https://bugs.kde.org/show_bug.cgi?id=431449
Bug ID: 431449
Summary: set new latency option to "prefer smoother animations"
by default to prevent stutter
Product: kwin
Version: git master
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: compositing
Assignee: kwin-bugs-n...@kde.org
Reporter: tempel.jul...@gmail.com
Target Milestone: ---
SUMMARY
Thanks to the recent vsync rework, upstream KWin now finally doesn't introduce
stutter to application window content anymore.
However, the default setting for new latency control "balance of latency and
smoothness" introduces stutter when moving windows.
STEPS TO REPRODUCE
1. Open www.vsynctester.com in Firefox (Webrender/OGL enabled) or Chromium
2. Drag another window (e.g. Dolphin)
OBSERVED RESULT
With "balance of latency and smoothness", the moving animation of the window
shows intermittent stutter, whereas vsynctester.com in the background remains
smooth. Oddly this stutter issue seems to be worse with the lower refresh rate
of 60Hz vs. 85Hz.
EXPECTED RESULT
The window movement should be smooth. It is when setting latency to "prefer
smoother animations", which still has very bearable latency.
Thus I suggest making "prefer smoother animations" the default setting. It
might also to be considered whether it would make sense to drop the options
with lower latency than "prefer smoother animations" if they can't deliver an
acceptable result with low GPU load and a fast GPU. Even better of course would
be if they significantly lowered latency while not introducing any stutter
under low GPU load conditions (kwin-lowlatency does achieve that).
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch 5.10
KDE Plasma Version: KWin git-master 8d84fe4b6ae26c501e416a5bc5eee8f5cf4a02bd
Mesa 21 git-master + xf86-video-amdgpu, RX 5700 XT
single 1440p display
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