https://bugs.kde.org/show_bug.cgi?id=492300
Bug ID: 492300
Summary: kwin_wayland misplaces Firefox subsurface
Classification: Plasma
Product: kwin
Version: master
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: kwin-bugs-n...@kde.org
Reporter: seria.warty...@icloud.com
Target Milestone: ---
Created attachment 173023
--> https://bugs.kde.org/attachment.cgi?id=173023&action=edit
Firefox in overview
BACKGROUND
Firefox has support for wl_subsurface, which has not received much updates over
last 3 years.
At the time it was decided to let Firefox perform it's own compositing on
Wayland instead, because system compositors were not good enough.
As compositors improved in that time, this feature is getting relevant again
because it's the only way to use power-efficient video overlays, otherwise
Firefox force composites everything on it's own.
The switch is gfx.webrender.compositor.force-enabled, unforunately it's heavily
gated and hardcoded to be ignored unless the build is marked as Firefox
Nightly.
It may be possible to bring this feature back to life after testing, fixes and
convincing upstream it's important because of power efficiency.
SUMMARY
KWin can randomly misplace part of the Firefox window while the proper place
becomes transparent, I can't seem to replicate that on mutter.
I also find it a little strange that even if the issue is proved to be on
Firefox side, KWin doesn't intersect the subsurface with parent surface, which
should eliminate it from view completely? Instead it creates this weird effect
seen in the overview.
STEPS TO REPRODUCE
1. Install Firefox nightly, go to about:config,
gfx.webrender.compositor.force-enabled change to true
2. Open some website like YouTube
3. Resize the window multiple times, use F11 multiple times etc.
OBSERVED RESULT
Ultimately the window will bug out after some time, subsurface will be
misplaced and it's proper place becomes transparent instead.
In the overview you can see that the subsurface is rendered outside of window
borders(the blue border once you focus the window)
EXPECTED RESULT
No bugs
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 40, KDE
KDE Plasma Version: 6.1
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
KWIN: 6.1.80/git master
ADDITIONAL INFORMATION
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