Bug 466027

Summary: alt-tabbing after a media player was used in fullscreen and then quitted or put in windowed result in empty previews for Firefox and sometimes Thunderbird
Product: [Plasma] kwin Reporter: Porkepix <porkepix>
Component: tabboxAssignee: KWin default assignee <kwin-bugs-null>
Status: REPORTED ---    
Severity: normal    
Priority: NOR    
Version First Reported In: master   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Screenshot of a messed-up preview for Firefox
Screenshot with both Firefox and Thunderbird

Description Porkepix 2023-02-18 18:58:10 UTC
Created attachment 156455 [details]
Screenshot of a messed-up preview for Firefox

STEPS TO REPRODUCE
1. Open Firefox and Thunderbird
2. Play whatever video in mpv, and switch mpv to fullscreen. I don't know why, but in such modes, task switcher doesn't show window previews anymore but only big icons. (I'm btw curious why most applications doesn't shows preview in such situations - and even stranger, GIMP present a pseudo-preview, showing the picture we work on, but not the window itself)
3. Escape full screen or quit mpv. Firefox and sometimes Thunderbird previews will be messed up as visible in the joined screen. When Thunderbird's one is messed up, hovering it in the task switcher fixes the preview. For Firefox, the only way is to switch to the application completely.

OBSERVED RESULT

Messed-up previews.

EXPECTED RESULT

Previews shouldn't be messed up.

SOFTWARE/OS VERSIONS
ArchLinux
Linux/KDE Plasma: 5.27.0
(available in About System)
I'm not seeing an "About System", where should it be looked for?
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version:
Comment 1 Porkepix 2023-02-20 10:18:06 UTC
Created attachment 156528 [details]
Screenshot with both Firefox and Thunderbird

Additional screenshot, where we can see that Firefox preview is completely empty while Thunderbird have the window decoration but everything else is empty.