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.

  • I have the same issue atm, wonder if you found a solution by now? – meijuh Dec 16 '15 at 8:57
  • @meijuh Nope still nothing but workarounds. What's your computer? Do you have the issue with the GDM as well? – Thibault Lemaire Dec 17 '15 at 9:56
  • I have a Lenovo W541 with Debian Jessie and, indeed, GDM. My workaround is to install xbacklight, and add xbacklight -set 100 to /etc/gdm3/Init/Default. But this only solves the issue for the login screen, not after I log in. – meijuh Dec 17 '15 at 14:06
  • @meijuh Since I don't use a second monitor that often, and because I consider it a messy fix, I have decided not to use an init script whether it be on desktop manager init or session init. So I'm still using the tty switch trick (which I added to my question btw) whenever I have to plug in a second monitor. But if you want you can apply the same xbacklight fix you used for the gdm to the gnome session itself. Simply add a brightness-fix.desktop entry to ~/.config/autostart with the same command you used [Desktop Entry] Exec=xbacklight -set 100 – Thibault Lemaire Dec 18 '15 at 18:21

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.

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