Bug 482665

Summary:	Overview is invisible with QT_QUICK_BACKEND=software
Product:	[Plasma] kwin	Reporter:	Balló György <ballogyor>
Component:	effects-overview	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	nate
Priority:	NOR	Keywords:	qt6
Version First Reported In:	6.0.1
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Rendering issue of Overview with QT_QUICK_BACKEND=software

Description Balló György 2024-03-07 08:56:02 UTC

SUMMARY
When I try to access the Overview, it doesn't show anything.


STEPS TO REPRODUCE
1. Set QT_QUICK_BACKEND=software environment variable in /etc/environment, then restart.
2. Start Plasma (Wayland) or Plasma (X11) session.
3. Hit Meta-W or move the mouse to the top left corner of the screen.

OBSERVED RESULT
Some flashing, but the overview does not shown.

EXPECTED RESULT
Overview should be displayed.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 6.0.1
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2

Comment 1 Vlad Zahorodnii 2024-03-07 13:41:29 UTC

> Overview should be displayed.

The overview and some other effects do not work with software rendering mode intentionally. As it would lead to really really bad performance.

Comment 2 Balló György 2024-03-07 14:09:31 UTC

Created attachment 166587 [details]
Rendering issue of Overview with QT_QUICK_BACKEND=software

The problem is that it enters into the Overview actually, but not rendered. The pointer appears repeatedly on the screen on Wayland until I exit the Overview with Esc or by left click.

And the following error messages are shown in the log:
kwin_wayland[9636]: QRhi is only compatible with default adaptation
kwin_wayland[9636]: QQuickWindow: No render target (neither swapchain nor custom target was provided)

If the Overview cannot be supported with software rendering, then probably it would be disabled instead of invisible/broken rendering.

Comment 3 Balló György 2024-03-07 14:28:07 UTC

So I think it should be disabled properly rather than displaying an invisible Overview with broken rendering.

Comment 4 Nate Graham 2024-03-07 21:29:12 UTC

Using QT_QUICK_BACKEND=software isn't supported; you're in "There be dragons" territory.

Comment 5 Balló György 2024-12-20 11:01:47 UTC

It seems to have been fixed. The overview is now visible with software rendering, except that the thumbnails of the windows are invisible, but it's probably a limitation of the software rendering. Tested with KWin 6.2.4 and Qt 6.8.1.