Bug 450036

Summary:	KWin effect animations and desktop switcher flicker and appear pixelated instead of blurred on screen attached to Thunderbolt dock (Wayland)
Product:	[Plasma] kwin	Reporter:	phrxmd <philipp.reichmuth>
Component:	general	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	fabian, nate
Priority:	NOR
Version First Reported In:	5.24.0
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description phrxmd 2022-02-11 19:28:02 UTC

SUMMARY
KWin effects that involve blur and animated transitions flicker and appear grainy and pixelated on a screen that is attached to a Thunderbolt 3 dock. On the built-in screen of my laptop, they appear smooth and blurred as they should.

It's hard to take videos or screenshots of KWin effects with Spectacle or OBS, but a phone video showing the effect on both monitors is here: https://youtu.be/ELo-a4dDKh0

The laptop is a Thinkpad X1 Yoga, the dock in question is a Lenovo Thunderbolt 3 dock.

The bug appears only on Wayland. It has been around for a while, it's not a 5.24 regression.

STEPS TO REPRODUCE
1. Place the mouse on the screen attached to the Thunderbolt dock
2. Invoke the virtual desktop switcher OR a KWin effect that involves animated transitions (tested with Cover Switch and Flip Switch)

OBSERVED RESULT
Animations and transitions flicker and appear grainy and pixelated, instead of smooth and blurred.

EXPECTED RESULT
The effects should look smooth and blurred everywhere.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20220207
KDE Plasma Version: 5.24.0
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2
Kernel Version: 5.16.5-1-default (64-bit)
Graphics Platform: Wayland
Processors: 8 × Intel® Core™ i7-8550U CPU @ 1.80GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 620

ADDITIONAL INFORMATION

Comment 1 phrxmd 2022-02-11 20:39:36 UTC

*** Bug 449961 has been marked as a duplicate of this bug. ***

Comment 2 phrxmd 2022-02-11 20:40:38 UTC

Applies to the Overview effect as well. I had reported earlier as bug 449961, without realizing that the behaviour there is monitor-specific.

Comment 3 Nate Graham 2022-02-11 22:44:08 UTC

> Graphics Processor: Mesa Intel® UHD Graphics 620
I wonder if this was caused by a recent Mesa regression, whose symptoms line up with what you're describing.

Fabian, do yo know if the fix for https://gitlab.freedesktop.org/mesa/mesa/-/issues/5731 has been shipped in Tumbleweed yet?

Comment 4 Fabian Vogt 2022-02-12 10:46:56 UTC

(In reply to Nate Graham from comment #3)
> > Graphics Processor: Mesa Intel® UHD Graphics 620
> I wonder if this was caused by a recent Mesa regression, whose symptoms line
> up with what you're describing.
> 
> Fabian, do yo know if the fix for
> https://gitlab.freedesktop.org/mesa/mesa/-/issues/5731 has been shipped in
> Tumbleweed yet?

FWICT, it's part of 21.3.6, which should be part of the next snapshot, 20220211.

Comment 5 phrxmd 2022-02-12 10:50:01 UTC

(In reply to Fabian Vogt from comment #4)
> FWICT, it's part of 21.3.6, which should be part of the next snapshot, 20220211.

OK, when that lands I will test again and report.

Comment 6 phrxmd 2022-02-22 18:06:11 UTC

The Mesa update has fixed the issue. Thank you!