I’ve been having issues with SDDM and now PLM, where my screens can have graphical issues, I have eventually worked out it’s because 144hz doesn’t quite work correctly with my monitors via my docking station. Once I hit the KDE desktop, of course my custom display configuration applies where it sets the screens from 144hz to 60hz, and the problem stops. Not sure if it’s a Dock or software issue.
Is there a way to limit the refresh rate of SDDM/PLM to 60hz, so I can use the login screen on my screens that are plugged in via the docking station, my current workaround is to autologin and then force the lockscreen to appear, as that uses the desktop custom display configuration, so then I can use my password and login, but it would be nice to not have to use the autologin, as it makes it so I have to login via the screensaver and then again for kwallet.
I have two laptops one has Fedora 43 with SDDM and fresh install of Fedora 44 on another, both have the issue, both are AMD iGPUs but their different generations.
I believe if there’s a way to force 60hz on any connected screen when PLM is running, that would resolve my issue.
I’ve searched the forum a bit, but couldn’t really find a similar issue being reported, ideally the display config would sync to PLM from the desktop, but of course on a laptop the last applied config maybe undocked.
Not 100% sure about PLM, as I still use SDDM (in Wayland mode), but with SDDM set it to 60Hz then at the “Login screen” settings do a ‘Apply Plasma Settings’ and after that set it back to 144 or whatever (without touching ‘Apply Plasma Settings’ again) should work.
As I used a different screen resolution and refresh rate on one of my Monitors in the past and from short monitor internal onscreen popups with something like “none native XXXXxXXXX XXHz” on SDDM that changed to “HDR on” (in my case) with the “correct” resolution and rate after login, I know that worked.
Edit: I do not use a docking station, though. Just unplug my 2 external monitors when I take the laptop with me, but at least it survived that.
Agree with this, there’s a separate config in /var/lib/plasmalogin/.config/kwinoutputconfig.json that handles settings for PLM.
I did some testing by logging in via SSH and then using kdoctor to change the display while on PLM, soon as I changed the screens to 60hz it worked great.
Problem with editing the saved config, if I undock or go to a different desk, the config gets reset.
So I’ve gotten a script that runs after the plasmalogin service, then if the login is running, then checks the displays and changes them to 60hz it their higher. Workaround but not really sure what the real fix is.
You should just be able to set all your monitors to 60hz in Desktop mode, and then use the "Apply Plasma Settings" button that was mentioned before to set them for your login manager.
Editing kwinoutputconfig.json is being reset because PLM/Kwin re-write the configs on logout as far as I know. You could temporarily disable sddm/plm, or isolate to multi-user.target and THEN edit the config files.
Won’t I keep hitting the issue, as I may logout at one desk with different monitors, then dock at the login or before login at a desk with 144hz monitors? So the issue repeats until I go in and re-apply the 60hz? Or does the PLM remember previous screen settings like it does in the desktop?