https://bugs.kde.org/show_bug.cgi?id=478938
Bug ID: 478938
Summary: The presentation time protocol is buggy with VRR on
Chromium
Classification: Plasma
Product: kwin
Version: 5.91.0
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: kwin-bugs-n...@kde.org
Reporter: t...@nitrosubs.live
Target Milestone: ---
SUMMARY
After setting VRR policy to "Always" (or going fullscreen on "Automatic"),
running Chromium with the Ozone hint property set to Wayland or auto, the
browser fails to VSync unless the hardware cursor is moved (software cursor has
no influence).
STEPS TO REPRODUCE
1. Set VRR policy to "Always" or "Automatic"
2. Launch Chromium with the Wayland backend (and go fullscreen if VRR policy is
set to "Automatic")
OBSERVED RESULT
The browser has a seemingly random frametime (easily observed with UFOTest,
simply scrolling a website, or with a YouTube video), but while moving the
mouse everything looks good - I get 165 FPS. (This isn't good for low framerate
video playback though, as moving the mouse sets the refresh rate back to
165Hz.)
EXPECTED RESULT
Chromium's draw/swap calls should dictate the refresh rate in a stable manner.
SOFTWARE/OS VERSIONS
Linux: Arch Linux, kernel version 6.6.7-zen1-1-zen
KDE Plasma Version: 5.91.0 (Plasma 6.0 Beta 2)
KDE Frameworks Version: 5.247.0
Qt Version: 6.7.0beta1
ADDITIONAL INFORMATION
Setting KWIN_FORCE_SW_CURSOR to 1 doesn't cause Chromium to sync properly while
moving the mouse - could this have something to do with cursor plane
separation?
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