.TH RADHARC 1 radharc
.SH NAME
radharc \- Adjust display colour temperature after the Sun

.SH SYNOPSIS
.B radharc
[-M
.IR method ]
[-S
.IR site ]
[-c
.IR crtc "] ..."
[-R
.IR rule ]
[-p
.IR priority ]
[-f
.IR fade-in ]
[-F
.IR fade-out ]
[-h
.RI [ high-temp ][\fB@\fP high-elev ]]
[-l
.RI [ low-temp ][\fB@\fP low-elev ]]
(-L
.IR latitude : longitude
| -t
.I temperature
[-d] | -x)

.SH DESCRIPTION
.B radharc
adjusts the colour temperature of your monitor according
the the elevation of the Sun. This is intended to reduce
eye strain and reduce deplayed sleep phase syndrome.
.PP
.B radharc
is inspired by
.BR redshift (1)
but uses
.BR libcoopgamma (7)
to allow it to be used alongside other programs that also
modify the monitors colour output, as long as the also use
.RB libcoopgamma (7).

.SH OPTIONS
The following options are supported:
.TP
.BR -c \ \fIcrtc\fP
Apply the filter to the CRTC with the monitor whose EDID is crtc.
By default, the filter is applied to all monitors.

If
.I crtc
is
.RB ' ? ',
all available CRTC's are listed.
.TP
.B -d
Keep the process alive and remove the filter on death.
.TP
.BR -f \ \fIfade-in\fP
Set effect fade-in time (gradual application when the program
starts). The value is interpreted a real number of seconds.
.TP
.BR -F \ \fIfade-out\fP
Set effect fade-out time (gradual restoration when the program
stops). The value is interpreted a real number of seconds.
.TP
.BR -h \ [\fIhigh-temp\fP][ @ \fIhigh-evel\fP]
Selects that the colour temperature shall be
.I high-temp
Kelvins when the Sun's elevation is
.I high-evel
degrees or higher above the horizon.

This option only has effect when combined with the
.B -L
option.
.TP
.BR -l \ [\fIlow-temp\fP][ @ \fIlow-evel\fP]
Selects that the colour temperature shall be
.I low-temp
Kelvins when the Sun's elevation is
.I low-evel
degrees or lower above the horizon.

This option only has effect when combined with the
.B -L
option.
.TP
.BR -L \ \fIlatitude\fP : \fIlongitude\fP
Selects the location the Sun's elevation shall be calculated
for. The program will run until it is manually terminated and
continually readjust the colour temperature according the
the Sun's elevation. The latitude and longitude shall be
specified in decimal format. Positive numbers shall be used
GPS coordinates north of the equator and GPS coordinates
east of the prime meridian. Negative number shall be used
for GPS coordinates south of the equator and GPS coordinates
west of the prime meridian.
.TP
.BR -M \ \fImethod\fP
Adjustment method name or number. Recognised names include:
.TS
tab(:);
l l.
\fBdummy\fP:Dummy method
\fBrandr\fP:X RAndR
\fBvidmode\fP:X VidMode
\fBdrm\fP:Linux DRM
\fBgdi\fP:Windows GDI
\fBquartz\fP:Quartz Core Graphics
.TE

The adjustment methods are supported via
.BR libgamma (7).
Only methods that were enabled when
.B libgamma
was compiled will be supported.

If
.I method
is
.RB ' ? ',
all available adjustment methods are printed.
.TP
.BR -p \ \fIpriority\fP
Set the priority of the filter. Filters with higher priority
are applied before filters with lower priority. The value must
be a signed 64-bit integer (between -9223372036854775807 and
9223372036854775807).
.BR radharc 's
default priority is -2305843009213693952.

If
.I priority
is
.RB ' ? ',
the utility's default priority is printed.
.TP
.BR -R \ \fIrule\fP
Set the rule of the filter to
.IR rule .
This is the last part of the filter's identifier
(class). The default rule is
.BR standard .
.TP
.BR -S \ \fIsite\fP
Select the site to which to connect. For example
.RB ' :0 ',
for local display 0 when using X.
.TP
.BR -t \ \fItemperature\fP
Colour temperature, in Kelvins, to apply.
.TP
.B -x
Remove the currently applied filter.

.SH OPERANDS
No operands are supported.

.SH SEE ALSO
.BR coopgammad (1),
.BR cg-tools (7),
.BR redshift (1),
.BR blueshift (1)