SUMMARY Direct scanout doesn't work with many fractional scaling values. STEPS TO REPRODUCE 1. Set fractional scaling to e.g. 175% or 115% or 225% on 3840x2160 monitor. 2. Enable red-text which shows "Compositing". 3. Open full screen video player or game. OBSERVED RESULT Direct scanout is not working (red text is visible). EXPECTED RESULT Direct scanout is working. SOFTWARE/OS VERSIONS KDE Plasma Version: 6.6.2 KDE Frameworks Version: 6.23.0 Qt Version: 6.10.2 ADDITIONAL INFORMATION Direct scanout works with some other fractional scaling values like 150% or 125%.
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwin/-/merge_requests/8950
Git commit 0e2e4258f61716c0e2c2386da389351d248cb858 by Vlad Zahorodnii, on behalf of Błażej Szczygieł. Committed on 10/03/2026 at 10:42. Pushed by vladz into branch 'master'. scene/workspace: change rounding policy in 'addCandidates()' Normal rounding matches how the renderer maps the surface coordinates to the screen. This allows direct scanout for various fractional scaling values. M +3 -3 src/scene/workspacescene.cpp https://invent.kde.org/plasma/kwin/-/commit/0e2e4258f61716c0e2c2386da389351d248cb858
Git commit efd01b1206bec39d69d35287d6bac976b52df48f by Vlad Zahorodnii. Committed on 10/03/2026 at 11:20. Pushed by vladz into branch 'Plasma/6.6'. scene/workspace: change rounding policy in 'addCandidates()' Normal rounding matches how the renderer maps the surface coordinates to the screen. This allows direct scanout for various fractional scaling values. (cherry picked from commit 0e2e4258f61716c0e2c2386da389351d248cb858) Co-authored-by: Błażej Szczygieł <mumei6102@gmail.com> M +3 -3 src/scene/workspacescene.cpp https://invent.kde.org/plasma/kwin/-/commit/efd01b1206bec39d69d35287d6bac976b52df48f