gnome-session does not handle three external monitors.
Problem
Having updated to version 3.35.91, I stopped being able to run a three external monitor setup (both on Wayland and Xorg).
I am using a T580 Lenovo laptop with the Thunderbolt docking station and three external monitors connected to it (one over a VGA, two over an HDMI). Before, I was using the following setup:
- the built-in display is switched off
- three external displays are on
- the middle one being the Primary display
After the update, I cannot use this setting any more because Gnome keeps one of the monitors switched-off and only displays on two monitors. The only way, I can use three screens is with the built-in monitor on. Otherwise, I can use any combinations of three monitors, providing one of them is the built-in, or I can use any combination with two monitors only.
With the built-in monitor switched off, the third external monitor (which happens to be the last one in the set-up) stays black.
What is also more interesting is that the Display settings do not complain about anything and shows that all displays are correctly used. Also, a screenshoting application takes a shot with all three screens active, it only does not show on the real device.
Attaching the Red Hat Bugzilla with pictures and journalctl info: https://bugzilla.redhat.com/show_bug.cgi?id=1809681
The following is an excerpt from the journal that could be related to the problem:
Mar 03 17:23:04 elefant gnome-control-c[6270]: Config not applicable: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Logical monitors not adjacent
...
Mar 03 17:23:11 elefant gnome-shell[5450]: Failed to post KMS update: Failed to set mode 1920x1080 on CRTC 93: No space left on device
Mar 03 17:23:11 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
Mar 03 17:23:11 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
Mar 03 17:23:12 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
Mar 03 17:23:12 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
Mar 03 17:23:17 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
Mar 03 17:23:18 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
Mar 03 17:23:18 elefant gnome-shell[5450]: Failed to post KMS update: Page flip of 93 failed, and no mode set available
The last message then repeats several times per second, continuously.
Version-Release number of selected component (if applicable): gnome-shell-3.35.91-1.fc32.x86_64
How reproducible
Always
Steps to Reproduce
- Go to Settings.
- Go to Displays.
- Add an external display and make it primary.
- Switch off the built-in display.
- Add one more external display and hit Apply (two external displays are correctly used)
- Add one more external display and hit Apply -> it seems that all displays are correctly used, but the real device stays black.
Actual results
Cannot use the three external screens setup.
Expected results
Three external screens should be possible to use with the built-in display switched off as it was the case in the previous version.
Additional info
See pictures and journal output: https://bugzilla.redhat.com/show_bug.cgi?id=1809681