Bug 445316

Summary: On Wayland containments are randomly moved between screens on login, often resulting in disappearing panel
Product: [Plasma] plasmashell Reporter: Bart Ribbers <bribbers>
Component: generic-multiscreenAssignee: Aleix Pol <aleixpol>
Status: RESOLVED FIXED    
Severity: normal CC: nate, plasma-bugs-null
Priority: NOR    
Version First Reported In: 5.23.0   
Target Milestone: 1.0   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In: 5.24
Sentry Crash Report:

Description Bart Ribbers 2021-11-11 07:02:27 UTC 
SUMMARY
On (practically) every login in a Wayland session, the containments are moved around between screens. This means the panel moves and wallpapers switch around. Often it means the panel appears on an unconnected screen connector, forcing me to recreate the panel from scratch on basically every login. When I then login to a X11 session, all panels show on top of each other and I can remove them one by one till I only have my original left. Then logging in to a Wayland session again, if I'm lucky it shows the panel but most often it's gone again.

This has only started happening from Plasma 5.22.90 and onwards (currently experiencing this on Plasma 5.23.3), but because of this bug has been the buggiest release so far for me.

My setup is 2 120hz 1080p screens, one of which has FreeSync enabled, a 60hz 1080p TV set to mirror my left 120hz 1080p screen, and a VR headset (Valve Index).

STEPS TO REPRODUCE
1. Have a multi-screen setup
2. Login to a Wayland session

OBSERVED RESULT
Containments get moved around meaning moved panel and wallpapers, and if you're unlucky your containment moved to a not-connected connector meaning you have to recreate your panel from scratch.

EXPECTED RESULT
Containments not to move around and remember what screen they're supposed to be displayed on

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Alpine Linux edge
KDE Plasma Version: 5.23.3 currently, but has been happening since 5.22.90
KDE Frameworks Version: 5.87.0
Qt Version: 5.15.3 with KDE patches
Comment 1 Bart Ribbers 2021-11-11 07:07:55 UTC 
I tried without the VR headset connected just to be sure, and it (sadly) made no difference. I don't think it's related to my particular display setup, just the fact that I have more than 1 screen.
Comment 2 Nate Graham 2021-11-12 21:58:44 UTC 
Any chance you can test with Plasma 5.24 from git master? The "Primary screen" setting was re-introduced, which is supposed to help with this.
Comment 3 Bart Ribbers 2021-11-13 00:14:06 UTC 
Not easily. Are there any kdesrc-build instructions you can give? I rather not package every single Plasma package with a git version, that is just too much work.
Comment 4 Bart Ribbers 2021-11-13 11:25:08 UTC 
I've backported the patches you listed in https://bugs.kde.org/show_bug.cgi?id=442158#c11 to 5.23.3 locally. It _seems_ to work? I've relogged a few times (actually for some reason it was impossible to logout, the desktop just restarted, so I restart SDDM instead) and rebooted twice, and so far the panel has remained and the wallpapers haven't switched. I'll try it a few more days.

I don't see how this would fix it though when it worked fine on 5.22.x and before. Back then Plasma Wayland didn't know about a primary monitor either. And I don't think this is something that can be backported to the 5.23.x branch no?
Comment 5 Nate Graham 2021-11-15 23:41:50 UTC 
Yeah, even though I would expect that to fix it, it's not really a bugfix so much as a re-imagining of how panels get assigned to screens on Wayland.

However, given that it's already been merged for 5.24 and it does fix the problem, and 5.23 isn't an LTS release, I doubt there are development resources to fix and produce a patch before 5.23's last bugfix release. Marking as fixed in 5.24.
Comment 6 Bart Ribbers 2021-11-16 08:58:47 UTC 
Actually, no it isn't resolved. It took a while but today when I logged in I suddenly had 2 panels (1 on both screens), and the wallpaper on my main screen was also on my second screen. It seems to be the panel that I kept on re-adding suddenly decided to show up on my 2nd monitor. I removed it manually but it'll probably happen again.
Comment 7 Bart Ribbers 2021-11-16 15:35:33 UTC 
Ah never mind, seems I had unintentionally unapplied those primary monitor patches. I re-applied them, and this time made sure they won't disappear from my system again, and they do work after all. I just wonder if I'm literally the only one with this issue, as to me it seems this would be an issue for _everybody_ using more than 1 monitor. If so, I really think this should be fixed rather than have people waiting till 5.24 which will take some months before release.