Bug 502877

Summary:	OpenGL apps break Alt+Tab order
Product:	[Plasma] kwin	Reporter:	LaserMoai <lasermoai>
Component:	tabbox	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	CONFIRMED ---
Severity:	minor	CC:	kdedev
Priority:	NOR	Keywords:	X11-only
Version First Reported In:	6.3.4
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Bug recording Settings

Description LaserMoai 2025-04-16 11:13:29 UTC

SUMMARY
After a window becomes the 3rd most recently used, KDE just forgets where it should be when alttabing for me (it drops to the bottom of the stack). I've only noticed this happen when I'm running OpenGL apps on Xorg with vsync enabled. xf86-video-amdgpu driver is not installed.

STEPS TO REPRODUCE
1. Open an OpenGL app.
2. Try to make a window the 3rd most recently used.

OBSERVED RESULT
See it drop to the bottom of the stack.

EXPECTED RESULT
It becomes the third window in the stack.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 6.3.4
KDE Frameworks Version: 6.12.0
Qt Version: 6.9.0

ADDITIONAL INFORMATION

Comment 1 TraceyC 2025-04-17 17:33:31 UTC

I tested this with DreamChess on git-master and can't reproduce the bug in either Wayland or X11

Setup: Firefox, Konsole and KWrite already open

1. Opened DreamChess (powered by OpenGL)
2. Switched to Konsole, then Firefox, using Alt-Tab. This made DreamChess the third most recently used (also tested clicking the applications to focus them)
3. Pressed Alt-Tab

Result: The applications are shown left to right in the order they were used as expected

I note that on my system, the windows are presented side by side when alt-tabbing. There is no stack bottom.

To clarify, you say you've only noticed this with X11. Have you tested with Wayland, and seen the expected behavior?
If you could attach a screen recording of reproducing the bug that would be very helpful. Thanks.

Comment 2 LaserMoai 2025-04-17 19:59:11 UTC

Yeah, it doesn't appear in Wayland. Here's extra context and a recording.
https://bbs.archlinux.org/viewtopic.php?id=304839

I've also just noticed that they tend to only be "drowned" by Firefox or Chromium windows.

Comment 3 LaserMoai 2025-04-17 20:00:07 UTC

Created attachment 180362 [details]
Bug recording

Comment 4 TraceyC 2025-04-18 14:48:52 UTC

Thanks for the additional details. I see exactly what you're describing in the video.

Can I ask you to send a screenshot of your Task Switcher settings? I want to try to reproduce with the same settings you have.
System Settings - Window Management - Task Switcher

Thanks.

Comment 5 LaserMoai 2025-04-18 15:01:06 UTC

Created attachment 180384 [details]
Settings

Sure.

Comment 6 TraceyC 2025-04-18 16:48:14 UTC

Thanks for sending the screenshot. Using the same settings, I am able t reproduce this on git-master

Comment 7 LaserMoai 2025-04-18 18:24:44 UTC

np

Comment 8 LaserMoai 2025-05-02 19:13:50 UTC

It seems to be the case of launching an OpenGL app causing the compositor to crash.