Created attachment 163418 [details] Screenshot of the issue SUMMARY With kwin_wayland multiscreen and no root window (no plasmashell), the black background on screens not at the (0,0) origin is not repainted properly when damaged. STEPS TO REPRODUCE 1. Configure multiple screens 2. killall plasmashell 3. Move things around (or just the mouse cursor if using software cursors) OBSERVED RESULT See attachment. It looks like the damage/repaint region for the black background is calculated incorrectly, and the background render happens at the wrong output coordinates within the framebuffer. Moving the mouse cursor causes black trails at the offset position on top of other window content (though I couldn't grab a screenshot of this). On the screenshot you can see that only the right band of the background is cleared to black. This is because the repaints are offset by the width of the leftmost screen (which is less wide than the rightmost screen). If there are two screens with dimensions 100x100 and 200x200 placed left to right in that order, top-aligned, then background damage at offset (0,0) in the rightmost screen, which is at (100,0) in absolute coordinates, gets repainted at (100,0) *relative to the rightmost screen*, which is (200,0) in absolute coordinates. Then the region at (100,0) is missing the background repaint, so whatever damaged that region just paints on top of the stray/damaged framebuffer (leading to cursor trails and the like), while the region at (200,0) gets clobbered with black even if there is some other window on top. EXPECTED RESULT Correct rendering SOFTWARE/OS VERSIONS Operating System: Fedora Linux Asahi Remix 39 KDE Plasma Version: 5.27.9 KDE Frameworks Version: 5.111.0 Qt Version: 5.15.11 Kernel Version: 6.6.0-asahi-00861-g9b58b16aa50d (64-bit) Graphics Platform: Wayland Processors: 12 Memory: 54.5 GiB of RAM Graphics Processor: Apple M2 Max Product Name: Apple MacBook Pro (16-inch, M2 Max, 2023)