Desktop is blank after logging in (remotely) without a monitor attached

[Scoot Lee]

On Ubuntu 20.04, I have an AMD system with an integrated GPU (Ryzen 3 3200G with Radeon Vega 8)
I am using lightdm instead of gdm3. My GPU is using the amdgpu driver. I have no specific xorg.conf in place. I am using x11vnc to login and view the desktop remotely. There is no monitor attached.

After logging into lightdm's greeter, I am presented with a blank desktop with the Focal Fossa background image and a mouse cursor, but no other visible interface or windows. There is no menu bar at the top of the desktop and no application bar on the left.

This all works perfectly fine if a monitor is attached before lightdm (and thus Xorg) is started.

If I change the settings at login to use fvwm for my session it works fine. This is also the case for Gnome Flashback mode (using metacity). But the default of gnome-shell/mutter does not work without the monitor. Nor does using Wayland.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xorg 1:7.7+19ubuntu14
ProcVersionSignature: Ubuntu 5.4.0-33.37-generic 5.4.34
Uname: Linux 5.4.0-33-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.2
Architecture: amd64
CasperMD5CheckResult: skip
Date: Sun May 31 13:34:20 2020
DistUpgraded: Fresh install
DistroCodename: focal
DistroVariant: ubuntu
DkmsStatus:
 evdi, 1.6.0+dfsg, 5.4.0-31-generic, x86_64: installed
 evdi, 1.6.0+dfsg, 5.4.0-33-generic, x86_64: installed
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
 Advanced Micro Devices, Inc. [AMD/ATI] Picasso [1002:15d8] (rev c9) (prog-if 00 [VGA controller])
   Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Picasso [1002:15d8]
InstallationDate: Installed on 2020-05-21 (10 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
MachineType: Gigabyte Technology Co., Ltd. B450 I AORUS PRO WIFI
ProcEnviron:
 TERM=screen-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-33-generic root=UUID=0030bb65-9e5e-4a70-bba3-da14892ec5b9 ro quiet splash vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/27/2019
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: F50
dmi.board.asset.tag: Default string
dmi.board.name: B450 I AORUS PRO WIFI-CF
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.asset.tag: Default string
dmi.chassis.type: 3
dmi.chassis.vendor: Default string
dmi.chassis.version: Default string
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF50:bd11/27/2019:svnGigabyteTechnologyCo.,Ltd.:pnB450IAORUSPROWIFI:pvrDefaultstring:rvnGigabyteTechnologyCo.,Ltd.:rnB450IAORUSPROWIFI-CF:rvrx.x:cvnDefaultstring:ct3:cvrDefaultstring:
dmi.product.family: Default string
dmi.product.name: B450 I AORUS PRO WIFI
dmi.product.sku: Default string
dmi.product.version: Default string
dmi.sys.vendor: Gigabyte Technology Co., Ltd.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.101-2
version.libgl1-mesa-dri: libgl1-mesa-dri 20.0.4-2ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.20.8-2ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20200226-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1

[Scoot Lee (scootley)]

based on my research so far (and summarized in the description), I don't think this is an xorg issue. I think it's a gnome issue.

[Daniel van Vugt (vanvugt)]

Can you please ssh into the machine while the desktop is "blank" and tell us how many 'gnome-shell' processes are running? And by which user IDs?

[Daniel van Vugt (vanvugt)]

Also from ssh please try running:

  env DISPLAY=:0 xrandr

or

  env DISPLAY=:1 xrandr

and tell us what output you get.

[Scoot Lee (scootley)]

Sure. For gnome-shell processes after login, I see:
root@redacted:/home/redacted# ps -elf | grep gnome-shell
0 S redacted 5868 823 4 80 0 - 1040028 poll_s 12:26 ? 00:00:02 /usr/bin/gnome-shell

That's just one process running as the user who logged in.

And for xrandr:
root@redacted:/home/redacted# env DISPLAY=:0 xrandr
No protocol specified
Can't open display :0

root@redacted:/home/redacted# env XAUTHORITY=/var/run/lightdm/root/:0 DISPLAY=:0 xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 16384 x 16384
HDMI-A-0 disconnected primary (normal left inverted right x axis y axis)
DisplayPort-0 disconnected (normal left inverted right x axis y axis)
HDMI-A-1 disconnected (normal left inverted right x axis y axis)

[Daniel van Vugt (vanvugt)]

Thanks. Yes indeed the X server has zero monitors attached, but still has a usable desktop area of 1024x768. For gnome-shell this just means it won't draw any panel/launcher etc. Because it prefers to only do that on the primary monitor, which there is none.

Next please report the bug to the gnome-shell developers at:

  https://gitlab.gnome.org/GNOME/gnome-shell/issues

and then tell us the new issue ID.

[Scoot Lee (scootley)]

Thanks. Here is the issue in the gnome-shell tracker:
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2883