https://bugs.kde.org/show_bug.cgi?id=527915
Bug ID: 527915
Summary: Title: Fullscreen windows flicker when cursor
hides/shows; with direct scanout disabled (or on
6.8.1), fullscreen drops frames while cursor is hidden
Classification: Plasma
Product: kwin
Version First 6.8.1
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 197730
--> https://bugs.kde.org/attachment.cgi?id=197730&action=edit
Kwin output
Summary
Fullscreen windows behave badly whenever the cursor is hidden. On KWin 6.8.0
the screen flickers when the cursor hides or appears. With
KWIN_DRM_NO_DIRECT_SCANOUT=1 set (confirmed in kwin_wayland’s environment), or
after updating to KWin 6.8.1, the flicker stops but fullscreen drops many
frames and input lags while the cursor is hidden. Windowed (non-fullscreen)
apps are fine in every case.
Steps to reproduce
Play a YouTube video fullscreen in Brave (Chromium) with “Stats for nerds”
open.
Leave the mouse still so the player controls and cursor auto-hide.
Alternatively, run World of Warcraft (Proton) in “Fullscreen (Windowed)” mode
and turn the camera with the mouse (cursor hidden).
Observed
KWin 6.8.0 with default settings: the screen flickers each time the cursor
hides or reappears. No dropped frames.
KWin 6.8.0 with KWIN_DRM_NO_DIRECT_SCANOUT=1, or KWin 6.8.1 with default
settings: no flicker, but YouTube reports heavy dropped frames once the
controls hide (none while they’re visible), and WoW lags during mouse camera
turning.
Windowed mode: no flicker and no frame drops on any version.
Happens on both monitors. Disabling the second monitor didn’t help.
Expected
Fullscreen windows render smoothly without flicker, whether or not the cursor
is visible.
Notes
The 6.8.1 behavior went away after rolling back to a pre-update Btrfs snapshot.
That update also included Mesa 26.2.4→26.2.5 and linux-firmware
20260916→20261019. Switching the kernel (7.3.0 vs LTS 6.18) didn’t change it.
VRR is not available on the main monitor. HDR is off.
System
Distro: CachyOS, Plasma 6.8.0 (issue also on 6.8.1), Wayland
GPU: AMD Radeon RX 9070 XT, Mesa 26.2.4 (26.2.5 on 6.8.1)
Kernel: linux-cachyos 7.2.9 (also tested 7.3.0 and LTS 6.18.55)
Monitors: 3440x1440@144 (DisplayPort) + 1920x1080@144 (HDMI)
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