Created attachment 164648 [details] screen cast showing the artifacts SUMMARY Running Neon unstable (Plasma 6.0 beta 2 with kwin 5.91.90) on Wayland, when external screens are connecting and are set for vertical orientation, when switching virtual desktops the animation shows large black blotches on the screen. See attached screen cast for details. This problem does not happen with the main screen or if the external screens are set in a horizontal configuration. Similar (though possibly not identical) artifacts can be seen when switching activities - it is not the same animation, but I believe it is the same issue. STEPS TO REPRODUCE 1. Set up one or more external screens to vertical mode 2. switch virtual desktop back and forth OBSERVED RESULT large black boxes are rendered in the middle of the screen, and parts of the animation appear to move in the wrong direction. EXPECTED RESULT Animation should be smooth. SOFTWARE/OS VERSIONS Operating System: KDE neon Unstable Edition KDE Plasma Version: 5.91.90 KDE Frameworks Version: 5.248.0 Qt Version: 6.6.1 Kernel Version: 6.2.0-39-generic (64-bit) Graphics Platform: offscreen Processors: 20 × 12th Gen Intel® Core™ i7-12700H Memory: 31.0 GiB of RAM Graphics Processor: Mesa Intel® Graphics ADDITIONAL INFORMATION I think the problem is caused by the animation trying to have the "virtual desktop" - that is a box constraining the entire multi-screen setup, that contains a lot of non-visible areas that are virtually drawn with black - animate as it "move through" to the next "virtual desktop" that is virtual "adjacent" to the current "virtual desktop". On Plasma 5 (and I'm guessing on X11, though I haven't run that for a while) this works well - I see the black areas but they are where I expect them to be and we move through them quickly - but now on kwin 5.91.90 the black areas are not located correctly and then remain on the screen for a few fractions of a second too long, until they are wiped by (I'm guessing) vsync.
Created attachment 164649 [details] screenshot in the middle of an animation, showing the problem This is a screenshot from the video showing the middle of the transition, as in - how bad this looks.
Created attachment 164650 [details] reupload of the screen cast in a more web friendly format
Created attachment 164678 [details] Some more animation artifacts on vertical screens I also get weird artifacts that look to be of a similar form, when moving windows. This may also relate to the wobbly windows effect I have - after disabling it, I could not immediately reproduce the problem.
*** This bug has been marked as a duplicate of bug 479217 ***
This issue is about the virtual desktop switching animation being broken with vertical screens, and not about the wobbly windows effect (bug #479217). As I've mentioned in comment #3, I have disabled the wobbly windows effect and that worked around the broken window moving animation - but the virtual desktop switching artifacts are still very much visible.
There were clipping issues in the wobbly windows effect. It's the same bug. Reopen the bug report if the issue is still reproducible after updating plasma *** This bug has been marked as a duplicate of bug 479217 ***
I can no longer reproduce the issue with Plasma 6.0 RC1