Public bug reported:
On an external monitor, the top bar flickers where content updates
regularly (clock, system-monitor-next extension). During the flicker,
the wallpaper is visible instead of the panel, i.e. the region appears
not to be painted in some frames. The internal display is not affected.
Ubuntu 26.04.1 LTS, GNOME Shell / Mutter (GNOME Shell 50.1)
Intel Panther Lake, xe kernel driver, kernel 7.2.0-070200rc1-generic
External monitor via USB-C dock in DP Alt Mode (no DisplayLink, no MST)
Scaling / refresh rates: internal: 166%, 120,00Hz; external: 100%, 59,99Hz
CLUTTER_PAINT=disable-clipped-redraws in
~/.config/environment.d/mutter-debug.conf fixes the issue completely.
Not affected by disabling FBC, PSR or Panel Replay (xe.enable_fbc=0,
xe.enable_psr=0, xe.enable_panel_replay=0), so the problem does not appear to
be in the driver's damage-clip handling.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: gnome-shell 50.1-0ubuntu1.2
Uname: Linux 7.2.0-070200rc1-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Thu Sep 24 13:10:00 2026
DisplayManager: gdm3
InstallationDate: Installed on 2026-07-04 (82 days ago)
InstallationMedia: Ubuntu 26.04 "Resolute Raccoon" - Release amd64 (20260423.1)
ProcEnviron:
LANG=de_DE.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
RebootRequiredPkgs: Error: path contained symlinks.
RelatedPackageVersions: mutter-common 50.1-0ubuntu2.4
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: gnome-shell (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2168433
Title:
Panel elements intermittently not drawn on external monitor (wallpaper
shows through, flickering)
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