} @item Action: Activate and deactivate LED:s on a keyboard. @item Required header: @code{Active} LED:s that should be turned on. If a LED is listed here but not in @code{Mask} that LED should be turned on if it is off, and turned off if it is on. The value is a single blank space separated list of LED:s: @table @code @item num @key{Num lock} @item caps @key{Caps lock} @item scrl @key{Scroll lock} @item compose @key{Compose} @end table Unsupported LED:s should be silently ignored. @item Required header: @code{Mask} LED:s listed here that do not appear in @code{Active} should be turned off. The value of this header follows the same rules as for @code{Active}. @item Optional header: @code{Keyboard} A string that identifies the keyboard that should be affected. If omitted all keyboard are affected. @item Purpose: Enable keyboard layout servers to activate and deactive LED:s on the keyboard to indicate active locks. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @pgindex @command{mds-keytrans} @command{mds-kkbd}, @command{mds-kbd} and @command{mds-keytrans} @end table @node get-keyboard-leds @subsection @code{get-keyboard-leds} @prindex @code{get-keyboard-leds} @cpindex Keyboard LED:s @cpindex LED:s, keyboard @table @asis @item Identifying header: @code{Command: get-keyboard-leds} @item Action: List exisiting LED:s on a keyboard and their state. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Keyboard} A string that identifies the keyboard that should be affected. @item Response: @prindex @code{set-keyboard-leds} The server implementing support for @code{Command: get-keyboard-leds} for the keyboard indicated by @code{Keyboard} should send a message back to the client indicated by the @code{Client ID}-header (using the @code{To}-header) with the headers: @table @code @item Active List of currently turned on LED:s. @item Present List of LED:s that the server believes to be present on the keyboards. @end table Both of these headers follows the rules of the @code{Active}-header under @code{Command: set-keyboard-leds}. @item Purpose: Enable keyboard layout servers to automatically set active locks when the server starts based on currently active LED:s @item Compulsivity: @prindex @code{set-keyboard-leds} Recommended. Required if you implement support for @code{Command: set-keyboard-leds}. If you do not support this protocol servers and clients and stall when they try to get the active LED:s. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @pgindex @command{mds-keytrans} @command{mds-kkbd}, @command{mds-kbd} and @command{mds-keytrans} @end table @node map-keyboard-leds @subsection @code{map-keyboard-leds} @prindex @code{map-keyboard-leds} @cpindex Keyboard LED:s, remap @cpindex LED:s, keyboard, remap @cpindex Remap keyboard LED:s @cpindex Remap LED:s, keyboard @table @asis @item Identifying header: @code{Command: map-keyboard-leds} @item Action: Remap LED:s on a keyboard. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Length} The length of the message. @item Optional header: @code{Keyboard} A string that identifies the keyboard that should be affected. If omitted all keyboard are affected. @item Message: Each line contains two single space delimited values, the first value is the LED's name, the second value is the LED's new position, either a zero-based index or the name of the LED that was originally mapped to that position. For example, @code{num num} sets the LED for @key{Num Lock} to its original position. This is equivalent to @code{num 0} on SPARC machines and @code{num 1} on non-SPARC machines. @example @group num caps caps num @end group @end example swaps the LED:s for @key{Num Lock} and @key{Caps Lock}. Valid LED names are @code{num}, @code{caps} and @code{scrl}, and on SPARC machines @code{compose}. @item Instructions: The server should remap the LED:s and update their activity accordingly. The server should do this atomically. @item Purpose: Allow the user to swap LED:s on the keyboard. Some keyboards use a non-standard layout, which can be very distracting or confusing. @item Purpose: Allow the user to correct invalid LED mappings. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @command{mds-kkbd} and @command{mds-kbd} @end table @node set-keyboard-rate @subsection @code{set-keyboard-rate} @prindex @code{set-keyboard-rate} @table @asis @item Identifying header: @code{Command: set-keyboard-rate} @item Action: Set the repeat rate and repeat delay on a keyboard. @item Optional header: @code{Rate} @cpindex Keyboard repeat rate A floating point value of the repeat rate, measured in cycles per second (hertz). Zero means no repeat. @item Optional header: @code{Delay} @cpindex Keyboard repeat delay An unsigned 16-bit integer of the number of milliseconds to wait before the first time a key is repeated. Zero means that the delay is matched with the rate, that is the reciprocal of the rate. @item Optional header: @code{Emulate} @table @code @item disallow Always use the keyboard's built in repeat feature. @item allow Use the keyboard's built in repeat feature when possible, otherwise emulate the feature. But if the selected settings are close enough to what the keyboard supports, use the closed settings the keyboard supports. @item if needed Use the keyboard's built in repeat feature when possible, otherwise emulate the feature. @item force Never use the keyboard's built in repeat feature, always emulate the feature. @end table @item Optional header: @code{Keyboard} A string that identifies the keyboard that should be affected. If omitted all keyboard are affected. @item Instructions: If neither of @code{Rate}, @code{Delay} and @code{Emulate} headers are used. The server should reapply the settings. @item Purpose: Enable the user to configure the repeat rate and repeat delay on keyboards. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @command{mds-kkbd} and @command{mds-kbd} @end table @node get-keyboard-rate @subsection @code{get-keyboard-rate} @prindex @code{get-keyboard-rate} @cpindex Keyboard repeat rate @cpindex Keyboard repeat delay @table @asis @item Identifying header: @code{Command: get-keyboard-rate} @item Action: Get the repeat rate and repeat delay on a keyboard. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Keyboard} A string that identifies the keyboard that should be affected. @item Response: @prindex @code{set-keyboard-rate} The server implementing support for @code{Command: get-keyboard-rate} for the keyboard indicated by @code{Keyboard} should send a message back to the client indicated by the @code{Client ID}-header (using the @code{To}-header) with the headers: @table @code @item Rate The current repeat rate. Same syntax as in @code{Command: set-keyboard-rate}. Set to @code{unknown} if the server does not know what the value is. @item Delay The current repeat delay. Same syntax as in @code{Command: set-keyboard-rate}. Set to @code{unknown} if the server does not know what the value is. @item Emulated @table @code @item yes The server implements the key repeat in software. @item no The server has set the rate on the keyboard, and lets the keyboard be responsible for the repeat. This value should also be used if the server does not support @code{Command: set-keyboard-rate} for the enquired keyboard, but is the server that should be responsible for it. @end table @end table @item Purpose: Enable the user to get the current repeat rate and repeat delay on the keyboard. @item Compulsivity: Optional. Recommended if implement support for @code{Command: set-keyboard-rate}. If you do not support this protocol servers and clients and stall when they try to get the current repeat rate and repeat delay on the keyboard. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @command{mds-kkbd} and @command{mds-kbd} @end table @node keycode-map @subsection @code{keycode-map} @prindex @code{keycode-map} @cpindex Keycodes, remapping @cpindex Keyboard, remapping @cpindex Remapping keycodes @cpindex Keys, swap @cpindex Swap keys @table @asis @item Identifying header: @code{Command: keycode-map} @item Action: Remap keyboard keycodes and query current mapping. @item Required header: @code{Action} @table @code @item remap Remap keys if the value of the header @code{Action} is @code{remap}. @item reset Reset all mappings to identity mapping if the value of the header @code{Action} is @code{reset}. @item query Query mapping if the value of the header @code{Action} is @code{query}. @end table Each affected server will send a message format like that of @code{Action: remap} with current mapping that are not identity mappings. @item Optional header: @code{Keyboard} A string that identifies the keyboard that should be affected. If omitted all keyboard are affected. @item Conditionally required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. Required if @code{Action: query} is included in the headers. @item Conditionally optional header: @code{Length} The length of the message. Available and optional if @code{Action: remap} is included in the headers. @item Message: Each line contains two single space delimited numbers, the first number is the keycode as determined by the scancode, the second number is keycode that scancode should generate. For example, @code{1 1} resets @key{Escape} to be mapped to @key{Escape}, and @code{1 59} remaps @key{Escape} to @key{F1}, while @example @group 1 59 59 1 @end group @end example swaps @key{Escape} and @key{F1}. @item Purpose: Enable the user to swap or replace keys on the keyboard. @item Purpose: Enable the user manually correct an incorrectly mapped keyboard. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-kbd} @pgindex @command{mds-kkbd} @command{mds-kbd} and @command{mds-kkbd} @end table @node new-keyboard @subsection @code{new-keyboard} @prindex @code{new-keyboard} @cpindex Keyboard, devices @cpindex Devices, keyboards @table @asis @item Identifying header: @code{Command: new-keyboard} @item Action: Announce the existance of a new keyboard. @item Required header: @code{Length} The length of the message. @item Message: List of strings that identifies the keyboards that have been added. @item Purpose: Enable servers and clients to detect new keyboards. @item Compulsivity: Recommended. @item Reference implementation: @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @command{mds-kbd} and @command{mds-kkbd} @end table @node old-keyboard @subsection @code{old-keyboard} @prindex @code{old-keyboard} @cpindex Keyboard, devices @cpindex Devices, keyboards @table @asis @item Identifying header: @code{Command: old-keyboard} @item Action: Announce the removal of an old keyboard. @item Required header: @command{Length} The length of the message. @item Message: List of strings that identifies the keyboards that have been removed. @item Purpose: Enable servers and clients to detect removal of keyboards. @item Compulsivity: Recommended. @item Reference implementation: @pgindex @command{mds-kbd} @command{mds-kbd} @end table @node Clipboard Protocols @section Clipboard Protocols @menu * clipboard:: Read or manipulate a clipboard. * clipboard-info:: Clipboard event announcements. @end menu @node clipboard @subsection @code{clipboard} @prindex @code{clipboard} @cpindex Clipboard @cpindex Clipstack @table @asis @item Identifying header: @code{Command: clipboard} @item Action: Read or manipulate a clipboard. @item Required header: @code{Level} The clipboard level, an [1, 3] integer: @table @code @item 1 Text copied/pasted using the keyboard or a menu item. (This level is called `primary'.) @item 2 Text copied/pasted using the rat. (This level is called `secondary'.) @item 3 Data to begin with a line describing the data type. (This level is called `tertiary'.) @end table @item Required header: @code{Action} What to do with the clipboard: @table @code @item add Write the message to the clipboard if the value of the header @code{Action} is @code{add}. @item read Read the clipboard if the value of the header @code{Action} is @code{read}. @item clear Clear all entries on the selected level on the clipboard if the value of the header @code{Action} is @code{read}. @item set-size Shrink/grow the clipstack if the value of the header @code{Action} is @code{set-size}. @item get-size Read the size of the clipstack if the value of the header @code{Action} is @code{get-size}. In the reply, the server will send a message containing the headers: @table @code @item Size The configured maximum size of the clipstack. @item Used The number of elements currently in the clipstack. @end table @end table @item Conditionally required header: @code{Length} Length of the message. Required if @code{Action: add} is included in the headers. @item Conditionally required header: @code{Size} The maximum number of elements in the clipstack. Required if @code{Action: set-size} is included in the headers. @item Conditionally required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. Required if @code{Action: read} or @code{Action: read} is included in the headers, or if @code{Action: add} is included in the headers and if the header @code{Time to live} is included and has a value starting with @code{until-death}. @item Conditionally optional header: @code{Index} The index of the item in the clipstack, starting at 0. Available and optional if the @code{Action: read} is included in the headers. @item Conditionally optional header: @code{Time to live} The number of seconds the entry should be available before it is removed by the server, or: @table @code @item until-death Remove entry when the client closes. @item until-death # Remove entry when the client closes, or @code{#} seconds have elapsed. @item forever Never remove it. (This is the default.) @end table The server will always remove the entry when either: @enumerate 1 @item it is at the bottom of the clipstack and a new entry is added to the clipstack, or @item @code{Action: clear} is issued for the clipstack. @end enumerate The entry will also be removed, unless @code{Time to live: forever} is used, if the server crashes or is re-executed. @sgindex @code{SIGALRM} It is up to the implementation to choose when the removal actually takes place. For example, the reference implementation will pop entries that have timed out when a new entry is added, the reading on the clipstack is requested or the server is reexecuted, but another implement may choose to pop entries asynchronously using another thread or an alarm an pop when @code{SIGALRM} is received. Available and optional if the @code{Action: add} is included in the headers. @item Message: The content to add to the clipboard. @item Purpose: Enable the user to duplicate content from one process into another process without requiring those processes to be aware of eathother to any extent. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-clipboard} @command{mds-clipboard} @end table @node clipboard-info @subsection @code{clipboard-info} @prindex @code{clipboard-info} @cpindex Clipboard @cpindex Clipstack @table @asis @item Identifying header: @code{Command: clipboard-info} @item Action: The clipboard server sends out some information about what it is doing, such as automatically removing entries. @item Included header: @code{Event} @table @code @item pop The value of the header @code{Event} is @code{pop} when an item in the clipstack has been removed. If the value header--value-pair is used the following headers will also be included in the message: @table @code @item Level The clipboard level that has been affected. @item Popped The index of the item in the clipstack that has been removed. @item Size The configured maximum size of the clipstack. @item Used The number of elements currently in the clipstack. @end table @item crash The value of the header @code{Event} is @code{crash} when the clipboard has been reset because of a software crash. @end table @item Purpose: @prindex @code{clipboard} Enable clients to get notification about changes to the clipboard, that cannot trivially derived from @code{Command: clipboard} @item Compulsivity: Optional add-on to the clipboard's functionallity. @item Reference implementation: @pgindex @command{mds-clipboard} @command{mds-clipboard} @end table @node Status Icon Protocols @section Status Icon Protocols @menu * add-tray-icon:: Add a status icons to the status icon tray. * update-tray-icon:: Change the status of a status icon. * tray-update:: Send updates about the status tray to the status icon. * new-tray:: Announce the existence of a new status icon trays. @end menu @node add-tray-icon @subsection @code{add-tray-icon} @prindex @code{add-tray-icon} @cpindex Status icon tray @cpindex System tray @cpindex Tray, status icons @cpindex Icon, status, tray @table @asis @item Identifying header: @code{Command: add-tray-icon} @item Action: Add a status icons to the status icon tray. The client should keep in mind that there can be any number of trays available on the system: zero, one, two or three, …, and that it will get a response once from every tray. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Package} The name of the package to which the program announced the icon belongs. @item Required header: @code{Icon ID} An ID of the icon that can be used to identify the icon, icon ID:s are not unique, but the combination of a package and a icon ID should be unique and can be used to ignore already added icons and hide icons that the user has been configured to be hidden. @item Required header: @code{Title} A title describing the icon for the user, used to configured when icons should be hidden and shown among other configuration. @item Required header: @code{Icon} The name or pathname of an icon to use together with the title. @item Response: Recipients will respond with a message containing the headers: @table @code @item To Will contain the value of the @code{Client ID} from the message that triggered this response. @item In response to Will contain the value of the @code{Message ID} from the message that triggered this response. @item Message ID Will contain a value as described in @ref{Message Passing}. @item Socket Will contain an ID to where the icon should be embeded. @item Will send update @prindex @code{tray-update} The value of this header will be @code{yes} if this message will be followed by a @code{Command: tray-update}-message. Otherwise the value will be @code{no}. @end table @item Purpose: Enable clients to add a small icon that displays the status of programs, particularly minimised programs and services. @item Compulsivity: Optional. @end table @node update-tray-icon @subsection @code{update-tray-icon} @prindex @code{update-tray-icon} @cpindex Status icon tray @cpindex System tray @cpindex Tray, status icons @cpindex Icon, status, tray @table @asis @item Identifying header: @code{Command: update-tray-icon} @item Action: Change the status of a status icon. @item Required header: @code{Status} @table @code @item hide Hide the icon if the value of the @code{Status}-header is @code{hide}. @item show Show the icon if the value of the @code{Status}-header is @code{show}. @item active The icon is active if the value of the @code{Status}-header is @code{active}. @item inactive The icon is inactive if the value of the @code{Status}-header is @code{inactive}. @end table @item Purpose: Enable status trays to automatically hide inactive icons. @item Purpose: Hide icons without actually removing them. @item Compulsivity: @prindex @code{add-tray-icon} Required if supporting @code{Command: add-tray-icon}, only @code{Status: hide} and @code{Status show} is required. @end table @node tray-update @subsection @code{tray-update} @prindex @code{tray-update} @cpindex Status icon tray @cpindex System tray @cpindex Tray, status icons @cpindex Icon, status, tray @table @asis @item Identifying header: @code{Command: tray-update} @item Action: Send updates about the status tray to the status icon. @item Required header: @code{Socket} Where the icon is embedded, used to identify the affected tray. @item Conditionally required header: @code{Max colour} The maximum colour component value, for example, if using 24-bit colour, which component will be 8-bit and the maximum value will be 255, this also applies to the alpha component. Required if either for the @code{Colour}-, @code{Foreground}- or @code{Alpha}-header are used. @item Conditionally required header: @code{Size} The width and height, in pixels, the icon should have. Required if the @code{Length}-header is used, otherwise this header is optional. @item Conditionally required header: @code{Has alpha} @table @code @item yes The message contains an alpha channel if the value of the @code{Has alpha}-header is @code{yes}. @item no The message does not contain an alpha channel if the value of the @code{Has alpha}-header is @code{no}. @end table Required if the @code{Length}-header is used. @item Conditionally required header: @code{Bytes} @cpindex Deep colour @cpindex Colour, deep @cpindex Endianness The number of bytes the subpixels used, for example, 24-bit colours will have this set to 1 because each subpixel has 8 bits, 48-bit colours will have this set to 2 because each subpixel has 16 bits. Allowed values are: 1, 2, 4 and 8. These values are used so that CPU:s with any endianness can be trivially used as the words sizes are guaranteed to be supported in C, and mixed/middle-endianness gets complicated if we go outside this. Required if the @code{Length}-header is used. @item Conditionally optional/required header: @code{Colour} Single blank space-separated [0, @code{}] sRGB 3-tuple. Available and optional if the @code{Length}-header is not used. Required if the @code{Foreground}-header but not @code{Length}-header is used. @item Conditionally optional header: @code{Foreground} Single blank space-separated [0, @code{}] sRGB 3-tuple. @item Optional header: @code{Alpha} The opacity of the tray. @item Optional header: @code{Length} Length of the message. @item Optional header: @code{Use urgency} @cpindex Notification of urgency @cpindex Urgency notification @table @code @item yes The icon tray may blink if the value of the @code{Use urgency}-header is @code{yes}. @item no The icon tray may not blink if the value of the @code{Use urgency}-header is @code{no}. @end table @item Message: Raw binary encoding of the background image, bytes are orders: row, pixel, channel (alpha, red, green, blue), subpixel value (native CPU encoding). The Alpha channel should be included but ignored if @code{Has alpha: no}, in such as it is best to set it to full. @ifset AFOURPAPER_OR_USLETTER Example image with @code{Bytes: 2}, @code{Has alpha: no} and @code{Size: 3}: @example @group sRGB(x0102, 0, 0), sRGB(0, x0304, 0), sRGB(0, 0, x0506) sRGB(x0708, 0, 0), sRGB(0, x090A, 0), sRGB(0, 0, x0B0C) sRGB(x0D0E, 0, 0), sRGB(0, x0F10, 0), sRGB(0, 0, x1112) @end group @end example Encoding of example image in hexadecimal representation: @example @group FFFF 0102 0000 0000 FFFF 0000 0304 0000 FFFF 0000 0000 0506 FFFF 0708 0000 0000 FFFF 0000 090A 0000 FFFF 0000 0000 0B0C FFFF 0D0E 0000 0000 FFFF 0000 0F10 0000 FFFF 0000 0000 1112 @end group @end example Note that on a big-endian system this would be: @footnote{x86_64 computers are big-endian.} @example @group FF FF 02 01 0 0 0 0 FF FF 0 0 04 03 0 0 FF FF 0 0 0 0 06 05 FF FF 08 07 0 0 0 0 FF FF 0 0 0A 09 0 0 FF FF 0 0 0 0 0C 0B FF FF 0E 0D 0 0 0 0 FF FF 0 0 10 0F 0 0 FF FF 0 0 0 0 12 11 @end group @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER Example image with @code{Bytes: 2}, @code{Has alpha: no} and @code{Size: 2}: @example @group sRGB(x0102, 0, 0), sRGB(0, x0304, 0) sRGB(x0708, 0, 0), sRGB(0, x090A, 0) @end group @end example Encoding of example image in hexadecimal representation: @example @group FFFF 0102 0000 0000 FFFF 0000 0304 0000 FFFF 0708 0000 0000 FFFF 0000 090A 0000 @end group @end example Note that on a big-endian system this would be: @footnote{x86_64 computers are big-endian.} @example @group FF FF 02 01 0 0 0 0 FF FF 0 0 04 03 0 0 FF FF 08 07 0 0 0 0 FF FF 0 0 0A 09 0 0 @end group @end example @end ifclear @cpindex Networking @cpindex Endianness It is up to the networking servers to translate the encoding between machines.@footnote{The host translates to big-endian unless they can confirm that they have the same endianness.} @item Purpose: Enable clients to be aware of the appearance of the tray, such as colours, transparency and background image. @item Purpose: Enable clients to be aware of how the user wants status icons to behave. @item Compulsivity: Optional. @end table @node new-tray @subsection @code{new-tray} @prindex @code{new-tray} @cpindex Status icon tray @cpindex System tray @cpindex Tray, status icons @cpindex Icon, status, tray @table @asis @item Identifying header: @code{Command: new-tray} @item Action: Announce the existence of a new status icon trays. @item Purpose: Allow clients to add their status icons to status icon trays that have been added to the display after those programs have started and attempted to add their icons. @item Compulsivity: @prindex @code{add-tray-icon} Required if supporting @code{Command: add-tray-icon}. @end table @node Colour Protocols @section Colour Protocols @menu * get-gamma-info:: Query gamma ramp information. * get-gamma:: Query gamma ramps. * set-gamma:: Modify gamma ramps. * list-colours:: Retrieve colour table. * get-colour:: Query colour table. * set-colour:: Modify colour table. * colour-added:: Announce new colours. * colour-removed:: Announce removal of colours. * colour-changed:: Announce modified colours. * dither:: Dither colours. * dither-stop:: Inform the dither server that a colour is no longer being dithered. * redither:: Announce that redithering is required. @end menu @node get-gamma-info @subsection @code{get-gamma-info} @prindex @code{get-gamma-info} @cpindex Gamma correction @table @asis @item Identifying header: @code{Command: get-gamma-info} @item Action: Query gamma ramp information. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{CRTC} The output name for the CRTC of interest. @item Response: The server will response with a @code{Command: error} on error, on success the server will respond with a message contain the headers: @table @code @item To Will contain the value of the header @code{Client ID} in the message that was received by the server. @item In response to Will contain the value of the header @code{Message ID} in the message that was received by the server. @item Cooperative Whether a server like @command{mds-coopgamma} is running. That is, if priorities and classes are respected. The value with be either @code{yes}, for cooperative, or @code{no}, for non-cooperative. @item Depth The bit-depth of the gamma ramps. Possible values are: 8, 16, 32 och 64. @item Red size The number of stops in the red gamma ramp. @item Green size The number of stops in the green gamma ramp. @item Blue size The number of stops in the blue gamma ramp. @item Gamma support Will have one of the following values: @table @code @item yes It is known that gamma ramps are supported. @item no It is known that gamma ramps are not supported. @item maybe It is not known whether gamma ramps are supported. @end table @item Red x @itemx Red y The `x' and `y' values, respectively, of the colour of the monitor's red channel, measured in CIE xyY, and multipled by 1024. The values must be an integer in the range [0, 1023]. Omitted if unknown or inapplicable. On a proper sRGB monitor, these values should be integers close to (655.36; 337.92), including multiplication by 1024. @item Green x @itemx Green y The `x' and `y' values, respectively, of the colour of the monitor's green channel, measured in CIE xyY, and multipled by 1024. The values must be an integer in the range [0, 1023]. Omitted if unknown or inapplicable. On a proper sRGB monitor, these values should be integers close to (307.2; 614.4), including multiplication by 1024. @item Blue x @itemx Blue y The `x' and `y' values, respectively, of the colour of the monitor's blue channel, measured in CIE xyY, and multipled by 1024. The values must be an integer in the range [0, 1023]. Omitted if unknown or inapplicable. On a proper sRGB monitor, these values should be integers close to (153.6; 61.44), including multiplication by 1024. @item White x @itemx White y The `x' and `y' values, respectively, of the monitor's default white point, measured in CIE xyY, and multipled by 1024. The values must be an integer in the range [0, 1023]. Omitted if unknown or inapplicable. On a proper sRGB monitor, these values should be integers close to (320.2048; 336.896), including multiplication by 1024. @item Colour space @table @code @item sRGB The monitor uses the standard RGB colour space. This is uncommon in practice. Although many monitors have a similar colour space. @item RGB A RGB colour space other than the standard RGB colour space is used by the monitor. This is the most common. @item non-RGB The monitor uses a non-RGB colour space. @item grey The monitor is monochrome or uses greyscale colour space. @end table Omitted if unknown. @end table If @code{Gamma support: no} is send in the response, the headers @code{Depth}, @code{Red size}, @code{Green size} and @code{Blue size} may be omitted. @c It is indeed correct that the range for the @c chromaticity values is [0, 1023], but the @c value is multipled by 1024 and not 1023. @item Purpose: Enable performance optimisation when manipulating gamma ramps. @item Compulsivity: @prindex @code{get-gamma} @prindex @code{set-gamma} Optional. Required if your implement support for @code{Command: get-gamma} or @code{Command: set-gamma}. @item Reference implementation: @pgindex @command{mds-hwgamma} @pgindex @command{mds-swgamma} @pgindex @command{mds-coopgamma} @pgindex @command{mds-cursorgamma} @command{mds-hwgamma}, @command{mds-swgamma}, @command{mds-coopgamma} and @command{mds-cursorgamma} @end table @node get-gamma @subsection @code{get-gamma} @prindex @code{get-gamma} @cpindex Gamma correction @cpindex Gamma correction, cooperative @cpindex Gamma correction, chain @cpindex Gamma correction, filters @cpindex Cooperative gamma correction @table @asis @item Identifying header: @code{Command: get-gamma} @item Action: Query gamma ramps. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{CRTC} The output name for the CRTC of interest. @item Required header: @code{Coalesce} Whether the received the full gamma ramp filter list, if the value is @code{yes}, rather than the result of them, if the value is @code{no}. @item Required header: @code{High priority} The upper bound of the priority range of the gamma ramps to received. This is a signed 64-bit integer. @item Required header: @code{Low priority} The lower bound of the priority range of the gamma ramps to received. This is a signed 64-bit integer. @item Response: @prindex @code{error} The server will response with a @code{Command: error} on error, on success the server will respond with a message contain the headers: @table @code @item Depth The bit-depth of the gamma ramps. Possible values are: 8, 16, 32 och 64. @item Red size The number of stops in the red gamma ramp. @item Green size The number of stops in the green gamma ramp. @item Blue size The number of stops in the blue gamma ramp. @item Tables The number of gamma ramp lookup tables that is included in the response's message. This header will not necessarily be included if @code{Coalesce: yes} was used in the query, rather reference implementations will exclude it. @end table These headers are included so you can make sure the no metadata for gamma ramps have changed, which could happen if the user switches between hardware and software gamma ramps. The response will also contain a @code{Length}-header and a message formatted in the same manner as for @code{Command: set-gamma}-messages. That is, assuming as an example that the gamma ramp depth is 16 bits, @code{Coalesce: yes} was used in the query, the red ramp is (1, 2, 3, 4, 5, 6), the green ramp is (17, 18, 19, 20, 21, 22, 23) and the blue ramp is (33, 34, 35, 36, 37, 38, 39, 40) then the message will be (hexadecimal representation): @example @group 0001 0002 0003 0004 0005 0006 0011 0012 0013 0014 0015 0016 0017 0021 0022 0023 0024 0025 0026 0027 0028 @end group @end example On a big-endian system this would be: @example @group 01 00 02 00 03 00 04 00 05 00 06 00 11 00 12 00 13 00 14 00 15 00 16 00 17 00 21 00 22 00 23 00 24 00 25 00 26 00 27 00 28 00 @end group @end example However if @code{Coalesce: no} was used in the query, the message will include multiple gamma ramps lookup tables. These will be in the order they are applied, that is, highest priority first. The tables will be encoded in the same way as for @code{Coalesce: yes} and they with be included without any delimiter. However, each table will be prefixed with the priority and the class. The priority will be encoded in native binary format as an @code{int64_t} and the class will be encoded as a NUL-terminated UTF-8 string @item Purpose: Enable analysis and readings of the current gamma ramps. @item Compulsivity: @prindex @code{get-gamma-info} @prindex @code{set-gamma} Optional. Required if your implement support for @code{Command: get-gamma-info} or @code{Command: set-gamma}. @item Reference implementation: @pgindex @command{mds-hwgamma} @pgindex @command{mds-swgamma} @pgindex @command{mds-coopgamma} @pgindex @command{mds-cursorgamma} @command{mds-hwgamma}, @command{mds-swgamma}, @command{mds-coopgamma} and @command{mds-cursorgamma} @end table @node set-gamma @subsection @code{set-gamma} @prindex @code{set-gamma} @cpindex Gamma correction @cpindex Gamma correction, cooperative @cpindex Gamma correction, chain @cpindex Gamma correction, filters @cpindex Cooperative gamma correction @table @asis @item Identifying header: @code{Command: set-gamma} @item Action: Modify gamma ramps. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{CRTC} The output name for the CRTC of interest. @item Required header: @code{Class} A UTF-8 string that identifies the filter. It should be formatted as @code{pkg::cmd::role}. @code{pkg} should be the package name the package was installed with on the system. @code{cmd} should be the basename of the command for the program. @item Required header: @code{Lifespan} The value may be one of the following: @table @code @item until-removal Remove the filter when @command{Lifespan: remove} is sent. @item until-death Remove the filter when the client dies. @item remove Remove the filter now. @end table @item Conditionally required header: @code{Priority} A signed 64-bit integer of the priority for the filter. Gamma correction should use zero priority. It is preferable that logical adjustment are sent with different priorities so other programs can insert filters between them. Available and required if @code{Lifespan: remove} is not included in the message. @item Conditionally required header: @code{Length} The length of the message. Available and required if @code{Lifespan: remove} is not included in the message. @item Message: The gamma ramps in binary encoding. As an example, assume the gamma ramp depth is 16 bits, the red ramp is (1, 2, 3, 4, 5, 6), the green ramp is (17, 18, 19, 20, 21, 22, 23) and the blue ramp is (33, 34, 35, 36, 37, 38, 39, 40) then the message will be (hexadecimal representation): @example @group 0001 0002 0003 0004 0005 0006 0011 0012 0013 0014 0015 0016 0017 0021 0022 0023 0024 0025 0026 0027 0028 @end group @end example Note that on a big-endian system this would be: @footnote{x86_64 computers are big-endian.} @example @group 01 00 02 00 03 00 04 00 05 00 06 00 11 00 12 00 13 00 14 00 15 00 16 00 17 00 21 00 22 00 23 00 24 00 25 00 26 00 27 00 28 00 @end group @end example It is up to the networking servers to translate the encoding between machines.@footnote{The host translates to big-endian unless they can confirm that they have the same endianness.} The use of binary rather than text here is chosen to increase performance for programs that try the change the adjustments fluently. For programs similar to @command{xgamma} that sets the ramps once this is however unnessary. However it does simplify the program code as one would only need to write the ramps to the message without creating a string with all stops converted and then measure the length of that string. @item Response: @prindex @code{error} The server will response with a @code{Command: error}. @item Instructions: @prindex @code{set-gamma} For optimal flexibility a system may run a server such as @command{mds-hwgamma} that applies the gamma ramps, and a server such as @command{mds-coopgamma} to let multiple programs adjust the output with their open filters that stack up. In a configuration like this, @command{mds-coopgamma} will keep track of all filters and when a modification is made it sends the grand result to @command{mds-hwgamma}, that is, what the filters together produce. To do this, @command{mds-coopgamma} listens for @code{Command: set-gamma} with priority @math{2^{62}} and modifies the message so the payload is filled with the result rather than to single filter. This modified message is then received by @command{mds-hwgamma} that listens with priority zero and applies the gamma ramps. @command{mds-hwgamma} will ignore the @code{Priority} and the @code{Class}-header, but it will respect the @code{Lifespan}-header, therefore @command{mds-coopgamma} will always modify the value of the @code{Lifespan}-header to @code{until-removal}. @item Purpose: Enable colour output correction such as gamma correction. @item Purpose: Enable colour output filters such colour temperature adjustments, colour invertion and dimming. @item Compulsivity: @prindex @code{get-gamma-info} @prindex @code{get-gamma} Optional. Required if your implement support for @code{Command: get-gamma-info} or @code{Command: get-gamma}. @item Reference implementation: @pgindex @command{mds-hwgamma} @pgindex @command{mds-swgamma} @pgindex @command{mds-coopgamma} @pgindex @command{mds-cursorgamma} @command{mds-hwgamma}, @command{mds-swgamma}, @command{mds-coopgamma} and @command{mds-cursorgamma} @end table @node list-colours @subsection @code{list-colours} @prindex @code{list-colours} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @table @asis @item Identifying header: @code{Command: list-colours} @item Action: Retrieve an exhaustive list of defined colours. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Optional header: @code{Include values} @table @code @item yes Include the values of the colours in addition to the name of the colours. @item no Include only the names of the colours. @end table @code{no} is used if omitted. @item Response: The server will response with a @code{Command: error} on error, on success the server will respond with a message whose payload is a list all defined colours. Each line in the payload represents a colour. If values where not requested, each line contain, exactly, the name of the colour it lists. If however values are requested, each name will be prefixed with the number of bytes with which each channel is encoded, the red value, the green value and the blue value of the colour, each of these values will be suffixed with a single regular blank space making the format @code{bytes red green blue name}. Note that the name may contain any whitespace@footnote{Tab space is discouraged.} except a line feed. Allowed values for the byte count are 1, 2, 4 and 8. The payload will end with a line break unless it is empty. No empty lines will otherwise be included (unless a colours name happend to be nothing @footnote{You should not define colours whose name is of zero length or containing non-ASCII or non-printable characters.}.) @item Purpose: Enable programs to list named colours, system colours or otherwise. @item Compulsivity: @prindex @code{get-colour} @prindex @code{set-colour} Optional. Required if your implement support for @code{Command: get-colour} or @code{Command: set-colour}. @item Reference implementation: @pgindex @command{mds-colour} @command{mds-colour} @end table @node get-colour @subsection @code{get-colour} @prindex @code{get-colour} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @table @asis @item Identifying header: @code{Command: get-colour} @item Action: Query the values of a defined colour. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Name} The name of the colour whose values you want to retrieve. @item Response: The server will response with a @code{Command: error} on error, on success the server will respond with a message contain the headers: @table @code @item Bytes The number of bytes with which each channel is encoded. Allowed values are 1, 2, 4 and 8. @item Red The value of the red channel. @item Green The value of the green channel. @item Blue The value of the blue channel. @end table If the colour is not defined, the @code{Command: error} message will return a custom error, with the message ``not defined''. @item Purpose: @cpindex Toolkits, colours @cpindex Colours, toolkits Provide a central place for retrieving system colours, such as text field background, for toolkits. @item Purpose: Provide a central place for retrieving themeable colours. @item Compulsivity: @prindex @code{list-colours} @prindex @code{set-colour} Optional. Required if your implement support for @code{Command: list-colours} or @code{Command: set-colour}. @item Reference implementation: @pgindex @command{mds-colour} @command{mds-colour} @end table @node set-colour @subsection @code{set-colour} @prindex @code{set-colour} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @table @asis @item Identifying header: @code{Command: set-colour} @item Action: Change the value of a defined colour, or remove it. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Name} The name of the colour you want to define, modify or undefine. @item Optional header: @code{Remove} @table @code @item yes Remove the colour definition. @item no Add or modify colour definition. @end table @code{no} is used if omitted. @item Conditionally required header: @code{Bytes} The number of bytes with which each channel is encoded. Allowed values are 1, 2, 4 and 8. Required unless @code{Remove: yes} is included in the headers. @item Conditionally required header: @code{Red} The value of the red channel. Required unless @code{Remove: yes} is included in the headers. @item Conditionally required header: @code{Green} The value of the green channel. Required unless @code{Remove: yes} is included in the headers. @item Conditionally required header: @code{Blue} The value of the blue channel. Required unless @code{Remove: yes} is included in the headers. @item Purpose: @cpindex Toolkits, colours @cpindex Colours, toolkits Provide a central place for defining system colours, such as text field background, for toolkits to use. @item Purpose: Provide a central place for defining themeable colours. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-colour} @command{mds-colour} @end table @node colour-added @subsection @code{colour-added} @prindex @code{colour-added} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @table @asis @item Identifying header: @code{Command: colour-added} @item Action: Announce that a new colour has been defined. @item Included header: @code{Name} The name of the new colour. @item Included header: @code{Bytes} The number of bytes with which each channel is encoded. @item Included header: @code{Red} The value of the colour's red channel. @item Included header: @code{Green} The value of the colour's green channel. @item Included header: @code{Blue} The value of the colour's blue channel. @item Included header: @code{Last update} @table @code @item yes No more updates are queued. @item changes No more additions or deletions are queued, but modifications are queued. @item no More additions or deletions are queued. @end table @item Purpose: @prindex @code{colour} Supplement @code{Command: list-colours} with automatic updating. @item Compulsivity: @prindex @code{list-colours} Optional. Recommended if your implement support for @code{Command: list-colours}. @item Reference implementation: @pgindex @command{mds-colour} @command{mds-colour} @end table @node colour-removed @subsection @code{colour-removed} @prindex @code{colour-removed} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @table @asis @item Identifying header: @code{Command: colour-removed} @item Action: Announce when colour definition is removed. @item Included header: @code{Name} The name of the removed colour. @item Included header: @code{Last update} @table @code @item yes No more updates are queued. @item changes No more additions or deletions are queued, but modifications are queued. @item no More additions or deletions are queued. @end table @item Purpose: @prindex @code{colour} Supplement @code{Command: list-colours} with automatic updating. @item Compulsivity: @prindex @code{list-colours} Optional. Recommended if your implement support for @code{Command: list-colours}. @item Reference implementation: @pgindex @command{mds-colour} @command{mds-colour} @end table @node colour-changed @subsection @code{colour-changed} @prindex @code{colour-changed} @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @table @asis @item Identifying header: @code{Command: colour-changed} @item Action: Announce when a defined colour changes value. @item Included header: @code{Name} The name of the modified colour. @item Included header: @code{Bytes} The number of bytes with which each channel is encoded. @item Included header: @code{Red} The new value of the colour's red channel. @item Included header: @code{Green} The new value of the colour's green channel. @item Included header: @code{Blue} The new value of the colour's blue channel. @item Included header: @code{Last update} @table @code @item yes No more updates are queued. @item no More changes are queued. @end table @item Instructions: The server must always send additions and deletions of colour definitions before modifitions, when sending multiple update. @item Purpose: Provide a way to detect when a themeable colour, or system colour, has changed, and the program needs to be redrawn with new colours. @item Compulsivity: @prindex @code{list-colours} @prindex @code{get-colour} Optional. Recommended if your implement support for @code{Command: list-colours} or @code{Command: get-colour}. @item Reference implementation: @pgindex @command{mds-colour} @command{mds-colour} @end table @node dither @subsection @code{dither} @prindex @code{dither} @cpindex Colour dithering @cpindex Dithering of colours @table @asis @item Identifying header: @code{Command: dither} @item Action: Request output device dependent colour dithering, and inform the dither server that the colour is being dithered. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Bytes} The number of bytes with which each channel is encoded. @item Required header: @code{Red} The value of the colour's red channel. @item Required header: @code{Green} The value of the colour's green channel. @item Required header: @code{Blue} The value of the colour's blue channel. @item Response: The server will response with a @code{Command: error} on error, on success the server will respond with a message contain a payload describing how the colour should be dithered on each output. Each line on the payload will decribed be dithering on an output. No empty lines will required, however the payload will end with a line feed unless it is empty@footnote{It can only be empty if there are no outputs.}. Each line will contain line single blank space-delimited values. These values are: @itemize @bullet{} @item The number of bytes with which each channel is encoded. @item The value of the primary colour's red channel. @item The value of the primary colour's green channel. @item The value of the primary colour's blue channel. @item A floating point value describing the predominance of the primary colour. A period is used as decimal comma. This value is between 0 and 1, but cannot be zero. If the value is @code{1}, the secondary colour is identical to the primary and no dithering is required. As an example, @code{0.75} means that there should be 75% of the primary colour and 25% of the secondary colour. @item The value of the secondary colour's red channel. @item The value of the secondary colour's green channel. @item The value of the secondary colour's blue channel. @item The name of the CRTC for which the line describes the colour's dithering. Note that thes value may contain whitespace. @end itemize Note that the pattern to use of dithering is not included in the response. It is up to the client to select a pattern. @item Instructions: @prindex @code{dither-stop} The dither server should count how many times the colour's dithering has be queried, per client. It should be decremented by one request each time @code{Command: dither-stop} is received for the colour and client. When the counter reaches zero for a client, the server knows that the client is no longer displaying the dithered colour. @item Purpose: Provide dithering for low colour-depth-output, that is gamma correction- and output filter-aware. @item Purpose: Provide gamma correction- and output filter-aware dither for low-delta colour gradients. @item Compulsivity: @prindex @code{redither} @prindex @code{dither-stop} Optional. Required if your implement support for @code{Command: redither} or @code{Command: dither-stop}. @item Reference implementation: @pgindex @command{mds-dither} @command{mds-dither} @end table @node dither-stop @subsection @code{dither-stop} @prindex @code{dither-stop} @cpindex Colour dithering @cpindex Dithering of colours @table @asis @item Identifying header: @code{Command: dither-stop} @item Action: Inform the dither server that a colour is no longer being dithered. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header @item Required header: @code{Bytes} The number of bytes with which each channel is encoded. @item Required header: @code{Red} The value of the colour's red channel. @item Required header: @code{Green} The value of the colour's green channel. @item Required header: @code{Blue} The value of the colour's blue channel. in response to a @code{Command: assign-id}-header. @item Purpose: Allow dithering server to know when a client is not longer dithering colours, or a specific colour. @item Compulsivity: @prindex @code{dither} @prindex @code{redither} Optional. Required if your implement support for @code{Command: dither} or @code{Command: redither}. @item Reference implementation: @pgindex @command{mds-dither} @command{mds-dither} @end table @node redither @subsection @code{redither} @prindex @code{redither} @cpindex Colour dithering @cpindex Dithering of colours @table @asis @item Identifying header: @code{Command: redither} @item Action: Announce that the client needs to redither its dithered colours. @item Included header: @code{Length} The length of the message. @item Message: A line feed-terminated, line feed-separated list of colours that need to be dithered on the client. Each line will be formatted @code{Bytes Red Green Blue}, where each these words are replaced by the values associated with the same headers of the same name in the @code{Command: dither} message that let the dither server know that the colour is being dithered. @item Purpose: @prindex @code{dither} Supplement @code{Command: dither} with automatic detection of when colours need to be redithered, without all clients needing to determine when, thus saving CPU time. @item Compulsivity: @prindex @code{dither} @prindex @code{dither-stop} Optional. Required if your implement support for @code{Command: dither} or @code{Command: dither-stop}. @item Reference implementation: @pgindex @command{mds-dither} @command{mds-dither} @end table @node Screensaver Protocols @section Screensaver Protocols @menu * configure-screensaver:: Configure screensaver settings. * start-screensaver:: Start the screensaver. * screensaver-start-test:: Test whether the screensaver may start. @end menu @node configure-screensaver @subsection @code{configure-screensaver} @prindex @code{configure-screensaver} @cpindex Screensaver @table @asis @item Identifying header: @code{Command: configure-screensaver} @item Action: Reconfigure screensaver settings, or tell the screensaver server that the screensaver may not start whilst a program is active. @item Optional header: @code{Screensaver} The command, in POSIX shell syntax, for the command to run to start the screensaver. The screensaver server will be inactive as long as the spawn command has not exited. To disable screensaving, the value for this header should be @command{true}. This command always starts without fail, and does nothing. Which means that the a screensaver will not start, and the panic action cannot start is it would if the values as set to @command{false}. The screensaver server may choose recognise the command @command{true} as meaning that does not need to start a screensaver. It is also possible to disable screensaving via the @code{Activate delay}-header. @item Optional header: @code{Activate delay} The number of seconds the display should be inactive before the screensaver should start. Floating points are allowed. The value @code{0} is discouraged, but has the same meaning as @code{disable}, which means that the screensaver should never start. @item Optional header: @code{Lock delay} @cpindex Screen locking @cpindex Locking, screen @vrindex @env{MDS_SCREENSAVER_LOCK} The number of seconds to wait after the screensaver starts before authentication via login passphrase is required to deactivate the screensaver. Floating points are allowed. If properly formatted, the environment variable @env{MDS_SCREENSAVER_LOCK} is set to have this value. If the value is @code{disable}, the environment variable @env{MDS_SCREENSAVER_LOCK} will be cleared, which should be interpreted by the screensaver as that it should not start the lock mechanism. @item Optional header: @code{Panic on error} @cpindex Security, screen locking The command, in POSIX shell syntax, to run if the screensaver exits without another value than 0. If you do no want anything to happen, choose either of the values @command{true} or @command{false}. This is intended as a security measure, in case the screensaver fails to start the lock mechanism. @item Optional header: @code{DPMS} @cpindex DPMS @cpindex Display Power Management Signaling @c [sic!] @cpindex VESA Display Power Management Signaling @c [sic!] @cpindex Power management, Display Power Management Signaling @c [sic!] TODO @item Optional header: @code{Inhibit} @table @code @item yes The screensaver may not start whilst the client is connected to the server. @item no Undo the action set by @code{Inhibit: yes} and the same client. @end table @item Conditionally required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. Required if @code{Inhibit} is included in the headers. @item Purpose: Allow the user to change screensaver settings. @item Purpose: Allow programs to stop the screensaver from starting. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-screensaver} @command{mds-screensaver} @end table @cpindex Screensaver @node start-screensaver @subsection @code{start-screensaver} @prindex @code{start-screensaver} @table @asis @item Identifying header: @code{Command: start-screensaver} @item Action: Start the screensaver, either timed or forced. @item Instructions: The screensaver server should broadcast this command when the display has been active for long enough for the screensaver to start. It should then intercept the message, including messages with this command that is not send from the screensaver server itself, with priority @math{-2^{63}}. The screensaver should be started when this message is intercepted by the screensaver server. All servers that need to perform actions before the switch takes place must have a priority higher than @math{-2^{63}}, preferably 0. Server that can perform their actions asynchronously should intercept the message without modifying capabilities. @item Purpose: Allow users to force the screensaver to start. @item Purpose: Allow the screensaver daemon to notify servers when the screensaver starts. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-screensaver} @command{mds-screensaver} @end table @node screensaver-start-test @subsection @code{screensaver-start-test} @prindex @code{screensaver-start-test} @cpindex Screensaver @table @asis @item Identifying header: @code{Command: screensaver-start-test} @item Action: Ask servers when they last were active. @item Required header: @code{Last active} The message broadcaster should set the value of this header to 0. Any server intercepting this message should set value to the last time (monotonic time, preferably raw) the server observed actions that means that the display is active, such as usage of the keyboard or rat. The servers should however not modify the value if the value they would set it to is lower than the already set value. Floating points are allowed. @item Instructions: The screensaver server should broadcast this message when it thinks it can start the screensaver. It should intercept this message with priority @math{-2^{63}}. When intercepted it should read the @code{Last active}-header to determine the next time the screensaver is allowed to start, which means that it should add the activate delay to this value. If the calculate time is in the past, the screensaver server should broadcast the @command{start-screensaver}-message to start the screensaver. @item Purpose: Allow the screensaver to as servers like the input device servers whether it is the for the screensaver to start, instead of needing to listening on all input devices. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-screensaver} @pgindex @command{mds-kkbd} @pgindex @command{mds-kbd} @pgindex @command{mds-rat} @command{mds-screensaver}, @command{mds-kkbd}, @command{mds-kbd} and @command{mds-rat} @end table @node Miscellaneous Protocols @section Miscellaneous Protocols @menu * echo:: Echo back a message. * kill:: The window killing protocol. @end menu @node echo @subsection @code{echo} @prindex @code{echo} @cpindex Ping @cpindex Debugging @cpindex Heartbeat @cpindex Network heartbeat @table @asis @item Identifying header: @code{Command: echo} @item Action: Echo back a message. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Optional header: @code{Length} Length of the message. @item Message: Message to echo. @item Purpose: Debugging and testing. @item Purpose: Network heartbeat. @item Compulsivity: Recommended for network enabled servers. @item Reference implementation: @pgindex @command{mds-echo} @command{mds-echo} @end table @node kill @subsection @code{kill} @prindex @code{kill} @cpindex Process killing @cpindex Killing processes @table @asis @item Identifying header: @code{Command: kill} @item Action: Kill and identify processes based on the their windows. @item Required header: @code{Client ID} Your ID, provided by the @code{ID assignment}-header in response to a @code{Command: assign-id}-header. @item Required header: @code{Window ID} The ID of the window whose owning process should be identified or signaled. @item Required header: @code{Signal} A numerical value of the signal to send to the process. It is up to networking protocols to translate these numbers of the display spans multiple operating systems. The signal zero can usually be used if no signal is to be sent, this is however dependent on the operating system. @item Response: @prindex @code{error} The server will respond with a @code{Command: error}-message. In this message the server all include an ad-hoc header: @code{Process ID}@. Its value will be the ID of the process that owns the window. @item Purpose: Identify and send signal to processes by refering to them by one of their windows. @item Compulsivity: Optional. @item Reference implementation: @pgindex @command{mds-kill} @pgindex @command{mds-slay} @command{mds-kill} and @command{mds-slay} @end table @node libmdsserver @chapter libmdsserver @cpindex Servers, library @cpindex Library, Servers libmdsserver is a library written for the reference implementation of the @command{mds} servers. llibmdsserver does not contain support for any protocols, rather it contains auxiliary functions, macros, data structures such as linked lists and hash tables, and support the basics of the message passing protocol: receiving message and decode it into headers and payloads. @menu * Macros:: Writing macroscopic systems. * Auxiliary Functions:: Auxiliary functions for servers. * Data Structures:: Data structures available in libmdsserver. @end menu @node Macros @section Macros The header file @file{} contains macros for readability and code reduction, it also contains macros and definitions for portability; they may either provide portability by nature, or provide one place to do modifications to port the system. @table @asis @item @code{xasprintf} [(@code{char* buffer, ...}) @arrow{} @code{int}] @fnindex @code{xasprintf} @cpindex Functions, printing @cpindex Printing fuction This is a wrapper for @code{asprintf} that has two important properties, the buffer is guaranteed to be @code{NULL} on failure, and it will return zero on and only on success. Unlike @code{asprintf}, @code{xasprintf} takes the buffer's variable as its first argument rather than the address of that variable. @item @code{xsnprintf} [(@code{char buffer[], ...}) @arrow{} @code{int}] @fnindex @code{xsnprintf} @cpindex Functions, printing @cpindex Printing fuction This is a wrapper for @code{snprintf} that allows you to forget about the buffer size. When you know how long a string can be, you should use @code{sprintf}. But when you cannot know for sure you should use @code{xsnprintf}. @code{xsnprintf} works exactly as @code{sprintf}, but it will require that the first argument is defined using @code{[]} rather than @code{*} because it will use this to find out how large the buffer is so it can call @code{snprintf} with that size. @item @code{eprint} [(@code{const char* format}) @arrow{} @code{int}] @fnindex @code{eprint} @cpindex Functions, printing, errors @cpindex Printing fuction, errors @cpindex Error printing function A wrapper for @code{fprintf} that prints a string prefixed with the value of @code{*argv} to @code{stderr}. This wrapper also as a line feed to the end of the text. Because @code{eprintf} naïvely wraps @code{fprintf}, all `%':s in the string must be duplicated. @item @code{eprintf} [(@code{const char* format, ...}) @arrow{} @code{int}] @fnindex @code{eprintf} @cpindex Functions, printing, errors @cpindex Printing fuction, errors @cpindex Error printing function @code{eprint} extends @code{eprint} with variadic arguments that can be used to insert values into the format string just like you can do in @code{fprintf}. @item @code{iprint} [(@code{const char* format}) @arrow{} @code{int}] @fnindex @code{iprint} @cpindex Functions, printing, state @cpindex Printing fuction, state @cpindex State printing function @sgindex @code{SIGINFO} @cpindex State dump @cpindex Statistics dump A wrapper for @code{fprintf} that prints a string prefixed with the value of @code{*argv}, as well a label telling the user that the output is part of a state and statistics dump, to @code{stderr}. This wrapper also as a line feed to the end of the text. Because @code{eprintf} naïvely wraps @code{fprintf}, all `%':s in the string must be duplicated. @item @code{iprintf} [(@code{const char* format, ...}) @arrow{} @code{int}] @fnindex @code{iprintf} @cpindex Functions, printing, state @cpindex Printing fuction, state @cpindex State printing function @sgindex @code{SIGINFO} @cpindex State dump @cpindex Statistics dump @code{eprint} extends @code{iprint} with variadic arguments that can be used to insert values into the format string just like you can do in @code{fprintf}. @item @code{with_mutex} [(@code{pthread_mutex_t mutex, instructions})] @fnindex @code{with_mutex} @cpindex Threading, synchronisation @cpindex Multi-threading, synchronisation @cpindex Synchronisation, threading @cpindex Mutex Wraps @code{instructions} with @code{errno = pthread_mutex_lock(mutex);} and @code{errno = pthread_mutex_unlock(mutex);}, so a set of instructions can be invoked inside mutex protection. @item @code{with_mutex_if} [(@code{pthread_mutex_t mutex, condition, instructions})] @fnindex @code{with_mutex_if} @cpindex Threading, synchronisation @cpindex Multi-threading, synchronisation @cpindex Synchronisation, threading @cpindex Mutex An alternative to @code{with_mutex} where @code{instructions} is wrapped around @code{if (condition)} which in turn is wrapped inside the mutex protection. @item @code{max} [(@code{a, b})] @fnindex @code{max} @cpindex Value comparision macro Returns the higher value of @code{a} and @code{b}. @item @code{min} [(@code{a, b})] @fnindex @code{min} @cpindex Value comparision macro Returns the lower value of @code{a} and @code{b}. @item @code{buf_cast} [(@code{char* buffer, type, size_t index})] @fnindex @code{buf_cast} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} Casts @code{buffer} to a @code{type} buffer and subscripts to the @code{index}:th element. You can either use this function as a getter or a setter. @item @code{buf_set} [(@code{char* buffer, type, size_t index, type variable}) @arrow{} @code{type}] @fnindex @code{buf_set} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} Wrapper for @code{buf_cast} that sets the addressed element to the value of @code{variable}. @item @code{buf_get} [(@code{const char* buffer, type, size_t index, type variable}) @arrow{} @code{type}] @fnindex @code{buf_get} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} Wrapper for @code{buf_cast} that sets the value of @code{variable} to the value of the addressed element. @item @code{buf_next} [(@code{char* buffer, type, size_t count}) @arrow{} @code{char*}] @fnindex @code{buf_next} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} Increases the pointer @code{buffer} by the size of @code{type} @code{count} types. @item @code{buf_prev} [(@code{char* buffer, type, size_t count}) @arrow{} @code{char*}] @fnindex @code{buf_prev} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} Decreases the pointer @code{buffer} by the size of @code{type} @code{count} types. @item @code{buf_set_next} [(@code{char* buffer, type, type variable}) @arrow{} @code{type}] @fnindex @code{buf_set_next} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} @example @group buf_set(buffer, type, 0, variable), buf_next(buffer, type, 1); @end group @end example @item @code{buf_get_next} [(@code{char* buffer, type, type variable}) @arrow{} @code{type}] @fnindex @code{buf_get_next} @cpindex Re-executing servers, macros @cpindex Updating, online, macros @cpindex Online updating, macros @cpindex Version update, macros @cpindex Serialisation macros @cpindex Marshalling macros @sgindex @code{SIGUPDATE} @example @group buf_get(buffer, type, 0, variable), buf_next(buffer, type, 1); @end group @end example @item @code{strequals} [(@code{const char* a, const char* b}) @arrow{} @code{int}] @fnindex @code{strequals} @cpindex String comparison Evaluates whether the strings @code{a} and @code{b} are equals, neither may be @code{NULL}@. @item @code{startswith} [(@code{const char* haystack, const char* needle}) @arrow{} @code{int}] @fnindex @code{startswith} @cpindex String comparison Evaluates whether the string @code{haystack} starts with the string @code{needle}, neither may be @code{NULL}@. @item @code{drop_privileges} [(@code{void}) @arrow{} @code{int}] @fnindex @code{drop_privileges} @cpindex Previleges @cpindex Security, previleges Sets the effective user to the real user and the effective group to the real group. This is used by most servers and ensure that they are not running with unnecessary privileges. Returns zero on and only on success. @item @code{monotone} [(@code{struct timespec* time_slot}) @arrow{} @code{int}] @fnindex @code{monotone} @cpindex Time, monotonic @cpindex Monotonic time Stores the time of an unspecified monotonic clock into @code{time_slot}. Returns zero on and only on success. @item @code{xclose} [(@code{int fd}) @arrow{} @code{void}] @fnindex @code{xclose} @cpindex Clean up Wrapper for the @code{close} function. This wrapper will retry if the call is interrupted by a signal. It will however not return value, but you can detect if an error have occured by inspecting @code{errno}, it is guaranteed to be zero on success and otherwise indicate the error that occurred. @item @code{xfclose} [(@code{FILE* f}) @arrow{} @code{void}] @fnindex @code{xfclose} @cpindex Clean up Wrapper for the @code{fclose} function. This wrapper will retry if the call is interrupted by a signal. It will however not return value, but you can detect if an error have occured by inspecting @code{errno}, it is guaranteed to be zero on success and otherwise indicate the error that occurred. @item @code{close_files} [(@code{condition}) @arrow{} @code{void}] @fnindex @code{close_files} @cpindex File descriptions, close all @cpindex Close all file descriptions Closes all file descriptors named by a variable @code{fd} for which @code{condition} evalutes to non-zero. @item @code{xfree} [(@code{void** array, size_t elements}) @arrow{} @code{void}] @fnindex @code{xfree} @cpindex Memory management Calls @code{free} on the first @code{elements} elements in @code{array}, and than calls @code{free} on @code{array}. This macro requires @code{size_t i} is declared. @item @code{xmalloc} [(@code{type* var, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{xmalloc} @cpindex Memory management Allocates a @code{type*} with @code{elements} elements and stores the allocated pointer to @code{var}. Returns zero on and only on success. @item @code{xbmalloc} [(@code{type* var, size_t bytes}) @arrow{} @code{int}] @fnindex @code{xbmalloc} @cpindex Memory management Allocates @code{bytes} bytes and stores the allocated pointer to @code{var}. Returns zero on and only on success. @item @code{xcalloc} [(@code{type* var, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{xcalloc} @cpindex Memory management Allocates a zero-initialised @code{type*} with @code{elements} elements and stores the allocated pointer to @code{var}. Returns zero on and only on success. @item @code{xbcalloc} [(@code{type* var, size_t bytes}) @arrow{} @code{int}] @fnindex @code{xbcalloc} @cpindex Memory management Allocates and zero-initialises @code{bytes} bytes and stores the allocated pointer to @code{var}. Returns zero on and only on success. @item @code{xrealloc} [(@code{type* var, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{xrealloc} @cpindex Memory management Reallocates @code{var} and updates the variable @code{var} accordingly. @code{var} will be allocated to have @code{elements} elements of the type @code{type}. If @code{var} is @code{NULL} a new allocation is created. If @code{elements} is zero, @code{var} will be deallocated. Returns zero on and only on success. On failure, @code{var} will be @code{NULL}, so you must store the @code{var} into another variable in case this macro fails. @item @code{xxrealloc} [(@code{type* old, type* var, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{xxrealloc} @cpindex Memory management Variant of @code{xrealloc} that will return with @code{old} set to @code{NULL} on success, and @code{old} set to @code{var} on error. Like @code{xrealloc}, @code{xxrealloc} returns zero on and only on success. @item @code{yrealloc} [(@code{type* tmp, type* var, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{yrealloc} @cpindex Memory management Variant of @code{xrealloc} that will store @code{var} to @code{tmp} before reallocating @code{var} and then restore @code{var} if the reallocation failed. Like @code{xrealloc}, @code{yrealloc} returns zero on and only on success. @item @code{growalloc} [(@code{type* old, type* var, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{growalloc} @cpindex Memory management When using this macro @code{var} should be a @code{type*} pointer allocated for @code{elements} elements of the type @code{type}. This macro will reallocate @code{var} to contain twice as many elements and update @code{elements} accordingly. On failure nothing changes. You must specify a auxiliary @code{type*} variable and specify it in as the @code{old} parameter. Returns zero on and only on success. @item @code{xstrdup} [(@code{char* var, const char* original}) @arrow{} @code{int}] @fnindex @code{xstrdup} @cpindex Memory management Wrapper for @code{strdup} that returns zero on and only on success. @code{original} is duplicate and the duplicate is stored in the variable @code{var}. If @code{original} is @code{NULL}, @code{var} is set to @code{NULL} and zero is returned. @item @code{xstrdup_nn} [(@code{char* var, const char* original}) @arrow{} @code{int}] @fnindex @code{xstrdup} @cpindex Memory management Wrapper for @code{strdup} that returns zero on and only on success. @code{original} is duplicate and the duplicate is stored in the variable @code{var}. @code{original} must not be @code{NULL}. This macro was added because GCC 6.1.1 warns if @code{xstrdup} is used and @code{original} is known not to be @code{NULL}. @item @code{xmemdup} [(@code{void* var, const void* original, size_t elements, type}) @arrow{} @code{int}] @fnindex @code{xmemdup} @cpindex Memory management Allocates a pointer of the type @code{type*} with room for @code{elements} elements and stores the pointer to @code{var}. If successful, the content of @code{original} (@code{elements} elements of size @code{sizeof(type*)}) is copied to @code{var}, and zero is returned. On failure, a non-zero value is returned. @item @code{xperror} [(@code{const char* str}) @arrow{} @code{void}] @fnindex @code{xperror} @cpindex Error management Invokes @code{perror(str)} if and only if @code{errno} is non-zero and then sets @code{errno} to zero. @code{str} should unless you have a specific reason be @code{*argv}. @item @code{fail_if} [(@code{condition}) @arrow{} @code{void}] @fnindex @code{fail_if} @cpindex Error management If @code{condition} is satisfied, a jump is made to the label @code{fail}. Additionally the location of failure will be printed to standard error. @item @code{exit_if} [(@code{condition, instructions}) @arrow{} @code{void}] @fnindex @code{exit_if} @cpindex Error management @cpindex Terminating If @code{condition} is satisfied, @code{instructions} is invoked and @code{1} is @code{return}:ed. @item @code{STREND} [(@code{const char* str}) @arrow{} @code{char*}] @fnindex @code{STREND} @cpindex Optimisations Expands to @code{(strchr(str, '\0'))}. It is here to remain us that @code{str = strchr(str, '\0')} is faster than @code{str += strlen(str)}. @end table @cpindex Signals @sgindex @code{SIGDANGER} @sgindex @code{SIGUPDATE} @sgindex @code{SIGINFO} Additionally, @file{} defines any missing signal name: currently @code{SIGDANGER}, @code{SIGINFO} and @code{SIGUPDATE}, and by inclusion of @file{}, variants of @code{atoi} for portability and convenience: @cpindex Integer parsing macros @table @code @item atoz @fnindex @code{atoz} @tpindex @code{size_t} Parse a human readable @code{const char*} 10-radix integer to a @code{size_t}. @item atosz @fnindex @code{atosz} @tpindex @code{ssize_t} Parse a human readable @code{const char*} 10-radix integer to a @code{ssize_t}. @item atoh @fnindex @code{atoh} @tpindex @code{short int} @tpindex @code{signed short int} Parse a human readable @code{const char*} 10-radix integer to a @code{short int}. @item atouh @fnindex @code{atouh} @tpindex @code{unsigned short int} Parse a human readable @code{const char*} 10-radix integer to an @code{unsigned short int}. @item atou @fnindex @code{atou} @tpindex @code{unsigned int} Parse a human readable @code{const char*} 10-radix integer to an @code{unsigned int}. @item atoul @fnindex @code{atoul} @tpindex @code{unsigned long int} Parse a human readable @code{const char*} 10-radix integer to an @code{unsigned long int}. @item atoull @fnindex @code{atoull} @tpindex @code{unsigned long long int} Parse a human readable @code{const char*} 10-radix integer to an @code{unsigned long long int}. @item ato8 @fnindex @code{ato8} @tpindex @code{int8_t} Parse a human readable @code{const char*} 10-radix integer to an @code{int8_t}. @item atou8 @fnindex @code{atou8} @tpindex @code{uint8_t} Parse a human readable @code{const char*} 10-radix integer to an @code{uint8_t}. @item ato16 @fnindex @code{ato16} @tpindex @code{int16_t} Parse a human readable @code{const char*} 10-radix integer to an @code{int16_t}. @item atou16 @fnindex @code{atou16} @tpindex @code{uint16_t} Parse a human readable @code{const char*} 10-radix integer to an @code{uint16_t}. @item ato32 @fnindex @code{ato32} @tpindex @code{int32_t} Parse a human readable @code{const char*} 10-radix integer to an @code{int32_t}. @item atou32 @fnindex @code{atou32} @tpindex @code{uint32_t} Parse a human readable @code{const char*} 10-radix integer to an @code{uint32_t}. @item ato64 @fnindex @code{ato64} @tpindex @code{int64_t} Parse a human readable @code{const char*} 10-radix integer to an @code{int64_t}. @item atou64 @fnindex @code{atou64} @tpindex @code{uint64_t} Parse a human readable @code{const char*} 10-radix integer to an @code{uint64_t}. @item atoj @fnindex @code{atoj} @tpindex @code{intmax_t} Parse a human readable @code{const char*} 10-radix integer to an @code{intmax_t}. @item atouj @fnindex @code{atouj} @tpindex @code{uintmax_t} Parse a human readable @code{const char*} 10-radix integer to an @code{uintmax_t}. @end table The header file @file{}, also define the macro @code{TEMP_FAILURE_RETRY} if missing, however without a return value but will clear @code{errno} if no error occurs@footnote{@code{glibc} will not clear @code{errno} on success, however this behaviour is defined @code{MDS_LIBMDSSERVER_MACROS_DEFINED_TEMP_FAILURE_RETRY} will be defined.}, and creates the alias @code{CLOCK_MONOTONIC_RAW} for @code{CLOCK_MONOTONIC} unless @code{CLOCK_MONOTONIC_RAW} is already defined. The header file also ensure that all aliases for socket protocol families and address families, for all definied protocol families and address families. The header file @file{}, also provides to macros to help write signal handlers. @table @code @item SIGHANDLER_START Normal signal handlers should place this macro at the top of the function. It will save the value of @code{errno}. @item SIGHANDLER_END Normal signal handlers should place this macro at the bottom of the function, or just before any @code{return}. It will restore the value of @code{errno} saved by @code{SIGHANDLER_START}. @end table These macros should be used, because signal handlers should not modify @code{errno}. The one occasion where exiting a signal handler with a modified @code{errno} is acceptable, is when the signal handler exits the program without returning. @node Auxiliary Functions @section Auxiliary Functions In the header file @file{}, libmdsserver defines common functions to help write servers more concisely. @table @asis @item @code{parse_client_id} [(@code{const char* str}) @arrow{} @code{uint64_t}] @fnindex @code{parse_client_id} @cpindex Client ID, parsing @cpindex Parsing client ID Convert a client ID string into a client ID integer. @item @code{getenv_nonempty} [(@code{const char* var}) @arrow{} @code{char*}] @fnindex @code{getenv_nonempty} @cpindex Environment variables, reading @cpindex Reading environment variables @cpindex Fetching environment variables Read an environment variable, return @code{NULL} if the variable's value is an empty string. @item @code{prepare_reexec} [(@code{void}) @arrow{} @code{int}] @fnindex @code{prepare_reexec} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Prepare the server so that it can re-execute into a newer version of the executed file. This is required for two reasons: @enumerate 1 @item We cannot use @code{argv[0]} as @env{PATH}-resolution may cause it to reexec into another pathname, and maybe to wrong program. Additionally @code{argv[0]} may not even refer to the program, and @code{chdir} could also hinter its use. @item The kernel appends @samp{ (deleted)} to @file{/proc/self/exe} once it has been removed, so it cannot be replaced. @end enumerate Returns zero on success and @code{-1} on error. @item @code{reexec_server} [(@code{int argc, char** argv, int reexeced}) @arrow{} @code{void}] @fnindex @code{reexec_server} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Re-execute the server. If @code{prepare_reexec} failed or has not been called, @code{argv[0]} will be used as a fallback. This functions has three input parameters: @table @code @item argc The number of elements in @code{argv}. @item argv The command line arguments. @item reexeced Whether the server has previously been re-executed. @end table This function only returns on failure. @item @code{xsigaction} [(@code{int signo, void (*function)(int signo)}) @arrow{} @code{int}] @fnindex @code{xsigaction} @fnindex @code{sigaction} @fnindex @code{signal} @cpindex Signals @code{sigaction} with the same parameters as @code{signal}. This function should only be used for common @command{mds} signals and signals that does not require any special settings. This function may choose to add additional behaviour depending on the signal, such as blocking other signals. Returns zero on success and @code{-1} on error. @item @code{send_message} [(@code{int socket, const char* message, size_t length}) @arrow{} @code{size_t}] @fnindex @code{send_message} @cpindex Communication over sockets @cpindex Socket communication Send the message @code{messsage}, of length @code{length} over the socket that is access with the file descriptor @code{socket}. Returns the number of bytes that have been sent, even on error. @item @code{strict_atoi} [(@code{const char* str, int* value, int min, int max}) @arrow{} @code{int}] @fnindex @code{strict_atoi} @fnindex @code{atoi} @cpindex Integer parsing @cpindex Error management A version of @code{atoi} that is strict about the syntax and bounds. Parses the string @code{str} into an @code{int} and stores it in @code{*value}. If the string is not a 10-radix integer or has a value outside [@code{min}, @code{max}], @code{-1} is returned, otherwise zero is returned. @item @code{strict_atou} @fnindex @code{strict_atou} @fnindex @code{atou} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{unsigned int} instead of @code{int} on its parameters. @item @code{strict_atoh} @fnindex @code{strict_atoh} @fnindex @code{atoh} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{short int} instead of @code{int} on its parameters. Note however that @code{min} and @code{max} is in @code{int}, because smaller types should not be passed as arguments. @item @code{strict_atouh} @fnindex @code{strict_atouh} @fnindex @code{atouh} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{unsigned short int} instead of @code{int} on its parameters. Note however that @code{min} and @code{max} is in @code{unsigned int}, because smaller types should not be passed as arguments. @item @code{strict_atol} @fnindex @code{strict_atol} @fnindex @code{atol} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{long int} instead of @code{int} on its parameters. @item @code{strict_atoul} @fnindex @code{strict_atoul} @fnindex @code{atoul} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{unsigned long int} instead of @code{int} on its parameters. @item @code{strict_atoll} @fnindex @code{strict_atoll} @fnindex @code{atoll} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{long long int} instead of @code{int} on its parameters. @item @code{strict_atoull} @fnindex @code{strict_atoull} @fnindex @code{atoull} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{unsigned long long int} instead of @code{int} on its parameters. @item @code{strict_atoj} @fnindex @code{strict_atoj} @fnindex @code{atoj} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{intmax_t} instead of @code{int} on its parameters. @item @code{strict_atouj} @fnindex @code{strict_atouj} @fnindex @code{atouj} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{uintmax_t} instead of @code{int} on its parameters. @item @code{strict_atoz} @fnindex @code{strict_atoz} @fnindex @code{atoz} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{size_t} instead of @code{int} on its parameters. @item @code{strict_atosz} @fnindex @code{strict_atosz} @fnindex @code{atosz} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{ssize_t} instead of @code{int} on its parameters. @item @code{strict_ato8} @fnindex @code{strict_ato8} @fnindex @code{ato8} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{int8_t} instead of @code{int} on its parameters. Note however that @code{min} and @code{max} is in @code{int}, because smaller types should not be passed as arguments. @item @code{strict_atou8} @fnindex @code{strict_atou8} @fnindex @code{atou8} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{uint8_t} instead of @code{int} on its parameters. Note however that @code{min} and @code{max} is in @code{int}, because smaller types should not be passed as arguments. @item @code{strict_ato16} @fnindex @code{strict_ato16} @fnindex @code{ato16} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{int16_t} instead of @code{int} on its parameters. Note however that @code{min} and @code{max} is in @code{int}, because smaller types should not be passed as arguments. @item @code{strict_atou16} @fnindex @code{strict_atou16} @fnindex @code{atou16} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{uint16_t} instead of @code{int} on its parameters. Note however that @code{min} and @code{max} is in @code{unsigned int}, because smaller types should not be passed as arguments. @item @code{strict_ato32} @fnindex @code{strict_ato32} @fnindex @code{ato32} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{int32_t} instead of @code{int} on its parameters. @item @code{strict_atou32} @fnindex @code{strict_atou32} @fnindex @code{atou32} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{uint32_t} instead of @code{int} on its parameters. @item @code{strict_ato64} @fnindex @code{strict_ato64} @fnindex @code{ato64} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{int64_t} instead of @code{int} on its parameters. @item @code{strict_atou64} @fnindex @code{strict_atou64} @fnindex @code{atou64} @cpindex Integer parsing @cpindex Error management A variant of @code{strict_atoi} that uses @code{uint64_t} instead of @code{int} on its parameters. @item @code{full_write} [(@code{int fd, const char* buffer, size_t length}) @arrow{} @code{int}] @fnindex @code{full_write} @cpindex File writing Send the buffer @code{buffer}, with the length @code{length}, into the file whose file descriptor is @code{fd} and ignores interruptions. Returns zero on success and @code{-1} on error. @item @code{full_read} [(@code{int fd, size_t* length}) @arrow{} @code{char*}] @fnindex @code{full_read} @cpindex File reading Read the file whose file descriptor is @code{fd} completely and ignore interruptions. If @code{length} if not @code{NULL}, the length of the read file is stored in @code{*length}. On success, the read content is retured, on error @code{NULL} is returned. @item @code{full_send} [(@code{int socket, const char* message, size_t length}) @arrow{} @code{int}] @fnindex @code{full_send} @cpindex Message passing Send the message @code{message}, with the length @code{length}, to the socket whose file descriptor is @code{socket} and ignores interruptions. Returns zero on success and @code{-1} on error. @item @code{startswith_n} [(@code{const char*, const char*, size_t, size_t}) @arrow{} @code{int}] @fnindex @code{startswith_n} @cpindex String comparison Check whether a string begins with a specific string, where neither of the strings are necessarily NUL-terminated. The parameters are: @table @code @item const char* haystack The string that should start with the other string. @item const char* needle The string the first string should start with. @item size_t haystack_n The length of @code{haystack}. @item size_t needle_n The length of @code{needle}. @end table Returns 1 if @code{haystack} beings with @code{needle}, otherwise zero is returned. @item @code{uninterruptable_waitpid} [(@code{pid_t pid, int* restrict status, int options}) @arrow{} @code{pid_t}] @fnindex @code{uninterruptable_waitpid} @fnindex @code{waitpid} @cpindex Process management Wrapper around @code{waitpid} that never returns on an interruption unless it is interrupted one hundred times within the same clock second. The parameters and return value are exactly those of @code{waitpid}. @item @code{verify_utf8} [(@code{const char* string, int allow_modified_nul}) @arrow{} @code{int}] @fnindex @code{verify_utf8} @cpindex Security, encoding, UTF-8 @cpindex UTF-8, security @cpindex Encoding, UTF-8, security Checks whether a NUL-terminated string's encoding matches UTF-8. This function will reject the string if it does not use the shorted possible byte-combination for each character. However, if @code{allow_modified_nul} is set, it will allow @code{192 128} in place of @code{0} for a NUL-character.@footnote{Remember @code{0} is used to terminated the string, but @code{192 128} is not.} This function returns zero if the @code{string} is properly formatted, and @code{-1} otherwise. @item @code{construct_error_message} [(@code{const char* restrict recv_client_id, const char* restrict recv_message_id, const char* restrict recv_command, int custom, int errnum, const char* restrict message, char** restrict send_buffer, size_t* restrict send_buffer_size, uint32_t message_id}) @arrow{} @code{size_t}] @cpindex @code{construct_error_message} @cpindex Error management This function constructs an error message to be sent to a client. It implements the @code{error} protocol with with identifying header @code{Command: error}. The parameters are: @table @code @item recv_client_id The client ID attached on the message that was received in the message that caused the error, that is, the value of the header @code{Client ID} on the received message and the header @code{To} in the message to construct. Must not be @code{NULL}. @item recv_message_id The message ID attached on the message that was received in the message that caused the error, that is, the value of the header @code{Message ID} on the received message and the header @code{In response to} in the message to construct. Must not be @code{NULL}. @item recv_command The value of the @code{Command}-header on the message that was received. Must not be @code{NULL}. @item custom If and only if set to zero, value of @code{errnum} is a value for @code{errno}. @item errnum A numeric value describing the error. A negative value, such as @code{-1} should be used if the error does not have a numeric value. Zero is reserved to indicate success. @item message The description of the error, the line feed at the end is added automatically and thus should not be included. The description should be a statement in mid-sentence case and without punctuation at the end. @code{NULL} if no description should be included. @item send_buffer Pointer to the buffer where the message should be stored, it should contain the current send buffer. Must not be @code{NULL} @item send_buffer_size Pointer to the allocation size of @code{*send_buffer}, it should contain the current size of @code{*send_buffer} and will be updated with the new size. Must not be @code{NULL} @item message_id The message ID of the message that is being constructed. @end table It is not allowed to have a negative value on @code{errnum} and a zero value on @code{custom} at the same time. This function returns the length of the constructed message on success, and zero on failure. On failure @code{errno} will be set accordingly. @item @code{send_error} [(@code{..., int socket_fd}) @arrow{} @code{int}] @fnindex @code{send_error} @cpindex Error management This function is a wrapper for @code{construct_error_message} that also sends constructed message to the socket whose file descriptor is @code{socket_fd}. This function has the same parameters as @code{construct_error_message}, but with one additional parameter as its last parameter: @code{socket_fd}. Also, instead of returning the length of the message, it returns zero on success and @code{-1} on error. @end table @fnindex @code{rawmemchr}. @file{} also defines @code{rawmemchr} if not already defined. @node Data Structures @section Data Structures @cpindex Data structures @cpindex Marshalling @cpindex Serialisation @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} libmdsserver provides a small set of data structures that are used by the @command{mds} servers. All of these are written with marshal-functionallity. @table @asis @item @code{client_list_t} @{also known as @code{struct client_list}@} @tpindex @code{client_list_t} @tpindex @code{struct client_list} @cpindex Client ID, lists @cpindex Lists of client ID:s In the header file @file{}, libmdsserver defines a dynamic list for storing client ID:s. @item @code{linked_list_t} @{also known as @code{struct linked_list}@} @tpindex @code{linked_list_t} @tpindex @code{struct linked_list} @cpindex Lists, linked @cpindex Linked lists In the header file @file{}, libmdsserver defines a linear array sentinel doubly linked list. @item @code{hash_table_t} @{also known as @code{struct hash_table}@} @tpindex @code{hash_table_t} @tpindex @code{struct hash_table} @cpindex Tables, hash @cpindex Maps, hash @cpindex Dictionary, hash @cpindex Hash table In the header file @file{}, libmdsserver defines a hash table. @item @code{fd_table_t} @{also known as @code{struct fd_table}@} @tpindex @code{fd_table_t} @tpindex @code{struct fd_table} @cpindex Tables, file descriptor @cpindex Maps, file descriptor @cpindex Dictionary, file descriptor @cpindex File descriptor table In the header file @file{}, libmdsserver defines a lookup table for small positive integer keys, intended as an alternative to hash tables for file descriptors as keys. @item @code{mds_message_t} @{also known as @code{struct mds_message}@} @tpindex @code{mds_message_t} @tpindex @code{struct mds_message} @cpindex Message passing, data structure In the header file @file{}, libmdsserver defines a data structure for message between the server or client and the master server, with the capability of reading for a socket. @item @code{hash_list} @{abstract@} @tpindex @code{hash_list} @cpindex Lists, hash @cpindex Hash lists @cpindex Tables, hash @cpindex Maps, hash @cpindex Dictionary, hash @cpindex Hash table In the header file @file{}, libmdsserver defines an abstract class known as hash list. It is intended as an alternative to hash tables, where the number of stored elements is low. @end table These data structures share a common set of associated methods. However, they do not use the same methods; they are identical except they are are named with the associated data structure. We will use @code{X_t} as an example. @table @asis @item @code{X_destroy} [(@code{X_t* restrict this}) @arrow{} @code{void}] @fnindex @code{client_list_destroy} @fnindex @code{linked_list_destroy} @fnindex @code{hash_table_destroy} @fnindex @code{fd_table_destroy} @fnindex @code{mds_message_destroy} @cpindex Memory management Releases all resouces in @code{*this}, @code{this} itself is however not @code{free}:d. However, @code{hash_table_destory} and @code{fd_table_destory} have another signature. @item @code{X_clone} [(@code{const X_t* restrict this, X_t* restrict out}) @arrow{} @code{int}] @fnindex @code{client_list_clone} @fnindex @code{linked_list_clone} @fnindex @code{hash_table_clone} @fnindex @code{fd_table_clone} @fnindex @code{mds_message_clone} @cpindex Memory management Create a deep duplicate of @code{*this} and store it in @code{*out}. @item @code{X_marshal_size} [(@code{const X_t* restrict this}) @arrow{} @code{size_t}] @fnindex @code{client_list_marshal_size} @fnindex @code{linked_list_marshal_size} @fnindex @code{hash_table_marshal_size} @fnindex @code{fd_table_marshal_size} @fnindex @code{mds_message_marshal_size} @cpindex Marshalling @cpindex Serialisation @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Calculates the exact allocate size needed for the parameter @code{data} in the method @code{X_marshal} if called with the same @code{this} parameter. @item @code{X_marshal} [(@code{const X_t* restrict this, char* restrict data}) @arrow{} @code{void}] @fnindex @code{client_list_marshal} @fnindex @code{linked_list_marshal} @fnindex @code{hash_table_marshal} @fnindex @code{fd_table_marshal} @fnindex @code{mds_message_marshal} @cpindex Marshalling @cpindex Serialisation @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Marshal the state of @code{*this} into @code{data}. The number of bytes that will be stored (contiguously) in @code{data} can be calculated with @code{X_marshal_size}. @item @code{X_unmarshal} [(@code{X_t* restrict this, char* restrict data)}) @arrow{} @code{int}] @fnindex @code{client_list_unmarshal} @fnindex @code{linked_list_unmarshal} @fnindex @code{hash_table_unmarshal} @fnindex @code{fd_table_unmarshal} @fnindex @code{mds_message_unmarshal} @cpindex Marshalling @cpindex Serialisation @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Unmarshal a @code{X_t} from @code{data} into @code{*this}. Returns zero on success and @code{-1} on error. The number of bytes read from @code{data} should, if required, have been precalculated with @code{X_marshal_size} and stored in an earlier location of @code{data}. However, @code{hash_table_unmarshal} and @code{fd_table_unmarshal} have another signature. @end table @menu * Client List:: The @code{client_list_t} data structure. * Linked List:: The @code{linked_list_t} data structure. * Tables:: The @code{fd_table_t} and @code{hash_table_t} data structures. * Hash List:: The @code{hash_list} abstract data structure. * Message Structure:: The @code{mds_message_t} data structure. @end menu @node Client List @subsection Client List @tpindex @code{client_list_t} @tpindex @code{struct client_list} @cpindex Client ID, lists @cpindex Lists of client ID:s @fnindex @code{client_list_create} To create a client list, allocate a @code{client_list_t*} or otherwise obtain a @code{client_list_t*}, and call @code{client_list_create} with that pointer as the first argument, and the @code{0} as the second argument, unless you want to tune the initialisation. @code{client_list_create} will return zero on and only on successful initialisation. @code{client_list_create}'s second parameter --- @code{size_t capacity} --- can be used to specify how many element the list should initially fit. It will grow when needed, but it is a good idea to tell it how many elements you are planning to populate it with. @code{client_list_t} has two associated methods for manipulating its content: @table @asis @item @code{client_list_add} [(@code{client_list_t* restrict this, uint64_t client}) @arrow{} @code{int}] @fnindex @code{client_list_add} This method will add the element @code{client} to the list @code{*this}, and return zero on and only on success. @item @code{client_list_remove} [(@code{client_list_t* restrict this, uint64_t client}) @arrow{} @code{void}] @fnindex @code{client_list_remove} This method will remove exactly one occurrence, provided that there is at least one occurrence, of the element @code{client} for the list @code{*this}. @end table To retrieve the number elements stored in a list, reads its variable @code{size_t size}. The variable @code{uint64_t* clients} is used to retrieve stored elements. @ifset AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @example void print_elements(client_list_t* this) @{ size_t i; for (i = 0; i < this->size; i++) printf("Element #%zu: %" PRIu64 "\n", i, this->elements[i]); @} @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @example void print_elements(client_list_t* this) @{ size_t i; for (i = 0; i < this->size; i++) printf("Element #%zu: %" PRIu64 "\n", i, this->elements[i]); @} @end example @end ifclear @node Linked List @subsection Linked List @tpindex @code{linked_list_t} @tpindex @code{struct linked_list} @cpindex Lists, linked @cpindex Linked lists @code{linked_list_t} is a linear array sentinel doubly linked list. This means that is implemented using arrays rather than node references. More specifically, since it is doubly linked@footnote{And not using XOR-linking.}, it is implemented using three arrays: @table @asis @item @code{values} [@code{size_t*}] The value stored in each node. @item @code{next} [@code{ssize_t*}] The next node for each node, @code{edge} if the current node is the last node, and @code{LINKED_LIST_UNUSED} if there is no node on this position. @item @code{previous} [@code{ssize_t*}] The previous node for each node, @code{edge} if the current node is the first node, and @code{LINKED_LIST_UNUSED} if there is no node on this position. @end table The linked list has a sentinel node that joins boths ends of the list. The index of this node is stored in the variable @code{edge}. @cpindex Memory management @fnindex @code{linked_list_pack} Because the list is implemented using arrays, if the number of elements in it shinks considerably, it will not be able to automatically free unused space. Instead you must call @code{linked_list_pack}: @table @asis @item @code{linked_list_pack} [(@code{linked_list_t* restrict this}) @arrow{} @code{int}] Pack the list so that there are no reusable positions, and reduce the capacity to the smallest capacity that can be used. Note that values (nodes) returned by the list's methods will become invalid. Additionally (to reduce the complexity) the list will be defragment so that the nodes' indices are continuous. This method has linear time complexity and linear memory complexity. @end table @fnindex @code{linked_list_create} To create a linked list list, allocate a @code{linked_list_t*} or otherwise obtain a @code{linked_list_t*}, and call @code{linked_list_create} with that pointer as the first argument, and the @code{0} as the second argument, unless you want to tune the initialisation. @code{linked_list_create} will return zero on and only on successful initialisation. @code{linked_list_create}'s second parameter --- @code{size_t capacity} --- can be used to specify how many element the list should initially fit. It will grow when needed, but it is a good idea to tell it how many elements you are planning to populate it with. There are five methods adding and removing items to and from a linked list: @table @asis @item @code{linked_list_insert_after} [(@code{this, size_t value, ssize_t predecessor}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_insert_after} Create a new node with the value @code{value} and add it to the list @code{*this} after the node @code{predecessor}. On success, the new node is returned, on failure @code{LINKED_LIST_UNUSED} is returned. @item @code{linked_list_insert_before} [(@code{this, size_t value, ssize_t successor}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_insert_before} Create a new node with the value @code{value} and add it to the list @code{*this} before the node @code{successor}. On success, the new node is returned, on failure @code{LINKED_LIST_UNUSED} is returned. @item @code{linked_list_remove_after} [(@code{this, ssize_t predecessor}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_remove_after} Remove and return the node in the list @code{*this} directly after the node @code{predecessor}. @item @code{linked_list_remove_before} [(@code{this, ssize_t successor}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_remove_before} Remove and return the node in the list @code{*this} directly before the node @code{predecessor}. @item @code{linked_list_remove} [(@code{this, ssize_t node}) @arrow{} @code{void}] @fnindex @code{linked_list_remove} Remove the node @code{node} from the list @code{*this}. @end table The data type for @code{this} is @code{linked_list_t*} with the @code{restrict} modifier for these and all other @code{linked_list_t} methods. Note that if the node @code{this->edge} is removed, the list become circularly linked and the sentinel will become missing which renders invokation of all macros undefined in behaviour. Further note that removing the sentinel while it is the only node in the list invokes undefined behaviour. Also note that addressing non-existing nodes invokes undefined behaviour. @file{} defines two macros for inserting nodes at the edges of a linked list and two macros for removing nodes from the edges of a linked list: @table @asis @item @code{linked_list_insert_beginning} [(@code{linked_list_t* this, size_t value}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_insert_beginning} Create a new node with the value @code{value} in insert it to the beginning of the list @code{*this}. On success, the new node is returned, on failure @code{LINKED_LIST_UNUSED} is returned. @item @code{linked_list_insert_end} [(@code{linked_list_t* this, size_t value}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_insert_end} Create a new node with the value @code{value} in insert it to the end of the list @code{*this}. On success, the new node is returned, on failure @code{LINKED_LIST_UNUSED} is returned. @item @code{linked_list_remove_beginning} [(@code{linked_list_t* this}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_remove_beginning} Remove and return the first node in the list @code{*this}. @item @code{linked_list_remove_end} [(@code{linked_list_t* this}) @arrow{} @code{ssize_t}] @fnindex @code{linked_list_remove_end} Remove and return the node node in the list @code{*this}. @end table Additionally the library defines a macro that wrappes the @code{for}-keyword to iterate over all nodes (except the sentinel node) the a linked list: @table @asis @item @code{foreach_linked_list_node} [(@code{linked_list_t this, ssize_t node})] @fnindex @code{foreach_linked_list_node} Wrapper for @code{for}-keyword that iterates over each element in the list @code{this}, and store the current node to the variable named by the parameter @code{node} for each iterations. @example void print_linked_list_values(linked_list_t* list) @{ ssize_t node; foreach_linked_list_node (*list, node) printf("%zi\n", list->values[node]); @} @end example Note that the data type for @code{this} in the macro is not a pointer. @end table There is also a method intended for debugging: @table @asis @item @code{linked_list_dump} [(@code{linked_list_t* restrict this, FILE* restrict output}) @arrow{} @code{void}] @fnindex @code{linked_list_dump} The all internal data of the list @code{*this} into the stream @code{output}. @end table @node Tables @subsection Tables @tpindex @code{fd_table_t} @tpindex @code{struct fd_table} @cpindex Tables, file descriptor @cpindex Maps, file descriptor @cpindex Dictionary, file descriptor @cpindex File descriptor table @tpindex @code{hash_table_t} @tpindex @code{struct hash_table} @cpindex Tables, hash @cpindex Maps, hash @cpindex Dictionary, hash @cpindex Hash table libmdsserver defines two similar data structures: @code{fd_table_t} and @code{hash_table_t}. Whenever a method exists for both data structures we will write @code{X_table} instead of @code{fd_table} and @code{hash_table}. Additionally, unless otherwise stated, a method's parameter named @code{this} will be of the type @code{hash_table_t*} if the method's name start with @code{hash_table} and @code{fd_table_t*} if the method's name start with @code{fd_table}, with the @code{restrict} modifier. @table @asis @item @code{X_table_create} [(@code{this}) @arrow{} @code{int}] @fnindex @code{hash_table_create} @fnindex @code{fd_table_create} Initialises @code{*this} so it can be used as a table. Returns zero on and only on success. These methods are defined as macros. @item @code{X_table_create_tuned} [(@code{this, size_t initial_capacity}) @arrow{} @code{int}] @fnindex @code{hash_table_create_tuned} @fnindex @code{fd_table_create_tuned} Initialises @code{*this} so it can be used as a table, and makes its initial capacity at least @code{initial_capacity}. Returns zero on and only on success. @code{hash_table_create_tuned} is defined as a macro. @item @code{hash_table_create_fine_tuned} [(@code{this, size_t initial_capacity, float load_factor}) @arrow{} @code{int}] @fnindex @code{hash_table_create_fine_tuned} Initialises @code{*this} so it can be used as a table, and makes its initial capacity at least @code{initial_capacity} and its load factor @code{load_factor}. Returns zero on and only on success. @item @code{X_table_destroy} [(@code{this, free_func* key_freer, free_func* value_freer}) @arrow{} @code{void}] @fnindex @code{hash_table_destroy} @fnindex @code{fd_table_destroy} Release all resources in the table @code{*this}, but do not @code{free} @code{this} itself. Should be called even if construction fails. If @code{keys_freer} is not @code{NULL}, this method will be called for each key. If @code{values_freer} is not @code{NULL}, this method will be called for each value. @item @code{X_table_contains_value} [(@code{const this, size_t value}) @arrow{} @code{int}] @fnindex @code{hash_table_contains_value} @fnindex @code{fd_table_contains_value} Check whether the value @code{value} is stored in the table @code{*this}. @item @code{X_table_contains_key} [(@code{const this, key}) @arrow{} @code{int}] @fnindex @code{hash_table_contains_key} @fnindex @code{fd_table_contains_key} Check whether the key @code{code} is used in the table @code{*this}. The data type for the parameter @code{key} is @code{size_t} for @code{hash_table} and @code{int} for @code{fd_table}. @item @code{X_table_get} [(@code{const this, key}) @arrow{} @code{size_t}] @fnindex @code{hash_table_get} @fnindex @code{fd_table_get} Look up a value by its key @code{key} in the table @code{*this}. Zero will be returned if the key was not used. @item @code{hash_table_get_entry} [(@code{const this, size_t key}) @arrow{} @code{hash_entry_t*}] @fnindex @code{hash_table_get_entry} Look up an entry by its key @code{key} in the table @code{*this}. @code{NULL} will be returned if the key was not used. @item @code{X_table_put} [(@code{this, key, size_t value}) @arrow{} @code{size_t}] @fnindex @code{hash_table_put} @fnindex @code{fd_table_put} Map the value @code{value} to the key @code{key} in the talbe @code{*this}. If a value was already mapped to the key, that value will be returned, otherwise zero will be returned. Zero will also be returned on error. @code{errno} will be set to zero on and only on success. The data type for the parameter @code{key} is @code{size_t} for @code{hash_table} and @code{int} for @code{fd_table}. @item @code{X_table_remove} [(@code{this, key}) @arrow{} @code{size_t}] @fnindex @code{hash_table_remove} @fnindex @code{fd_table_remove} Unmaps the key @code{key} for the table @code{*this}. If a value was mapped to the key, that value will be returned, otherwise zero will be returned. The data type for the parameter @code{key} is @code{size_t} for @code{hash_table} and @code{int} for @code{fd_table}. @item @code{X_table_clear} [(@code{this}) @arrow{} @code{void}] @fnindex @code{hash_table_clear} @fnindex @code{fd_table_clear} Unmaps all keys in the table @code{*this}. @item @code{X_table_unmarshal} [(@code{this, char* restrict data, remap_func* remapper}) @arrow{} @code{int}] @fnindex @code{hash_table_unmarshal} @fnindex @code{fd_table_unmarshal} As described in @ref{Data Structures} but with one additional parameter: @code{remapper}. If this parameter is not @code{NULL} this method is used to edit values. It will be called once for each value and the output of the method will be used inplace of the input value. @end table @file{} also defines as wrapper macro for the @code{for}-keyword: @table @asis @item @code{foreach_hash_table_entry} [(@code{hash_table_t this, size_t i, hash_entry_t* entry})] @fnindex @code{foreach_hash_table_entry} Iterates over entry element in the hash table @code{this}. On each iteration, the entry will be stored to the variable @code{entry} and the bucket index will be stored to the variable @code{i}. @ifset AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @example void print_hash_table(hash_table_t* table) @{ hash_entry_t* entry; size_t i; foreach_hash_table_entry (*table, i, entry) printf("%zu --> %zu\n", entry->key, entry->value); @} @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @example void print_hash_table(hash_table_t* table) @{ hash_entry_t* entry; size_t i; foreach_hash_table_entry (*table, i, entry) printf("%zu --> %zu\n", entry->key, entry->value); @} @end example @end ifclear Note that the data type for the parameter @code{this} is not a pointer. @end table @vrindex @code{value_comparator}, @code{hash_table_t} @vrindex @code{value_comparator}, @code{hash_table_t} @vrindex @code{hash_table_t.value_comparator} @vrindex @code{fd_table_t.value_comparator} The structures @code{hash_table_t} and @code{fd_table_t} contain the variable @code{value_comparator} which by default is @code{NULL}@. If this variable is set to @code{NULL}, two values will be considered equal if and only if they are numerically identical; otherwise two values will be considered equal if and only if @code{value_comparator} returned a non-zero value if those two values are used for the method's arguments. The data type for @code{value_comparator} is @code{compare_func*}. @code{hash_table_t} also contains two other variables: @table @asis @item @code{key_comparator} [@code{compare_func*}] @vrindex @code{key_comparator}, @code{hash_table_t} @vrindex @code{hash_table_t.key_comparator} Identical to @code{value_comparator}, except it is used for keys rather the values. @item @code{hasher} [@code{hash_func*}] @vrindex @code{hasher}, @code{hash_table_t} @vrindex @code{hash_table_t.hasher} By default, the hash value for key is identical to the key itself. However, if this variable is not @code{NULL}, it will be used to calculate the hash value for keys. @end table @tpindex @code{hash_entry_t} @tpindex @code{struct hash_entry} There is a secondary data structure defined for hash tables: @code{hash_entry_t} @{also known as @code{struct hash_entry}@}. It is the data structure used for entries in a hash table. @code{hash_entry_t} contains three variables you may be interested in: @table @asis @item @code{key} [@code{size_t}] @tpindex @code{key}, @code{hash_entry_t} @tpindex @code{hash_entry_t.key} The key. @item @code{value} [@code{size_t}] @tpindex @code{value}, @code{hash_entry_t} @tpindex @code{hash_entry_t.value} The value associated with the key. @item @code{hash} [@code{size_t}] @tpindex @code{hash}, @code{hash_entry_t} @tpindex @code{hash_entry_t.hash} The hash value of the key. @end table By inclusion of @file{}, @file{} and @file{} defines four @code{typedef}:s for method signatures: @table @asis @item @code{compare_func} [(@code{size_t a, size_t b}) @arrow{} @code{int}] @tpindex @code{compare_func} A method that performs a comparison of two objects. Should return non-zero if and only if @code{a} and @code{b} are to be considered equal in the given context. @item @code{hash_func} [(@code{size_t value}) @arrow{} @code{size_t}] @tpindex @code{hash_func} A method that hashes an object or a value. Should return the hash value for @code{value}. @item @code{free_func} [(@code{size_t obj}) @arrow{} @code{void}] @tpindex @code{free_func} A method that, to the extent that is appropriate, releases the object @code{obj}'s resources and @code{free}:s it. @item @code{remap_func} [(@code{size_t obj}) @arrow{} @code{size_t}] @tpindex @code{remap_func} A method that translates a object into a new object. The method should return new object that should replace the object @code{obj}. @end table If you are working with strings, you may consider including the header file @file{}. It defines to useful methods: @table @asis @item @code{string_hash} [(@code{const char* str}) @arrow{} @code{size_t}] @fnindex @code{string_hash} Calculate and returns the hash value of the string @code{str}. @item @code{string_comparator} [(@code{char* str_a, char* str_b}) @arrow{} @code{int}] @fnindex @code{string_comparator} @cpindex String comparison Returns non-zero if either both @code{str_a} and @code{str_b} are @code{NULL} or neither are @code{NULL} but are identical strings by content upto their first NUL characters (or by address.) @end table These methods are defined as pure and @code{static inline}. @node Hash List @subsection Hash List @tpindex @code{hash_list} @cpindex List, hash @cpindex Hash list @cpindex Tables, hash @cpindex Maps, hash @cpindex Dictionary, hash @cpindex Hash table @code{hash_list} is an abstract data structure, provided as an alternative to hash tables with a low number of elements. @code{hash_list} is a associated dynamic list, with hash keys, that keeps removed slot free for reuse until they are as many as the occupied slots. @fnindex @code{CREATE_HASH_LIST_SUBCLASS} To use @code{hash_list}, a concrete subclass of it must be created. To do this, call the macro @code{CREATE_HASH_LIST_SUBCLASS}. It takes four parameters: @enumerate 1 @item The name of the subclass, this must not be a string, but rather formated as an identifier. This text will replace the @code{hash_list} in all that the macro defines. @item @tpindex @code{KEY_T} The data type of the keys. We will hence refer to this as @code{KEY_T}. @item A @code{const} version of the data type of the keys. We will hence refer to this as @code{const KEY_T}. @item @tpindex @code{VALUE_T} The data type of the values. We will hence refer to this as @code{VALUE_T}. It is however internally type-defined as @code{hash_list_value_t}, but this is not guaranteed to be true in the future. @end enumerate @code{CREATE_HASH_LIST_SUBCLASS} will define two structures, two method type definitions, four @code{static inline} methods for the creator of the subclass to implement, and a set of methods, as well as one auxiliary type definition@footnote{This type definition would be @code{hash_list_value_t} as specified above.}. @tpindex @code{hash_list_entry_t} @tpindex @code{struct hash_list_entry} The first structure is called @code{hash_list_entry_t} @{also known as @code{struct hash_list_entry}@}. Keep in mind that @code{hash_list} is replaced by the first argument in the call to @code{CREATE_HASH_LIST_SUBCLASS}. This structure represents a entry, or slot, the hash list, it contains three elements: @table @asis @item @code{key} [@code{KEY_T}] @vrindex @code{key}, @code{hash_list_entry_t} @vrindex @code{hash_list_entry_t.key} The key of the entry. Will be @code{NULL} if the slot is unused; a @code{NULL} on a key is disallowed. Note that @code{NULL} is equivalent to zero if the data type is numeral primitively. @item @code{key_hash} [@code{size_t}] @vrindex @code{key_hash}, @code{hash_list_entry_t} @vrindex @code{hash_list_entry_t.key_hash} The hash of the key. This element is transparent to the user of the class. @item @code{value} [@code{VALUE_T}] @vrindex @code{value}, @code{hash_list_entry_t} @vrindex @code{hash_list_entry_t.value} The value. @end table @tpindex @code{hash_list_t} @tpindex @code{struct hash_list} The other structure is called @code{hash_list_t} @{also known as @code{struct hash_list}@}. This structure represents the entire hash list. It contains six elements: @table @asis @item @code{allocated} [@code{size_t}] @vrindex @code{allocated}, @code{hash_list_t} @vrindex @code{hash_list_t.allocated} The number of allocated slots. This element is transparent to the user of the class. @item @code{unused} [@code{size_t}] @vrindex @code{unused}, @code{hash_list_t} @vrindex @code{hash_list_t.unused} The number of unused slot that has previously be used. This element is transparent to the user of the class. @item @code{used} [@code{size_t}] @vrindex @code{used}, @code{hash_list_t} @vrindex @code{hash_list_t.used} The number of slots that have been used, even if no longer used. This element is transparent to the user of the class. @item @code{last} [@code{size_t}] @vrindex @code{last}, @code{hash_list_t} @vrindex @code{hash_list_t.last} @fnindex @code{hash_list_get} @fnindex @code{hash_list_put} @fnindex @code{hash_list_remove} This variable is used for optimisation, any time @code{hash_list_get} finds an element, its will be stored, and it will be the first inspected element by @code{hash_list_put} and @code{hash_list_remove}. This element is transparent to the user of the class. @item @code{slots} [@code{hash_list_entry_t*}] @vrindex @code{slots}, @code{hash_list_t} @vrindex @code{hash_list_t.slots} The allocation for the slots. This element is transparent to the user of the class. @item @code{freer} [@code{hash_list_entry_free_func*}] @vrindex @code{freer}, @code{hash_list_t} @vrindex @code{hash_list_t.freer} @tpindex @code{hash_list_entry_free_func} Method used to free keys and values of entries. If left @code{NULL}, no keys or values are freed. This value must be set after @code{hash_list_create} or @code{hash_list_unmarshal} is called, not before. @item @code{hasher} [@code{hash_list_key_hash_func*}] @vrindex @code{hasher}, @code{hash_list_t} @vrindex @code{hash_list_t.hasher} @tpindex @code{hash_list_key_hash_func} method used to calculate the hash of a key. If left @code{NULL}, the identity hash is used, that is, the address of the key, or if it is numeral, it is casted to @code{size_t}. This value must be set after @code{hash_list_create} or @code{hash_list_unmarshal} is called, not before. @end table The two method-type definitions are: @table @asis @item @code{hash_list_entry_free_func} [(@code{hash_list_entry_t* entry}) @arrow{} @code{void}] @tpindex @code{hash_list_entry_free_func} The method shall free the key and value, if defined in such a way that they can be freed. It is guaranteed that neither @code{entry} or @code{entry->key} are @code{NULL}. @item @code{hash_list_key_hash_func} [(@code{const KEY_T key}) @arrow{} @code{size_t}] @tpindex @code{hash_list_key_hash_func} The method shall return the hash of the @code{key}. It is guaranteed that @code{key} is not @code{NULL}. @end table There are five methods specific to @code{hash_list_t}. The @code{this}-parameter's data type for this methods are @code{hash_list_t*} with the @code{restrict} modifier. @table @asis @item @code{hash_list_create} [(@code{this, size_t capacity}) @arrow{} @code{int}] @fnindex @code{hash_list_create} Create a hash list, and store it in @code{this}. The hash list's initial capacity will be at least the value @code{capacity}. If, however, @code{capacity} is zero, a default capacity will be used. Zero is returned on success, @code{-1} is returned on error. @item @code{hash_list_pack} [(@code{this}) @arrow{} @code{int}] @fnindex @code{hash_list_pack} Pack the list so that there are no reusable positions, and reduce the capacity to the smallest capacity that can be used. This method has linear time complexity and constant memory complexity. Zero is returned on success, @code{-1} is returned on error. Errors are however non-fatal and can be ignored, it only means that the capacity could not be reduces, because a called to @code{realloc} failed. @item @code{hash_list_get} [(@code{this, const KEY_T key, VALUE_T* restrict value}) @arrow{} @code{int}] @fnindex @code{hash_list_get} Look up a value, with the key @code{key}, in the hash list @code{this}. The found value will be stored in @code{*value}. This method cannot fail, therefore it cannot return a value indicating that it failed. Instead it returns one if the entry was found and nought if it was not found. Note that @code{this} is not specified with @code{const}; this is because internal caching is done. @item @code{hash_list_put} [(@code{this, KEY_T key, const VALUE_T* restrict value}) @arrow{} @code{int}] @fnindex @code{hash_list_put} Store the value stored in @code{*value} to the hash list @code{this}. The value will be stored with the key @code{key}. If a value with this key already exists, that entry will be freed and replaced. @code{key} will be stored in the hash list, and the caller is not longer responsble for freeing it unless the call to this function fails. Zero is returned on success, @code{-1} is returned on error. If however @code{value} is @code{NULL}, the entry with the key @code{key} will be removed if it exists. And zero is always returned. The caller will be responsible for freeing @code{key} in this case. @item @code{hash_list_remove} [(@code{this, const KEY_T key}) @arrow{} @code{void}] @fnindex @code{hash_list_remove} Calling this function is equivalent to calling @code{hash_list_put} with the last argument being @code{NULL}. However, it allows the key to be stored with @code{const} and it does not have a return value. @end table Keep in mind that the methods @itemize @bullet{} @item @code{hash_list_destroy} @item @code{hash_list_clone} @item @code{hash_list_marshal_size} @item @code{hash_list_marshal} @item @code{hash_list_unmarshal} @end itemize also have @code{hash_list} exchanged with whatever is in the first argument of the on the call to @code{CREATE_HASH_LIST_SUBCLASS}. Additionally @code{hash_list_clone} cannot clone keys or values that are pointers. So if freeing method is set, you need to manually clone keys and values after calling @code{hash_list_clone}. @code{CREATE_HASH_LIST_SUBCLASS} also defines the prototypes for four functions the user of the class is required to implement. This four functions are defined with @code{static inline}. The @code{entry} parameter is defined with the type @code{hash_list_entry_t*}@footnote{Keep in mind that @code{hash_list} is replaced with the value of the first argument in @code{CREATE_HASH_LIST_SUBCLASS}}. @table @asis @item @code{hash_list_key_comparer} [(@code{const KEY_T key_a, const KEY_T key_b}) @arrow{} @code{int}] @fnindex @code{hash_list_key_comparer} Compare two keys, @code{key_a} and @code{key_b}. The function shall return zero on inequality and non-zero on equality. @item @code{hash_list_submarshal_size} [(@code{const entry}) @arrow{} @code{size_t}] @fnindex @code{hash_list_submarshal_size} The function shall return the number of bytes required to marshal @code{entry->key} and @code{entry->value}. @item @code{hash_list_submarshal} [(@code{const entry, char* restrict data}) @arrow{} @code{size_t}] @fnindex @code{hash_list_submarshal} The function shall marshal @code{entry->key} and @code{entry->value} into the buffer @code{data}. The function shall then return the number of written bytes, that is, the value returned by @code{hash_list_submarshal_size}. @item @code{hash_list_subunmarshal} [(@code{entry, char* restrict data}) @arrow{} @code{size_t}] @fnindex @code{hash_list_subunmarshal} The function shall unmarshal the key and value of an entry stored in the beginning of @code{data}. The unmarshaled key and value should be stored to @code{entry->key} and @code{entry->value}, respectively. The function shall then return the number of read bytes, that is, the value @code{hash_list_submarshal_size} returned when the marshal took place, or equivalently, the will it would return after the unmarshalling. The function shall return zero on error. @end table @file{} also defines two macros that is uneffected by @code{CREATE_HASH_LIST_SUBCLASS}. @table @asis @item @code{foreach_hash_list_entry} [(@code{hash_list_t this, size_t i, hash_list_entry_t* entry})] This marcro is a warpper for the @code{for}-keyword. It iterates over entry element in the hash list @code{this}. On each iteration, the entry (used slots) will be stored to the variable @code{entry}. The variable @code{i} defined as a @code{size_t} must be available for the macro to use freely. @ifset AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @example void print_hash_list(hash_list_t* table) @{ hash_list_entry_t* entry; size_t i; foreach_hash_table_entry (*table, i, entry) printf("%zu --> %zu\n", entry->key, entry->value); @} @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @example void print_hash_list(hash_list_t* table) @{ hash_list_entry_t* entry; size_t i; foreach_hash_lsit_entry (*table, i, entry) printf("%zu --> %zu\n", entry->key, entry->value); @} @end example @end ifclear Note thay the data type for the parameter @code{this} is not a pointer. @item @code{HASH_LIST_EXPECTED} [(@code{...})] This macro is defined as @code{__builtin_expect(__VA_ARGS__, 1)}. This means that the input value is evaluated, and may contain the sequence-operator (comma-operator), and the the value is expected to evaluate to @code{1}. It is encourage to run @code{hash_list_get} before @code{hash_list_put} and @code{hash_list_remove}. This way, you know exactly what is happening. There is an optimisation in place to let @code{hash_list_put} and @code{hash_list_remove} skip the search for the item (unless it is the first element) if @code{hash_list_get} was used directly prior to @code{hash_list_put} or @code{hash_list_remove} to find the element. This macro used to tell the compiler that position of the element is most likely already known but is not zero. If you however choose to not call @code{hash_list_get} before @code{hash_list_put} and @code{hash_list_remove} you should define this macro before including the header file, but with the @code{1} changed to a @code{0}. If you on the other hand do not know if you are going to call @code{hash_list_get} before @code{hash_list_put} and @code{hash_list_remove} you should define it to expand to the input verbatim, that is, have the value @code{__VA_ARGS__}. @end table @node Message Structure @subsection Message Structure @tpindex @code{mds_message_t} @tpindex @code{struct mds_message} @cpindex Message passing, data structure Apart from internal data @code{mds_message_t} contains four variables: @table @asis @item @code{headers} [@code{char**}] @vrindex @code{headers}, @code{mds_message_t} @vrindex @code{mds_message_t.headers} The headers in the message, each element in this list as an unparsed header, it consists of both the header name and its associated value, joined by @w{`: '}. A header cannot be @code{NULL} (unless its memory allocation failed,) but @code{headers} itself is @code{NULL} if there are no headers. The @code{Length}-header should be included in this list. @item @code{header_count} [@code{size_t}] @vrindex @code{header_count}, @code{mds_message_t} @vrindex @code{mds_message_t.header_count} The number of headers in the message. @item @code{payload} [@code{char*}] @vrindex @code{payload}, @code{mds_message_t} @vrindex @code{mds_message_t.payload} The payload of the message, @code{NULL} if none (of zero-length). @item @code{payload_size} [@code{size_t}] @vrindex @code{payload_size}, @code{mds_message_t} @vrindex @code{mds_message_t.payload_size} The length of the message's payload. This value will be the same as the value of the @code{Length}-header. @end table There are six methods specific to @code{mds_message_t}. The @code{this}-parameter's data type for this methods are @code{mds_message_t*} with the @code{restrict} modifier. @table @asis @item @code{mds_message_initialise} [(@code{this}) @arrow{} @code{int}] @fnindex @code{mds_message_initialise} Initialises @code{*this} so that it can be used by @code{mds_message_read}. Returns zero on and only on success. On failure you should destroy @code{*this} using @code{mds_message_destroy}. @item @code{mds_message_zero_initialise} [(@code{this}) @arrow{} @code{void}] @fnindex @code{mds_message_zero_initialise} This method is similar to @code{mds_message_initialise}, however it cannot fail and thus have no return value. The difference it is action is that it will not allocate an internal buffer. @item @code{mds_message_extend_headers} [(@code{this, size_t extent}) @arrow{} @code{int}] @fnindex @code{mds_message_extend_headers} Ensures that @code{extent} additional headers can be stored in the @code{*this}. Returns zero on and only on success. @item @code{mds_message_read} [(@code{this, int fd}) @arrow{} @code{int}] @fnindex @code{mds_message_read} Reads the next message from the socket file descriptor @code{fd} and stores it in @code{*this}. Returns zero on success and non-zero on error or interruption. @code{*this} should be destroyed using @code{mds_message_destroy} on error but not on interruption. If @code{-2} is returned @code{errno} will not have been set; @code{-2} indicates that the message is malformated, which is a state that cannot be recovered from. @item @code{mds_message_compose_size} [(@code{const this}) @arrow{} @code{size_t}] @fnindex @code{mds_message_compose_size} This method is to @code{mds_message_compose} as @code{mds_message_marshal_size} is to @code{mds_message_marshal}. @item @code{mds_message_compose} [(@code{const this, char* restrict data}) @arrow{} @code{void}] @fnindex @code{mds_message_compose} This method is similar to @code{mds_message_marshal}. The only difference is that it will not store internal data and instead create a message that can be broadcasted in the display server message passing system. @end table @node mds-base.o @chapter @file{mds-base.o} @cpindex Servers, library @cpindex Library, Servers @cpindex @file{mds-base} @file{mds-base.c} and @file{mds-base.h} as an object filepair whose purpose is similar to libmdsserver. @file{mds-base} is compiled into all @command{mds} servers and implements common procedures including @code{main}. It also complements procedures that are weakly defined, that is, if the server implementation also defines them, the server implementations procedure replaces @file{mds-base}'s implementation at compile-time. @file{mds-base} defines one function that you can call from threads you create and functions that should be implement depending on specified conditions: @table @asis @item @code{trap_signals} [(@code{void}) @arrow{} @code{int}] @fnindex @code{trap_signals} @cpindex Signals Set up signal traps for all especially handled signals. Returns zero on and only on success. @end table @file{mds-base} weakly defines functions that you can replace if they do not suit your needs: @table @asis @item @code{parse_cmdline} [(@code{void}) @arrow{} @code{int}] @fnindex @code{parse_cmdline} @cpindex Parse command line @cpindex Command line, parse Parses command line arguments. Returns zero on and only on success. This function will parse the following options: @table @option @item --initial-spawn @opindex @option{--initial-spawn} It is the first time the server is spawn by its spawner process. @item --respawn @opindex @option{--respawn} The server was respawned. @item --re-exec @opindex @option{--re-exec} The server is re-executing. @item --alarm=SECONDS @opindex @option{--alarm} @sgindex @code{SIGALRM} Kill the process after @var{SECONDS} seconds. At most one minute. @item --on-init-fork @opindex @option{--on-init-fork} Fork the process to detach it from its parent when the server has been initialised. @item --on-init-sh=COMMAND @opindex @option{--on-init-sh} When the server has been initialised, run the command @var{COMMAND}@. @item --immortal @opindex @option{--immortal} The server should do its best not to die. For example do not die if @code{SIGDANGER} is received even if that is the server's default action. @end table @item @code{connect_to_display} [(@code{void}) @arrow{} @code{int}] @fnindex @code{connect_to_display} @cpindex Connecting to the display Connects to the display. Returns zero on and only on success. @item @code{server_initialised} [(@code{void}) @arrow{} @code{int}] @fnindex @code{server_initialised} @cpindex Initialisation This function should be called when the server has been properly initialised but before initialisation of anything that is removed at forking is initialised. Returns zero on and only on success. @item @code{signal_all} [(@code{int signo}) @arrow{} @code{void}] @fnindex @code{signal_all} @cpindex Signals, multi-threading @cpindex Multi-threading, signals @cpindex Treading, signals This function should be implemented by the actual server implementation if the server is multi-threaded. It sends the singal @code{signo} to all threads except the current thread. @item @code{received_danger} [(@code{int signo}) @arrow{} @code{void}] @fnindex @code{received_danger} @sgindex @code{SIGDANGER} @vrindex @code{server_characteristics.danger_is_deadly} @vrindex @code{danger_is_deadly}, @code{server_characteristics} @cpindex Memory release, automatic @cpindex Memory release, forced @cpindex Automated memory release @cpindex Forcing memory release @cpindex Releasing memory @vrindex @code{danger} This function is called when a signal that signals the system is running out of memory has been received. The exact received signal is specified by the parameter @code{signo}. When this function is invoked, the server should free up all memory it can spare. When this function is invoked, it should set the variable @code{danger} to a non-zero value. If @code{server_characteristics.danger_is_deadly} is set, this function will never be called. @item @code{received_reexec} [(@code{int signo}) @arrow{} @code{void}] @fnindex @code{received_reexec} @vrindex @code{reexecing} @vrindex @code{terminating} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} This function is called when a signal that signals the server to re-execute has been received. The exact received signal is specified by the parameter @code{signo}. When this function is invoked, it should set the variables @code{reexecing} and @code{terminating} to a non-zero value. @item @code{received_terminate} [(@code{int signo}) @arrow{} @code{void}] @fnindex @code{received_terminate} @vrindex @code{terminating} @cpindex Terminating @sgindex @code{SIGTERM} @sgindex @code{SIGINT} This function is called when a signal that signals the server to terminate has been received. The exact received signal is specified by the parameter @code{signo}. When this function is invoked, it should set the variable @code{terminating} to a non-zero value. @item @code{received_info} [(@code{int signo}) @arrow{} @code{void}] @fnindex @code{received_info} @sgindex @code{SIGINFO} @cpindex State dump @cpindex Statistics dump This function is called when a signal that signals the server to dump state information and statistics has been received. The exact received signal is specified by the parameter @code{signo}. @item @code{fork_cleanup} [(@code{int status}) @arrow{} @code{void}] @fnindex @code{fork_cleanup} @vrindex @code{server_characteristics.fork_for_safety} @vrindex @code{fork_for_safety}, @code{server_characteristics} @cpindex Initialisation This function should be implemented by the actual server implementation if the server has set @code{server_characteristics.fork_for_safety} to be a non-zero value. This function is called by the parent server process when the child server process exits, if the server has completed its initialisation. The parameter @code{status} specifies the child process exit status as returned by @code{waitpid}. @end table Additionally, @file{mds-base} expects the server implementation to define and implement a set of functions: @table @asis @item @code{preinitialise_server} [(@code{void}) @arrow{} @code{int}] @fnindex @code{preinitialise_server} @fnindex @code{initialise_server} @fnindex @code{unmarshal_server} @cpindex Initialisation This function will be invoked before @code{initialise_server} (if not re-executing) or before @code{unmarshal_server} (if not re-executing). Returns zero on and only on success. @item @code{initialise_server} [(@code{void}) @arrow{} @code{int}] @fnindex @code{initialise_server} @cpindex Initialisation This function should initialise the server. It not invoked after a re-execution. Returns zero on and only on success. @item @code{postinitialise_server} [(@code{void}) @arrow{} @code{int}] @fnindex @code{postinitialise_server} @fnindex @code{initialise_server} @fnindex @code{unmarshal_server} @cpindex Initialisation This function will be invoked after @code{initialise_server} (if not re-executing) or after @code{unmarshal_server} (if re-executing). Returns zero on and only on success. @item @code{marshal_server_size} [(@code{void}) @arrow{} @code{size_t}, pure] @fnindex @code{marshal_server_size} @fnindex @code{marshal_server} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Calculate and returns the number of bytes that will be stored by @code{marshal_server}. On failure the server should call @code{abort} or exit with failure status by other means. However it should not be possible for this function to fail. @code{marshal_server_size} must be pure@footnote{That is, define with and conforming to @code{__attribute__((pure))}.}. @item @code{marshal_server} [(@code{char* state_buf}) @arrow{} @code{int}] @fnindex @code{marshal_server} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Marshal server implementation specific data into the buffer @code{state_buf}. Returns zero on and only on success. @item @code{unmarshal_server} [(@code{char* state_buf}) @arrow{} @code{int}] @fnindex @code{unmarshal_server} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Unmarshal server implementation specific data from the buffer @code{state_buf} and update the servers state accordingly. Returns zero on and only on success. @fnindex @code{reexec_failure_recover} On critical failure the program should call @code{abort} or exit with failure status by other means. That is, do not let @code{reexec_failure_recover} run successfully, if it unrecoverable error has occurred or one severe enough that it is better to simply respawn. @item @code{reexec_failure_recover} [(@code{void}) @arrow{} @code{int}] @fnindex @code{reexec_failure_recover} @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Attempt to recover from a re-execution failure that has been detected after the server successfully updated it execution image. Returns zero on and only on success. @item @code{master_loop} [(@code{void}) @arrow{} @code{int}] @fnindex @code{master_loop} @cpindex Initialisation Perform the server's mission. Returns zero on and only on success. @end table @file{mds-base} also defines a number of global variables. @table @asis @item @code{argc} [@code{int}] @vrindex @code{argc} @cpindex Command line Number of elements in @code{argv}. @item @code{argv} [@code{char**}] @vrindex @code{argv} @cpindex Command line Command line arguments. @item @code{is_respawn} [@code{int}] @vrindex @code{is_respawn} @cpindex Initialisation @vrindex @code{is_reexec} Whether the server has been respawn rather than this being the initial spawn. This will be at least as true as @code{is_reexec}. @item @code{is_reexec} [@code{int}] @vrindex @code{is_reexec} @cpindex Initialisation @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} Whether the server is continuing from a self-reexecution. @item @code{is_immortal} [@code{int}] @vrindex @code{is_immortal} @opindex @option{--immortal} Whether the server should do its best to resist event triggered death. @item @code{on_init_fork} [@code{int}] @vrindex @code{on_init_fork} @cpindex Initialisation Whether to fork the process when the server has been properly initialised. @item @code{on_init_sh} [@code{char*}] @vrindex @code{on_init_sh} @cpindex Initialisation Command the run (@code{NULL} for none) when the server has been properly initialised. @item @code{master_thread} [@code{pthread_t}] @vrindex @code{master_thread} @cpindex Threading @cpindex Multi-threading The thread that runs the master loop. @item @code{terminating} [@code{volatile sig_atomic_t}] @vrindex @code{terminating} @cpindex Terminating Whether the server has been signaled to terminate. @item @code{reexecing} [@code{volatile sig_atomic_t}] @vrindex @code{reexecing} @cpindex Initialisation @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update Whether the server has been signaled to re-execute. @item @code{danger} [@code{volatile sig_atomic_t}] @vrindex @code{danger} @sgindex @code{SIGDANGER} @cpindex Memory release, automatic @cpindex Memory release, forced @cpindex Automated memory release @cpindex Forcing memory release @cpindex Releasing memory Whether the server has been signaled to free unneeded memory. @item @code{socket_fd} [@code{int}] @vrindex @code{socket_fd} @cpindex Connecting to the display The file descriptor of the socket that is connected to the server. @end table @cpindex Server characteristics @file{mds-base} expects the server implementation to define a variable that specifies how @file{mds-base} should behave: @table @asis @item @code{server_characteristics} [@code{server_characteristics_t}] @vrindex @code{server_characteristics} This variable should declared by the actual server implementation. It must be configured before @code{main} is invoked. That is, it should be configured by a constructor. If it is configured at its definition, it is configured by a constructor; that is normally how you want to configured it. @end table @tpindex @code{server_characteristics_t} @tpindex @code{struct server_characteristics} @code{server_characteristics_t} @{also known as @code{struct server_characteristics}@} is a packed @footnote{That is, define with @code{__attribute__((packed))}.} with the following fields: @table @asis @item @code{require_privileges} [@code{unsigned : 1}] @vrindex @code{require_privileges} @cpindex Previleges @cpindex Security, previleges Setting this to zero will cause the server to drop privileges as a security precaution. @item @code{require_display} [@code{unsigned : 1}] @vrindex @code{require_display} @cpindex Connecting to the display Setting this to non-zero will cause the server to connect to the display. @item @code{require_respawn_info} [@code{unsigned : 1}] @vrindex @code{require_respawn_info} @opindex @option{--initial-spawn} @opindex @option{--respawn} @cpindex Initialisation Setting this to non-zero will cause the server to refuse to start unless either @option{--initial-spawn} or @option{--respawn} is used. @item @code{sanity_check_argc} [@code{unsigned : 1}] @vrindex @code{sanity_check_argc} @cpindex Command line, security @cpindex Security, command line Setting this to non-zero will cause the server to refuse to start if there are too many command line arguments. @item @code{fork_for_safety} [@code{unsigned : 1}] @vrindex @code{fork_for_safety} @cpindex Initialisation @fnindex @code{fork_cleanup} Setting this to non-zero will cause the server to place itself in a fork of itself when initialised. This can be used to let the server clean up fatal stuff after itself if it crashes. When the child exits, no matter how it exits, the parent will call @code{fork_cleanup} and then die in the same manner as the child. @item @code{danger_is_deadly} [@code{unsigned : 1}] @vrindex @code{danger_is_deadly} @sgindex @code{SIGDANGER} @vrindex @code{fork_for_safety} @fnindex @code{server_initialised} @cpindex Memory release, automatic @cpindex Memory release, forced @cpindex Automated memory release @cpindex Forcing memory release @cpindex Releasing memory Setting this to non-zero without setting a signal action for @code{SIGDANGER} will cause the server to die if @code{SIGDANGER} is received. It is safe to set both @code{danger_is_deadly} and @code{fork_for_safety} to non-zero, during the call of @code{server_initialised} the signal handler for @code{SIGDANGER} in the parent process will be set to @code{SIG_IGN} independently of the value of @code{danger_is_deadly} if @code{fork_for_safety} is set to non-zero. @opindex @option{--immortal} This setting will be treated as set to zero if @option{--immortal} is used. @end table @node libmdsclient @chapter libmdsclient @cpindex Clients, library @cpindex Library, clients libmdsclient is a library written for @code{mds} clients. But can also be used for @code{mds} servers. However, reference servers use libmdsserver (@pxref{libmdsserver}.) @cpindex @command{pkg-config} @pgindex @command{pkg-config} To use libmdsclient, include @file{} in your source files. @file{} includes all libmdsclient headers; you may cherrypick them if you so choose. When compiling and linking your programs, use the @command{pkg-config} package @code{libmdsclient}. Definitions@footnote{Structures, unions, enumerations, type-definitions, functions, macros and variables.} in libmdsclients use the prefixes @code{libmds_} and @code{LIBMDS_}@footnote{@code{LIBMDS_} is reserved for macros, but function-like macros and lvalue-macros use @code{libmds_}.}, rather than @code{libmdsclient_} and @code{LIBMDSCLIENT_}. This is to make the identifiers shorter. Inclusion-guards are formatted @code{MDS_LIBMDSCLIENT_*_H}. libmdsclient is not yet capable of state marshalling which is required for online updating to newer versions of the client. @menu * Protocol Utilties:: Low-level functions for implementing protocols. * Communication Utilities:: Low-level communication functions. * Receiving Messages:: Low-level functions for receiving messages. @end menu @node Protocol Utilties @section Protocol Utilties @cpindex Implementing protocols @cpindex Protocols, implementing The header file @file{} provides functions that can be used in implementing protocols. Using these functions will make it easy to implement the protocol, the implementing may however be more efficient if you implement everything by hand. In particular, protocols that are expected to be used very often with similar data may be faster if implemented using caching techniques. The header file provides a function for retrieving header files of interest: @table @asis @item @code{libmds_headers_cherrypick} [(@code{char** restrict headers, size_t header_count, size_t* restrict found, libmds_cherrypick_optimisation_t optimisation, ...}) @arrow{} @code{int}] @fnindex @code{libmds_headers_cherrypick} @cpindex Headers, cherrypicking @cpindex Cherrypicking headers @cpindex Headers, reading @cpindex Reading headers This function takes an list of headers as input. The headers are provided by the parameter @code{headers}, and the number of headers is specified by the parameter @code{header_count}. These headers must include both the names and values. For example: @example headers = (char[][]) @{ "Client ID: 0:1", "Message ID: 12", @}; @end example The function will store the number headers it found to @code{*found}, unless @code{found} is @code{NULL}. Only requested headers are counted. The function can use optimisations based on the input The parameter @code{optimisation} is used to provide hints required for optimal optimisation. @tpindex @code{libmds_cherrypick_optimisation_t} @tpindex @code{enum libmds_cherrypick_optimisation} @code{optimisation} is defined with the type @code{libmds_cherrypick_optimisation_t} @{also known as @code{enum libmds_cherrypick_optimisation}@}. Values of @code{optimisation} should combine, using bit-wise OR, two values defined in @code{libmds_cherrypick_optimisation_t}. One of the values should be from the header input optimisation group: @table @code @item DO_NOT_SORT = 0 @code{headers} is neither sorted nor may it its elements be reordered. However, the function may choose to create a copy of @code{headers} and sort that copy, if it sees it as beneficial. @item SORT @code{headers} is not sorted, but the function may sort it without copying it, if it sees it as beneficial. @item SORTED @code{headers} is already sorted in ascending order. This means that the function will not reorder its elements. @end table The other value should be from the header request optimisation group: @table @code @item ARGS_UNSORTED = 0 The header request list is not sorted. @item ARGS_SORTED The header request list is sorted in ascending order. @end table Note that @code{DO_NOT_SORT} and @code{ARGS_UNSORTED} are both guaranteed to have the value 0. The other definitions do not have a guaranteed value, but they are guaranteed to be unique and only consist of one set bit. The variadic arguments are used for the header request list. The first argument in the variadic argument list should be a @code{const char*} that names a requested header. It should only contain the name of the header. The follow argument should be of the type @code{char**}. The first element in this argument will be set the the value of the header named by the previous argument, or @code{NULL} if not found. This, pair of arguments, is repeated once for every requested header. The end of the variadic argument list must be marked with a @code{NULL}. For example: @example char* recv_client_id; char* recv_message_id; char* recv_command_id; r = libmds_headers_cherrypick(headers, n, NULL, 0, /* Header request starts here */ "Client ID", &recv_client_id, "Message ID", &recv_message_id, "Command", &recv_command, NULL); @end example The function's behaviour is undefined for if a header is requested more than once, or in an order contrary to the specifications provided by @code{optimisation}. The function's behaviour is also undefined if the input headers are in an order contrary to the specifications provided by @code{optimisation}. Upon successful completion, even if no requested headers are found, this function returned zero. On error, @code{-1} is returned and @code{errno} is set to indicate the error. This function can fail with errno set to @code{ENOMEM}, if the process cannot allocate required memory. The call must not free returned header values. They are freed automatically when corresponding element in the header input list is freed. The input headers are returned with an offset. This also means that the returned values will be modified if the value part of the input headers are modified. @end table The header file also provides four pre-optimised version of @code{libmds_headers_cherrypick}. These functionf behaves like @code{libmds_headers_cherrypick}, except they does not have the optimisation parameter, and return the number of found headers rather than storing it using a pointer. Additionally these function cannot fail. @table @asis @item @code{libmds_headers_cherrypick_linear_unsorted} [(@code{char** restrict headers, size_t header_count, ...}) @arrow{} @code{size_t}] @fnindex @code{libmds_headers_cherrypick_linear_unsorted} This function is not optimised. Because of its low overhead it can still be the fastest choice. @item @code{libmds_headers_cherrypick_linear_sorted} [(@code{char** restrict headers, size_t header_count, ...}) @arrow{} @code{size_t}] @fnindex @code{libmds_headers_cherrypick_linear_sorted} This function uses linear search, but uses an optimised based on the assumption that both the input header list and the header request list are sorted in ascending order. Because of its low overhead it can still be faster than @code{libmds_headers_cherrypick_binary_sorted}. @item @code{libmds_headers_cherrypick_binary_unsorted} [(@code{char** restrict headers, size_t header_count, ...}) @arrow{} @code{size_t}] @fnindex @code{libmds_headers_cherrypick_binary_unsorted} This function uses binary search. It assumes that the header input list sorted in ascending order, header request list is unsorted. @item @code{libmds_headers_cherrypick_binary_sorted} [(@code{char** restrict headers, size_t header_count, ...}) @arrow{} @code{size_t}] @fnindex @code{libmds_headers_cherrypick_binary_sorted} This function uses binary search. It assumes that the both the header input list and header request list are sorted in ascending order. It seeks for the headers in the order the are provided in the header request list, and adjusts the lower bound on the binary search each time it founds a header. @end table Currently it is assumed that these are the only useful optimisations. This may however change in the future, and some optimisations may even be removed. Therefore the user of the library can check at compile time whether the functions are still available. This is done by checking that a macro with exactly the same name as the function is defined. @cpindex Sorting headers @cpindex Headers, sorting If you want to sort a list of headers. You need to be aware that the header should treated as ending at the first occurrence of a colon followed by a blank space. Because of this, @file{} provides a function for sorting a list of headers. @table @asis @item @code{libmds_headers_sort} [(@code{char** restrict headers, size_t header_count}) @arrow{} @code{void}] @fnindex @code{libmds_headers_sort} This function takes the list of headers in the parameter @code{headers} and the number of headers in the parameter @code{header_count}. It cannot fail, and thus does not return a value. This function sorts the headers in ascending order, and is used internally by @code{libmds_headers_cherrypick} if it chooses to sort headers. @end table @file{} also provides a function for composing messages: @table @asis @item @code{libmds_compose} [(@code{char** restrict buffer, size_t* restrict buffer_size, size_t* restrict length, const char* restrict payload, const size_t* restrict payload_length, ...}) @arrow{} @code{int}] @fnindex @code{libmds_compose} @cpindex Messages, composing @cpindex Composing messages @cpindex Messages, writting @cpindex Writting messages This function provides a simple way for writting message that can be send to the display server. The function writes the message on a buffer provides by the caller. This buffer is reallocationed by the function if necessary. The buffer is provided by a pointer, @code{buffer} to the buffer. @code{*buffer} is changed to the new buffer pointer if it is reallocated. The current size of @code{*buffer} should be stored @code{*buffer_size}. @code{*buffer_size} will be updated with the new allocation size if the buffer is reallocated. Neither if these pointers may be @code{NULL}. However, @code{*buffer} should be @code{NULL} if @code{*buffer_size} is zero, and vice versa. The length of the written message will be saved to @code{length}. @code{length} must not be @code{NULL}. If the message should include a payload. It should be provided using the parameter @code{payload}. If the message should not have a payload @code{payload} should be @code{NULL}. The argument @code{payload_length} should point to a value with the length of the message, or be @code{NULL} if the function should measure the @code{payload} by searching for a NUL bytes which must exists in such a cass. If @code{payload_length} is not @code{NULL}, there is not requirement for a NUL byte. If @code{payload} is @code{NULL}, @code{payload_length} is unused and may have any value. The function uses variadic arguments for header input. The first argument in the variadic argument list should be an @code{printf}-formatted format-string that describes a header line (header name, colon, blank space, header value.) The following arguments are the formatting-arguments for that format string. At the end of the list of formatting-arguments, this is begin anew for the next header, and so on. After the last header, a @code{NULL} should be used to mark the end of the list. The header formatting string, may include any extensions provided by your C library. Nut is has one additional extension: if the formatting-string begins with a question mark, the first formatting-argument is if type @code{int} and the header is only included if that argument is non-zero. This is no way to escape a question mark at the beginning of the formatting-string, because headers should never begin with a question mark. Upon successful completion, this function returns zero. On error, this function returns @code{-1} and sets @code{errno} to indicate the error. This function may fail with @code{errno} set to @code{ENOMEM} if the process cannot allocate more memory. The function's behaviour is undefined if a header is longer than @iftex 2@sup{15} @end iftex @ifnottex 2 to the power of 15 @end ifnottex bytes. This function shall not be used if there must be a guarantee that the written data can be securely erased. @end table The header file also provides a function for finding the next unused message ID: @table @asis @item @code{libmds_next_message_id} [(@code{uint32_t* restrict message_id, int (*test)(uint32_t message_id, void* data), void* data}) @arrow{} @code{int}] The parameter @code{message_id} is a pointer to the message ID counter. It should contain the ID of the previous message,@footnote{For the first message, it is preferred that this value is @code{UINT32_MAX}, so the first message is the ID 0, but it is not a requirement, it should however be initialised.} it will be updated with the message ID for the new message upon successful completion. @code{message_id} must not be @code{NULL}. The parameter @code{test} can either point to a function that is used to test if a message ID is unused, or be @code{NULL} if no testing should be done. @code{*test} tests whether the message ID provided as the first argument is free to be used. The second argument in @code{*test} will be the value of the parameter @code{data} in the call to the function @code{libmds_next_message_id}. @code{data} can e used to deal with threading or any other issues. @code{data} may be @code{NULL}. @code{data} is unused if @code{test} is @code{NULL}. Upon successful completion zero is returned. On error @code{-1} is returned and @code{errno} is set to indicate the error. This function can fail with errno set to any error thrown by @code{*test}, as well as @code{EAGAIN}. @code{EAGAIN} is thrown if the function cannot find any free message ID to use. It is advisable to make @code{*test} throw this immediately if there are no free message ID:s. The function cannot fail if @code{test} is @code{NULL}. @end table @fnindex @code{libmds_headers_cherrypick_v} @fnindex @code{libmds_headers_cherrypick_linear_unsorted_v} @fnindex @code{libmds_headers_cherrypick_linear_sorted_v} @fnindex @code{libmds_headers_cherrypick_binary_unsorted_v} @fnindex @code{libmds_headers_cherrypick_binary_sorted_v} @fnindex @code{libmds_compose_v} All functions that uses variadic arguments, have a variant that uses @code{va_list} instead. These functions are suffixed @code{_v}. @node Communication Utilities @section Communication Utilities @cpindex Communication foundation The header file @file{} provides functions for connecting to the display server and performing thread-safe communication. @cpindex Descriptor, connection @cpindex Connection descriptor @tpindex @code{libmds_connection_t} @tpindex @code{struct libmds_connection} These functions use the structured @code{libmds_connection_t}. @{also known as @code{struct libmds_connection}@}. Instances of this structure are referred to as connection descriptors. This structure should be considered opaque. For these functions, the @code{this} parameter has the type @code{libmds_connection_initialise* restrict}. @table @asis @item @code{libmds_connection_initialise} [(@code{this}) @arrow{} @code{int}] @fnindex @code{libmds_connection_initialise} Initialises a connection descriptor, but does not connect it to the display server. Upon successful completion, zero is returned. On error, @code{-1} is returned and @code{errno} is set to indicate the error. This function may fail with @code{errno} set to @code{EAGAIN}, @code{ENOMEM} or @code{EPERM}, as specified for @code{pthread_mutex_init(3)}. @item @code{libmds_connection_create} [(@code{void}) @arrow{} @code{libmds_connection_t*}] @fnindex @code{libmds_connection_create} Wrapper for @code{libmds_connection_initialise} that also allocates the connection descriptor. Upon successful completion, the descriptor is returned. On error, @code{NULL} is returned and @code{errno} is set to indicate the error. This function may fail for any reason, with @code{errno} is to the same value, as @code{libmds_connection_initialise}. It may also fail with @code{errno} set to @code{ENOMEM} if the descriptor cannot be allocated. This is, on memory exhaustion. @item @code{libmds_connection_destroy} [(@code{this}) @arrow{} @code{void}] @fnindex @code{libmds_connection_destroy} Release all resources held by a connection descriptor. This also means that the connection to the display server will close. Nothing will happen if @code{this} is @code{NULL}. @item @code{libmds_connection_free} [(@code{this}) @arrow{} @code{void}] @fnindex @code{libmds_connection_free} Wrapper for @code{libmds_connection_destroy} that also calls @code{free} on the descriptor to deallocate the descriptor itself. @item @code{libmds_connection_establish} [(@code{this, const char** restrict display}) @arrow{} @code{int}] @fnindex @code{libmds_connection_establish} Establishes a connection to the display server. It is preferred to use @code{libmds_connection_establish_address}, over using @code{libmds_connection_establish}. @code{display} must either be a pointer to a string, or a pointer to @code{NULL}. It pointer @code{display} itself must not be @code{NULL}. If @code{display} points to @code{NULL}, it will be update with the value of the environment variable @env{MDS_DISPLAY}, or left @code{NULL} if not set. This function will parse value @code{display} points to (after it has been updated if it points to @code{NULL},) and attempt to connect to the display server it addresses. Upon successful completetion, zero is returned. On error, @code{-1} is returned and @code{errno} is set to indicate the error. This function may fail with @code{errno} set to @code{EFAULT} if @env{MDS_DISPLAY} is not set (if @code{display} pointed to, and will in such case still point to, @code{NULL}, or if the display server's address is not properly formatted, or specifies an unsupported protocol. It may also fail with @code{errno} set to @code{ENAMETOOLONG} if the pathname of the display server's socket is too long. The function may also fail with any value on @code{errno} specified for @code{socket(2)} or @code{connect(2)}, except @code{EINTR}. @item @code{libmds_connection_establish_address} [(@code{this, const libmds_display_address_t* restrict address}) @arrow{} @code{int}] @fnindex @code{libmds_connection_establish_address} This function is an alternative to @code{libmds_connection_establish}, which is preferred because it is easier to find out why it potentially failed. And it can be done reliably. Instead of a pointer to a string formated as @env{MDS_DISPLAY}, or a pointer to @code{NULL}. This function takes a, by @code{libmds_parse_display_address}, preparsed address. Upon successful completetion, zero is returned. On error, @code{-1} is returned and @code{errno} is set to indicate the error. This function may fail with @code{errno} set to @code{EFAULT} if the address is not full set, this can happen even if @code{libmds_parse_display_address} returns successfully; it means that the display server address is not properly formatted or specifies an unsupported protocol. This function may also fail with any value on @code{errno} specified for @code{socket(2)} or @code{connect(2)}, except @code{EINTR}. @item @code{libmds_connection_send} [(@code{this, const char* restrict message, size_t length}) @arrow{} @code{size_t}] @fnindex @code{libmds_connection_send} This function locks a connection descriptor and --- when it is entered the lock --- it will send a message to the display server over the connection, and ignores all interrupts. The message is specified by the parameter @code{message}, and this length is specified by the parameter @code{length}. Note that this function treats @code{message} as a raw memory segment rather than as a NUL-terminated string. Undefined behaviour is invoked if @code{message} is @code{NULL} or if @code{length} is zero. Upon successful completeion, the number of sent bytes are returned. On error, zero is returned and @code{errno} is set to indicate the error. This function may fail with errno set to any error specified for @code{pthread_mutex_lock(3)}, or any of the errors @code{EACCES}, @code{EWOULDBLOCK} (but only if the socket has been modified to be nonblocking,) @code{EBADF}, @code{ECONNRESET} --- if connection to the display server is lost, --- @code{EDESTADDRREQ}, @code{EFAULT}, @code{EINVAL}, @code{ENOBUFS}, @code{ENOMEM}, @code{ENOTCONN}, @code{ENOTSOCK} or @code{EPIPE}, as specified for @code{send(2)}. @item @code{libmds_connection_send_unlocked} [(@code{this, const char* restrict message, size_t length, int continue_on_interrupt}) @arrow{} @code{size_t}] @fnindex @code{libmds_connection_send_unlocked} Variant of @code{libmds_connection_send} that does not perform a lock on the connection descriptor. This is not intended for single-threaded programs, rather, it is intended to be used instead of @code{libmds_connection_send} if the thread already holds a lock on the connection descriptor. This function is otherwise identical to @code{libmds_connection_send}, except it has one additional parameter: @code{continue_on_interrupt}, and cannot fail because of failure to call @code{pthread_mutex_lock}. It can however also fail with @code{errno} set to @code{EINTR} if @code{continue_on_interrupt} is zero. The function will continue sending the message if it gets interrupted by a signal only if @code{continue_on_interrupt} is non-zero. @end table @file{} also provides a few macros for use with connection descriptors. For these macros, the @code{this} parameter has the type @code{libmds_connection_initialise* restrict}. @table @asis @item @code{libmds_connection_lock} [(@code{this}) @arrow{} @code{int}] @fnindex @code{libmds_connection_lock} Wrapper for @code{pthread_mutex_lock} that locks @code{this}'s mutex. One difference from the wrapped function, is that rather than returning a value for @code{errno}, it sets @code{errno} and returns zero on success and @code{-1} on failure.@footnote{POSIX threading and reenterant functions has a weird property of returning an error code rather than setting it on @code{errno}, despite that all other C functions sets @code{errno} (provided that they have error codes specified in @file{}.)} @item @code{libmds_connection_trylock} [(@code{this}) @arrow{} @code{int}] @fnindex @code{libmds_connection_trylock} Wrapper for @code{pthread_mutex_trylock} that locks @code{this}'s mutex. One difference from the wrapped function, is that rather than returning a value for @code{errno}, it sets @code{errno} and returns zero on success and @code{-1} on failure. @item @code{libmds_connection_timedlock} [(@code{this, const struct timespec *restrict deadline}) @arrow{} @code{int}] @fnindex @code{libmds_connection_timedlock} Wrapper for @code{pthread_mutex_timedlock} that locks @code{this}'s mutex. One difference from the wrapped function, is that rather than returning a value for @code{errno}, it sets @code{errno} and returns zero on success and @code{-1} on failure. Neither parameter may be @code{NULL}. @item @code{libmds_connection_unlock} [(@code{this}) @arrow{} @code{int}] @fnindex @code{libmds_connection_unlock} Wrapper for @code{pthread_mutex_unlock} that unlocks @code{this}'s mutex. One difference from the wrapped function, is that rather than returning a value for @code{errno}, it sets @code{errno} and returns zero on success and @code{-1} on failure. @item @code{LIBMDS_HEADER_CLIENT_ID} [(@code{this})] @fnindex @code{LIBMDS_HEADER_CLIENT_ID} @fnindex @code{libmds_compose} Macro to be used with @code{libmds_compose}, to add the connection's client ID to a message. @item @code{LIBMDS_HEADER_MESSAGE_ID} [(@code{this})] @fnindex @code{LIBMDS_HEADER_MESSAGE_ID} @fnindex @code{libmds_next_message_id} Macro to be used with @code{libmds_compose}, to add the connection's next message ID to a message. @code{libmds_next_message_id} shall have been called prior to using this macro. @item @code{LIBMDS_HEADERS_STANDARD} [(@code{this})] @fnindex @code{LIBMDS_HEADERS_STANDARD} Macro that can be used in place of using both @code{LIBMDS_HEADER_CLIENT_ID} and @code{LIBMDS_HEADER_MESSAGE_ID}. @end table @file{} includes @file{}, with defines the structure @code{libmds_display_address_t} @{also known as @code{struct libmds_display_address}@}, and the function @code{libmds_parse_display_address}. @tpindex @code{libmds_display_address_t} @tpindex @code{struct libmds_display_address} @code{libmds_display_address_t} holds parsing results from @code{libmds_parse_display_address}. Its members are: @table @asis @item @code{domain} [@code{int}] @vrindex @code{domain}, @code{libmds_display_address_t} @vrindex @code{libmds_display_address_t.domain} The domain (protocol family), that is the first argument for @code{socket(2)}. This is a value whose constant is prefixed @code{PF_}.@footnote{It is common to use @code{AF_}-constants instead, however this practice is not portable.} @code{-1} if not detected. @item @code{type} [@code{int}] @vrindex @code{type}, @code{libmds_display_address_t} @vrindex @code{libmds_display_address_t.type} The socket type, that is the second argument for @code{socket(2)}. This is a value whose constant is prefixed @code{SOCK_}. @code{-1} if not detected. @item @code{protocol} [@code{int}] @vrindex @code{protocol}, @code{libmds_display_address_t} @vrindex @code{libmds_display_address_t.protocol} The protocol, that is the third argument for @code{socket(2)}. This is a value whose constant is affixed @code{PROTO_}. Zero can be used for the default protocol. For example, for stream IP sockets, the protocol can only be TCP, thus zero would indicate @code{IPPROTO_TCP}. @code{-1} if not detected. @item @code{address} [@code{struct sockaddr*}] @vrindex @code{address}, @code{libmds_display_address_t} @vrindex @code{libmds_display_address_t.address} The address. @code{NULL} if not detected. You are responsible for freeing this. @item @code{address_len} [@code{socklen_t}] @vrindex @code{address_len}, @code{libmds_display_address_t} @vrindex @code{libmds_display_address_t.address_len} The allocation size of @code{.address}. This value may be set even if @code{address} is @code{NULL}. @item @code{gai_error} [@code{int}] @vrindex @code{gai_error}, @code{libmds_display_address_t} @vrindex @code{libmds_display_address_t.gai_error} Code for an error that has occured when parsing the address, whose description can be retrieved using @code{gia_strerror}, zero if none. @end table @fnindex @code{libmds_parse_display_address} The function @code{libmds_parse_display_address} is used to parse the a display address string: @table @asis @item @code{libmds_parse_display_address} [(@code{const char* restrict display, libmds_display_address_t* restrict address}) @arrow{} @code{int}] @code{display} should be the address of the display server, formatted as a value for @env{MDS_DISPLAY}. The address of the display will be stored in @code{*address}. Neither parameter may be @code{NULL}. Upon successful completion, zero is returned. On error, @code{-1} is returned and errno is set to indicate the error. Parsing-failure is not considered an error, instead data that could not retrieved from the address string will be set to @code{-1} or @code{NULL}. This function may fail with @code{errno} set to @code{ENOMEM} on memory exhaustion, or @code{ENAMETOOLONG} if the addressed socket's filename is too long. @end table @node Receiving Messages @section Receiving Messages @cpindex Communication foundation @cpindex Messages, receiving @cpindex Messages, inbound @cpindex Receiving messages @cpindex Inbound messages libmdsclient's low-level facilities for receiving messages are found in the header file @file{}. These facilites are thread-safe. The header file defines three structures: @table @asis @item @code{libmds_message_t} @{also known as @code{struct libmds_message}@} @tpindex @code{libmds_message_t} @tpindex @code{struct libmds_message} Messages sent between clients@footnote{Including servers.}, are stored in this format when received. It holds information pointers to the headers and the payload in a message. @item @code{libmds_mspool_t} @{also known as @code{struct libmds_mspool}@} @tpindex @code{libmds_mspool_t} @tpindex @code{struct libmds_mspool} @cpindex Message spools @cpindex Spools, messages @cpindex Communication, multithreaded @cpindex Multithreaded communication @cpindex Threaded communication A queue structured spool of received messages, to be parsed and acted upon by other threads. Although a stack structure would be more efficient, this must be a queue. The reason for this is that it sometimes is important the mesages are parsed in the order they were sent. @item @code{libmds_mpool_t} @{also known as @code{struct libmds_mpool}@} @tpindex @code{libmds_mpool_t} @tpindex @code{struct libmds_mpool} @cpindex Message allocation pools @cpindex Pools, message allocations @cpindex Memory allocation resue @cpindex Reuse of allocations This structures provides an efficient way to reuse allocations of messages, so that the process does not need to perform the costly procedure of allocating memory. This is referred to as an allocation pool. This structures implements a specialision for messages: a message allocation pool, or message pool for short. The pool is stack-based. @end table @tpindex @code{libmds_message_t} @tpindex @code{struct libmds_message} The members of the structure @code{libmds_message_t} are: @table @asis @item @code{headers} [@code{char**}] @vrindex @code{headers}, @code{libmds_message_t} @vrindex @code{libmds_message_t.headers} Array of all headers in the messages, include the @code{Length}-header. The headers are never @code{NULL}, and are unparsed. Unparsed means that the name of the header and its value is stored as one string: the header's name, a colon, a blank space, the header's value, and a NUL byte that terminates the header. This member is @code{NULL} if there are no headers. This member's elements must not be freed, they are subpointers of @code{.buffer}. @item @code{header_count} [@code{size_t}] @vrindex @code{header_count}, @code{libmds_message_t} @vrindex @code{libmds_message_t.header_count} The number of headers, that is, the number of elements in @code{.headers}. @item @code{payload} [@code{char*}] @vrindex @code{payload}, @code{libmds_message_t} @vrindex @code{libmds_message_t.payload} The payload in the message. This member is @code{NULL} if there is no payload in the message. This is a raw memory segment, it is not terminated by a NUL byte. This member must not be freed, it is a subpointer of @code{.buffer}. @item @code{payload_size} [@code{size_t}] @vrindex @code{payload_size}, @code{libmds_message_t} @vrindex @code{libmds_message_t.payload_size} The length of @code{payload}. Zero if there is no payload. This value holds the value of the @code{Length}-header. @item @code{buffer} [@code{char*}] @vrindex @code{buffer}, @code{libmds_message_t} @vrindex @code{libmds_message_t.buffer} Read buffer, for the message. The entire message is stored in this buffer. The member is intended for internal use only. @item @code{buffer_size} [@code{size_t}] @vrindex @code{buffer_size}, @code{libmds_message_t} @vrindex @code{libmds_message_t.buffer_size} The allocation size of @code{.buffer}. The member is intended for internal use only. @item @code{buffer_ptr} [@code{size_t}] @vrindex @code{buffer_ptr}, @code{libmds_message_t} @vrindex @code{libmds_message_t.buffer_ptr} The number of bytes written to @code{.buffer}. The member is intended for internal use only. @item @code{buffer_off} [@code{size_t}] @vrindex @code{buffer_off}, @code{libmds_message_t} @vrindex @code{libmds_message_t.buffer_off} The number of parsed by from @code{.buffer}. The member is intended for internal use only. @item @code{flattened} [@code{size_t}] @vrindex @code{flattened}, @code{libmds_message_t} @vrindex @code{libmds_message_t.flattened} If zero, @code{.headers} and @code{.buffer} pointers that can be freed. Otherwise, @code{.headers} and @code{.buffer} are subpointers of the instance of the structure itself, which means the the object is actually larger than @code{sizeof(libmds_message_t)}, which arrays of such objects must@footnote{Lest you want to make really ugly code.} be arrays of pointer. If this member is non-zero, it specifies the allocation size of the message object. The member is intended for internal use only. @item @code{stage} [@code{int}] @vrindex @code{stage}, @code{libmds_message_t} @vrindex @code{libmds_message_t.stage} Specifies the state of the message parsing. The member is intended for internal use only. @end table @tpindex @code{libmds_mspool_t} @tpindex @code{struct libmds_mspool} The members of the structure @code{libmds_mspool_t} are: @table @asis @item @code{message} [@code{libmds_message_t**}] @vrindex @code{message}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.message} Array of spooled message. The member is intended for internal use only. @item @code{size} [@code{size_t}] @vrindex @code{size}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.size} The number of elements @code{.message} is allocated to hold. The member is intended for internal use only. @item @code{head} [@code{size_t}] @vrindex @code{head}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.head} The index of the next message to be pushed to the queue. The member is intended for internal use only. @item @code{tail} [@code{size_t}] @vrindex @code{tail}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.tail} The index of the next message to be polled from the queue. The member is intended for internal use only. @item @code{spooled_bytes} [@code{size_t}] @vrindex @code{spooled_bytes}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.spooled_bytes} The sum of the sizes of all spooled messages. The member is intended for internal use only. @item @code{spool_limit_bytes} [@code{size_t}] @vrindex @code{spooled_limit_bytes}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.spooled_limit_bytes} The spooler may only spool message when this value is larger than @code{.spooled_bytes}. It is a restriction on the amount of memory can be spooled in form of messages. The spooling function blocks until this limit is not longer reached. It should be noted that the limit can be exceeded by one message, but only if the limit has not already been reached, this is because it would otherwise not be possible to spool messages larger than the limit, causing a deadlock. @item @code{spool_limit_messages} [@code{size_t}] @vrindex @code{spooled_limit_messages}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.spooled_limit_messages} This is similar to @code{.spool_limit_bytes}, but it measures the number of message rather than their size. @item @code{please_post} [@code{int}] @vrindex @code{please_post}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.please_post} The spooling function increases this number by one, if enters an blocked state, and the pooler decreases it when it has signaled the spooler to stop waiting and try again. It counts the number of blocked spoolers. The member is intended for internal use only. @item @code{lock} [@code{sem_t}] @vrindex @code{lock}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.lock} This is a binary semaphore, with 1 as its initial value, that is used to lock the spool when it is being used. It is a non-reenterant mutex. The member is intended for internal use only. @item @code{semaphore} [@code{sem_t}] @vrindex @code{semaphore}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.semaphore} Semaphore used to signal addition of messages. Each time a message is spooled, this semaphore is increased, the polling thread decreases the semaphore before despooling a message, causing it to block when the spool is empty The member is intended for internal use only. @item @code{wait_semaphore} [@code{sem_t}] @vrindex @code{wait_semaphore}, @code{libmds_mspool_t} @vrindex @code{libmds_mspool_t.wait_semaphore} The spooling function acquires this semaphore when the spool is full. When it does so it also increases @code{.please_post}. The poller will post this semaphore if @code{.please_post} is non-zero, causing one blocked spooler to continue when the poller unlocks @code{.lock}, and the decrease it. The member is intended for internal use only. @end table These semaphores, and the one in @code{libmds_mpool_t}, a process-private@footnote{Thread-shared, rather than process-shared, meaning child processes cannot use them.} POSIX semaphores. POSIX semaphores are not as functional as XSI (System V) semaphore arrays, they are however much lighter weight can offers the few functions needed by the library. @tpindex @code{libmds_mpool_t} @tpindex @code{struct libmds_mpool} The members of the structure @code{libmds_mpool_t} are: @table @asis @item @code{messages} [@code{libmds_message_t**}] @vrindex @code{messages}, @code{libmds_mpool_t} @vrindex @code{libmds_mpool_t.messages} Array of allocations stored in the pool The member is intended for internal use only. @item @code{size} [@code{size_t size}] @vrindex @code{size}, @code{libmds_mpool_t} @vrindex @code{libmds_mpool_t.size} The number of allocations the pool can contain. The member is intended for internal use only. @item @code{tip} [@code{volatile size_t}] @vrindex @code{tip}, @code{libmds_mpool_t} @vrindex @code{libmds_mpool_t.tip} The number of available allocations. The member is intended for internal use only. @item @code{lock} [@code{sem_t}] @vrindex @code{lock}, @code{libmds_mpool_t} @vrindex @code{libmds_mpool_t.lock} This is a binary semaphore, with 1 as its initial value, that is used to lock the pool when it is being used. It is a non-reenterant mutex. The member is intended for internal use only. @end table The idea behind these structures is to, per connection, have one thread that reads messages as fast as possible and then delegate the handling of the message, minimising congestion. The feature optimise the performance of the receiving thread a pool use used for allocation of messages to minimise the time the thread spends performing memory allocations, which is costly. @tpindex @code{libmds_message_t} @tpindex @code{struct libmds_message} @code{libmds_message_t} have four associated functions. The parameters @code{this} have the type @code{libmds_message_t* restrict}. @table @asis @item @code{libmds_message_initialise} [(@code{this}) @arrow{} @code{int}] @fnindex @code{libmds_message_initialise} Initialise a @code{libmds_message_t} so it can be used to read messages from a socket. Upon successful completion, zero is returned. On error, @code{-1} is returned and @code{errno} is set to describe the error. This function may fail with @code{errno} set to @code{ENOMEM} if the process cannot allocate enough memory. @item @code{libmds_message_destroy} [(@code{this}) @arrow{} @code{void}] @fnindex @code{libmds_message_destroy} Release all resource in a @code{libmds_message_t}. This is only required if the object was initialised by @code{libmds_message_initialise}. Objects returned by @code{libmds_message_duplicate} or polled from a spool or pool does not need to be destroy with this function. @item @code{libmds_message_duplicate} [(@code{this, libmds_mpool_t* restrict pool}) @arrow{} @code{libmds_message_t*}] @fnindex @code{libmds_message_duplicate} Creates duplicate of a message, and returns it. On error @code{NULL} is returned and @code{errno} is set to describe the error. This function may fail with @code{errno} set to @code{ENOMEM} if the process cannot allocate enough memory. If @code{pool} is not @code{NULL}, the function will try to reuse an allocation from @code{pool} before it creates a new allocation. @item @code{libmds_message_read} [(@code{this, int fd}) @arrow{} @code{int}] @fnindex @code{libmds_message_read} Read the next message from the socket with the file descriptor @code{fd}. Upon successful completion, zero is returned. On error, either @code{-1} or @code{-2} is returned. If @code{-1} is returned, @code{errno} is set to indicate the error. If @code{-2} is returned, a corrupt message has been received and you have no other choice than resetting the connection or exit. This function may fail with @code{errno} set to: @code{ENOMEM} if the process cannot allocate the resources required to store the message; @code{EINTR} if the process was interrupted by a signal, in which case it is safe to simply call the funtion again with the sama arguments; @code{ECONNRESET} if the connection was closed; or any other error specified for @code{recv(3)}. Both @code{this} and @code{fd} must be unique for all threads that uses this function concurrently. Additionally, @code{this} to @code{fd} must be a bijective mapping. @end table @tpindex @code{libmds_mspool_t} @tpindex @code{struct libmds_mspool} @code{libmds_mspool_t} have five associated functions. The parameters @code{this} have the type @code{libmds_mspool_t* restrict}. @table @asis @item @code{libmds_mspool_initialise} [(@code{this}) @arrow{} @code{int}] @fnindex @code{libmds_mspool_initialise} Initialises a message spool. Upon successful completion, zero is returned. On error @code{-1} is returned and @code{errno} is set to describe the error. This function may fail with @code{errno} set to @code{ENOMEM} if the process cannot allocate enough memory. @item @code{libmds_mspool_destroy} [(@code{this}) @arrow{} @code{void}] @fnindex @code{libmds_mspool_destroy} Release all resources stored in a message spool. @item @code{libmds_mspool_spool} [(@code{this, libmds_message_t* restrict message}) @arrow{} @code{int}] @fnindex @code{libmds_mspool_spool} Spool a message. The message must have been returned from @code{libmds_message_duplicate}. Upon successful completion, zero is returned. On error, @code{-1} is returned and @code{errno} is set to describe the error. This function may fail with @code{errno} set to @code{ENOMEM} if the process cannot allocate enough memory, @code{EINTR} if the call was interrupted by a signal, in which case it is safe to simply recall the function with the same arguments. @item @code{libmds_mspool_poll} [(@code{this}) @arrow{} @code{libmds_message_t*}] @fnindex @code{libmds_mspool_poll} Fetch the next message from a message spool. Upon successful completion a message is returned, on error @code{NULL} is returned and @code{errno} is set to describe the errror. If the spool is empty, the function will wait until a message is added. This function may fail with @code{errno} set to @code{EINTR} if the call was interrupted by a signal, in which case it is safe to simply recall the function with the same argument. @item @code{libmds_mspool_poll_try} [(@code{this, const struct timespec* restrict deadline}) @arrow{} @code{libmds_message_t*}] @fnindex @code{libmds_mspool_poll_try} This function is similar to @code{libmds_mspool_poll}. However, if @code{deadline} is @code{NULL} the funtion will return immediately if the spool is empty, and set @code{errno} to @code{EAGAIN}. If the spool is empty, but @code{deadline} is not @code{NULL}, the function will wait until a message is added, but if the timepoint specified by @code{deadline} is passed without a message being added, the function will return and set @code{errno} to @code{ETIMEDOUT}. The function may also fail with @code{errno} to @code{EINTR} as described for @code{libmds_mspool_poll}, and with @code{errno} to @code{EINVAL} if @code{deadline->tv_necs} is less than zero or is equal to or greater than a milliard. @code{deadline} shall be specified in an absolute time measured with the @code{CLOCK_REALTIME} clock. @end table @tpindex @code{libmds_mpool_t} @tpindex @code{struct libmds_mpool} @code{libmds_mpool_t} have four associated functions. The parameters @code{this} have the type @code{libmds_mpool_t* restrict}. @table @asis @item @code{libmds_mpool_initialise} [(@code{this, size_t size}) @arrow{} @code{int}] Initialise a pool of reusable message allocations. The pool will be able to hold @code{size} allocations. Upon successful completion, zero is returned. On error, @code{-1} is returned and @code{errno} is set to describe the error. This function may fail with @code{errno} set to @code{ENOMEM} if the process cannot allocate enough memory. @item @code{libmds_mpool_destroy} [(@code{this}) @arrow{} @code{void}] Release all resources stored in a message allocation pool. @item @code{libmds_mpool_offer} [(@code{this, libmds_message_t* restrict message}) @arrow{} @code{int}] Adds a message allocation to a pool. The message must have been returned from @code{libmds_message_duplicate}, @code{libmds_mspool_poll} or @code{libmds_mspool_poll_try}. If the pool is full, the function will free the allocation, and return with a success status. Upon successful completion, zero is returned. On error @code{-1} is returned and @code{errno} is set to describe the error. @item @code{libmds_mpool_poll} [(@code{this}) @arrow{} @code{libmds_message_t*}] Fetches a message allocation from a pool. If the pool is empty, @code{NULL} is returned and @code{errno} is set to zero. On error @code{NULL} is returned and @code{errno} is set describe teh error, the value of @code{errno} will not be zero in this case. @end table @node libmdslltk @chapter libmdslltk @cpindex Toolkits, library @cpindex Library, toolkits libmdslltk is a planned library. It provides low-level toolkit functionallity to facilitate development of @code{mds} toolkits. @node Keyboard Codes @chapter Keyboard Codes @cpindex Scancodes Keyboard servers receive scancodes from keyboard drivers. A scancode can either be comprised of one byte or three bytes. In each byte, the most significant bit (assuming unsigned bytes) is ignore, however for it first byte in the scancode it signifies whether the key was released: it is set of the key is released, and not set if the key was pressed or is being held down. A scancode is comprised of three bytes if the lower 7-bits of the first byte is are all cleared, and the highest bit in the two following bytes are set. @cpindex Keycodes Ignoring the most significant bit in all bytes, the keycode is the value of the byte if the scancode is a single byte scancode. If the scancode is comprised of three bytes, the first byte is ignored and the keycode is @math{a \cdot 128 + b} where @math{a} is the value of the second byte and @math{b} is the value of the third byte. @menu * 105-keys Keycodes:: List of keycodes for 105-keys keyboards. @end menu @node 105-keys Keycodes @section 105-keys Keycodes This is a list of keyboards for the 105-keys keyboards, using QWERTY-layout for reference. @table @asis @item @code{1} @key{Escape} key @item @code{2}--@code{11} Keys: @key{1}, @key{2}, @key{3}, @key{4}, @key{5}, @key{6}, @key{7}, @key{8}, @key{9}, @key{0} @item @code{12} Key right of @key{0}. @item @code{13} Key left of @key{Backspace} @item @code{14} @key{Backspace} key @item @code{15} @key{Tab} key @item @code{16}--@code{25} Keys: @key{q}, @key{w}, @key{e}, @key{r}, @key{t}, @key{y}, @key{u}, @key{i}, @key{o}, @key{p} @item @code{26} Key right of @key{p}, once removed @item @code{27} Key right of @key{p}, twice removed @item @code{28} @key{Return} key @item @code{29} Left @key{Control} key @item @code{30}--@code{38} Keys: @key{a}, @key{s}, @key{d}, @key{f}, @key{g}, @key{h}, @key{j}, @key{k}, @key{l} @item @code{39} Key right of @key{l}, once removed @item @code{40} Key right of @key{l}, twice removed @item @code{41} Key left of @key{1} @item @code{42} Left @key{Shift} key @item @code{43} Key right of @key{l}, three times removed @item @code{44}--@code{50} Keys: @key{z}, @key{x}, @key{c}, @key{v}, @key{b}, @key{n}, @key{m} @item @code{51} Key right of @key{m}, once removed @item @code{52} Key right of @key{m}, twice removed @item @code{53} Key right of @key{m}, three times removed @item @code{54} Right @key{Shift} key @item @code{55} @key{Multiply} key on the keypad @item @code{56} @key{Alternative} key @item @code{57} @key{Space} key @item @code{58} @key{Caps Lock} key @item @code{59}--@code{68} Keys: @key{F1} through @key{F10} @item @code{69} @key{Num Lock} key @item @code{70} @key{Scroll Lock} key @item @code{71}--@code{73} @key{7}, @key{8}, @key{9} keys on the keypad @item @code{74} @key{Minus} key on the keypad @item @code{75}--@code{77} @key{4}, @key{5}, @key{6} keys on the keypad @item @code{78} @key{Plus} key on the keypad @item @code{79}--@code{82} @key{1}, @key{2}, @key{3}, @key{0} keys on the keypad @item @code{83} @key{Comma} key on the keypad @item @code{86} Key left of @key{z} @item @code{87} @key{F11} key @item @code{88} @key{F12} key @item @code{96} @key{Return} key on the keypad @item @code{97} Right @key{control} key @item @code{98} @key{Divide} key on the keypad @item @code{99} @key{System Request}/@key{Print Screen} key @item @code{100} @key{Alternative Graphic} key @item @code{102} @key{Home} key @item @code{103} @key{Up} arrow key @item @code{104} @key{Page up} key @item @code{105} @key{Left} arrow key @item @code{106} @key{Right} arrow key @item @code{107} @key{End} key @item @code{108} @key{Down} arrow key @item @code{109} @key{Page down} down @item @code{110} @key{Insert} key @item @code{111} @key{Delete} key @item @code{119} @key{Pause}/@key{Break} key @item @code{125} Left @key{Super} key @item @code{126} Right @key{Super} key @item @code{127} @key{Application Menu} key @end table @node Keyboard Layouts @chapter Keyboard Layouts @cpindex Keyboard layouts, files @cpindex Keyboard layouts, compile @cpindex Compiling keyboard layouts @fnindex @command{mds-kbdc} Keyboard layouts are compiled from one or more files. When compiling a layout from multiple files, it is important that the files are specified in the correct order. The general rule is that the layout file, for example the Swedish QWERTY-keyboard, is specified first and is followed by add-ons such as the compose table and layout modifiers. @command{mds-kbdc} is used to compile layouts. Installed keyboard layout files are located in @file{/usr/share/mds/keyboard}.@footnote{If you are hacking in the source tree, you will find this under @file{res/keyboard}.} Layouts are located in the subdirectory @file{layout}, modifiers are located in the subdirectory @file{mods} and compose tables are located in the subdirectory @file{compose}. @command{mds-kbdc} prefixes @file{/usr/share/mds/keyboard} unless the specifed files starts with @file{/}, @file{./} or @file{../}. Dead keys are implemented by compose tables and not in the layouts. @menu * Keyboard Layout Syntax:: How to write your how layouts. * Builtin Functions:: Functions provided by the compiler. @end menu @node Keyboard Layout Syntax @section Keyboard Layout Syntax @cpindex Keyboard layout, files, syntax @cpindex Syntax of keyboard layout file Similar to the C programming language, keyboard layout files are parsed from the top down. This means that any function or macro can only be used from lines below the definition of said callable. However, the order of the mapping statements themself, in respect to each other, does not matter. Additionally, the layout files are parsed line by line, and leading whitespace is ignored. Comment can be started with a #-character and end at the end of the line. It is important to know that modifiers like @key{Shift} and @key{Control} needs to be mapped from a keycode, this and similar that many keyboards have in common, except dead key composition and compose sequences, is already available in the @file{layout/common} directory and can be included from the layout file. Compositions are implement in the @file{compose} directory and should be selected by the user at compile-time. Keyboard layout files must be written in UTF-8 (without UTF-8 BOM) and with line feeds for new lines. @menu * Mapping Statements:: Mapping keycodes to logical keys and text. * Sequence Mapping:: Implementing dead keys and compositions. * Keyboard Layout Identification:: Specifing the layout language, country and variant. * Layout Assumptions:: Making assumption about the keyboard layout. * Include Statement:: Including base files. * Layout Macros and Functions:: Reducing repetition. * Escaping:: Backslashes have so many uses. @end menu @node Mapping Statements @subsection Mapping Statements The most fundamental part of the layout files are mapping statements. These specify which keycode the keys have and what happens when certain keys pressed, combined or pressed and a sequence. If we want to map keycode 57 to the space key we write @example : @end example but then we also want the space key to product a blank space when we are writting so we add @example : " " @end example giving us @example @group : : " " @end group @end example Because the order of the mapping statements does not matter we can just as well write @example @group : " " : @end group @end example @code{" "} represents a text string with one blank space, but it is possible to have multiple characters. If we want to extend this to @kbd{altgr+space} producing a no-break space, we can add either of the lines @example @group : "\u00A0" # no-break space (# comment) : "\u00A0" # no-break space @end group @end example However, we also need a mapping to @kbd{altgr}: @example : @end example If we want to add a mapping to @kbd{ultra} from @kbd{altgr+menu} we can write @example @group : : <-altgr ultra> @end group @end example @code{-altgr} means that @kbd{altgr} should not be reported as held down. @cpindex Lock keys @cpindex Keys, lock As can be seen in these examples it is not possible to distinguish between modifiers and keys. It is up to the keyboard layout server and keyboard layout compiler to know this. However, it is defined in the keyboard layout files whether modifiers keys are lock keys or not. To map the keycode 58 to @kbd{caps lock}, write @example : @end example But if you do not want it be a lock key, but instead be required to be held down, similar to how is normal for @key{Shift}, instead write @example : @end example Any modifier may be a lock key. Another, just as important, use of mappings to is map letter keys. Unlike @key{Control} keys like @key{Space} and @key{Shift}, there are no predefined letters@footnote{With letters with mean any character other than space.}. Therefore the letter is prefixed with the word `letter'. For example: @ifset AFOURPAPER_OR_USLETTER @example : # The Q-key has keycode 16 (on QWERTY) : "q" # The Q-key should produce a `q' : "Q" # but `Q' when shift is used : "Q" # or when caps is used : "q" # but not when both are used @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER @example # The Q-key has keycode 16 (on QWERTY) : # The Q-key should produce a `q' : "q" # but `Q' when shift is used : "Q" # or when caps is used : "Q" # but not when both are used : "q" @end example @end ifclear Special characters like simple double quotes, backspace and, in @code{<>}-notation, greater than sign must be escaped with a prepending backslash. @cpindex Dead keys @cpindex Compose key @cpindex Modifier keys @cpindex Keys, dead @cpindex Keys, compose @cpindex Keys, modifiers Many keyboard layouts also have dead keys. Dead keys are keys that affect the next key-press. For example, `´' followed by `e' may product `é'. @kbd{compose} may be a dead key, just like it is in X.org, but it can also be a modifer. To define @kbd{´}, with keycode 13, @kbd{compose}, with keycode 125, as a dead keys write @example @group : : @end group @end example @cpindex Duplicate keys @cpindex Keys, duplicates Some may appear on multiple locations on the keyboard, for example, there may be a left and a right @key{Shift} key, and a normal @key{Return} key and one on the keypad: @example : : : : @end example @cpindex Arrow keys @cpindex Keys, arrows Because @code{} and @code{} are valid keys --- they are arrow keys --- it is important to place them directly before the key, and not after. For instance @code{} denotes the left @key{Shift} key, whilst @code{} denotes the @key{Left} arrow key with a @key{Shift} key held down. Modifiers goes first. @cpindex Void mapping, keys @cpindex Mapping, void, keys @cpindex Key mapping, void @cpindex Inferred key mapping @cpindex Inferred mapping, keys @cpindex Key mapping, inferred @cpindex Mapping, inferred, keys Mapping to @code{} can be used to suppress an inferred mapping. For example, @example : @end example removes all actions from the normal @key{Return} key when @key{Num} is active. Note well, this cannot be used to remove an explicit mapping. Explicit mappings may not conflict. @node Sequence Mapping @subsection Sequence Mapping @cpindex Dead keys @cpindex Compose key @cpindex Keys, dead @cpindex Keys, compose @cpindex Compose tables @cpindex Key sequences @cpindex Sequence, keys Compose tables use mapping statements to map key sequences. For example the compose key followed by two `s':es makes an `ß': @example "s" "s" : "ß" @end example It is also possible to map a sequence to another sequence: @example : @end example Of course, the input does not need to be a sequence: @example : @end example An alternative to @key{Compose} as a dead key, is @key{Compose} as a modifier. If you use this, the compose table need to be written for just that. There two ways do this this. Either you can write for example @example : "ß" @end example This maps two `s':es to a `ß', but requires that @key{Compose} is held down during both key-presses. The other way is to write @example : "ß" # Note the `,' @end example This also requires that @kbd{compose} is not released between the key-presses. The compose table is filled with compositions where it does not matter in which order you press some of the keys. For example, instead of @example @group "S" "|" : "$" "|" "S" : "$" @end group @end example you can write @example ("S" "|") : "$" @end example @cpindex Key subsequences, unordered @cpindex Subsequence, unordered, keys @cpindex Unordered subsequence, keys @cpindex Alternation, keys @cpindex Key alternations @code{( )} denotes an unordered subsequence. You can also use @code{[ ]} for alternation. For example, instead of @example @group ("S" "|") : "$" ("s" "|") : "$" @end group @end example you can write @example (["S" "s"] "|") : "$" @end example Inside an alternation you can use a dot for specify that no key press is needed. For example, instead of @example @group "|" "S" : "$" "|" "|" "S" : "$" @end group @end example you can write @example "|" ["|" .] "S" : "$" @end example It is undefined in which order alternations and unordered subsequences are expanded; neither sequencewise or levelwise. Thus, there should not be side-effects where either one is used, nor does it make since to nest the two constructs in any other way than alternation or unordered subsequence inside unordered subsequence. The compiler may however choose to discourage unordered subsequence inside unordered subsequence because of readability issues. Unordered subsequences longer than 5 elements cannot compile under normal circumstances. Eliminiation of unordered subsequences grows superexponentially, and thus is probably an error than can cause memory exhaustion and unrealistic compilation-time. Therefore, if an unordered subsequences longer than 5 elements is used the compiler required that the @option{--force} flag is used and that the unordered subsequences uses double brackets: @ifset AFOURPAPER_OR_USLETTER @example ("1" "2" "3" "4" "5") : "120" (("1" "2" "3" "4" "5" "6")) : "720" (("1" "2" "3" "4" "5" "6" "7")) : "5040" (("1" "2" "3" "4" "5" "6" "7" "8")) : "40320" (("1" "2" "3" "4" "5" "6" "7" "8" "9")) : "362880" @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER @ifset SMALLBOOK_WITH_SMALLFONT @example ("1" "2" "3" "4" "5") : "120" (("1" "2" "3" "4" "5" "6")) : "720" (("1" "2" "3" "4" "5" "6" "7")) : "5040" (("1" "2" "3" "4" "5" "6" "7" "8")) : "40320" @end example @end ifset @ifclear SMALLBOOK_WITH_SMALLFONT @example @group ("1" "2" "3" "4" "5") : "120" (("1" "2" "3" "4" "5" "6")) : "720" (("1" "2" "3" "4" "5" "6" "7")) : "5040" @end group @end example @end ifclear @end ifclear @node Keyboard Layout Identification @subsection Keyboard Layout Identification @cpindex Keyboard layout identification @cpindex Identification of keyboard layouts Whilst it is possible to write a comment that states what keyboard layout a file implements, there is a standardise way to do this in code. The intention with this is to make it possible for graphical tools to easily list the layouts and easy to understand descriptions. There are three things a keyboard layout file should specify: the language, the country where it is used, and the variant. For example the Swedish QWERTY layout used in Sweden would have the code. @example information language "Swedish" country "Sweden" variant "QWERTY" end information @end example @cpindex Keyboard layout country @cpindex Keyboard layout language @cpindex Keyboard layout variant @cpindex Country, keyboard layout @cpindex Language, keyboard layout @cpindex Variant, keyboard layout If the layout is used multiple countries, or even for multiple lanuages, @code{country} and @code{language} may be specified on multiple lines. For example: @example information language "Spanish" country "Argentina" country "Bolivia, Plurinational State of" country "Chile" country "Colombia" country "Costa Rica" country "Cuba" country "Dominican Republic" country "Ecuador" country "El Salvador" country "Guatemala" country "Haiti" country "Honduras" country "Mexico" country "Nicaragua" country "Panama" country "Paraguay" country "Peru" country "Puerto Rico" country "Uruguay" country "Venezuela, Bolivarian Republic of" variant "Latin American, QWERTY" end information @end example or @example information language "Norwegian" language "Bokmål" language "Nynorsk" country "Norway" variant "QWERTY" end information @end example @node Layout Assumptions @subsection Layout Assumptions @cpindex Keyboard layout, file inclusion @cpindex File inclusion, keyboard layout @cpindex Inclusion of file, keyboard layout When writing generic compose tables it can be helpful to let the compiler assume that a certain set of keys will be provided by the layout file and not making other assumptions. This is helpful because if you want to make an compose table that can compose all characters given only the ASCII letters, modifiers and a compose key, rather than written a phony layout file and select it each time you compile to compose table you can state in the compose table file that the compiler should as that those keys are provided when the compose table file is compile by itself. If this is done, the compiler can warn when one of the compositions cannot be reached from those basic keys. If we want to make the compiler assume that @key{compose} is available as a dead key, that @key{shift}, @key{altgr} and @key{space} are available and that the ASCII letters, digits and some basic special characters are available we can write. @example assumption have have have have have_range "0" "9" have_range "a" "z" have_range "A" "Z" have_chars "!\"@@#$%&/@{([)]=@}?\\^~*'<>|,;.:-_" end assumption @end example @node Include Statement @subsection Include Statement @cpindex Keyboard layout, file inclusion @cpindex File inclusion, keyboard layout @cpindex Inclusion of file, keyboard layout Writing layout files from scratch is probably something you want to avoid. For instance you would we need to create mappings for `A' to `Z' and `0' to `9' (assuming its a latin-based language), and map up all specific key, like modifiers, space, arrow keys, and the keypad. And you would have to make sure do only that the keys are mapped but that they are mapped to the text the should product and that they word correcly with the modifiers. These are things most keyboards have in common with many other layouts. For instance @file{layout/sv/qwerty} has two include statements to implement its basics: @example @group include "../common/qwerty" include "../common/base" @end group @end example @node Layout Macros and Functions @subsection Layout Macros and Functions @cpindex Keyboard layout, macros @cpindex Macros, keyboard layout There is a lot of repetitive work in layouts, for instance all letters need mapping for any combination of use of @key{shift} and @key{compose}. To reduce this, you can define macros. For example instead of writing @example : "a" : "A" : "A" : "a" : "b" : "B" : "B" : "b" # and so on ... @end example you can use a macro and write @example macro letter/2 : "\1" : "\2" : "\2" : "\1" end macro letter("a" "A") letter("b" "B") # and so on ... @end example The name of this macro is @code{letter/2}, but it is called with the name @code{letter} and two arguments. The @code{/2}-suffix means that it is invoked with exactly two arguments. You can use this do define multiple version of the same macro, with the same invocation name but with different number of arguments. For example: @example macro letter/2 : "\1" : "\2" : "\2" : "\1" end macro macro letter/1 letter(\1 \add(\sub(\1 "a") "A")) end macro letter("a") letter("b") # and so on ... letter("å" "Å") letter("ä" "Ä") letter("ö" "Ö") @end example @code{\add( )} and @code{\sub( )} are calls to two built-in functions named @code{add/2} and @code{sub/2}. @cpindex Alternation, keys @cpindex Key alternations Alternation can be used to invoke a macro: @ifset AFOURPAPER_OR_USLETTER_OR_SMALLFONT @example @group letter(["a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m"]) letter(["n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"]) @end group @end example @end ifset @ifclear AFOURPAPER_OR_USLETTER_OR_SMALLFONT @example @group letter(["a" "b" "c" "d" "e" "f" "g" "h" "i" "j"]) letter(["k" "l" "m" "n" "o" "p" "q" "r" "s" "t"]) letter(["u" "v" "w" "x" "y" "z"]) @end group @end example @end ifclear @cpindex Alternation, keys @cpindex Key alternations You may use @code{.} in an alternation, in that case macro is called once with the argument, causing it to invoke for example @code{letter/0} instead of @code{letter/1}. A related issue are for-loops. If we for example want to call the macro @code{letter/1} for all letters between and including `a' and `z' we can just write @example @group for "a" to "z" as \1 letter(\1) end for @end group @end example instead of using the alternation-trick. You call also use if-statments. For example @example for "à" to "þ" as \1 # times sign is not upper case of division sign if \not(\equals(\1 "\u00F7")) letter(\1 \add(\sub(\1 "à") "À")) end if end for @end example or equivalently @example for "à" to "þ" as \1 if \equals(\1 "\u00F7") continue # times sign is not upper case of division sign end if letter(\1 \add(\sub(\1 "à") "À")) end for @end example @code{continue} can be used to stop the iteration of the innermost for-loop and skip to the next iteration. You can also use @code{break}, but it also has the effect to stop the entire loop. Similarly, @code{return} can be used to break an entire macro call, or function call. You can also use @code{if} for more example things, and use @code{else if} and @code{else if}: @example macro latter/1 if \not(\greater(\1 "z")) letter(\1 \add(\sub(\1 "a") "A")) else if \not(\greater(\1 "þ")) letter(\1 \add(\sub(\1 "à") "À")) else letter(\1 \sub(\1 1)) end if end macro @end example Note that there is no quotes around the `a' in @code{letter(\1 \sub(\1 1))}. This means that the argument will be than value 1 rather than the code point of the character `1'. Note however that values lower than zero or equals to or greater than 2 to the power of 31 not allowed and can either cause compile-time error or erroneous compiled files. @cpindex Keyboard layout, macros @cpindex Macros, keyboard layout Functions are similar to function macros, the difference is that a function is called inline and is prefixed with slash, and rather than inline the code inside it, the evalutes to the last value it evaluted before it returned. For example instead of @code{\not(\greater(\1 "z"))} you can write @code{\less_eq(\1 "z")} after you have defined the function @code{less_eq/2} with the following code: @example @group function less_eq/2 \not(\greater(\1 \2)) end function @end group @end example A final construct to make layout code less repetitive is @code{let}-statements. This can be used to assign values to variables. The code @example macro latter/1 if \not(\greater(\1 "z")) letter(\1 \add(\sub(\1 "a") "A")) else if \not(\greater(\1 "þ")) letter(\1 \add(\sub(\1 "à") "À")) else letter(\1 \sub(\1 1)) end if end macro @end example can equivalently be written using @code{let} as @example macro latter/1 if \not(\greater(\1 "z")) let \2 : \sub("a" "A") else if \not(\greater(\1 "þ")) let \2 : \sub("à" "À") else let \2 : 1 end if letter(\1 \sub(\1 \2)) end macro @end example It is also possible to declare arrays: @example let \1 : @{ "å" "ä" "ö" "à" "é" "ü" @} @end example Arrays may however not have arrays for values. Because arrays can be very large, they, but only them, may span multiple lines. For example you may write @example @group let \1 : @{ "å" "ä" "ö" "à" "é" "ü" @} @end group @end example but not @example @group let \1 : @{ "å" "ä" "ö" "à" "é" "ü" @} @end group @end example See @ref{Builtin Functions} for how they are used. Variable names can only be numerical and most not start with a zero. `0' is not valid variable name, and thus @code{\0} does not address a variable. Macro and function names, may only include `0'--`9', `a'--`z', `A'--`Z' and `_', but must and not start with `0'--`9'. Additionally, when declared macro and function names must be suffixed with `/' follwed by the exact number of arguments the macro or function takes. Variable indices are constrained to the 31:th power of 2, exclusively. Attempts to use higher variable indices invoke undefined behaviour. Additionally there is no guarantee that the compiler allocates indexwise spares variables efficiently. Like variables, the size of arrays are also restricted to the 31:th power of 2. @node Escaping @subsection Escaping @cpindex Keyboard layout, escaping special character @cpindex Keyboard layout, special character, escaping @cpindex Escaping special character, keyboard layout @cpindex Special character, escaping, keyboard layout Similar to most, if not all, programming language, a backslash inside quotes can be used to parse the next character with special meaning. For instance, `\"' is parsed as a literal `"', and `\\' is parsed as a literal `\'. `\>' is too parsed as a literal `>', for example you may need to write @code{>}. The characters `(', `)', `[', `]', `@{', `@}', `<' and `,' also follow this rule to make those character accesible inside a @code{< >}. But `\' can also be used to specify characters by their code point, for example if you want an `æ' you can write @code{"\u00E6"} or @code{"\uE6"}, instead of @code{"æ"}. You can also write @code{"\0346"}, the difference between @code{\0} and @code{\u} is that @code{\0} uses octal whereas @code{\u} uses hexadecimal. A noteworthy side-effect of this is that function names cannot start with a lower case `u'. `\' can also be used to access variables and parameters. For example @code{\1} in @example macro letter/2 : "\1" : "\2" : "\2" : "\1" end macro letter("å" "Å") @end example is expanded to an `å', where as @code{\2} is expanded to an `Å'. `\' is also used to call functions, for example if you want to call the function @code{f/0} you write @code{\f()}. Because numerical (possibly prefixed with an `u') are of variable length, it is possible to specify the escape's termination point with a dot. For instance, if you want the value of the first variable (@code{\1}) followed by two zeroes, you do not write @code{\100} as that would expand to the value of the hundredth variable. Instead you write @code{\1.00}. Use of function calls and variables inside @code{include}-statments invokes undefined behaviour. Escaped numerals greater than or equal to the 31th power of 2 also invoke undefined behaviour. @node Builtin Functions @section Builtin Functions @cpindex Keyboard layout, functions, builtin @cpindex Keyboard layout, builtin functions @cpindex Functions, builtin, keyboard layout @cpindex Builtin functions, keyboard layout To help you write meaningful functions in your keyboard layout files, the compiler defines an almost minimal set of basic functions: @table @code @item add/2 @fnindex @code{add/2} The code points in @code{\1} plus the code points of the corresponding characters in @code{\2}. If @code{\1} and @code{\2} are not of the same length, the returned string will be of the length of the longer of the parameters, and modulo is used to map to the corresponing character. @item sub/2 @fnindex @code{sub/2} Like @code{add/2} but subtraction. @item mul/2 @fnindex @code{mul/2} Like @code{add/2} but multiplication. @item div/2 @fnindex @code{div/2} Like @code{add/2} but division. @item mod/2 @fnindex @code{mod/2} Like @code{add/2} but modulo. @item rsh/2 @fnindex @code{rsh/2} Like @code{add/2} but rightward bitwise shift. If a character in @code{\2} is has a code point greater than 30, undefined behaviour is invoked. @item lsh/2 @fnindex @code{lsh/2} Like @code{add/2} but leftward bitwise shift. If a character in @code{\2} is has a code point greater than 30, undefined behaviour is invoked. @item or/2 @fnindex @code{or/2} Like @code{add/2} but bitwise OR@. @item and/2 @fnindex @code{and/2} Like @code{add/2} but bitwise AND@. @item xor/2 @fnindex @code{xor/2} Like @code{add/2} but bitwise XOR@. @item not/1 @fnindex @code{not/1} For each character in @code{\1}, evaluate to zero if the character is not zero, and one if the character is zero. @item equals/2 @fnindex @code{equals/2} For each character, evalute to one if the characters in @code{\1} and @code{\2} are equal and zero otherwise. @item greater/2 @fnindex @code{greater/2} Like @code{equals/2} but @code{\1} greater than @code{\2} rather than @code{\1} equals @code{\2}. @item less/2 @fnindex @code{less/2} Like @code{equals/2} but @code{\1} less than @code{\2} rather than @code{\1} equals @code{\2}. @item set/3 @fnindex @code{set/3} Set the element with index @code{\2}, in the array with variable index @code{\1}, to @code{\3}, and return @code{\3}. For example @code{\set(1 0 4)} sets the first element in @code{\1} to 4. @item get/2 @fnindex @code{get/2} Return the element with index @code{\2} in the array with variable index @code{\1}. For example after @code{\set(1 0 4)} or @code{let \1 : @{ 4 3 2 1 0 @}} has been used, @code{\get(1 0)} evaluates to 4. @end table @node Default Keyboard Layouts @chapter Default Keyboard Layouts @cpindex Compose tables The chapter is about the special keyboard layouts and compose tables included with @command{mds}. @menu * Dead Compose Table:: The compose table for the dead compose key. @end menu @node Dead Compose Table @section Dead Compose Table @cpindex Dead keys @cpindex Compose key @cpindex Keys, dead @cpindex Keys, compose This section describes the structure for the mappings used in the compose table for the dead key version of the compose key. @menu @c * Aegean Numbers:: Aegean Numbers. @c * Alchemical Symbols:: Alchemical Symbols. @c * Alphabetic Presentation Forms:: Alphabetic Presentation Forms. @c * Ancient Greek Musical Notation:: Ancient Greek Musical Notation. @c * Ancient Greek Numbers:: Ancient Greek Numbers. @c * Ancient Symbols:: Ancient Symbols. @c * Arabic:: Arabic. @c * Arabic Extended-A:: Arabic Extended-A@. @c * Arabic Mathematical Alphabetic Symbols:: Arabic Mathematical Alphabetic Symbols. @c * Arabic Presentation Forms-A:: Arabic Presentation Forms-A@. @c * Arabic Presentation Forms-B:: Arabic Presentation Forms-B@. @c * Arabic Supplement:: Arabic Supplement. @c * Armenian:: Armenian. * Arrows:: Arrows. @c * Avestan:: Avestan. @c * Balinese:: Balinese. @c * Bamum:: Bamum. @c * Bamum Supplement:: Bamum Supplement. * Basic Latin:: Basic Latin. @c * Bassa Vah:: Bassa Vah. @c * Batak:: Batak. @c * Bengali:: Bengali. * Block Elements:: Block Elements. @c * Bopomofo:: Bopomofo. @c * Bopomofo Extended:: Bopomofo Extended. * Box Drawing:: Box Drawing. * Braille Patterns:: Braille Patterns. @c * Brahmi:: Brahmi. @c * Buginese:: Buginese. @c * Buhid:: Buhid. @c * Byzantine Musical Symbols:: Byzantine Musical Symbols. @c * C0 Controls:: C0 Controls. @c * C1 Controls:: C1 Controls. @c * Carian:: Carian. @c * Caucasian Albanian:: Caucasian Albanian. @c * Chakma:: Chakma. @c * Cham:: Cham. @c * Cherokee:: Cherokee. @c * CJK Compatibility:: CJK Compatibility. @c * CJK Compatibility Forms:: CJK Compatibility Forms. @c * CJK Compatibility Ideographs:: CJK Compatibility Ideographs. @c * CJK Compatibility Ideographs Supplement:: CJK Compatibility Ideographs Supplement. @c * CJK Radicals Supplement:: CJK Radicals Supplement. @c * CJK Strokes:: CJK Strokes. @c * CJK Symbols and Punctuation:: CJK Symbols and Punctuation. @c * CJK Unified Ideographs:: CJK Unified Ideographs. @c * CJK Unified Ideographs Extension A:: CJK Unified Ideographs Extension A@. @c * CJK Unified Ideographs Extension B:: CJK Unified Ideographs Extension B@. @c * CJK Unified Ideographs Extension C:: CJK Unified Ideographs Extension C@. @c * CJK Unified Ideographs Extension D:: CJK Unified Ideographs Extension D@. @c * Combining Diacritical Marks:: Combining Diacritical Marks. @c * Combining Diacritical Marks Extended:: Combining Diacritical Marks Extended. @c * Combining Diacritical Marks for Symbols:: Combining Diacritical Marks for Symbols. @c * Combining Diacritical Marks Supplement:: Combining Diacritical Marks Supplement. @c * Combining Half Marks:: Combining Half Marks. @c * Common Indic Number Forms:: Common Indic Number Forms. @c * Control Pictures:: Control Pictures. @c * Coptic:: Coptic. @c * Coptic Epact Numbers:: Coptic Epact Numbers. @c * Counting Rod Numerals:: Counting Rod Numerals. @c * Cuneiform:: Cuneiform. @c * Cuneiform Numbers and Punctuation:: Cuneiform Numbers and Punctuation. @c * Currency Symbols:: Currency Symbols. @c * Cypriot Syllabary:: Cypriot Syllabary. @c * Cyrillic:: Cyrillic. @c * Cyrillic Extended-A:: Cyrillic Extended-A@. @c * Cyrillic Extended-B:: Cyrillic Extended-B@. @c * Cyrillic Supplement:: Cyrillic Supplement. @c * Deseret:: Deseret. @c * Devanagari:: Devanagari. @c * Devanagari Extended:: Devanagari Extended. @c * Dingbats:: Dingbats. * Domino Tiles:: Domino Tiles. @c * Duployan:: Duployan. @c * Egyptian Hieroglyphs:: Egyptian Hieroglyphs. @c * Elbasan:: Elbasan. @c * Emoticons:: Emoticons. * Enclosed Alphanumeric Supplement:: Enclosed Alphanumeric Supplement. @c * Enclosed Ideographic Supplement:: Enclosed Ideographic Supplement. * Enclosed Alphanumerics:: Enclosed Alphanumerics. @c * Enclosed CJK Letters and Months:: Enclosed CJK Letters and Months. @c * Ethiopic:: Ethiopic. @c * Ethiopic Extended:: Ethiopic Extended. @c * Ethiopic Extended-A:: Ethiopic Extended-A@. @c * Ethiopic Supplement:: Ethiopic Supplement. * General Punctuation:: General Punctuation. * Geometric Shapes:: Geometric Shapes. * Geometric Shapes Extended:: Geometric Shapes Extended. @c * Georgian:: Georgian. @c * Georgian Supplement:: Georgian Supplement. @c * Glagolitic:: Glagolitic. @c * Gothic:: Gothic. @c * Grantha:: Grantha. @c * Greek and Coptic:: Greek and Coptic. @c * Greek Extended:: Greek Extended. @c * Gujarati:: Gujarati. @c * Gurmukhi:: Gurmukhi. @c * Halfwidth and Fullwidth Forms:: Halfwidth and Fullwidth Forms. @c * Hangul Compatibility Jamo:: Hangul Compatibility Jamo. @c * Hangul Jamo:: Hangul Jamo. @c * Hangul Jamo Extended-A:: Hangul Jamo Extended-A@. @c * Hangul Jamo Extended-B:: Hangul Jamo Extended-B@. @c * Hangul Syllables:: Hangul Syllables. @c * Hanunoo:: Hanunoo. @c * Hebrew:: Hebrew. @c * Hiragana:: Hiragana. @c * Ideographic Description Characters:: Ideographic Description Characters. @c * Imperial Aramaic:: Imperial Aramaic. @c * Inscriptional Parthian:: Inscriptional Parthian. @c * Inscriptional Pahlavi:: Inscriptional Pahlavi. * IPA Extensions:: IPA Extensions. @c * Javanese:: Javanese. @c * Kaithi:: Kaithi. @c * Kana Supplement:: Kana Supplement. @c * Kangxi Radicals:: Kangxi Radicals. @c * Kannada:: Kannada. @c * Katakana:: Katakana. @c * Katakana Phonetic Extensions:: Katakana Phonetic Extensions. @c * Kanbun:: Kanbun. @c * Kayah Li:: Kayah Li. @c * Kharoshthi:: Kharoshthi. @c * Khmer:: Khmer. @c * Khmer Symbols:: Khmer Symbols. @c * Khojki:: Khojki. @c * Khudawadi:: Khudawadi. @c * Lao:: Lao. @c * Latin Extended Additional:: Latin Extended Additional. * Latin Extended-A:: Latin Extended-A@. * Latin Extended-B:: Latin Extended-B@. * Latin Extended-C:: Latin Extended-C@. @c * Latin Extended-D:: Latin Extended-D@. @c * Latin Extended-E:: Latin Extended-E@. * Latin-1 Supplement:: Latin-1 Supplement. @c * Lepcha:: Lepcha. @c * Letterlike Symbols:: Letterlike Symbols. @c * Limbu:: Limbu. @c * Linear A:: Linear A@. @c * Linear B Ideograms:: Linear B Ideograms. @c * Linear B Syllabary:: Linear B Syllabary. @c * Lisu:: Lisu. @c * Lycian:: Lycian. @c * Lydian:: Lydian. @c * Mahajani:: Mahajani. * Mahjong Tiles:: Mahjong Tiles. @c * Malayalam:: Malayalam. @c * Mandaic:: Mandaic. @c * Manichaean:: Manichaean. @c * Mathematical Alphanumeric Symbols:: Mathematical Alphanumeric Symbols. * Mathematical Operators:: Mathematical Operators. @c * Meetei Mayek:: Meetei Mayek. @c * Meetei Mayek Extensions:: Meetei Mayek Extensions. @c * Mende Kikakui:: Mende Kikakui. @c * Meroitic Cursive:: Meroitic Cursive. @c * Meroitic Hieroglyphs:: Meroitic Hieroglyphs. @c * Miao:: Miao. * Miscellaneous Mathematical Symbols-A:: Miscellaneous Mathematical Symbols-A@. * Miscellaneous Mathematical Symbols-B:: Miscellaneous Mathematical Symbols-B@. @c * Miscellaneous Symbols:: Miscellaneous Symbols. * Miscellaneous Symbols and Arrows:: Miscellaneous Symbols and Arrows. @c * Miscellaneous Symbols and Pictographs:: Miscellaneous Symbols and Pictographs. @c * Miscellaneous Technical:: Miscellaneous Technical. @c * Modi:: Modi. @c * Modifier Tone Letters:: Modifier Tone Letters. @c * Mongolian:: Mongolian. @c * Mro:: Mro. @c * Musical Symbols:: Musical Symbols. @c * Myanmar:: Myanmar. @c * Myanmar Extended-A:: Myanmar Extended-A@. @c * Myanmar Extended-B:: Myanmar Extended-B@. @c * Nabataean:: Nabataean. @c * New Tai Lue:: New Tai Lue. @c * NKo:: NKo. * Number Forms:: Number Forms. @c * Ogham:: Ogham. @c * Ol Chiki:: Ol Chiki. @c * Old North Arabian:: Old North Arabian. @c * Old Italic:: Old Italic. @c * Old Permic:: Old Permic. @c * Old Persian:: Old Persian. @c * Old South Arabian:: Old South Arabian. @c * Old Turkic:: Old Turkic. @c * Optical Character Recognition:: Optical Character Recognition. @c * Osmanya:: Osmanya. @c * Ornamental Dingbats:: Ornamental Dingbats. @c * Oriya:: Oriya. @c * Palmyrene:: Palmyrene. @c * Pahawh Hmong:: Pahawh Hmong. @c * Pau Cin Hau:: Pau Cin Hau. @c * Phaistos Disc:: Phaistos Disc. @c * Phags-pa:: Phags-pa. @c * Phoenician:: Phoenician. @c * Phonetic Extensions:: Phonetic Extensions. @c * Phonetic Extensions Supplement:: Phonetic Extensions Supplement. * Playing Cards:: Playing Cards. @c * Psalter Pahlavi:: Psalter Pahlavi. @c * Rejang:: Rejang. @c * Rumi Numeral Symbols:: Rumi Numeral Symbols. @c * Runic:: Runic. @c * Samaritan:: Samaritan. @c * Saurashtra:: Saurashtra. @c * Sharada:: Sharada. @c * Shavian:: Shavian. @c * Shorthand Format Controls:: Shorthand Format Controls. @c * Siddham:: Siddham. @c * Sinhala:: Sinhala. @c * Sinhala Archaic Numbers:: Sinhala Archaic Numbers. @c * Small Form Variants:: Small Form Variants. @c * Sora Sompeng:: Sora Sompeng. @c * Spacing Modifier Letters:: Spacing Modifier Letters. @c * Specials:: Specials. @c * Sundanese:: Sundanese. @c * Sundanese Supplement:: Sundanese Supplement. * Superscripts and Subscripts:: Superscripts and Subscripts. * Supplemental Arrows-A:: Supplemental Arrows-A@. * Supplemental Arrows-B:: Supplemental Arrows-B@. * Supplemental Arrows-C:: Supplemental Arrows-C@. * Supplemental Mathematical Operators:: Supplemental Mathematical Operators. @c * Syloti Nagri:: Syloti Nagri. @c * Syriac:: Syriac. * Tags:: Tags. @c * Tagalog:: Tagalog. @c * Tagbanwa:: Tagbanwa. @c * Tamil:: Tamil. @c * Tai Le:: Tai Le. @c * Tai Tham:: Tai Tham. @c * Tai Viet:: Tai Viet. @c * Tai Xuan Jing Symbols:: Tai Xuan Jing Symbols. @c * Takri:: Takri. @c * Telugu:: Telugu. @c * Thaana:: Thaana. @c * Thai:: Thai. @c * Tibetan:: Tibetan. @c * Tifinagh:: Tifinagh. @c * Tirhuta:: Tirhuta. @c * Transport and Map Symbols:: Transport and Map Symbols. @c * Unified Canadian Aboriginal Syllabics:: Unified Canadian Aboriginal Syllabics. @c * Unified Canadian Aboriginal Syllabics Extended:: Unified Canadian Aboriginal Syllabics Extended. @c * Ugaritic:: Ugaritic. @c * Vai:: Vai. * Variation Selectors:: Variation Selectors and Variation Selectors Supplement. @c * Vertical Forms:: Vertical Forms. @c * Vedic Extensions:: Vedic Extensions. @c * Warang Citi:: Warang Citi. @c * Yi Radicals:: Yi Radicals. @c * Yi Syllables:: Yi Syllables. @c * Yijing Hexagram Symbols:: Yijing Hexagram Symbols. @end menu @node Arrows @subsection Arrows @ubindex Arrows 970 @node Basic Latin @subsection Basic Latin @ubindex Basic Latin @ubindex Latin, Basic 125 @node Block Elements @subsection Block Elements @ubindex Block Elements 1648 @node Box Drawing @subsection Box Drawing @ubindex Box Drawing Most of the box drawing glyphs can be composed by typing @kbd{} followed by two glyphs that should be combined to form the desired glyphs. If the two glyphs are identical the glyph becomes heavy. More general, common parts of the glyphs become heavy. Glyphs that contain a heavy part be transformed so that the heavy parts become double stroked. Glyphs that do not contain heavy parts be transformed so the entire glyphs becomes double stroked. This is done by typing @kbd{} followed by, in any order, @kbd{"+"} and the glyph to modify. Note that this is not possible for all glyphs, as not all glyphs have a double stroked variant, but all double stroked glyphs can be composed this way. The horizontal and the vertical light glyphs, as well as the combination of the two, can be made double stroked by typing @kbd{} followed by, in any order, @kbd{"="} and the glyph. The light corners can be made rounded by by typing @kbd{} followed by, in any order, @kbd{"o"} and the glyph or @kbd{"O"} and the glyph. The sequences @kbd{ "-" "|"} and @kbd{ "|" "-"} can be used to create a light horizontal line crossed with a light vertical line. Basic box drawing glyphs are created with sequences starting either with @kbd{ "b"} or @kbd{ "B"}. The former creates light glyphs, and the latter creates heavy glyphs. Note that glyphs with diagonal lines do not have an heavy variants. The base sequences are followed by a sequence describing the glyphs to compose. @table @kbd @item "-" Horizontal line. @item "|" Vertical line. @item "+" Horizontal line combined with vertical line. @item "/" Diagonal upper right to lower left. @item "\" Diagonal upper left to lower right. @item "X" Diagonal cross. @item "<" Left part of a horizontal line. @item "^" Upper part of a vertical line. @item ">" Right part of a horizontal line. @item "v" Lower part of a vertical line. @end table Simple arrows can be used instead of @kbd{"<"}, @kbd{"^"}, @kbd{">"} and @kbd{"v"}. @kbd{"-"}, @kbd{"|"} can be prefixed with a key to modify the lines. @table @kbd @item "=" Double stroke. This modifier is also available for @kbd{"+"}. @item "." Triple dash. @item ":" Quadruple dash. @end table Double dashed horizonal line is composed with @kbd{ "b" "." "."} for the light variant and @kbd{ "B" "." "."} for the heavy. variant. @kbd{"." ":"}, or a broken pipe, instead of @kbd{"." "."} can be used to create a double dashed vertical line. @node Braille Patterns @subsection Braille Patterns @ubindex Braille Patterns The sequence @kbd{ "b" } can be used to create a blank braille pattern. A single-dot braille pattern can be composed with @kbd{ "b"} followed by a digit key between @kbd{"1"} and @kbd{"8"}, representing the index of the dot. A dual-dot braille pattern can be composed with @kbd{ "B"} followed by two digit keys between @kbd{"1"} and @kbd{"8"}, representing the indices of the dots. More complex braille patterns are composed by overlaying two braille patterns. This is done by typing @kbd{} followed by the two braille patterns to overlay. If the two braille patterns are identical, the braille pattern will be overlays with its mirror pattern. @node Domino Tiles @subsection Domino Tiles @ubindex Domino Tiles @c TODO compose tiles together There are two types of domino tile glyphs: horizontal and vertical. Each tile has two halfs with 0 to 6 dots. Additonally there is one horizontal tile, and one vertical tile, with the back facing the user. Horizontal tiles are composed with @kbd{ "d" "t" "-"} followed by the number of dots on the left side and the number of dots on the right side. Horizontal tile with the back facing the user is composed with either @kbd{"-"} or @kbd{} instead of the two digits. Vertical tiles are composed with @kbd{ "d" "t" "|"} followed by the number of dots on the top and the number of dots on the bottom. Vertical tile with the back facing the user is composed with either @kbd{"|"} or @kbd{} instead of the two digits. @node Enclosed Alphanumeric Supplement @subsection Enclosed Alphanumeric Supplement @ubindex Enclosed Alphanumeric Supplement 1476 @node Enclosed Alphanumerics @subsection Enclosed Alphanumerics @ubindex Enclosed Alphanumerics 3133 @node General Punctuation @subsection General Punctuation @ubindex General Punctuation @ubindex Punctuation, General 730 @node Geometric Shapes @subsection Geometric Shapes @ubindex Geometric Shapes 1687 @node Geometric Shapes Extended @subsection Geometric Shapes Extended @ubindex Geometric Shapes Extended 3194 @node IPA Extensions @subsection IPA Extensions @ubindex IPA Extensions 568 @node Latin Extended-A @subsection Latin Extended-A @ubindex Latin Extended-A 236 @node Latin Extended-B @subsection Latin Extended-B @ubindex Latin Extended-B 364 @node Latin Extended-C @subsection Latin Extended-C @ubindex Latin Extended-C 2834 @node Latin-1 Supplement @subsection Latin-1 Supplement @ubindex Latin-1 Supplement 136 @node Mahjong Tiles @subsection Mahjong Tiles @ubindex Mahjong Tiles Unnumbered mahjong tiles are composed with @kbd{ "m" "t"} followed by one additional key: @table @kbd @item < West tile @item v South tile @item > East tile @item ^ North tile @item r Red dragon tile @item g Green dragon tile @item w White dragon tile @item m Plum (mei) tile @item l Orchid (lan) tile @item z Bamboo (zhu) tile @item j Chrysanthemum (ju) tile @item 1 Spring tile @item 2 Summer tile @item 3 Autumn tile @item 4 Winter tile @item * Joker tile @item / The back of a mahjong tile @end table The numbered tiles are composed with @kbd{ "m" "t"} followed by with additional keys: one for the suit, and one for the value. The value is is encoded with either @kbd{"1"} to @kbd{"9"}. The suits is encoded @table @kbd @item W Characters (wan) @item T Bamboos (tiao) @item B Circles (bing) @end table @node Mathematical Operators @subsection Mathematical Operators @ubindex Mathematical Operators 1118 @node Miscellaneous Mathematical Symbols-A @subsection Miscellaneous Mathematical Symbols-A @ubindex Miscellaneous Mathematical Symbols-A @ubindex Mathematical Symbols-A, Miscellaneous 1824 @node Miscellaneous Mathematical Symbols-B @subsection Miscellaneous Mathematical Symbols-B @ubindex Miscellaneous Mathematical Symbols-B @ubindex Mathematical Symbols-B, Miscellaneous 2119 @node Miscellaneous Symbols and Arrows @subsection Miscellaneous Symbols and Arrows @ubindex Miscellaneous Symbols and Arrows @ubindex Symbols and Arrows, Miscellaneous @ubindex Arrows, Miscellaneous Symbols and 2594 @node Number Forms @subsection Number Forms @ubindex Number Forms 889 @node Playing Cards @subsection Playing Cards @ubindex Playing Cards @kbd{ "p" "c"} composes the character presenting the back of a playing card. Jokers and trumps are composed using the playing card back and two additional characters. @table @asis @item joker, red @kbd{ "j" "r"} @item joker, white @kbd{ "j" "w"} @item joker, black @kbd{ "j" "b"} @end table The red joker can be composed with the sequence @kbd{ "p" "c" "j" "r"}, becuase @kbd{} can be composed with the sequence @kbd{ "p" "c"}. The trumps are number 1 through 21, and are composed with @kbd{ "1" } through @kbd{ "2" "1"}. Additionally, the fool card is composed with through @kbd{ "0" }. The Playing Cards block in Unicode also contains ace, 2--10, jack, knight, queen och king for the suits spades/swords, hearts/cups, diamonds/pentacles and clubs/wands. These are composed with the @kbd{} followed by, in any order, the suit and value. The values are encoded @table @asis @item Ace @kbd{"A"}, @kbd{"a"} or @kbd{"1"} @item 2--9 @kbd{"2"} through @kbd{"9"} @item 10 @kbd{"0"} @item Jack @kbd{"J"} or @kbd{"j"} @item Knight @kbd{"C"} or @kbd{"c"} @item Queen @kbd{"Q"} or @kbd{"q"} @item King @kbd{"K"} or @kbd{"k"} @end table and the suits are encoded @table @asis @item Spades or Swords Black or white spades symbol @item Hearts or Cups Black or white hearts symbol @item Diamonds or Pentacles Black or white diamonds symbol @item Clubs or Wands Black or white clubs symbol @end table @node Superscripts and Subscripts @subsection Superscripts and Subscripts @ubindex Superscripts and Subscripts @ubindex Subscripts, Superscripts and 840 @node Supplemental Arrows-A @subsection Supplemental Arrows-A @ubindex Supplemental Arrows-A @ubindex Arrows-A, Supplemental 1900 @node Supplemental Arrows-B @subsection Supplemental Arrows-B @ubindex Supplemental Arrows-B @ubindex Arrows-B, Supplemental 1973 @node Supplemental Arrows-C @subsection Supplemental Arrows-C @ubindex Supplemental Arrows-C @ubindex Arrows-C, Supplemental 3284 @node Supplemental Mathematical Operators @subsection Supplemental Mathematical Operators @ubindex Supplemental Mathematical Operators @ubindex Mathematical Operators, Supplemental 2286 @node Tags @subsection Tags @ubindex Tags The ``Tags'' block in Unicode has been deprecated. Characters in this block is therefore not mapped in the compose table. @node Variation Selectors @subsection Variation Selectors @ubindex Variation Selectors @ubindex Variation Selectors Supplement @c TODO Variation Selectors, Variation Selectors Supplement There are 256 variation selectors, numbered 1 through 256. These can be composed with the sequence @kbd{ "v" "s"} followed by exactly three digits. These digits should form the index of the variation selector. Indices lower than 100, require leading @kbd{"0"}:s. Alternatively, variation selectors with an index lower than 100, can be composed with a trailing @kbd{} instead of leading @kbd{"0"}:s. @node Accessibility @chapter Accessibility @menu * Sticky Keys:: Ephemeral key-locking. * Bounce Keys:: Key repetition-elimination. * Slow Keys:: Key press-acceptance delay. * Loud Keys:: Keyboard tiggered sound cues. * Mouse Keys:: Controlling the mouse with the keyboard. @end menu @c TODO vector grapics compatible magnifier @node Sticky Keys @section Sticky Keys @pgindex @command{mds-keystick} @cpindex Sticky keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard Sticky keys is an accessibility feature that lets the user process modifier keys instead of holding them down. Sticky keys is implemented by the @command{mds-keystick} server. When @command{mds-keystick} is active, any key that is mapped in @command{mds-keystick} to be a modifier is held down once press and not released until an non-modifier is released. It is possible for map any key to have this feature, that do not have to be actual modifiers, that is, modifiers according to @command{mds-keytrans}. If a key is press three times without any intermediate keys, and is a modifier, that key released until it is pressed again. Note that @command{mds-keystick} is not aware of which keys are considered modifiers by @command{mds-keytrans}, but it is affected of remappings in @command{mds-kbd} and @command{mds-kkbd}, therefore it is better to swap, for example, @kbd{control} and @kbd{caps lock} in the keyboard servers than in @command{mds-keytrans}. Doing so means that you do not have to configure @command{mds-keystick} to know the original @kbd{caps lock} is a modifier but the original @kbd{control} is not. @cpindex Mode lock key @cpindex Keys, mode lock For greater accessibility you can, in @command{mds-keytrans}, replace a key with the @kbd{mode lock}-key. If this is done, pressing a sequence of modifiers and then the @kbd{mode lock}-key will caused those modifiers to be locked until the next time you press @kbd{mode lock}. Any modifier pressed directly before, optionally with intermediate modifiers, the second @kbd{mode lock} will stay locked. The action of @kbd{mode lock} is to release all modifiers it is locked and the lock those that are currently held down; active stickly keys are artificially held down and thus included. @node Bounce Keys @section Bounce Keys @pgindex @command{mds-keybounce} @cpindex Bounce keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard Bounce keys is an accessibility feature that filters out rapidly repeated key strokes. Bounce keys is implemented by the @command{mds-keybounce} server. @node Slow Keys @section Slow Keys @pgindex @command{mds-slowkey} @cpindex Slow keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard Slow keys is an accessibility feature that filters out brief key strokes. Slow keys is implemented by the @command{mds-slowkey} server. @node Loud Keys @section Loud Keys @pgindex @command{mds-keycue} @cpindex Loud keys @cpindex Keyboard, accessibility @cpindex Accessibility, keyboard Loud keys is an accessibility feature that can emulate key clicking sounds when a key is pressed or generate tones when certain keys are pressed. For example if @kbd{caps lock} is actived by a key stroke a high-pitched tone can be generated when when it is deactived by a key stroke a low-pitched tone can be generated. Loud keys is implemented by the @command{mds-keycue} server. @node Mouse Keys @section Mouse Keys @pgindex @command{mds-kbd2rat} @cpindex Keyboard to rat bindings @cpindex Rat keys @cpindex Mouse keys Rat keys (also known as mouse keys) is an accessibility and usability feature that lets the user use the keyboard as a pointing device. This feature is implemented by the @command{mds-kbd2rat} server, and this section covers the details of that server. If @command{mds-kbd2rat} is used, the keypad acts as a pointing device when @kbd{num lock} is not active. It is also possible to configure @command{mds-kbd2rat} to disregard @kbd{num lock} and always be active, until it receives a signal to toggle its state. For example, if @command{mds-kbd2rat} is configured to disregard @kbd{num lock}, @command{mds-kbdtrans} can be configured to send to fauxkey @kbd{rat} when @kbd{alt+shift+num} is pressed, and this key can be caught by @command{mds-keybind} that sends a signal to @command{mds-kbd2rat} to toggle. When @command{mds-kbd2rat} is active, it maps the keypad to the rat according to the following table: @table @kbd @item division Right-hand left (primary) rat button. @item multiplication Middle (modifier) rat button. @item subtraction Right-hand (alternate) right rat button. @item addition Scroll up. @item return Scroll down. @item comma Cancel actions waiting by @kbd{0} and @kbd{5}. @item 0 Hold down the next selected rat button until that rat button is selected again. This is a dead key, that is, you do not have to hold it down. @item 1 Cursor left down. @item 2 Cursor down. @item 3 Cursor right down. @item 4 Cursor left. @item 5 Double click with the next selected rat button. This is a dead key, that is, you do not have to hold it down. If pressed twice, a triple click triggered instead, and so on. If this key is prefixed by @kbd{0}, the last click will be replaced by hold down action. @item 6 Cursor right. @item 7 Cursor left up. @item 8 Cursor up. @item 9 Cursor right up. @end table This table is not affected by mappings in @command{mds-keytrans}, but it is affected by remappings in @command{mds-kbd} and @command{mds-kkbd}. @command{mds-kbd2rat} can be configured to permute the rat button keys. It is independent of permutations in @command{mds-rat}. If multiple direction keys@footnote{@kbd{1}, @kbd{2}, @kbd{3}, @kbd{3}, @kbd{4}, @kbd{6}, @kbd{7}, @kbd{8} and @kbd{9}} are used, the average direction is used. @command{mds-kbd2rat} is five parameters that control with which speed it moves the cursor: @table @asis @item delay The delay it takes before the first time a mouse event is repeated when a key is held down. The default is for the server to wait for the keyboard to send another key press. @item interval The time it takes before a mouse event is repeated since its previous repear when a key is held down. The default is for the server to wait for the keyboard to send another key press. @item max speed The maximum speed with which the cursor can move. @item time to max speed The time a key has to be held down before the maximum speed is reached. The cursor accelerate with each mouse event repeat. @item curve Ramp used to reach pointer speed. @end table The pointer's speed, not taking caps into consideration, is calculated by @iftex @math{max~speed \left ( hold~down~time ~-~ delay \over time~to~max~speed \right)^{1 ~+~ curve}} @end iftex @ifnottex max speed ((hold down time - delay) / time to max speed)^(1 + curve) @end ifnottex @node Specifications @chapter Specifications @menu * Rat Cursors:: Rat cursor specifications. * Colour Names:: Recommended colour names. * Nesting Applications:: Specifications for nesting applications. * The Real Display Server:: Identifying the real display server. @end menu @node Rat Cursors @section Rat Cursors @cpindex Cursor, specifications @cpindex Rat cursor, specifications @cpindex Mouse cursor, specifications @pgindex @command{mds-cursorshadow} @cpindex Cursor shadow @cpindex Rat cursor shadow @cpindex Mouse cursor shadow @cpindex Shadow, cursor Rat cursor themes should not add shadows to the cursors. Shadows are added by the @command{mds-cursorshadow} server according to the user's specifications. @command{mds}'s rat cursors specifications are based on @url{http://www.freedesktop.org/wiki/Specifications/cursor-spec}. All rat cursor themes should include the cursors listed below. The icons are conceptual examples of how they can look. @cpindex Cursor animation @cpindex Rat cursor animation @cpindex Mouse cursor animation @cpindex Animation, cursors In addition to the cursors below, each of the may be accompanied with @code{X-press}, @code{X-hold} and @code{X-release}, where @code{X} is the name of the master icon. @code{X-press} is an animation from @code{X} to @code{X-hold} and is used when the cursor should transition from @code{X} to @code{X-hold}. @code{X-hold} is the version of @code{X} that should be used if any rat button is held down. @code{X-release} is an animation from @code{X-hold} to @code{X} and is used when the cursor should transition from @code{X-hold} to @code{X}@. Clients should not set the cursor to either of them, it is up to the server to do this based on events from the rat device. @ifset AFIVEPAPER @page @end ifset @table @code @item default This is the default cursor. It is used as a fallback if no more fitting cursor is found; for example if a programs wants the cursor to be @command{pointer}, but the server is unable to find it, it will fallback to @command{default}. The server should provide its own fallback in case the theme is missing this cursor too. This cursor indicates that the interface is idle and prepared to accept commands from the user. This cursor is usually a north-west- or north-north-west-pointing arrow. For left-handed themes this cursor is usually a north-east- or north-north-east-pointing arrow. @example @group ## #### ###### ######## ########## ############ ############## ################ ################## ############ ###### #### #### ###### ## #### ###### #### #### @end group @end example @page @item context-menu @cpindex Menus, context menus @cpindex Context menus This cursor indicates the same state as @command{default} with he addition that the object beneath it can be right-clicked (left-clicked if left-handed) to open a context menu. This cursor is typically @command{default} combined with a small menu. @example @group ## ############ #### ############ ###### ## ## ######## ############ ########## ## ## ############ ############ ############## ## ## ################ ############ ################## ############ ###### #### #### ###### ## #### ###### #### #### @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER @page @end ifset @item text @cpindex Text, horizontal @cpindex Horizontal text This cursor should be used when the rat pointers is above an horizontal text that can be selected and possibly edited. This cursor is usually a vertical I-beam. @example @group ############## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ############## @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @item vertical-text @cpindex Text, vertical @cpindex Vertical text @cpindex Text, rotated @cpindex Rotated text This cursor should be used when the rat pointers is above an vertical text that can be selected and possibly edited. If this cursor is missing, @code{text} should be used as the first fallback. This cursor is usually a horizontal I-beam. @example @group ## ## ## ## ## ## ################################ ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item progress @cpindex Wait cursor @cpindex Progress cursor This cursor indicates that the interface can be used as when @command{default} is used. But that the program is working in the background with command the user previously issued. This cursor is usually rendered as a combination of @command{default} and @command{wait}. @example @group ## ############ #### ############ ###### ######## ######## #### ########## #### ############ ######## ############## ############ ################ ############ ################## ############ ###### #### #### ###### ## #### ###### #### #### @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @item wait @cpindex Wait cursor @cpindex Progress cursor This cursor indicates that the interface cannot be used because it is working or is blocked by an external resource. This cursor is typically rendered as a hourglass, watch, sundial or some sort of animated ring. @example @group #################### #################### ################ ############ ######## #### #### #### #### #### #### ######## ############ ################ #################### #################### @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifset @item pointer @cpindex Clickable @cpindex Links This cursor indicates that the object beneath it is clickable. Typically a link in a Web browser. However, it should not be used for pushbuttons and other user interface elements where it is apparent by design that the object is clickable. This cursor is usually a right hand (left hand if left-handed) pointing with the index-finger. @example @group #### #### #### #### #### #### #### #### #### ## #### #### #### #### ###### ################ #### ############################## ############################ ########################## ########################## ######################## ######################## #################### ################ @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @item help @cpindex Help mode This cursor indicates that the interface is in context help mode. This is usually activated by clicking an help button --- which usally has a question mark on it --- on the titlebar. This cursor is typically renderas as @code{default} with a question mark next to it. @example @group ## ###### #### ########## ###### #### #### ######## #### ########## #### ############ #### ############## #### ################ #### ################## ############ #### ###### #### #### #### ###### ## #### ###### #### #### @end group @end example @vskip 0pt plus 1filll @item drag @cpindex Drag-and-drop This cursor indicates that an object is being dragged. This cursor is usually a closed right hand, or closed left hand if left-handed. @example @group #### #### #### ################ #### ############################ ############################ ############################ ########################## ######################## ######################## #################### ################ @end group @end example @vskip 0pt plus 1filll @page @item copy @cpindex Drag-and-drop, copy @cpindex Copy, drag-and-drop This cursor indicates that the dragged object will be copied or listed upon release. If this cursor is missing, @code{drag} should be used as the first fallback. This cursor is usually rendered as @code{drag} with a plus-sign next to it. @example @group ## ## ########## ## ## #### #### #### ################ #### ############################ ############################ ############################ ########################## ######################## ######################## #################### ################ @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER @page @end ifset @item move @cpindex Drag-and-drop, move @cpindex Move, drag-and-drop This cursor indicates that the dragged object will be moved upon release, or otherwise acted upon. If this cursor is missing, @code{drag} should be used as the first fallback. This cursor is usually rendered as @code{drag} with an arrow next to it. The arrow is usually point north-east, or north-west if left-handed. @example @group ###### #### ## ## ## ## #### #### #### ################ #### ############################ ############################ ############################ ########################## ######################## ######################## #################### ################ @end group @end example @vskip 0pt plus 1filll @page @item alias @cpindex Drag-and-drop, link @cpindex Link, drag-and-drop @cpindex Drag-and-drop, alias @cpindex Alias, drag-and-drop This cursor indicates that the dragged object will be aliased upon release, or otherwise acted upon. This may entail creating a symlink. If this cursor is missing, @code{drag} should be used as the first fallback. This cursor is usually rendered as @code{drag} with an two or three linked links next to it, or an arced arrow. @example @group #### #### ## ## ## ######## ## ## ## #### #### #### #### #### ################ #### ############################ ############################ ############################ ########################## ######################## ######################## #################### ################ @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER @ifclear SMALLBOOK_WITH_SMALLFONT @ifclear USLETTER_WITH_SMALLFONT @page @end ifclear @end ifclear @end ifclear @item no-drop @cpindex Drag-and-drop This cursor indicates that the dragged object cannot be release where the rat pointer is located, but that the object beneath it usually allow drops of objects with similar class to the dragged object. If this cursor is missing, @code{not-allowed} should be used as the first fallback, and @code{drag} should be used as the second fallback. This cursor is typically rendered as a combination of @code{drag} and @code{not-allowed}. @example @group ######## ## #### ## ## ## ## ## ## #### ## ######## #### #### #### ################ #### ############################ ############################ ############################ ########################## ######################## ######################## #################### ################ @end group @end example @vskip 0pt plus 1filll @page @item not-allowed @cpindex Invalid @cpindex Not allowed This cursor indicates that the region beneath the rat pointer is invalid for the current operation. This cursor is often rendered as a circle with a diagonal line through it. @example @group ######## #### #### ## ## ## #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ## ## ## #### #### ######## @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER @page @end ifset @item all-scroll @cpindex Scrolling This cursor is used to indicate that moving the rat will also move the object beneath below the cursor This cursor is often rendered as a combined vertical and horizontal twin-headed arrow. @example @group ## ###### ########## ## ## ## ## ## #### ## #### ############################## #### ## #### ## ## ## ## ## ########## ###### ## @end group @end example @vskip 0pt plus 1filll @ifclear AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifclear @item up-arrow @cpindex Insertion point This cursor is typically used to identify an insertion point. It is often rendered an upwards-pointing arrow. @example @group ## ###### ########## ############## ###### ###### ###### ###### ###### ###### ###### @end group @end example @vskip 0pt plus 1filll @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item cell @cpindex Spread-sheets @cpindex Cell selection @cpindex Tables, selection This cursor is often used in spread-sheet applications when selecting cells. It is typically rendered as a thick plus-sign. @example @group ###### ###### ###### ###### ###### ########################## ########################## ########################## ###### ###### ###### ###### ###### @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @item col-resize @cpindex Tables, resize @cpindex Columns, resize @cpindex Resize table columns This cursor is used to indicate that the cursor is within a region that allows it rat to be used to resize a column. If this cursor is missing, @code{ew-resize} should be used as the first fallback, and @code{ew-select} should be used as the second fallback. This cursor is typically rendered as a vertical bar with an arrow from the left side pointing horizontally towards it and an arrow from the right side pointing horizontally towards it. @example @group ## ## ## ## ## ## ## ## #### ## #### ############ ## ############ #### ## #### ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER @ifclear USLETTER_WITH_SMALLFONT @page @end ifclear @end ifclear @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item row-resize @cpindex Tables, resize @cpindex Rows, resize @cpindex Resize table rows This cursor is used to indicate that the cursor is within a region that allows it rat to be used to resize a column. If this cursor is missing, @code{ns-resize} should be used as the first fallback, and @code{ns-select} should be used as the second fallback. This cursor is typically rendered as a horizontal bar with an arrow from the left side pointing vertically towards it and an arrow from the right side pointing vertically towards it. @example @group ## ## ## ########## ###### ## ############################## ## ###### ########## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear USLETTER @ifclear SMALLBOOK_WITH_SMALLFONT @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @end ifclear @ifset USLETTER_WITH_SMALLFONT @page @end ifset @item crosshair @cpindex Drawing @cpindex Precision drawing @cpindex Crosshair cursor This cursor is used for precision drawing or precision manipulation of an area. This cursor typically a thin crosshair. @example @group ## ## ## ## ## ## ## ############################## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @item w-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{w-select} should be used as the first fallback, @code{ew-resize} should be used as the second fallback, @code{ew-select} should be used as the third fallback, and @code{col-resize}. should be used as the fourth fallback. This cursor is typically rendered as a west-pointing arrow, optionally with a wall at the arrowhead. @example @group ## ## ## ## ## ## ## ############################ ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item w-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{w-resize} should be used as the first fallback, @code{ew-select} should be used as the second fallback, @code{ew-resize} should be used as the third fallback, and @code{col-resize}. should be used as the fourth fallback. This cursor is typically rendered as a west-pointing arrow. @example @group ## ## ## ############################ ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear AFIVEPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @ifset USLETTER_WITH_SMALLFONT @page @end ifset @item e-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{e-select} should be used as the first fallback, @code{ew-resize} should be used as the second fallback, @code{ew-select} should be used as the third fallback, and @code{col-resize}. should be used as the fourth fallback. This cursor is typically rendered as a east-pointing arrow, optionally with a wall at the arrowhead. @example @group ## ## ## ## ## ## ############################ ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @ifclear USLETTER_WITH_SMALLFONT @page @end ifclear @end ifset @item e-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{e-resize} should be used as the first fallback, @code{ew-select} should be used as the second fallback, @code{ew-resize} should be used as the third fallback, and @code{col-resize}. should be used as the fourth fallback. This cursor is typically rendered as a east-pointing arrow. @example @group ## ## ## ############################ ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset SMALLBOOK @ifclear SMALLFONT @page @end ifclear @end ifset @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item n-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{n-select} should be used as the first fallback, @code{ns-resize} should be used as the second fallback, @code{ns-select} should be used as the third fallback, and @code{row-resize}. should be used as the fourth fallback. This cursor is typically rendered as a north-pointing arrow, optionally with a wall at the arrowhead. @example @group ############## ## ###### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLBOOK @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @ifset SMALLBOOK_WITH_SMALLFONT @page @end ifset @item n-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{n-resize} should be used as the first fallback, @code{ns-select} should be used as the second fallback, @code{ns-resize} should be used as the third fallback, and @code{row-resize}. should be used as the fourth fallback. This cursor is typically rendered as a north-pointing arrow. @example @group ## ###### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear AFOURPAPER_OR_USLETTER_OR_SMALLBOOK_WITH_SMALLFONT @page @end ifclear @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item s-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{s-select} should be used as the first fallback, @code{ns-resize} should be used as the second fallback, @code{ns-select} should be used as the third fallback, and @code{row-resize}. should be used as the fourth fallback. This cursor is typically rendered as a south-pointing arrow, optionally with a wall at the arrowhead. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ###### ## ############## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLBOOK @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @item s-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{s-resize} should be used as the first fallback, @code{ns-select} should be used as the second fallback, @code{ns-resize} should be used as the third fallback, and @code{row-resize}. should be used as the fourth fallback. This cursor is typically rendered as a south-pointing arrow. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ###### ## @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifset @item nw-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{nw-select} should be used as the first fallback, @code{nwse-resize} should be used as the second fallback, @code{nwse-select} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a north-west-pointing arrow, optionally with a corner at the arrowhead. @example @group ################## ## ## ## ############ ## #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLBOOK @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @item nw-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{nw-resize} should be used as the first fallback, @code{nwse-select} should be used as the second fallback, @code{nwse-resize} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a north-west-pointing arrow. @example @group ############ #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifset @item se-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{se-select} should be used as the first fallback, @code{nwse-resize} should be used as the second fallback, @code{nwse-select} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a south-east-pointing arrow, optionally with a corner at the arrowhead. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ## ############ ## ## ## ################## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLBOOK @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @item se-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{se-resize} should be used as the first fallback, @code{nwse-select} should be used as the second fallback, @code{nwse-resize} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a south-east-pointing arrow. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ############ @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifset @item ne-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{ne-select} should be used as the first fallback, @code{nesw-resize} should be used as the second fallback, @code{nesw-select} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a north-east-pointing arrow, optionally with a corner at the arrowhead. @example @group ################## ## ## ############ ## #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLBOOK @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @item ne-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{ne-resize} should be used as the first fallback, @code{nesw-select} should be used as the second fallback, @code{nesw-resize} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a north-east-pointing arrow. @example @group ############ #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifset @item sw-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{sw-select} should be used as the first fallback, @code{nesw-resize} should be used as the second fallback, @code{nesw-select} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a south-west-pointing arrow, optionally with a corner at the arrowhead. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ## ############ ## ## ################## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLBOOK @ifclear AFOURPAPER_WITH_SMALLFONT @page @end ifclear @end ifclear @item sw-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{sw-resize} should be used as the first fallback, @code{nesw-select} should be used as the second fallback, @code{nesw-resize} should be used as the third fallback, and @code{all-resize}. should be used as the fourth fallback. This cursor is typically rendered as a south-west-pointing arrow. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ############ @end group @end example @vskip 0pt plus 1filll @item ew-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{ew-select} should be used as the first fallback, and @code{col-resize}. should be used as the second fallback. This cursor is typically rendered as an east- and west-pointing twin-arrow, optionally with a wall at the arrowheads. @example @group ## ## ## ## ## ## ## ## ## ## ## ## ## ######################## ## ## ## ## ## ## ## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifset SMALLFONT @ifset AFOURPAPER_OR_AFIVEPAPER @page @end ifset @end ifset @item ew-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{ew-resize} should be used as the first fallback, and @code{col-resize}. should be used as the second fallback. This cursor is typically rendered as an east- and west-pointing twin-arrow. @example @group ## ## ## ## ## ## ######################## ## ## ## ## ## ## @end group @end example @vskip 0pt plus 1filll @ifclear AFIVEPAPER_OR_AFOURPAPER_WITH_SMALLFONT @page @end ifclear @item ns-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{ns-select} should be used as the first fallback, and @code{row-resize}. should be used as the second fallback. This cursor is typically rendered as a north- and south-pointing twin-arrow, optionally with a wall at the arrowheads. @example @group ############## ## ###### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ###### ## ############## @end group @end example @vskip 0pt plus 1filll @item ns-select @cpindex Cell selection @cpindex Tables, selection If this cursor is missing, @code{ns-resize} should be used as the first fallback, and @code{row-resize}. should be used as the second fallback. This cursor is typically rendered as a north- and south-pointing twin-arrow. @example @group ## ###### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ###### ## @end group @end example @vskip 0pt plus 1filll @ifclear SMALLFONT @ifclear AFIVEPAPER @page @end ifclear @end ifclear @ifset USLETTER_WITH_SMALLFONT @page @end ifset @ifset AFOURPAPER_WITH_SMALLFONT @page @end ifset @item nwse-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{all-resize} should be used as the first fallback. This cursor is typically rendered as a north-west- and south-east-pointing twin-arrow, optionally with a corner at the arrowheads. @example @group ################## ## ## ## ############ ## #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ## ############ ## ## ## ################## @end group @end example @vskip 0pt plus 1filll @ifset AFIVEPAPER @page @end ifset @item nesw-resize @cpindex Resizing @cpindex Window resizing If this cursor is missing, @code{all-resize} should be used as the first fallback. This cursor is typically rendered as a north-east- and south-west-pointing twin-arrow, optionally with a corner at the arrowheads. @example @group ################## ## ## ############ ## #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### ## ############ ## ## ################## @end group @end example @vskip 0pt plus 1filll @page @item all-resize @cpindex Resizing @cpindex Window resizing This cursor is typically rendered as a cross between a north-east and south-west-pointing twin-arrow and a north-west- and south-east-pointing twin-arrow, optionally with a corner at the arrow heads. @example @group ########## ########## #### #### ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## #### #### ########## ########## @end group @end example @end table @cpindex Cell selection @cpindex Tables, selection In addition, it is advised that @code{nwse-select} and @code{nesw-select} are rendered in the same mannar as the other @code{*-select} cursors and analogously to @code{nwse-resize} and @code{nesw-resize}, respectively. @cpindex Text, rotated @cpindex Rotated text It is also advised to make cursors intermediate to @code{text} and @code{vertical-text}. These are named with the pattern @code{text-*}, where @code{*} is replaced by the number of degrees the text is rotated anti-clockwise. This means that @code{text} should be used if @code{text-0} is requested but missing, and @code{vertical-text} should be used if @code{text-90} is requested but missing. Finally, the closest existing cursor should be used, and the cursor rotated 180 degrees of what is requested should be used if there is no matching cursor with a rotation distance within, but excluding, 90@tie{}degrees. @code{*} should be in the interval [0,@tie{}360[, and a period@tie{}(`.') should be used as a decimal pointer, as it is used in most programming languages. @node Colour Names @section Colour Names @cpindex Colour names @cpindex System colours @cpindex Colours, system @cpindex Colours, names @command{mds} protocols provide an optional way to name colours. This is used primarily for colours used by toolkits. These are called system colours. But it is also possible to have names for common colours that should be tunable. These are called named colours. There are no colours is guaranteed to exist. Nor is it guaranteed that value of named colours reflect the names of them, in any aspect. For example `red' could be a light blue, and `light-red` could be a dark green. In fact, you use assume that the names does not reflect the actual colour. For example, if a terminal uses named colours for the colours choosen by programs via ANSI escape sequences, the use can change these colours to create a theme she likes better, even if the colours are no longer what ANSI defines them. There is however a list of recommended colour names, with recommended definitions: @table @code @item black It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 30 m} or @code{CSI 40 m}. This colour is usually pure black. @item red It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 31 m} or @code{CSI 41 m}. This colour is usually a medium red. @item green It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 32 m} or @code{CSI 42 m}. This colour is usually a medium green. @item yellow It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 33 m} or @code{CSI 43 m}. This colour is usually a medium yellow or medium orange. @item blue It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 34 m} or @code{CSI 44 m}. This colour is usually a medium blue. @item purple It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 35 m} or @code{CSI 45 m}. This colour is usually a medium purple, medium lilac or medium fuchsia/magenta. @item teal It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 36 m} or @code{CSI 46 m}. This colour is usually a medium teal or medium turquoise/cyan @item grey It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequences @code{CSI 37 m} or @code{CSI 47 m}. This colour is usually around 50% grey. @item dark-grey It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 30 m}. This colour is usually around 25% grey. @item light-red It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 31 m}. This colour is usually the same colour as, but brighter than, @code{red}. @item light-green It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 32 m}. This colour is usually the same colour as, but brighter than, @code{green}. @item light-yellow It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 33 m}. This colour is usually a bright yellow. @item light-blue It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 34 m}. This colour is usually the same colour as, but brighter than, @code{blue}. @item light-purple It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 35 m}. This colour is usually the same colour as, but brighter than, @code{purple}. @item light-teal It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 36 m}. This colour is usually the same colour as, but brighter than, @code{teal}. @item white It is recommended that terminals use this as the default colour for the colour selected by the ANSI escape sequence @code{CSI 1 ; 37 m}. This colour is usually a pure white or very bright grey. @item background It is recommended that terminals use this as the default background colour. This should be noted, that it is not recommened for or programs. @item foreground It is recommended that terminals use this as the default text colour. This should be noted, that it is not recommened for or programs. @item desktop-background The default background colour on the desktop. @item desktop-foreground The colour for text on icons and gadgets on the desktop. @item desktop-selection The background for text on icons that have been selected on the desktop. @item desktop-selection-foreground The colour for text on icons that have been selected on the desktop. @item desktop-foreground-hover The colour for text on icons on the desktop, when the icon is being hovered. @item desktop-selection-hover The background for text on icons that have been selected on the desktop, when the icon is being hovered. @item desktop-selection-foreground-hover The colour for text on icons that have been selected on the desktop, when the icon is being hovered. @item window-background The background on windows. @item window-foreground The colour on text on windows, as well as the colour of frames. @item window-foreground-disabled The colour on text, associated with disabled components, on windows. @item window-cursor The colour on text cursors for selectable text on windows. @item window-selection The colour on text-selection highlight for selectable text on windows. @item window-selection-foreground The colour on text on selected for text on windows. @item link-foreground The colour on text for unvisited links. @item link-active-foreground The colour on text for links that are currently being visited. @item link-visited-foreground The colour on text for visited links. @item link-broken-foreground The colour on text for broken links. @item link-background-foreground The background colour for unvisited links. @item link-active-background The background colour for links that are currently being visited. @item link-visited-background The background colour for visited links. @item link-broken-background The background colour for broken links. @item link-selection The colour on text highlight for selected text on unvisited links. @item link-active-selection The colour on text highlight for selected text on links that are currently being visited. @item link-visited-selection The colour on text highlight for selected text on visited links. @item link-broken-selection The colour on text highlight for selected text on broken links. @item link-selection-foreground The colour on selected text on unvisited links. @item link-active-selection-foreground The colour on selected text on links that are currently being visited. @item link-visited-selection-foreground The colour on selected text on visited links. @item link-broken-selection-foreground The colour on selected text on broken links. @item link-foreground-hover The colour on text for unvisited links, when the link is being hovered. @item link-active-foreground-hover The colour on text for links that are currently being visited, when the link is being hovered. @item link-visited-foreground-hover The colour on text for visited links, when the link is being hovered. @item link-broken-foreground-hover The colour on text for broken links, when the link is being hovered. @item link-background-foreground-hover The background colour for unvisited links, when the link is being hovered. @item link-active-background-hover The background colour for links that are currently being visited, when the link is being hovered. @item link-visited-background-hover The background colour for visited links, when the link is being hovered. @item link-broken-background-hover The background colour for broken links, when the link is being hovered. @item link-selection-hover The colour on text highlight for selected text on unvisited links, when the link is being hovered. @item link-active-selection-hover The colour on text highlight for selected text on links that are currently being visited, when the link is being hovered. @item link-visited-selection-hover The colour on text highlight for selected text on visited links, when the link is being hovered. @item link-broken-selection-hover The colour on text highlight for selected text on broken links, when the link is being hovered. @item link-selection-foreground-hover The colour on selected text on unvisited links, when the link is being hovered. @item link-active-selection-foreground-hover The colour on selected text on links that are currently being visited, when the link is being hovered. @item link-visited-selection-foreground-hover The colour on selected text on visited links, when the link is being hovered. @item link-broken-selection-foreground-hover The colour on selected text on broken links, when the link is being hovered. @item link-foreground-disabled The colour on text for unvisited links, when the link is disabled. @item link-active-foreground-disabled The colour on text for links that are currently being visited, when the link is disabled. @item link-visited-foreground-disabled The colour on text for visited links, when the link is disabled. @item link-broken-foreground-disabled The colour on text for broken links, when the link is disabled. @item link-background-disabled The background colour for unvisited links, when the link is disabled. @item link-active-background-disabled The background colour for links that are currently being visited, when the link is disabled. @item link-visited-background-disabled The background colour for visited links, when the link is disabled. @item link-broken-background-disabled The background colour for broken links, when the link is disabled. @item link-selection-disabled The colour on text highlight for selected text on unvisited links, when the link is disabled. @item link-active-selection-disabled The colour on text highlight for selected text on links that are currently being visited, when the link is disabled. @item link-visited-selection-disabled The colour on text highlight for selected text on visited links, when the link is disabled. @item link-broken-selection-disabled The colour on text highlight for selected text on broken links, when the link is disabled. @item link-selection-foreground-disabled The colour on selected text on unvisited links, when the link is disabled. @item link-active-selection-foreground-disabled The colour on selected text on links that are currently being visited, when the link is disabled. @item link-visited-selection-foreground-disabled The colour on selected text on visited links, when the link is disabled. @item link-broken-selection-foreground-disabled The colour on selected text on broken links, when the link is disabled. @item button-background The background colour on buttons and button-like controls. @item button-foreground The colour on text on buttons and button-like controls. @item button-aura The colour on aura around buttons and button-like controls to mark that they have focus. @item button-background-toggled The background colour on buttons and button-like controls, under that condition that the button is toggled. @item button-foreground-toggled The colour on text on buttons and button-like controls, under that condition that the button is toggled. @item button-aura-toggled The colour on aura around buttons and button-like controls to mark that they have focus, under that condition that the button is toggled. @item button-background-hover The background colour on buttons and button-like controls, when the button is being hovered. @item button-foreground-hover The colour on text on buttons and button-like controls, when the button is being hovered. @item button-aura-hover The colour on aura around buttons and button-like controls to mark that they have focus, when the button is being hovered. @item button-background-toggled-hover The background colour on buttons and button-like controls, when the button is being hovered, under that condition that the button is toggled. @item button-foreground-toggled-hover The colour on text on buttons and button-like controls, when the button is being hovered, under that condition that the button is toggled. @item button-aura-toggled-hover The colour on aura around buttons and button-like controls to mark that they have focus, when the button is being hovered, under that condition that the button is toggled. @item button-background-disabled The background colour on disabled buttons and button-like controls. @item button-foreground-disabled The colour on text on disabled buttons and button-like controls. @item button-aura-disabled The colour on aura around disabled buttons and button-like controls to mark that they have focus. @item button-background-toggled-disabled The background colour on disabled buttons and button-like controls, under that condition that the button is toggled. @item button-foreground-toggled-disabled The colour on text on disabled buttons and button-like controls, under that condition that the button is toggled. @item button-aura-toggled-disabled The colour on aura around disabled buttons and button-like controls to mark that they have focus, under that condition that the button is toggled. @item button-background-change The background colour on buttons and button-like controls, under the condition that the button is being clicked. @item button-foreground-change The colour on text on buttons and button-like controls, under the condition that the button is being clicked. @item button-aura-change The colour on aura around buttons and button-like controls to mark that they have focus, under the condition that the button is being clicked. @item button-background-toggled-change The background colour on buttons and button-like controls, under that condition that the button is toggled and is being clicked. @item button-foreground-toggled-change The colour on text on buttons and button-like controls, under that condition that the button is toggled and is being clicked. @item button-aura-toggled-change The colour on aura around buttons and button-like controls to mark that they have focus, under that condition that the button is toggled and is being clicked. @item button-background-hover-change The background colour on buttons and button-like controls, under the condition that the button is being clicked. @item button-foreground-hover-change The colour on text on buttons and button-like controls, under the condition that the button is being hovered and clicked. @item button-aura-hover-change The colour on aura around buttons and button-like controls to mark that they have focus, under the condition that the button is being hovered and clicked. @item button-background-toggled-hover-change The background colour on buttons and button-like controls, under that condition that the button is toggled and is being hovered and clicked. @item button-foreground-toggled-hover-change The colour on text on buttons and button-like controls, under that condition that the button is toggled and is being hovered and clicked. @item button-aura-toggled-hover-change The colour on aura around buttons and button-like controls to mark that they have focus, under that condition that the button is toggled and is being hovered and clicked. @item input-background The background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables. @item input-background-alternate The alternate background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables. @item input-foreground The colour on text on text-input components, such as comboboxes and text-fields, as well as lists and tables. @item input-selection The colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables. This colour is usually blue. @item input-selection-alternate The alternate colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables. This colour is usually blue. @item input-selection-foreground The colour on selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables. @item input-mark The colour on text highlight for secondarily selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables. This colour is usually yellow. @item input-mark-foreground The colour on secondarily selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables. This colour is usually yellow. @item input-cursor The colour on the text cursor on text-input components, such as comboboxes and text-fields, as well as lists and tables. @item input-aura The colour on the aura around text-input components, such as comboboxes and text-fields, as well as lists and tables, to mark that they have focus. @item input-background-hover The background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-background-alternate-hover The alternate background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-foreground-hover The colour on text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-selection-hover The colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-selection-alternate-hover The alternate colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-selection-foreground-hover The colour on selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-mark-hover The colour on text highlight for secondarily selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-mark-foreground-hover The colour on secondarily selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-cursor-hover The colour on the text cursor on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is being hovered. @item input-aura-hover The colour on the aura around text-input components, such as comboboxes and text-fields, as well as lists and tables, to mark that they have focus, under the condition that the component is being hovered. @item input-background-disabled The background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-background-alternate-disabled The alternate background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-foreground-disabled The colour on text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-selection-disabled The colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-selection-alternate-disabled The alternate colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-selection-foreground-disabled The colour on selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-mark-disabled The colour on text highlight for secondarily selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-mark-foreground-disabled The colour on secondarily selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-cursor-disabled The colour on the text cursor on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the component is disabled. @item input-aura-disabled The colour on the aura around text-input components, such as comboboxes and text-fields, as well as lists and tables, to mark that they have focus, under the condition that the component is disabled. @item input-background-selected The background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-background-alternate-selected The alternate background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-foreground-selected The colour on text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-selection-selected The colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-selection-alternate-selected The alternate colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-selection-foreground-selected The colour on selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-cursor-selected The colour on the text cursor on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected. @item input-aura-selected The colour on the aura around text-input components, such as comboboxes and text-fields, as well as lists and tables, to mark that they have focus, under the condition that the item is selected. @item input-background-selected-hover The background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-background-alternate-selected-hover The alternate background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-foreground-selected-hover The colour on text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-selection-selected-hover The colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-selection-alternate-selected-hover The alternate colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-selection-foreground-selected-hover The colour on selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-cursor-selected-hover The colour on the text cursor on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected and is being hovered. @item input-aura-selected-hover The colour on the aura around text-input components, such as comboboxes and text-fields, as well as lists and tables, to mark that they have focus, under the condition that the item is selected and is being hovered. @item input-background-selected-disabled The background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected but disabled. @item input-background-alternate-selected-disabled The alternate background colour on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected but disabled. @item input-foreground-selected-disabled The colour on text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected but disabled. @item input-selection-selected-disabled The colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected but disabled. @item input-selection-alternate-selected-disabled The alternate colour on text highlight for selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected but disabled. @item input-selection-foreground-selected-disabled The colour on selected text on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected butdisabled. @item input-cursor-selected-disabled The colour on the text cursor on text-input components, such as comboboxes and text-fields, as well as lists and tables, under the condition that the item is selected but disabled. @item input-aura-selected-disabled The colour on the aura around text-input components, such as comboboxes and text-fields, as well as lists and tables, to mark that they have focus, under the condition that the item is selected but disabled. @item input-delimiter The colour on lines in tables used to delimit rows or coloumns. @item input-delimiter-disabled The colour on lines in tables used to delimit rows or coloumns, when the table is disabled. @item option-background The background colour for the box on checkboxes and radioboxes, under the condition that the box is not checked. @item option-foreground The colour on text for checkboxes and radioboxes, under the condition that the box is not checked. @item option-aura The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is not checked. @item option-background-active The background colour for the box on checkboxes and radioboxes, under the condition that the box is checked. @item option-foreground-active The colour on text for checkboxes and radioboxes, under the condition that the box is checked. @item option-aura-active The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is checked. @item option-background-intermediate The background colour for the box on checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-foreground-intermediate The colour on text for checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-aura-intermediate The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-background-hover The background colour for the box on hovered checkboxes and radioboxes, under the condition that the box is not checked. @item option-foreground-hover The colour on text for hovered checkboxes and radioboxes, under the condition that the box is not checked. @item option-aura-hover The colour of the aura around hovered checkboxes and radioboxes to mark them as having focus, under the condition that the box is not checked. @item option-background-active-hover The background colour for the box on hovered checkboxes and radioboxes, under the condition that the box is checked. @item option-foreground-active-hover The colour on text for hovered checkboxes and radioboxes, under the condition that the box is checked. @item option-aura-active-hover The colour of the aura around hovered checkboxes and radioboxes to mark them as having focus, under the condition that the box is checked. @item option-background-intermediate-hover The background colour for the box on hovered checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-foreground-intermediate-hover The colour on text for hovered checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-aura-intermediate-hover The colour of the aura around hovered checkboxes and radioboxes to mark them as having focus, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-background-disabled The background colour for the box on disabled checkboxes and radioboxes, under the condition that the box is not checked. @item option-foreground-disabled The colour on text for disabled checkboxes and radioboxes, under the condition that the box is not checked. @item option-aura-disabled The colour of the aura around disabled checkboxes and radioboxes to mark them as having focus, under the condition that the box is not checked. @item option-background-active-disabled The background colour for the box on disabled checkboxes and radioboxes, under the condition that the box is checked. @item option-foreground-active-disabled The colour on text for disabled checkboxes and radioboxes, under the condition that the box is checked. @item option-aura-active-disabled The colour of the aura around disabled checkboxes and radioboxes to mark them as having focus, under the condition that the box is checked. @item option-background-intermediate-disabled The background colour for the box on disabled checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-foreground-intermediate-disabled The colour on text for disabled checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-aura-intermediate-disabled The colour of the aura around disabled checkboxes and radioboxes to mark them as having focus, under the condition that the box is in intermediate mode, that is, paritally checked. @item option-background-change The background colour for the box on checkboxes and radioboxes, under the condition that the box is not checked but is being clicked. @item option-foreground-change The colour on text for checkboxes and radioboxes, under the condition that the box is not checked but is being clicked. @item option-aura-change The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is not checked but is being clicked. @item option-background-active-change The background colour for the box on checkboxes and radioboxes, under the condition that the box is checked and is being clicked. @item option-foreground-active-change The colour on text for checkboxes and radioboxes, under the condition that the box is checked and is being clicked. @item option-aura-active-change The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is checked and is being clicked. @item option-background-intermediate-change The background colour for the box on checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked and is being clicked. @item option-foreground-intermediate-change The colour on text for checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked, and is being clicked. @item option-aura-intermediate-change The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is in intermediate mode, that is, paritally checked and is being clicked. @item option-background-hover-change The background colour for the box on checkboxes and radioboxes, under the condition that the box is not checked but is being hovered and clicked. @item option-foreground-hover-change The colour on text for checkboxes and radioboxes, under the condition that the box is not checked but is being hovered and clicked. @item option-aura-hover-change The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is not checked but is being hovered and clicked. @item option-background-active-hover-change The background colour for the box on checkboxes and radioboxes, under the condition that the box is checked and is being hovered and clicked. @item option-foreground-active-hover-change The colour on text for checkboxes and radioboxes, under the condition that the box is checked and is being hovered and clicked. @item option-aura-active-hover-change The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is checked and is being hovered and clicked. @item option-background-intermediate-hover-change The background colour for the box on checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked and is being hovered and clicked. @item option-foreground-intermediate-hover-change The colour on text for checkboxes and radioboxes, under the condition that the box is in intermediate mode, that is, paritally checked, and is being hovered and clicked. @item option-aura-intermediate-hover-change The colour of the aura around checkboxes and radioboxes to mark them as having focus, under the condition that the box is in intermediate mode, that is, paritally checked and is being hovered and clicked. @item tabpane-background Background overriding @code{window-background} inside tabpanes. @item tabpane-frame The colour on tabpane frames. @item tabgroup-background The colour on the background on tab groups. @item tabgroup-background-hover The colour on the background on tab groups, for hovered groups. @item tab-background The background colour on tabs. @item tab-foreground The colour on text on tabs. @item tab-head The colour of a the head on tabs. @item tab-background-active The background colour on active tabs. @item tab-foreground-active The colour on text on active tabs. @item tab-head-active The colour of a the head on active tabs. @item tab-background-hover The background colour on hovered tabs. @item tab-foreground-hover The colour on text on hovered tabs. @item tab-head-hover The colour of a the head on hovered tabs. @item tab-background-active-hover The background colour on active and hovered tabs. @item tab-foreground-active-hover The colour on text on active and hovered tabs. @item tab-head-active-hover The colour of a the head on active and hovered tabs. @item slider-background The background colour in sliders. @item slider-selected The background colour in sliders, marking the area that is selected. @item slider-unselected The background colour in sliders, marking the area that is not selected. @item slider-foreground The colour on text over sliders indicating the current value. @item slider-knob The colour of the knob used to change the value on sliders. @item slider-aura The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus. @item slider-stop The colour of the stop lines for sliders. @item slider-background-hover The background colour in sliders, under the condition that the slider is being hovered. @item slider-selected-hover The background colour in sliders, marking the area that is selected, under the condition that the slider is being hovered. @item slider-unselected-hover The background colour in sliders, marking the area that is not selected, under the condition that the slider is being hovered. @item slider-foreground-hover The colour on text over sliders indicating the current value, under the condition that the slider is being hovered. @item slider-knob-hover The colour of the knob used to change the value on sliders, under the condition that the slider is being hovered. @item slider-aura-hover The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus, under the condition that the slider is being hovered. @item slider-stop-hover The colour of the stop lines for sliders, under the condition that the slider is being hovered. @item slider-background-hover-selected The background colour in sliders, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-selected-hover-selected The background colour in sliders, marking the area that is selected, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-unselected-hover-selected The background colour in sliders, marking the area that is not selected, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-foreground-hover-selected The colour on text over sliders indicating the current value, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-knob-hover-selected The colour of the knob used to change the value on sliders, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-aura-hover-selected The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-stop-hover-selected The colour of the stop lines for sliders, under the condition that the slider is being hovered on the side of the slider that marks the selection. @item slider-background-hover-unselected The background colour in sliders, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-selected-hover-unselected The background colour in sliders, marking the area that is selected, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-unselected-hover-unselected The background colour in sliders, marking the area that is not selected, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-foreground-hover-unselected The colour on text over sliders indicating the current value, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-knob-hover-unselected The colour of the knob used to change the value on sliders, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-aura-hover-unselected The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-stop-hover-unselected The colour of the stop lines for sliders, under the condition that the slider is being hovered on the side of the slider that does not mark the selection. @item slider-background-hold The background colour in sliders, under the condition that the slider is being pressed. @item slider-selected-hold The background colour in sliders, marking the area that is selected, under the condition that the slider is being pressed. @item slider-unselected-hold The background colour in sliders, marking the area that is not selected, under the condition that the slider is being pressed. @item slider-foreground-hold The colour on text over sliders indicating the current value, under the condition that the slider is being pressed. @item slider-knob-hold The colour of the knob used to change the value on sliders, under the condition that the slider is being pressed. @item slider-aura-hold The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus, under the condition that the slider is being pressed. @item slider-stop-hold The colour of the stop lines for sliders, under the condition that the slider is being pressed. @item slider-background-hold-selected The background colour in sliders, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-selected-hold-selected The background colour in sliders, marking the area that is selected, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-unselected-hold-selected The background colour in sliders, marking the area that is not selected, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-foreground-hold-selected The colour on text over sliders indicating the current value, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-knob-hold-selected The colour of the knob used to change the value on sliders, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-aura-hold-selected The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-stop-hold-selected The colour of the stop lines for sliders, under the condition that the slider is being pressed on the side of the slider that marks the selection. @item slider-background-hold-unselected The background colour in sliders, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-selected-hold-unselected The background colour in sliders, marking the area that is selected, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-unselected-hold-unselected The background colour in sliders, marking the area that is not selected, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-foreground-hold-unselected The colour on text over sliders indicating the current value, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-knob-hold-unselected The colour of the knob used to change the value on sliders, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-aura-hold-unselected The colour of the aura around knob, used to change the value on sliders, marking the slider as having focus, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-stop-hold-unselected The colour of the stop lines for sliders, under the condition that the slider is being pressed on the side of the slider that does not mark the selection. @item slider-background-disabled The background colour in disabled sliders. @item slider-selected-disabled The background colour in disabled sliders, marking the area that is selected. @item slider-unselected-disabled The background colour in disabled sliders, marking the area that is not selected. @item slider-foreground-disabled The colour on text over disabled sliders indicating the current value. @item slider-knob-disabled The colour of the knob used to change the value on disabled sliders. @item slider-aura-disabled The colour of the aura around knob, used to change the value on disabled sliders, marking the slider as having focus. @item slider-stop-disabled The colour of the stop lines for disabled sliders. @item scroll-background The background colour on scrolls. @item scroll-foreground The icon colour on buttons associated with scrolls. @item scroll-knob The colour of the knob on scrolls. @item scroll-button The background colour on buttons associated with scrolls. @item scroll-background-hover The background colour on scrolls, under the condition that the area is being hovered. @item scroll-foreground-hover The icon colour on buttons associated with scrolls, under the condition that the button is being hovered. @item scroll-knob-hover The colour of the knob on scrolls, under the condition that the knob is being hovered. @item scroll-button-hover The background colour on buttons associated with scrolls, under the condition that the button is being hovered. @item scroll-background-hold The background colour on scrolls, under the condition that the area is being pressed. @item scroll-foreground-hold The icon colour on buttons associated with scrolls, under the condition that the button is being pressed. @item scroll-knob-hold The colour of the knob on scrolls, under the condition that the knob is being pressed. @item scroll-button-hold The background colour on buttons associated with scrolls, under the condition that the button is being pressed. @item scroll-background-disabled The background colour on scrolls, under the condition that the scroll is disabled. @item scroll-foreground-disabled The icon colour on buttons associated with scrolls, under the condition that the button is disabled. @item scroll-knob-disabled The colour of the knob on scrolls, under the condition that the scroll is disabled. @item scroll-button-disabled The background colour on buttons associated with scrolls, under the condition that the button is disabled. @item progress-background The background colour on progressbars. @item progress-progress The colour of the bar, on progressbars, indicating how much progress has been made, or the colour of a marquee bar. This colour is usually blue, but sometimes green. @item progress-good The colour of the bar, on progressbars, when the progressbar is used to indicate a state rather than a progress, and the state is considered good. This colour is usually green. @item progress-normal The colour of the bar, on progressbars, when the progressbar is used to indicate a state rather than a progress, and the state is considered normal. This colour is usually yellow or green. @item progress-bad The colour of the bar, on progressbars, when the progressbar is used to indicate a state rather than a progress, and the state is considered bad. This colour is usually orange or yellow. @item progress-critical The colour of the bar, on progressbars, when the progressbar is used to indicate a state rather than a progress, and the state is considered critical. This colour is usually red. @item progress-foreground The colour of text on progressbars, on the area that is not covered by a bar. @item progress-foreground-progress The colour of text on progressbars, on the area that is covered by a bar indicating how much progress has been made or a marquee bar. @item progress-foreground-good The colour of text on progressbars, on the area that is covered by a bar indicating a good state. @item progress-foreground-normal The colour of text on progressbars, on the area that is covered by a bar indicating a normal state. @item progress-foreground-bad The colour of text on progressbars, on the area that is covered by a bar indicating a bad state. @item progress-foreground-critical The colour of text on progressbars, on the area that is covered by a bar indicating a critical state. @item menu-background The background colour on menus and menu-items. @item menu-foreground The colour on text on menus and menu-items. @item menu-delimiter The colour on group-separation lines in menus. @item menu-tear The colour on lines on menu-tearing menu-items. @item menu-background-disabled The background colour on disabled menus and menu-items. @item menu-foreground-disabled The colour on text on disabled menus and menu-items. @item menu-tear-disabled The colour on lines on disabled menu-tearing menu-items. @item menu-background-hover The background colour on menus and menu-items that are being hovered. @item menu-foreground-hover The colour on text on menus and menu-items that are being hovered. @item menu-tear-hover The colour on lines on menu-tearing menu-items. @item menu-background-disabled-hover The background colour on disabled menus and menu-items that are being hovered. @item menu-foreground-disabled-hover The colour on text on disabled menus and menu-items that are being hovered. @item menu-tear-disabled-hover The colour on lines on disabled menu-tearing menu-items that are being hovered. @item menu-background-open The background colour on menus and menu-items that are opened, that is submenus are visible. @item menu-foreground-open The colour on text on menus and menu-items that are opened, that is submenus are visible. @item toolbar-background The background colour on toolbars. @item toolbar-foreground The colour on text on toolbars. @item toolbar-delimiter The colour on group-separation lines in toolbars. @item toolbar-handle The colour on the handle used to move toolbars. @item tooltip-background The background colour on tooltips. @item tooltip-foreground The colour on text on tooltips. @item notification-background The background on notification. @item notification-foreground The colour on text on notification. @item notification-low Colour on notifications to indicate that they are of low priority. This colour is usually green or blue. @item notification-normal Colour on notifications to indicate that they are of normal priority. This colour is usually blue or the same as @code{notification-background}. @item notification-high Colour on notifications to indicate that they are of high priority. This colour is usually orange. @item notification-critical Colour on notifications to indicate that they are of critical priority. This colour is usually red. @end table @node Nesting Applications @section Nesting Applications @cpindex Nesting applications @cpindex Applications, nesting @cpindex Embedding applications @cpindex Applications, embedding @vrindex @env{MDS_EMBED} Applications that want to embed another other application within it, should create a socket and start the other application with the environment variable @env{MDS_EMBED} set to the windows ID of the socket that the application should be embedded in. All @command{mds} applications must be aware of the environment variable @env{MDS_EMBED}@. The application may choose not to embed itself in the announced socket, however it should have good reason for not doing this. All @command{mds} application must unset the environment variable @env{MDS_EMBED} before it starts any other program. @comment TODO @c How do we solve this for compatibility with X, Wayland and Mir? @node The Real Display Server @section The Real Display Server @cpindex Real display server @cpindex Actual display server @cpindex Preferred display server @cpindex Display server, real @cpindex Display server, actual @cpindex Display server, preferred @cpindex Compatibility layers @vrindex @env{PREFERRED_DISPLAY} The environment variable @env{PREFERRED_DISPLAY}, should be set with the value @command{mds}, if and only if @command{mds} is started as a display server and not as a compatibility layer. @env{PREFERRED_DISPLAY} is a space-separated (U+0020) list of supported display server protocol, ordered by preference. If @command{mds} is started as a compatibility layer, @command{mds} should be added to @env{PREFERRED_DISPLAY} if and only if @env{PREFERRED_DISPLAY} lists any other display protocol. If a compatibility server is successfully started, it should be listed in @env{PREFERRED_DISPLAY}@. Be sure to keep the list ordered by preference. @table @code @item mir @pgindex @command{mds-mmds} @cpindex Compatibility layer, Mir @cpindex Mir compatibility layer Should be added if you are running a @command{mir}-to-@command{mds} server, like @command{mds-mmds}. @item wayland @pgindex @command{mds-wmds} @cpindex Compatibility layer, Wayland @cpindex Wayland compatibility layer Should be added if you are running a @command{wayland}-to-@command{mds} server, like @command{mds-wmds}. @item x11 @pgindex @command{mds-xmds} @cpindex Compatibility layer, X.org @cpindex X.org compatibility layer Should be added if you are running an @command{X}-to-@command{mds} server, like @command{mds-xmds}. @end table @node New Concepts @chapter New Concepts @menu * Metadisplay Server:: Goals and features of metadisplays. * Endomonitor:: Goals and features of endomonitors. @end menu @node Metadisplay Server @section Metadisplay Server @cpindex Metadisplay server @pgindex @code{mds-meta} @cpindex Display server, meta @cpindex Multi-display systems A metadisplay server is a server that is connected to one or more display server's simultaneously. Additionally, it is acting as a display server on its own. Any server, or even client, running in this display will effectively be running in all of the displays connected to the metadisplay. The idea of the metadisplay server came from the idea of letting the user have the clipboard shared across any number of @emph{selected} display servers. Rather than having a clipboard server written specifically for this, it was seen as more appropriate to have a server than could let any server run inside any number of display server. Not only will this let the user run any server this way. It also makes it possible to run them across any number of computers. @pgindex @code{@command{mds-host}} @pgindex @command{mds-remote} @cpindex Networking If a hosting server, like @command{mds-host}, runs inside a metadisplay, any number of computers can connect to the metadisplay using a server like @command{mds-remote}. This creates a metadisplay with multiple display from multiple computers. If a clipboard server runs in this metadisplay, all of these display on all of these computers will share clipboard server. Whilst not removing or degrading any functionality. A negative property of this setup it that it is centralised rather than distributed. If the computer hosting the metadisplay crashes, the other computers will no longer share this metadisplay, and lose the connection to any server running in it. In addition to a the clipboard server, there is a host of other servers that makes sense to run in multiple displays or across multiple computer: drag-and-drop servers, human input device servers, output servers, and even windowing servers. @node Endomonitor @section Endomonitor @pgindex @command{mds-endomon} @cpindex CRTC @cpindex Cathode ray tube controller @cpindex Presentation @cpindex Display of content @cpindex Content, display @cpindex Endomonitor @cpindex Monitor, endo- @cpindex Cinerama @pgindex @command{mds-cinerama} There are two forms of logical monitors: cineramas and endomonitor. A cinerama combines monitors into one monitor. Endomonitors takes a subset of a single monitor. Similar to having two monitors with overlaping output,@footnote{For example a monitor with mode--position 1600x1200+0+0 and a monitor with mode--position 1600x1200+800+600.} An endomonitor overlaps with another monitor, but only with that monitor and cannot be outside it even partially. But it does not need to cover it completely. This allows you to put a full-screen window on the endomonitor and thus only partially cover the physical monitor; for example keeping the clock visible. Endomonitors do not need to be placed inside a physical monitor. They can be placed inside logical monitor too. Putting an endomonitor inside a cinerama lets you create a logical monitor that covers multiple monitors partially. @node Discussion @chapter Discussion @menu * Server Architecture:: Discussion on fundamental design choices. * Fixing X.org Issues:: Can we avoid the problems X.org has? * Why Not Wayland:: Why Wayland Won't Cut It. * Why Not Mir:: Why Mir Won't Cut It. * Desktop Environments:: What are desktop environments' relationship to mds? * Why Dither Colours:: Is dithering not a thing of the past? @end menu @node Server Architecture @section Server Architecture @cpindex Server architecture @cpindex Architecture, servers This chapter aims to enumerate advantages and disadvantages with micro-display servers, traditional monolithic display servers and other possible designs. Please chime in with any insight. @menu * The Microserver Architecture:: The microserver architecture. * The Monolithic Server Architecture:: The monolithic server architecture. * The Hybrid Server Architecture:: The hybrid server architecture. * The Megalithic Server Architecture:: The megalithic server architecture. * The Modular Server Architecture:: The modular server architecture. * The Modular Microserver Architecture:: The modular microserver architecture. * The Exoserver Architecture:: The exoserver architecture. @end menu @node The Microserver Architecture @subsection The Microserver Architecture @cpindex Microserver architecture @cpindex Architecture, microserver @cpindex Microdisplay servers Description: The display server is implement with multiple binaries that speak with each other using a well defined protocol. @noindent Implementations: mds. @noindent Advantages: @itemize @bullet{} @item @cpindex Code quality @cpindex Quality of code Knowing the names of the servers you use and their purpose makes it very easy to find where you want to do patching in the source code. @item @cpindex Code quality @cpindex Quality of code Spaghetti code to a larger extent is virtually impossible; the microserver architecture guarantees a certain quality of the code architecture for the display server. @item @cpindex Flexibility If the message passing used in the display server allows for message modification and retrieval ordering, extending, modifying and using the display server in unforeseen ways becomes much easier, and will often not require any modifications to the existing servers. @item @cpindex Flexibility Replacing the display server is easier for a micro-display server than it is for a monolithic display server, because the servers could be replaced one by one and could even support running under two distinct protocol during the transitional period. @item @cpindex Code quality @cpindex Quality of code Not as many subprotocols needs to be defined. For example, recording the output of the display does not require a special protocol, one only needs to write a server that listens on messages passed between servers. @item @cpindex Stability If a server crashes it does not crash the entire session. Crashes can most often be repaired. @item @cpindex Flexibility Because servers can easily be omitted and replaced when starting the display server, it becomes much easier to mount the display server on top of an already running display server. For example, if you want the performance of @code{weston} but then flexibility and functionallity of @command{mds}, you could start @command{mds} inside @code{weston} and replace a small set of the servers with variants written to running on top of Wayland; of course with some functionallity of @command{mds} missing. @item @cpindex Security It is trivial to only have setuid on for the part of the display server where it is required. @end itemize @node The Monolithic Server Architecture @subsection The Monolithic Server Architecture @cpindex Monolithic server architecture @cpindex Architecture, monolithic server @cpindex Monolithic display servers Description: The display server is implemented as one binary. @noindent @cpindex X11 @cpindex X.org @cpindex Mir @cpindex Wayland @cpindex Weston @cpindex Surface Flinger @cpindex Android/Linux, Surface Flinger @cpindex Quartz Compositor @cpindex Mac OS X, Quartz Compositor @cpindex OS X, Quartz Compositor @cpindex Desktop Window Manager @cpindex Windows, Desktop Window Manager Implementations: X11@footnote{X11 is a protocol, I beleave all X11 servers are monolithic, atleast the major ones are}, Mir, Wayland@footnote{Wayland is not actually monolithic, it is just a protocol. But Wayland is written with a monolithic mindset, and it is preferred that the display server implementation is monolithic.}, Surface Flinger, Quartz Compositor, Desktop Window Manager. @noindent Advantages: @itemize @bullet{} @item @cpindex Confidentiality @cpindex Privacy @cpindex Security @cpindex Flexibility The monolithic architecture makes it trivial to isolate information for clients to achieve confidentiality. Prioritising confidentiality however leads to problems implementing features such as screenshooting and global hotkeys. @item @cpindex Performance Monolithic server does not need to pass messages between modules, but can rather perform normal function calls and achieve greater performance. @item @cpindex Size Monolithic display servers can have a smaller memory footprint than its full-fledged counterparts. @end itemize @node The Hybrid Server Architecture @subsection The Hybrid Server Architecture @cpindex Hybrid server architecture @cpindex Architecture, hybrid server @cpindex Hybrid display servers @cpindex Milliserver architecture @cpindex Architecture, milliserver @cpindex Millidisplay servers @cpindex Macroserver architecture @cpindex Architecture, macroserver @cpindex Macrodisplay servers Description: The display server is implemeneted with the microserver architecture except some components are built into the master server for performance or security reasons. @noindent Hybrid display server could arguably be called milli-display servers@footnote{Playing of the International System of Units and its illogical prefix names.} to emphasis that they are small, but not as small as micro-display servers, are much more closely related to micro-display servers than monolithic display servers, and, in constrast with OS kernels, have a proper distinction from monolithic systems and microsystems. @footnote{I don't know about calling them macro-display servers, that implies that they are the total opposite of micro-display servers, since ‘macro’ means large and ‘micro’ means small.} @noindent Implementations: none? @noindent Advantages: @itemize @bullet{} @item Can achieve most of the microserver architecture's advantages, but not always to the same extent. @item @cpindex Confidentiality @cpindex Privacy @cpindex Security @cpindex Flexibility By integrating some servers into the master server, the hybrid architecture can isolate information for clients to achieve confidentiality. Prioritising confidentiality however leads to problems implementing features such as screenshooting and global hotkeys. @item @cpindex Performance Large and high frequency messages does not need to be passed around to other servers if they are integrated into the master server. This lets hybrid display server achieve the same perfomance performance as monolithic display servers for tasks where it is desirable. @end itemize @noindent The mds protocol and its reference implemention can easily be made into a hybrid display server protocol and an implementation thereof. @node The Megalithic Server Architecture @subsection The Megalithic Server Architecture @cpindex Megalithic server architecture @cpindex Architecture, megalithic server @cpindex Megalithic display servers @cpindex Megaserver architecture @cpindex Architecture, megaserver @cpindex Megadisplay servers Description: A monolithic display server where applications are loaded or compiled into the display server itself. @noindent These are also known as mega-display servers. @noindent Implementations: none? @noindent Advantages: @itemize @bullet{} @item @cpindex Performance No interprocess communication is required, apart from letting the display server know to load modules if it does not compile in its programs. This lets megalithic display server achieve even greater performance than monolithic display servers. @end itemize @noindent Disadvantages: @itemize @bullet{} @item @cpindex Code quality @cpindex Quality of code Imposes restrictions on which languages applications can use. @item @cpindex Flexibility Imposes restrictions on how applications can behave. @item @cpindex Flexibility @cpindex Code quality @cpindex Quality of code Cannot be networked without exposing an alternative display server protocol. @item @cpindex Stability The display becomes more crash prune; if an application crashes it is likely to crash the entire display. @item @cpindex Security Applications will run with the same privileges as the display server, which is root on most operating systems. @end itemize @noindent @cpindex Gaming Megalithic display servers could be interesting for high-performing gaming consoles. @node The Modular Server Architecture @subsection The Modular Server Architecture @cpindex Modular server architecture @cpindex Architecture, modular server @cpindex Modular display servers Description: A monolithic display server where server-like programs can be loaded as modules into the display server but applicates are connected with interprocess communication. @noindent Implementations: none?@footnote{Desktop Window Manager is partially modular, but as of yet, this cannot be utilised by end-users.} @noindent Advantages: @itemize @bullet{} @item @cpindex Flexibility Can achieve that flexibility of micro-display servers, but not when networked, with the same memory footprint as monolithic display servers. @item Has the same advantages as monolithic kernels. @item @cpindex Performance Applications that require absolute performance can be loaded as modules and achieve the same performance as megalithic kernels, however with the same caveats. @end itemize @noindent With a little work the mds protocol could be transformed into a modular server display protocol, and with some work the reference implementation could be made into a modular server display. @node The Modular Microserver Architecture @subsection The Modular Microserver Architecture @cpindex Modular microserver architecture @cpindex Architecture, modular microserver @cpindex Modular microdisplay servers Description: A modular display server with a module that enables clients to act as modules that communicates via interprocess communication rather than being loaded into the display server. @noindent Implementations: none? @noindent Advantages: @itemize @bullet{} @item The modular microserver architecture seem to provide all of the advantages of the other architecture but none of the disadvantages. However, modules can still crash and bring down the display server, but the idea is to not load unstable modules but let the be servers. Therefore exo-diplay server are slightly more robust. @end itemize @noindent With a little work the mds protocol could be transformed into a modular server display protocol, and with some work the reference implementation could be made into a modular server display. Then the untransformed version of @command{mds-server} could be made into a module for the transformed version. @node The Exoserver Architecture @subsection The Exoserver Architecture @cpindex Exoserver architecture @cpindex Architecture, exoserver @cpindex Exodisplay servers Description: An exo-display server is a tiny display server that attempts to let applications access the underlaying system directly and implements basic interprocess communication to let applications share vital information and coordinate with each other. @noindent Implementations: none? @noindent Advantages: @itemize @bullet{} @item @cpindex Performance Can achieve the same performance as megalithic display servers. @item @cpindex Stability Can achieve the same robustness as micro-display servers. @end itemize @noindent Disadvantages: @itemize @bullet{} @item @cpindex Flexibility @cpindex Code quality @cpindex Quality of code Cannot be networked without exposing an alternative display server protocol. @end itemize @noindent Exo-display servers could be interesting for high-performing gaming consoles. @node Fixing X.org Issues @section Fixing X.org Issues X.org is been critiqued for several shortcoming, some of which have caused people to start on new display servers to replace X.org. This chapter will list some issues and discuss how they can be avoided in mds. @menu * Automatic Cleanup:: Cleanup up after applications. * Input Problems:: Problems related to human input. * Other Issues:: Other issues in X.org. @end menu @node Automatic Cleanup @subsection Automatic Cleanup @cpindex Automatic cleanup @cpindex Cleanup, automatic @cpindex Resolution change @cpindex Games A common critique of X.org is that the monitor resolution is not restored if a game change the resolution and for some reason, for instance a software crash, does not switch back before exiting. This problem is not intrinsic to the protocol, but rather because of a lacking protocol. You can run a program like @command{xrandr} to change the monitor resolution for the entirety of the session and @command{xrandr} can exit when the resolution has changed. This is how it should be. However, there is no way to tell an X.org server to switch back if the connection between the program and server is lost. This is easily fixed by adding a lifespan parameter as found in @ref{set-gamma}. @cpindex Gamma correction A similar critique of X.org is that gamma ramps are not restored when an application exits. Either the ones complaining about this do not understand why gamma ramps exists, namely so you can calibrate the monitor's output in respect to the colours, and just think it is a way to make the video in games brighter. Or they think we should have daemons running idly to have gamma adjustments. Or, more likely and more validly, its is poorly phrased and they actually want a way for applications, like games, to inform the display server to undo its modifications to the gamma ramps when the program exits. This is already supported by the mds protocol. @node Input Problems @subsection Input Problems @cpindex Grab, input @cpindex Keyboard, grab @cpindex Mouse, grab @cpindex Input grabbing X11 allows programs to exclusively grab keyboard and mouse input. When a program that does this misbehaves or become unresponsive, you cannot do anything but manage it from another computer or restart the computer. In mds exclusively grabbing is achieved by setting the client priority for the related message to the highest priority. @footnote{If multiple clients do this, it is arbitrary who gets the message first and can stop the others from getting it.} This is however not allowed (but nothing will stop you) as the idea is that clients should either select a predefined priority, select a priority between servers it to be between, or select a priority of 50 percent or 150 percent of another servers priority. Thus, unless a client breaks this rule, you can always have your server for switching to the TTY at a higher priority than other programs. A similar, and probably related, problem in X.org is that global keybindings don't work when a popup or menu has focus. (Thankfully GTK+ will close that item if it receives unexpected input.) I have hard time seeing how this could become an issue in mds. @cpindex Hotkeys @cpindex Keyboard bindings @cpindex Bindings, keyboard @cpindex Keyboard shortcuts @cpindex Shortcuts, keyboard Another issue related to the keyboard in X.org is that hotkeys in programs do not work in a few situtations because the program was not designed with another keyboard layout in mind than the keyboard layout the developer used. I suggest that programs restrain themself from including @key{Alternative Graph} in their hotkeys and only use @key{Shift} for @key{a} through @key{Z} and @key{Space}. However, what I would really like to see is that toolkits lets users modify all hotkeys. If program additionally restrain themself to having all hotkeys contain control or alt the keyboard layouts with non-latin alphabets would not suffer because they do not use the latin alphabet. @node Other Issues @subsection Other Issues @cpindex Re-executing servers @cpindex Updating, online @cpindex Online updating @cpindex Version update @sgindex @code{SIGUSR1} @sgindex @code{SIGUPDATE} X11 display servers do not let you upgrade or otherwise replace graphics drivers online. Or other parts of it. X11 display servers could allow you to send a signal, for instance @code{SIGUSR1}, to upgrade the whole server, however this is not favourable, and X.org does not do this. The reference implemention of the mds protocol lets you safely upgrade any part of it online by sending @code{SIGUSR1} to the server that should be upgraded. On catastrophic failure in this process the server would restart and lose volatile data, but the server should be upgraded and it would ask all running clients for resend information the server lost. @cpindex Threading @cpindex Multi-threading @cpindex Pervasively parallel processing @cpindex Pervasive threading Another issue with X.org is that it is not multithreaded, which can cased intensive programs to freeze your desktop. mds is inherently pervasively parallel and only subsystems, rather than the whole system, can suffer from this. It is however easy for mds servers to implement pervasive threading, that is, letting each request spin up a new thread in the server. @node Why Not Wayland @section Why Not Wayland @cpindex Wayland Development of @command{mds} started out of concern that Wayland would not meet our needs, and the knowledge that X does not. We are now however aware that Wayland meets our needs even less than X@. @footnote{Not even counting that the documentation for Wayland is way more lacking that X's documentation.} @cpindex Flexibility Wayland only has protocols for drawing onto a buffer and input devices, and some very limited output protocols. Wayland is inherently inflexible. If anyone wants to add additional functionally, must do so in the compositor --- the window manager --- and publish the protocol. It is then up to all other compostors (window managers) to implement the protocol. It should be noted that Wayland does not even have an official protocol for applying gamma corrects. Some compositors (window managers) choose to implement it by using @command{colord}. Additionally, screenshooting, screen recording and global hotkeys must be implemented in the compositor (window manager). Why? Because of security. In Wayland, security always trumps useability and usefulness. Another huge limitation of Wayland is that it does not have any network protocol. For it to be network, the compositor must implement a network protocol --- and there is no official network protocol. When this is all done, a compositor proxy must be written that can communicate with it. @node Why Not Mir @section Why Not Mir @cpindex Mir The major problem with Mir, and why we need @command{mds} instead, is that contributions to Mir are subject Canonical's contributions-limiting agreement (CLA). @cpindex Flexibility Mir, like Wayland, is very limited. Mir is however easier to extend. Ignoring the CLA, Mir is better tham Wayland, but for similar reasons it is still not good enough. Mir is however licensed under the GNU General Public License version 3 and GNU Lesser General Public License version 3. Much better than the MIT license, and hopefully we can steal some stuff. @node Desktop Environments @section Desktop Environments @cpindex Goals of @command{mds} @cpindex Desktop environments @cpindex Environment, desktop A design goal of @command{mds} is to bring unity to the graphical environment. Something desktop environments traditionally have been impairing. Traditionally a desktop environment would implement, or implement some of: @itemize @bullet{} @item Window layout management (window manager) @item Window decoration (window manager) @item Workspaces (window manager) @item Compositor (window manager) @item Taskbars @item Status icon trays @item Launchers @item Application menus @item Autostart of applications @item Keyboard bindings @item Rat bindings @item Rat barriers @item Desktop @item Widgets @item Their own display manager (login screen) @item Their own screensaver and screenlocker @item Their own graphical toolkit @item A bunch of random graphical tools @end itemize This is absolute madness, a waste of time and creates fragmentation. There is no problem for a desktop environment development team to implement all this for their desktop environment for @command{mds}. However doing so is discourage for the mentioned reasons as well as because doing so means that the user needs to know what not to launch, that is, what the desktop environment will start. @menu * Window Management:: Window management in mds. * Application Management:: Application management in mds. * Input Management:: Management of input peripherals in mds. * The Desktop:: The desktop in mds. @end menu @node Window Management @subsection Window Management @cpindex Window management @cpindex Widdow layout managers @cpindex Hotkeys @cpindex Keyboard bindings @cpindex Bindings, keyboard @cpindex Keyboard shortcuts @cpindex Shortcuts, keyboard @pgindex @command{mds-keybind} For @command{mds}, a desktop environment should not have its own window layout manager. A better solution is to have a few well written window layout manager that are different from each other in how windows are layed out. These should not listen for keyboard actions to figure out how it shall rearrange the windows. Instead they should listen on the display server's messaging system for such commands, and @command{mds-keybind} or similar server should be configured with all hotkeys. @cpindex Window decorators @cpindex Decorators, windows There are a few classes of window decorator. A desktop environment still do not need its own. They can however create themes for existing decorators. What we need here is a small set of window decorators that are very customisable. @cpindex Workspaces @cpindex Pagers Workspaces in X is poorly done. Window managers implement it, and pagers are window manager dependent @footnote{Well, there is Extended Window Manager Hints (EWMH), but it is very restricted.}. Yet there are very few properties they can have: @itemize @bullet{} @item Do workspaces span outputs, screens or the display? @item Are workspaces dependent on outputs, screens or displays? @item Do workspaces have a geometrical position? @item Are new workspaces created when needed? @end itemize Clearly what we need is one workspace manager where these can be configured. And the desktop environments can create their own pagers if they see fit, but all pagers work everywhere. @cpindex Compositors @cpindex Fancy effects @cpindex Effects, fancy Traditionally desktop environments wrote their own compositor for flash or otherwise fancy effects, or write a quirks to a common one so the common on could be used. With all other parts, of what has traditionally be the window manager, independent of the desktop environment, creating one universal compositor with plugin support for effects the desktop environment want to have, such be no problem. @node Application Management @subsection Application Management @cpindex Application management @cpindex Taskbars @cpindex Extended Window Manager Hints @cpindex EWMH (Extended Window Manager Hints) Many X desktop environments provide taskbars, where all windows are listed. However because of Extended Window Manager Hints (EWMH), and the ability to read windows' position and wait for windows to move, this is not actually necessary. Of course, desktop environments may need to do this to theme the environment. A taskbar for @command{mds} should: @itemize @bullet{} @item be about to restrict listed windows a those under specific outputs, and @item be about to restrict listed windows to viewed workspaces. @end itemize @cpindex Status icon tray @cpindex System tray @cpindex Tray, status icons @cpindex Icon, status, tray Traditionally, status icon trays have been implemented with window embed method. And apart from there being two competing standard, this is pretty sane. But ther have been some restrictions @command{mds} does not suffer: @itemize @bullet{} @item icons should not be rearranged, and @item embedder did not know of the background looked where the icon was added. @end itemize Desktop environments should feel free to create their own themed application launchers and application menus. This functionally is already de facto standardised, and there is no reason to change anything. @cpindex Startup of applications, automatic @cpindex Automatic startup of application @cpindex Application, startup, automatic @pgindex @file{mdsinitrc} Some desktop environments provide a method to for automatically starting applications during the startup of a desktop environment. This is discouraged. It is better to teach the user to edit @file{~/.mdsinitrc}. @node Input Management @subsection Input Management @cpindex Input management @cpindex Window management @cpindex Hotkeys @cpindex Keyboard bindings @cpindex Bindings, keyboard @cpindex Keyboard shortcuts @cpindex Shortcuts, keyboard @pgindex @command{mds-keybind} Many desktop environments and window managers for X implement global keyboard bindings. This is not how you should do this. The servers should recognise commands passed via @command{mds}'s interprocess communication. Configurations of the keyboard bindings should be done in a server like @command{mds-keybind}. @pgindex @command{mds-ratbind} @cpindex Rat bindings @cpindex Mouse bindings @cpindex Pointer bindings @cpindex Hotcorners @pgindex @command{mds-ratbarrier} @cpindex Cursor barriers @cpindex Rat pointer barriers @cpindex Mouse pointer barriers @cpindex Pointer barriers @cpindex Screen edges, barriers @cpindex Barriers, rat Similarily some desktop environments implement rat bindings@footnote{Notably hot corners.} and rat barriers. This too should be done via servers like like @command{mds-ratbind} and like @command{mds-ratbarrier}. @node The Desktop @subsection The Desktop @cpindex Desktop @cpindex File manager @cpindex Background @cpindex Root window @cpindex Window, root Desktop environments provide their own desktop because they want it to fit the rest of the environment. For example, it can use components of the desktop environment's file manager. This practice is however problematic, because they also implement the background, which is also implemented on top of the root windows. @command{mds} desktops should use a transparent background and let the root window be used for implementing the background. @cpindex Desktop widgets @cpindex Widgets, desktop Additionally, some desktop environments provide desktop widgets. These can either be drawn on the root window, the desktop window or as always-on-bottom windows. In @command{mds}, windows can have Z-order priority. That is, you can specify how important it is that your window is at the bottom or at the top. For widgets with input, it is recommended to use this to put the widget just above the desktop window. For windows without input, it is recommended draw on the root windows. However doing so requires that be listen for updates to the backgrund. @node Why Dither Colours @section Why Dither Colours @cpindex Colour dithering @cpindex Dithering of colours Now that almost all computers, and all modern computers, have support for 24-bit colour, colour dithering have faded to unexistence. The common logic is that the colours are good enough, or that we can only perceive 10 million colours, and 24-bit colour gives us almost 17 million colours. However, we can see the difference between two colours if they are next to each other and painted on large areas, even if the difference is the smallest that 24-bit colour can bring us. So whilst 24-bit colour is good enough in most cases, it is not enough in gradients where the difference between the end colours are low, especially when these colours are bright. Therefore we still need dithering in some cases. Now that we get increasingly higher pixel pitch our display output, dithering is going to look increasingly better. Since we somehow got stuck at 24-bit colour, dithering is important. @node GNU General Public License @appendix GNU General Public License @include gpl.texinfo @node GNU Free Documentation License @appendix GNU Free Documentation License @include fdl.texinfo @node Concept index @unnumbered Concept index @printindex cp @node Data type index @unnumbered Data type index @printindex tp @node Function index @unnumbered Function index @printindex fn @node Option index @unnumbered Option index @printindex op @node Program index @unnumbered Program index @printindex pg @node Protocol index @unnumbered Protocol index @printindex pr @node Signal index @unnumbered Signal index @printindex sg @node Unicode block index @unnumbered Unicode block index @printindex ub @node Variable index @unnumbered Variable index @printindex vr @bye TODO toolkit guidelines screen reading keyboard commands rat commands look and feel configurations TODO other input devices 3d pointer joystick gamepad infrared remote steering wheel pedals gloves multitouch (screen, rat) acceleroscope gyroscope camera 3d camera TODO 3d output TODO protocol: embed: embedding windows inside other windows such as a status icon tray TODO protocol: arcade: a game takes over control over outputs for increased performance TODO protocol: startup: a mechanism allowing a desktop environment to track application startup TODO protocol: drag;; drag and drop should be usable for saving files. TODO protocol: keytrans: changing keyboard layout TODO protocol: rat TODO protocol: cursor TODO protocol: state TODO protocol: focus;; multifocus TODO protocol: compositor TODO protocol: crtc TODO protocol: presentation TODO protocol: network TODO protocol: decorator TODO protocol: workspace TODO protocol: ping TODO notifications (balloons, bubbles) TODO virtual resolution (the screen is larger than the output) TODO taskbar features: progress bars (any number) with colours control buttons such as play, pause, previous and next urgency alert stack all windows that belongs to the same process stack all windows with the same class extensible right-click menu right-click menu includes actions to start a new process TODO application menu features: different ways to start an program, for example, browers may include a safe-browsing mode. TODO In `Rat Cursors` use anchors and references to hyperlink names.