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@@ -1,95 +0,0 @@ -This is a document describing how redshift works. It might be useful -if the normal docs don't answer a question, or when you want to hack -on the code. - - -Programs -======== - -redshift --------- - -redshift is a program written in C that tries to figure out the user's -location during startup, and then goes into a loop setting the display -gamma according to the time of day every couple seconds or minutes -(details?). - -On systems that support signals, it reacts to the SIGUSR1 signal by -switching to day/night immediately, and when receiving SIGINT or -SIGTERM, it restores the screen gamma (to 6500K). - -Redshift knows short and long transitions, short transitions being -used at start and when reacting to signals. Short transitions take -about 10 seconds; long transitions about 50 minutes. - -Once running, redshift currently doesn't check location providers -again. - - -redshift-gtk ------------- - -redshift-gtk is a small program written in Python that shows a status -icon (what is an appindicator versus a GTK status icon?) (does it -change the icon according to internal program state of redshift? -doesn't seem so) and run an instance of the "redshift" program, and -will send it SIGUSR1 each time the user clicks the icon. - - -Alternative Features -==================== - -Redshift interacts with the rest of the system in two ways: reading -the location, and setting the gamma. Both can be done in different -ways, and so for both areas there are configure options to -enable/disable compilation of the various methods. ./configure --help -shows more about what parts of the program that can be conditionally -compiled. - -NOTE: some features have to be disabled explicitely, like ---disable-gnome-clock to prevent the gnome-clock code from being built -in. - -The two groups of features shall be called: "location providers" and -"adjustment methods". - -These are probably not the best names for these things but at least -I've been mostly consistent with the naming throughout the source code -(I hope). - -First adjustment methods: There is "randr" which is the preferred -because it has support for multiple outputs per X screen which is lacking -in "vidmode". Both are APIs in the X server that allow for manipulation -of gamma ramps, which is what Redshift uses to change the screen color -temperature. There's also "wingdi" which is for the Windows version, -and "drm" which allows manipulation of gamma ramps in a TTY in Linux. - -Then there are location providers: "manual", "geoclue2" and "corelocation". -Some time ago there was only one way to specify the -location which had to be done manually with the argument "-l LAT:LON". -Then later, automatic "location providers" were added and the syntax -had to be changed to "-l PROVIDER:OPTIONS" where OPTIONS are arguments -specific to the provider. But to make people less confused about the -change I decided to still support the "-l LAT:LON" syntax, so if the -PROVIDER is a number, the whole thing is parsed as LAT:LON. You could -run redshift with "-l manual:lat=55:lon=12" and get the same effect as -"-l 55:12". - -So there are currently two automatic location providers "gnome-clock" -and "geoclue". From the beginning I was looking for a way to get the -location automatically (from e.g. GPS) and Geoclue seemed like a good -idea, but upon closer investigation it turned out to be horribly -unstable. At this time GNOME had a clock applet which was present by -default (at least in Ubuntu) that allowed the user to set a home town. -This setting was registered in the gconf key -/apps/panel/applets/clock_screen*/prefs/cities. -The idea was to use this information until Geoclue had become more -stable. To me, it always was a hack. Now that the Clock applet has -gone (at least in Ubuntu) the "gnome-clock" makes little sense and -causes a lot of trouble, so I really want to get rid of it as soon as -possible. The problem is that Geoclue is still problematic for some -people. - -Lastly, there's the support for configuration files for which there's -no real documentation, but all the options that can be set on the -command line can also be set in the config file. |