Created attachment 142124 [details] sddm login screen settings screenshot SUMMARY The sddm login screen wallpaper does not get updated the the plasma theme wallpaper when you click on the 'Apply Plasma Settings...' button. STEPS TO REPRODUCE 1. Run Systemsettings 2. Change your wallpaper 3. Click on Startup and Shutdown 4. Click on 'Apply Plasma Settings...' OBSERVED RESULT The wallpaper on the sddm theme thumbnail is updated with the new wallpaper (see the attached screenshot) but the actual sddm login screen shows the old wallpaper EXPECTED RESULT The sddm login screen wallpaper should show the newly selected wallpaper SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 5.22.90 KDE Frameworks Version: 5.86.0 Qt Version: 5.15.2 Kernel Version: 5.12.15-arch1-1 (64-bit) Graphics Platform: X11 Processors: 12 × Intel® Core™ i7-8700 CPU @ 3.20GHz Memory: 31.3 GiB of RAM Graphics Processor: GeForce GTX 1080/PCIe/SSE2 ADDITIONAL INFORMATION The new wallpaper selection has been updated to the file /usr/share/sddm/themes/breeze/theme.conf but the file /usr/share/sddm/themes/breeze/theme.conf.user is overriding that selection. The file /usr/share/sddm/themes/breeze/theme.conf.user contains the lines... [General] background=Plasma 5.22 1920x1080.png type=image This is not a file that I have created or edited. Perhaps it is no longer used or it's update has been omitted.
It's not that simple, unfortunately. The SDDM theme can have exactly one wallpaper and it must be a still image. The rest of Plasma lets you use a slideshow, a picture of the day, something else, and it lets you put a different one on each of your screens and activities. So there's no way for this feature to guess which of your potentially many wallpapers you want to go on to the SDDM theme. It would work for the simple case of a single image wallpaper on one screen and one activity. But for anything else, it would break down. We would need to teach SDDM how to do those things, and that's another undertaking entirely since SDDM isn't a KDE project.
Observation: The wallpaper in the login screen (breeze) thumbnail was updated. The same wallpaper could also be set for the sddm login screen. Alternatively, as a simple solution, you could let the user decide which wallpaper to use as a selection in the login screen settings. As a workaround I have disabled the theme.conf.user file. This causes sddm to display the correct wallpaper, which plasma updated in the theme.conf file.