https://bugs.kde.org/show_bug.cgi?id=520488
Bug ID: 520488
Summary: Brightness flicker / skipping cursor when switching
between direct scanout and compositing with
VRR-capable monitor
Classification: Plasma
Product: kwin
Version First 6.6.90
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: platform-drm
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
Created attachment 192514
--> https://bugs.kde.org/attachment.cgi?id=192514&action=edit
moving cursor and opening/closing context menu with monitor osd showing current
refresh rate
DESCRIPTION
Using a regular application like a browser in fullscreen with auto-hiding
panels enters direct scanout. Opening a context menu or showing the panels will
temporarily force compositing and the switch from and back to direct scanout
causes a brightness flicker and the cursor to skip a few frames with VRR. My
monitor osd also shows a brief drop in refresh rate.
This happens regardless of Adaptive sync actually being off or on in system
settings; the only workarounds are disabling VRR on the monitor itself or
forcing compositing by slightly resizing the window or setting `Color accuracy`
to `Prefer color accuracy`. With VRR turned off on the monitor there is no
dropped frames when switching between direct scanout and compositing, and with
`Prefer color accuracy` there is obviously no switch in the first place.
I've reproduced this on both my main 240Hz OLED and my second 144Hz IPS
monitor, though it's a lot more pronounced on the 240Hz OLED of which I've
attached a 120fps slowmo recording.
STEPS TO REPRODUCE
1. On VRR-capable monitor launch Firefox and maximize the window
2. Auto-hide panels
3. Move cursor and right-click/left-click to open and close context menu
OBSERVED RESULT
Brightness flicker and skipping cursor.
EXPECTED RESULT
Smooth framerate and no flicker or skipping cursor.
SOFTWARE/OS VERSIONS
Operating System: CachyOS (kde-unstable arch repo enabled)
KDE Plasma Version: 6.6.90
KDE Frameworks Version: 6.26.0
Qt Version: 6.11.1
ADDITIONAL INFORMATION
Kernel: 7.0.9-1-cachyos-eevdf-lto
GPU: Radeon RX 9070 XT [Mesa 26.2.0-devel (git-94a7d50433)]
CPU: Ryzen 9 5950X
Displays: MSI MPG 321URX QD-OLED 3840x2160@240Hz, LG UltraGear 27GN800-B
2560x1440@144Hz
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