Brightness falls at 0 when plugging second monitor

backlightbrightnessgdmgnomemulti-monitor

This only happens when using Gnome.

I have an Acer Aspire V3-772GTX54206G1TMakk laptop with an NVIDIA GeForce GTX 760M graphics card running Debian 8 (jessie) 64-bit, and I'm using Gnome 3.14.1.

The problem is every time I plug in a second monitor the brightness of my (built-in) primary monitor falls at 0, turning the backlight off and making the monitor unusable.

Luckily when this happens whilst a session is already open, the brightness can easily be turned back up, making the issue a minor inconvenience. But the real problem is it happens with GDM as well, and when I try to increase the brightness with the built-in keyboard shortcut (Fn + right arrow) the brigntess icon shows up (on both screens even if can only see the second one) but the bar doesn't move. It remains stuck at 0 no matter what I do.

Thus I have found another temporary workaround : Switching to another tty then switching back to the main tty. This somehow resets the brightness to 100%.

I said this bug is gnome specific because both SLiM (as an alternative to GDM) and XFCE (as an alternative to Gnome) work perfectly well with dual monitors. I have tried them on the same computer with the same setup.

Best Answer

Confirmed Gnome Bug

Why hello there 2015, here's 2017 and we've got Debian 9 Stretch as the stable branch.

So just upgrade Gnome was the answer you were looking for. I am currently using the exact same setup but with Gnome 3.22.2, and it works great.

Related Solutions

Ubuntu – Dual monitors on dual video cards on Ubuntu

Use nvidia-settings to configure your display adapter. Maybe you should try installing the latest proprietary NVIDIA driver.

After googling for a while, I learned that if I want to use two displays, I have to enable TwinView or Xinerama in nvidia-settings. Xinerama is out of question because it disables compiz. If you don't want to use compositing, which is required for compiz, just use Xinerama.

I have 2 video cards and if I turned on TwinView for both of them, Unity panel stretched on the whole 2 monitor desktop and app windows kept opening in the middle near the edge of the two displays.

Finally I decided to stick with separate X screens. The problem with this was compiz only started on the primary screen only, so I had to write two scripts to start it on Screen1 and Screen2 (I’m not using Screen3):

#!/bin/bash
DISPLAY=`echo $DISPLAY | sed s/[.]0$//`.1
compiz --replace &
sleep 5
google-chrome --user-data-dir=/home/nonoo/.config/google-chrome1 &

#!/bin/bash
DISPLAY=`echo $DISPLAY | sed s/[.]0$//`.2
compiz --replace &
sleep 5
google-chrome --user-data-dir=/home/nonoo/.config/google-chrome2 &

As you can see, the scripts also autostart Chrome on those displays automatically. The sleep lines are needed because without them Chrome’s window titlebar will show up behind the Unity panel.

I had another problem: there was no wallpaper on the screens, just a solid white background. To fix this, I installed “Advanced Settings” in the Software Center, and switched off “Have file manager handle the desktop”.

Set the screen brightness: xbacklight does not work on HDMI, xrandr –brightness does not stick

Are you using redshift?

I had your exact same issue and it was resolved by killing redshift.

killall redshift

xrandr --output HDMI-0 --brightness .5

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