SDDM Wayland freezes with black screen and cursor, never shows login screen

[matterhorn103]

Anyone got any insight on this or should I open a proper bug report?

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SUMMARY
If I force SDDM to use Wayland by creating /etc/sddm.conf.d/10-wayland.conf with:

[General]
DisplayServer=wayland
GreeterEnvironment=QT_WAYLAND_SHELL_INTEGRATION=layer-shell

[Wayland]
CompositorCommand=kwin_wayland --drm --no-lockscreen --no-global-shortcuts

then userspace only ever shows one thing on booting: a black screen with the cursor in the centre, frozen.

STEPS TO REPRODUCE

1. Add config file as described
2. Shutdown
3. Boot

OBSERVED RESULT
A black screen with the cursor in the centre, frozen.

EXPECTED RESULT
The normal login screen.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE Tumbleweed 20240911
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
sddm version: 0.21.0

ADDITIONAL INFORMATION
The Wayland Plasma session works well on this system. GPU is AMD Ryzen 6600.

[matterhorn103]

Happy to provide traces etc. if given hints on what I should do to produce them The openSUSE guide seems mostly focussed on applications that crash and can be run from the CLI.

[jonzn4SUSE]

See this thread.

Plasma 6: Lock screen renders black (troubleshooting help)

Just my two cents, which can hopefully help with reproducing this. It most consistently occurs for me when the screen automatically locks, but the mouse is moved to stop it fully locking before the “Allow unlocking without password” period of 5 seconds is over. It attempts to show the lock screen before going black. It doesn’t let me unlock with the password, but fingerprint (configured through KDE) works on the black screen, with only the cursor visible. I am running KDE Plasma 6.0.5 on Manja…

[matterhorn103]

Thanks but no, it’s not the lock screen that’s the issue for me, it’s the login screen.

[Dean]

@matterhorn103 Did you ever manager to resolve this? FWIW, I get almost the same symptoms when trying to launch SDDM in wayland mode. The only difference is the cursor is still able to move, and I can switch to a VT allowing me to edit sddm.conf and reboot etc. FWIW, I’m currently running Leap 15.5 as a guest in a VirtualBox environment. When I get a chance I will test on a laptop with Intel graphics.

[vbgunz]

Hello,

Every time this has happened to me, it was because I was trying to login to an account that was already logged in. KDE on Arch does not warn the user (hey, you’re already logged in) and tries logging you in again but then hangs on a black screen with a cursor only.

The way I fixed this was to add ReuseSession=true to /etc/sddm.conf.

e.g.,

[Users]
ReuseSession=true

With this change, rather than hang on a black screen, I will immediately log into an already existing session for the same user.

This has helped me immensely. I hope it helps <3

[matterhorn103]

@Dean no sadly, I gave up. I can’t remember if I ended up opening a bug report or not, I’ll have a dig.

@vbgunz

Every time this has happened to me, it was because I was trying to login to an account that was already logged in.

For me this was after fresh boots so different situations I should think, but that’s still interesting to know.