monitors.xml is not parsed or applied correctly during login after reboot or shutdown

[Chris Rainey]

WORKAROUND

Replace gdm3 with slick-greeter + lightdm-settings + gnome-screensaver + numlockx(optionally)

TL;DR

Correct positioning and working of multiple displays until reboot or shutdown and then subsequent login from gdm3. HDMI monitor(projector) goes blank and the VGA monitor only shows 'Secondary' monitor screen without any user visible controls or windows as they are all being painted to the now blanked 'Primary' HDMI connected display.

REPRODUCTION

After a clean install of Ubuntu 18.10, connecting a FHD(1920x1080) LED monitor to the VGA port of a DELL Optiplex 390 desktop tower, connecting a wireless HDMI Tx/Rx(LKV HDbitT-4K) to the HDMI port with a FHD projector and then configuring the logical monitor layout in the "Displays" settings dialog, I can successfully create and use a multi monitor setup in my current session.

However, after a reboot or power cycle of the computer and a successful login from GDM(gdm3), the HDMI goes dark(blank?) and the VGA monitor shows as 'Secondary' monitor even though I set it as 'Primary' in the "Displays" dialog.

The monitors.xml file, attached, shows the correct layout and survives the reboot without alteration.

I am unable to see anything on the 'Primary' display, which has incorrectly been given to the HDMI projector. Unseating the HDMI cable does not restore the VGA to 'Primary' display automatically and I must reboot the computer while leaving the HDMI unplugged in order to restore my ability to see the 'Primary' display on the VGA connection.

Replacing GDM(gdm3) with LightDM(slick-greeter) fixes the issue and is repeatedly provable through multiple reboots or changes to the logical layout of the screens in the 'Displays' settings of gnome-control-center.

ERRORS(syslog)

"Failed to get current display configuration state: GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: Name "org.gnome.Mutter.DisplayConfig" does not exist"

gnome-shell[3007]: JS ERROR: Exception in callback for signal: loaded: TypeError: monitor is null#012_prepareStartupAnimation@resource:///org/gnome/shell/ui/layout.js:653:17#012wrapper@resource:///org/gnome/gjs/modules/_legacy.js:82:22#012_loadBackground/signalId<@resource:///org/gnome/shell/ui/layout.js:608:13#012_emit@resource:///org/gnome/gjs/modules/signals.js:128:27#012_init/id<@resource:///org/gnome/shell/ui/background.js:512:17

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: gdm3 3.30.1-1ubuntu5.1
ProcVersionSignature: Ubuntu 4.18.0-16.17-generic 4.18.20
Uname: Linux 4.18.0-16-generic x86_64
ApportVersion: 2.20.10-0ubuntu13.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Mar 16 13:50:52 2019
InstallationDate: Installed on 2019-03-07 (8 days ago)
InstallationMedia: Ubuntu 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.3)
SourcePackage: gdm3
UpgradeStatus: No upgrade log present (probably fresh install)

[Sebastien Bacher (seb128)]

Thank you for your bug report. What's the issue exactly? The configuration is not restored in the session after logging? Or it it only about the login screen? Lightdm doesn't import the session configuration either so that's not really a workaround solution?

[Chris Rainey (ckrzen)]

@seb128 I have edited the bug description to provide more information on how the issue is triggered. The bug occurs during the handoff of gdm3 ---> gnome-shell(mutter?) _after_ login. The issue is repeatedly and consistently triggered until GDM(gdm3) is replaced by LightDM(slick-greeter) and then the issues disappears completely and the system is works across multiple reboots or changes to the monitors.xml through the "Displays" settings.

This is clearly related to how GDM appears to set-up or create the user session and I would be glad to test any ideas you have to solve it while using GDM, however---after 4-hours of messing with it, I had to go with a solution that "Just Works": slick-greeter or lightdm.

Please let me know what else I can provide or do to clarify this issue.

[Sebastien Bacher (seb128)]

Thanks for upstreaming the issue

[Daniel van Vugt (vanvugt)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1768137, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.