https://bugs.kde.org/show_bug.cgi?id=522791
Bug ID: 522791
Summary: Banding / posterized CSS shadows in Chromium-based
browsers on Plasma Wayland after KWin 6.6.5 update
Classification: Plasma
Product: kwin
Version First 6.6.5
Reported In:
Platform: Ubuntu
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Summary:
After updating KDE Plasma/KWin from 6.6.4 to 6.6.5, Chromium-based browsers
on Plasma Wayland started rendering
CSS shadows and filter: drop-shadow() with visible banding / posterization,
as if gradients are low bit-depth.
Firefox renders the same pages correctly. The issue disappears when launching
Chrome/Vivaldi with --ozone-
platform=x11.
System:
OS: Ubuntu 26.04
Session: KDE Plasma Wayland
KWin: 6.6.5-0ubuntu0.1
GPU: AMD Radeon 780M, amdgpu, Mesa 26.0.3
Display: eDP-1, 2560x1600@120Hz, scale 1.5
KScreen: Color resolution automatic (10), sRGB profile
Chrome: 150.0.7871.46
Vivaldi: 8.0.4033.54
Regression:
Worked before recent updates. Local package history:
2026-07-02: kwin-wayland/libkwin6/kwin-common 6.6.4 -> 6.6.5
2026-07-03: plasma-workspace/plasma-session-wayland 6.6.4 -> 6.6.5
Vivaldi was not updated after 2026-06-26, but it is affected too.
Steps to reproduce:
1. Log into KDE Plasma Wayland.
2. Open Chrome or Vivaldi normally.
3. Open a page with large CSS box-shadow or filter: drop-shadow().
4. Observe visible banding/stepped shadows.
5. Relaunch browser with --ozone-platform=x11.
6. The same shadows look smooth or significantly improved.
Expected:
Soft CSS shadows/gradients render smoothly, similar to Firefox or Chromium
through XWayland.
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