This is a very simple library and command line tool for changing the backlight on a Linux system.
To keep the dependencies of the library down, the command line tool is in this repo as an example. This means you need to pass an extra flag when you're running or installing it.
To run the tool, you will need Rust installed (ideally through Rustup). You can try it out by running
cargo run --example brightr
or install it with your other Cargo binaries using
cargo install --path . --locked --examples
In my environment, after installing brightr, I've set up the
increase-brightness and decrease-brightness keys to run, respectively,
brightr -m 1 -e 4 up 10
brightr -m 1 -e 4 down 10
The -m may not be necessary if your display doesn't turn all the way off at
zero --- in my testing some do, some don't. The value given to -e determines
the exponent used to map internal backlight levels to perceived brightness, and
may also want to be tweaked (try values between 2 and 4, including fractional).
The command line interface currently looks like this (run without arguments, or
with help, to get the current instructions):
Adjust display backlight
Usage: brightr [OPTIONS] <COMMAND>
Commands:
get Print the current backlight setting in the format "x/y", where x
is the current setting, and y is the max
set Set the backlight to a specific value
up Increase the backlight brightness relative to its current level,
saturating at the top of the device's range
down Decrease the backlight brightness relative to its current level,
saturating at the requested minimum brightness level
help Print this message or the help of the given subcommand(s)
Options:
-p, --picky Exit with a non-zero status if the device was already at the
edge of its range and could not be adjusted further. This can
be useful for detecting when the top or bottom of the scale
has been reached, to provide user feedback
-h, --help Print help
Device Options:
-n, --name <NAME> Name of backlight device to adjust. Use this to
override the automatic detection logic
-r, --raw Use the driver's raw brightness values for all input
and output instead of percentages
-e, --exponent <N> Map percentages to raw values using this exponent, to
apply gamma correction. A value of 2-4 is often about
right; the default of 1 makes the mapping linear
[default: 1]
-m, --min <RAW> Saturate the bottom end of the brightness range at
this (raw) value rather than zero. This is useful for
systems that shut the backlight off completely at
zero, if you don't want them to do that [default: 0]