Bug 462811

Summary: Software cursor on Wayland causes artifacts over blurred surfaces
Product: [Plasma] kwin Reporter: Asahi Lina <lina>
Component: platform-drmAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED DUPLICATE    
Severity: normal CC: m.kurz, xaver.hugl
Priority: NOR    
Version: 5.26.4   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed In:

Description Asahi Lina 2022-12-09 10:44:39 UTC 
SUMMARY

On kwin_wayland (DRM backend) with software cursors (e.g. on Apple M1 platforms where we don't have hardware cursor planes yet, or with KWIN_FORCE_SW_CURSOR=1 on any system), moving the mouse over a blurred surface causes visual artifacts. It seems the blur isn't being recomputed with the required expansion to correctly fill the damaged area, so the edges of the box around the moving cursor become darker. Setting blur strength lower makes what is happening more obvious.

STEPS TO REPRODUCE
1. Set KWIN_FORCE_SW_CURSOR=1 when starting kwin_wayland
2. Move the mouse over a blurred surface (e.g. the Plasma task bar, Konsole with the background set to transparent/blurred

OBSERVED RESULT

Trails of glitch boxes wherever the mouse moves.

EXPECTED RESULT

No artifacts.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.26.4
KDE Frameworks Version: 5.100.0
Qt Version: 5.15.7
Comment 1 Zamundaaa 2022-12-10 14:35:16 UTC 

*** This bug has been marked as a duplicate of bug 455526 ***