xrandr brightness settings permanent

[Michal Srb]

On středa 14. listopadu 2018 10:52:59 CET Riccardo Berto wrote:
> I have a low quality screen. It's very bright, even at minimum settings
> in the monitor menu. I'm able to reduce the brightness with `xrandr
> --output HDMI-0 --brightness 0.25` but sometimes the brightness goes
> back to the default levels when downloading something from the browser
> or doing peculiar interactions with the Xorg server, like opening the
> file manager. I guess this is caused by a re-read of the xorg.conf file
> under certain circumstances that I'm not aware of.
> The question is: is it possible to make the previously mentioned xrandr
> command permanent via some /etc/X11/xorg.conf.d/ conf file?

The xrandr's brightness parameter is just a multiplier for gamma, so you 
should be able to achieve the same thing with configuration like this:

Section "Monitor"
  ...

  Gamma 0.25
EndSection

This is alternative way of setting the initial value instead of using xrandr, 
but it probably won't fix the random changing back at runtime. X server does 
not normally reload xorg.conf while it is running. It seems that some 
application is intentionally changing the gamma at runtime, you should try to 
find out which one it is. Maybe some color management app? Don't you have 
redshift installed?

Michal