Bug 450319

IIRC there is some mean of testing these setting in KCM itself, does it apply immediately there?
Can you test other apps (Konsole, etc.)?
I don't remember this problem so might be a regression if nothing helps. So would be helpful if you test prev release also (5.23 or whatever).

I get the same result testing with Konsole and 'Test area' field of the KCM. Plasma 5.23.x had the same bug on my machine.

Can you reproduce it Till?

It is 100% reproducible here. It was definitely working previously. I would have noticed this during testing for Bug 443721. Regarding my comment 7 there, I have tested at least 5.23.2 as working version. Thus, this seems to be a recent regression.

Operating System: Gentoo Linux
KDE Plasma Version: 5.24.0
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2
Kernel Version: 5.15.23-gentoo (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i7-4810MQ CPU @ 2.80GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4600

(In reply to Patrick Silva from comment #2)
> Plasma 5.23.x had the same bug on my machine.
This contradicts with the above, 5.23.2 was claimed as a working version.
Do you have an explanation guys?

I do not remember exactly which point release of 5.32.x was buggy on my machine. Probably the bug appeared after 5.23.2.

Could you try Neon with KDE 5.23.4 (and if possible, 5.23.3)?
That way we could narrow it down.

Cannot reproduce with 5.23.4.

Operating System: KDE neon 5.23
KDE Plasma Version: 5.23.4
KDE Frameworks Version: 5.89.0
Qt Version: 5.15.3
Kernel Version: 5.11.0-43-generic (64-bit)
Graphics Platform: Wayland

I do not know any distro with 5.23.3.

(In reply to Patrick Silva from comment #6)
> I do not remember exactly which point release of 5.23.x was buggy on my
> machine. Probably the bug appeared after 5.23.2.

> Cannot reproduce with 5.23.4.
Odd. We could assume it was introduced in 5.24 then, but you are saying you had it in 5.23.x..

Are there other parts involved that may be independent of the plasma version? E.g., frameworks, qt?

This change looks suspected:
https://invent.kde.org/plasma/kwin/-/merge_requests/540

Can somebody build kwin without it and retest?

(In reply to Andrey from comment #11)
> This change looks suspected:
> https://invent.kde.org/plasma/kwin/-/merge_requests/540
> 
> Can somebody build kwin without it and retest?
Oops, wrong link, here it  is:
https://invent.kde.org/plasma/kwin/-/merge_requests/1490

(In reply to Till Schäfer from comment #10)
> Are there other parts involved that may be independent of the plasma
> version? E.g., frameworks, qt?
Probably not, it's KWaylandServer which tied to KWin closely.
So I suspect the bug was introduced in 5.24 and not in 5.23..

(In reply to Andrey from comment #12)
> (In reply to Andrey from comment #11)
> > This change looks suspected:
> > https://invent.kde.org/plasma/kwin/-/merge_requests/540
> > 
> > Can somebody build kwin without it and retest?
> Oops, wrong link, here it  is:
> https://invent.kde.org/plasma/kwin/-/merge_requests/1490

I would love to do so, but getting a reverse patch that applies to 5.24.1 does not seem to be easy. Lot of conflicts, that I do not know to handle properly. 
Thus, if you can provide a proper reverse patch, I will try it out here.

(In reply to Till Schäfer from comment #14)
> Thus, if you can provide a proper reverse patch, I will try it out here.
If you are familiar with Git a bit, better way to achieve that would be just checkout versions of KWin (and maybe KWaylandServer) needed.
It should build and run without changing other components.

(In reply to Andrey from comment #15)
> (In reply to Till Schäfer from comment #14)
> > Thus, if you can provide a proper reverse patch, I will try it out here.
> If you are familiar with Git a bit, better way to achieve that would be just
> checkout versions of KWin (and maybe KWaylandServer) needed.
> It should build and run without changing other components.

I am sorry, but the kwin_wayland crashes with such version. X11 is working though....

I have tried
EGIT_OVERRIDE_COMMIT_PLASMA_KWIN="4206046f" EGIT_OVERRIDE_COMMIT_DATE_PLASMA_KWAYLAND_SERVER="2021-11-01" emerge -av1 --nodeps =kde-plasma/kwayland-server-9999 =kde-plasma/kwin-9999 --jobs=1 --quiet

and 

EGIT_OVERRIDE_COMMIT_DATE_PLASMA_KWIN="2021-10-25" EGIT_OVERRIDE_COMMIT_DATE_PLASMA_KWAYLAND_SERVER="2021-10-25" emerge -av1 --nodeps =kde-plasma/kwayland-server-9999 =kde-plasma/kwin-9999 --jobs=1 --quiet

both version show the same behaviour. Does kwin_wayland depend on something else here, that might be relevant? e.g., an older version of libinput or something similar?

here is the error 

Feb 16 22:32:36 nb-algecraft ksplashqml[23919]: Failed to create wl_display (No such file or directory)
Feb 16 22:32:36 nb-algecraft ksplashqml[23919]: qt.qpa.plugin: Could not load the Qt platform plugin "wayland" in "" even though it was found.
Feb 16 22:32:36 nb-algecraft ksplashqml[23919]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
                                                
                                                Available platform plugins are: minimal, offscreen, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.
Feb 16 22:32:36 nb-algecraft systemd[1]: Started Process Core Dump (PID 23927/UID 0).
Feb 16 22:32:36 nb-algecraft systemd-coredump[23930]: [🡕] Process 23919 (ksplashqml) of user 1000 dumped core.

*** This bug has been marked as a duplicate of bug 408943 ***