https://bugs.kde.org/show_bug.cgi?id=494156
Bug ID: 494156
Summary: Windows flicker and contents deform when
connecting/turning on monitors
Classification: Plasma
Product: kwin
Version: 6.1.5
Platform: Gentoo Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: multi-screen
Assignee: kwin-bugs-n...@kde.org
Reporter: k...@kaishome.de
Target Milestone: ---
Created attachment 174442
--> https://bugs.kde.org/attachment.cgi?id=174442&action=edit
smartphone recording showing the issue
SUMMARY
I have a setup of three monitors:
- left 16:18 2880p, plasma bar left
- main 16:9 4k, plasma bar bottom
- right 16:9 4k, plasma bar right
- scaling set to 125%
Almost always when I turn my monitors back on, windows get moved from one
monitor to another - which is expected (although this does not work properly
and windows often end up on a monitor different from that one when I left the
computer, but that's a probably different bug).
But what happens now is that windows often start to flicker between two states:
One image is just the contents scaled from the previous monitor (take into
account that depending on the plasma bar position, all monitors have different
real estate and maximized window aspect ratio), the other image is the properly
re-rendered video.
This flickering stops as soon as I click into the window. I'm not sure if this
simply triggers a redraw, or somehow resyncs the rendering/composition. To me,
this looks like out of sync buffer bouncing in double or triple buffer
rendering. I've seen similar effects 1-2 years ago with plasma 5 and using
gamescope to render games where games would render frames out of order
resulting in extreme flickering.
STEPS TO REPRODUCE
1. setup a asymmetric monitor/desktop layout as above
2. turn monitors off step by step, xrandr should show them as disconnected,
windows should move to a remaining display
3. turn monitors back on, the order should not matter but may differ from the
order in step 2
4. find flickering windows until you click into them
OBSERVED RESULT
Window contents flicker between two states (rescaled and properly rerendered).
See attached mp4 video. Clicking into a windows fixes it. I see this most
prominently with Chrome windows but that's just because most of my windows are
Chrome windows. Other apps should be affected, too.
EXPECTED RESULT
Windows should properly rerender after being repositioned on a monitor, and
should not flicker.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Gentoo Linux 2.15
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
NVIDIA RTX 3080 Ti
Driver 560.35.03 (kernel open driver with drm framebuffer)
ADDITIONAL INFORMATION
See attached video.
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