https://bugs.kde.org/show_bug.cgi?id=427628
Bug ID: 427628
Summary: Black window flashes after restarting compositing
Product: kwin
Version: 5.18.5
Platform: Kubuntu Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: compositing
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 132317
--> https://bugs.kde.org/attachment.cgi?id=132317&action=edit
KWin config file (~/.config/kwinrc)
SUMMARY
After restarting compositing in KWin (for example, due to a Nvidia driver crash
or via a hotkey or VT switch), contents of some windows begin flashing black
upon certain activities. For example, when "Open/Save File" dialog window
opens, Firefox window in the background momentarily turns black and then back
to normal.
This is not tied to any particular applications or GUI toolkits. I've seen
black flashes with both GTK and Qt applications. This is also not reliably
reproducible and may not show right away after restarting compositing.
STEPS TO REPRODUCE
1. Restart KWin compositing.
2. Try interacting with desktop, like open or close windows, resize windows,
etc.
OBSERVED RESULT
Some windows begin flashing black.
EXPECTED RESULT
No black flashing is expected.
SOFTWARE/OS VERSIONS
Linux: Kubuntu 20.04 x86_64, X11
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Nvidia driver: 455.26.1 (also reproducible with other versions)
ADDITIONAL INFORMATION
In my /etc/environment I have:
KWIN_TRIPLE_BUFFER=1
KWIN_USE_BUFFER_AGE=0
KWIN_PERSISTENT_VBO=1
__GL_YIELD="USLEEP"
__GL_SYNC_TO_VBLANK=1
KWin is started with the command line `__GL_THREADED_OPTIMIZATIONS=0 kwin_x11
"$@"`. The __GL_THREADED_OPTIMIZATIONS env variable has no effect on the issue,
it is just used to reduce CPU consumption by kwin_x11.
The usual workaround is to restart KWin by running `kwin_x11 --replace` from
krunner.
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