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.Dd $Mdocdate: November 17 2022 $
.Dt LUXGET 3
.Os Linux
.Sh NAME
.Nm luxget ,
.Nm luxmax ,
.Nm luxgetp
.Nd query the current or maximum brightness of a display
.Sh LIBRARY
.Lb liblux
.Sh SYNOPSIS
.In lux.h
.Ft int
.Fn luxget "lux_t *disp"
.Ft int
.Fn luxmax "lux_t *disp"
.Ft double
.Fn luxgetp "lux_t *disp"
.Sh DESCRIPTION
The
.Fn luxget
function takes a pointer to a
.Vt lux_t
structure and returns the raw brightness value of the associated display.
If the function returns \-1 it means that an error has occurred, however this is
only possible if
.Va disp
has not yet been passed to any other library function that interacts with the
current brightness level, whether that be to get the current brightness or set
the current brightness.
.Pp
The
.Fn luxmax
function behaves identically to the
.Fn luxget
function except it returns the maximum supported brightness of the display
referred to by
.Va disp .
Additionally, this function can only error if
.Va disp
has not yet been used as a parameter to an invocation of either
.Fn luxmax
or any of the
.Fn lux*p
functions.
.Pp
The
.Fn luxgetp
function takes a pointer to a
.Vt lux_t
structure and returns the brightness of the associated display as a percentage.
A return value of 100.0 means the display is at 100% brightness.
If the function returns \-1 it means that an error has occurred.
Internally this function calls both
.Fn luxget
and
.Fn luxmax ,
so if both of those functions are in a state where they can no longer fail, then
you do not need to error check this function.
.Sh RETURN VALUES
The
.Fn luxget
function returns the raw brightness value of the associated display.
.Pp
The
.Fn luxmax
function returns the maximum raw brightness value of the associated display.
.Pp
The
.Fn luxgetp
function returns the current brightness percentage of the associated display.
A value of 100.0 is equivalent to 100% brightness.
.Pp
On error, all the above functions will return \-1 and
.Va errno
is set to indicate the error.
.Sh EXAMPLES
The following program queries and prints information regarding displays current
brightness.
.Bd -literal -offset indent
#include <err.h>
#include <stdio.h>
#include <stdlib.h>

#include <lux.h>

int
main(void)
{
	int cur, max;
	double curp;
	lux_t disp;

	luxinit(&disp);

	if ((cur = luxget(&disp)) == -1)
		err(EXIT_FAILURE, "luxget");
	if ((max = luxmax(&disp)) == -1)
		err(EXIT_FAILURE, "luxmax");

	/* Because we already passed disp to luxget() and luxmax() previously,
	 * we don't need to do error checking!
	 */
	curp = luxgetp(&disp);

	printf("Current Brightness (Raw):        %d/%d\en", cur, max);
	printf("Current Brightness (Percentage): %d%%/100%%\en", (int) curp);

	luxfree(&disp);
	return EXIT_SUCCESS;
}
.Ed
.Sh ERRORS
.Fn luxget ,
.Fn luxmax ,
and
.Fn luxgetp
can fail with any of the errors specified for
.Fn fdopen
or
.Fn openat .
.Sh SEE ALSO
.Xr luxdec 3 ,
.Xr luxdecp 3 ,
.Xr luxfree 3 ,
.Xr luxinc 3 ,
.Xr luxincp 3 ,
.Xr luxinit 3 ,
.Xr luxset 3 ,
.Xr luxsetp 3 ,
.Xr lux.h 3head
.Sh AUTHORS
.An Thomas Voss Aq Mt mail@thomasvoss.com