LightDM - Jul 2013 - How to adjust display brightness using keyboard keys?

I have tried everything I can think of to adjust display brightness via the
keyboard keys at the lightdm unity-greeter login screen.

Once you login to an Ubuntu desktop session the keys work fine. However, at the
login screen and when you are logged in to a non-Ubuntu desktop session, e.g.
xfreerdp then the brightness keys do not work.

I have verified that I can change the brightness by doing ctrl+alt+f1 at the
lightdm login screen and issuing either of these commands:

sudo /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 150

echo 150 | sudo tee /sys/class/backlight/radeon*/brightness

The question is how to I execute these commands from the brightness keys or any
other combination of keys if that makes it possible?

I have tried to use xbindkeys and a .xbindkeyrc file with the following
contents:

/usr/bin/pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper
--set-brightness 150
c:68

/usr/bin/pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper
--set-brightness 255
c:69

This works, but again you have to be logged in to an Ubuntu desktop session!

I have tried to use an upstart job to start xbindkeys.

I have tried to place the .xbindkeysrc file in /var/lib/lightdm.

Nothing works and I have no other options right now other than to tell my
users...sorry but you can't change display brightness or if you need to
I'll have to ssh into your machine and run the command above :(

Something this simple must be possible I just don't know how.

Hi Jonathan,

Did you try the display setup script in /etc/lightdm/lightdm.conf to start a
daemon listing for this hotkey in the background?

Regards, Andre

Jonathan <dev at puppeq.com> wrote:
>I have tried everything I can think of to adjust display brightness via
>the keyboard keys at the lightdm unity-greeter login screen.
>
>Once you login to an Ubuntu desktop session the keys work fine.
>However, at the login screen and when you are logged in to a non-Ubuntu
>desktop session, e.g. xfreerdp then the brightness keys do not work.
>
>I have verified that I can change the brightness by doing ctrl+alt+f1
>at the lightdm login screen and issuing either of these commands:
>
>sudo /usr/lib/gnome-settings-daemon/gsd-backlight-helper
>--set-brightness 150
>
>echo 150 | sudo tee /sys/class/backlight/radeon*/brightness
>
>The question is how to I execute these commands from the brightness
>keys or any other combination of keys if that makes it possible?
>
>I have tried to use xbindkeys and a .xbindkeyrc file with the following
>contents:
>
>/usr/bin/pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper
>--set-brightness 150
>c:68
>
>/usr/bin/pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper
>--set-brightness 255
>c:69
>
>This works, but again you have to be logged in to an Ubuntu desktop
>session!
>
>I have tried to use an upstart job to start xbindkeys.
>
>I have tried to place the .xbindkeysrc file in /var/lib/lightdm.
>
>Nothing works and I have no other options right now other than to tell
>my users...sorry but you can't change display brightness or if you need
>to I'll have to ssh into your machine and run the command above :(
>
>Something this simple must be possible I just don't know how.
>_______________________________________________
>LightDM mailing list
>LightDM at lists.freedesktop.org
>http://lists.freedesktop.org/mailman/listinfo/lightdm
-- 
Andre Kl?rner

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