What is the Recommended Solution to Make SDDM Work Again With External Screen?

Desktop Environments Plasma
1

As many others (1), I am experiencing SDDM issues since one of the last updates.

  • I am able to do a usual login when laptop is not connected to an external screen
  • I am not able to login when laptop is connected to an external screen, the display freezes

It is quite annoying to disconnect the laptop first when booting the machine.

There are recommendations to change the Display Manager to LightDM or Ly, but isn’t there any solution for SDDM available yet?

(1) Sources:

2 Likes
2

Me I would patiently wait but yer you could try a different DM if you want, there is no recommended solution as different hardware can cause different issues.

1 Like
3

Using arch (eos) as a desktop has risks like this as it is a rolling release and the system can break at times

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4

change the sddm theme from the settings. Someone mentioned mavic (?) I have three monitors and only can login on the secondary. This requires me to mouse over from my primary monitor.

5

That would require a successfully submitted bug report about the responsible SDDM package, no? I cannot find such a thing yet. Or did I miss something?

6

IMHO: it’s not and sddm bug, the configuration for sddm needs to be updated by the distro mantainers, since the developers themselves created a config file to be used as reference here:

Quoting

https://invent.kde.org/plasma/plasma-workspace/-/blob/master/sddm-wayland-session/plasma-wayland.conf < we uploaded this upstream for others to reuse. This issue doesn’t belong in sddm anyway. If there’s problems in the documentation, please point them out and we then can address them.

the reference file is

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

[Wayland]
CompositorCommand=kwin_wayland --no-global-shortcuts --no-lockscreen --inputmethod maliit-keyboard --locale1

I think at least the display server (maybe) + greeter environment + compositor command are the required lines which are missing right now

The arch wiki also has some references for this file which would probably fix this issue

https://wiki.archlinux.org/title/SDDM#Wayland

Quoting

Warning: By default, KWin starts up with global shortcuts enabled. This could be dangerous for a login screen, since it becomes possible to bypass the login prompt using default key bindings. Specifying --no-global-shortcuts fixes this.[5]

Adding the following lines to your configuration file sets the Wayland compositor to KWin and enables the wlr_layer_shell Wayland protocol extension. This requires layer-shell-qt and layer-shell-qt5 for SDDM themes using Qt6 and Qt5, respectively.

Reference file

/etc/sddm.conf.d/10-wayland.conf

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

[Wayland]
CompositorCommand=kwin_wayland --drm --no-lockscreen --no-global-shortcuts --locale1

it also explains the various settings for the compositor commands.

If you want to wait, eos mantainers will publish an update to the config file since they have been notified (but I don’t know when, it must avoid breaking stuff for users with x11)

Since we have a folder which accepts multiple config files (/etc/sddm.conf.d/) I’d put a file with a different name from kde_settings.conf with these settings. The conf files are parsed in alphabetical order so create a file with a name starting after k so it gets applied last. This is linux and changing a config file to fix something is the “standard” experience ;D

7

https://bugs.kde.org/show_bug.cgi?id=494804
https://bugreports.qt.io/browse/QTBUG-130767

Not sure if this is exactly what you have^