Created attachment 193368 [details]
Picture of multimonitor setup with my secondary monitor in portrait mode afer pressing META+W (Present windows)

DESCRIPTION
After upgrading to Plasma 6.7.0, using the "Present Windows" effect (Meta+W) causes severe rendering regressions on a multi-monitor configuration utilizing mixed orientations and fractional scaling. Specifically, when a secondary monitor is rotated into portrait mode, entering the Present Windows view causes rapid, aggressive screen flashing/flickering and cleanly cuts off the window geometry on that display.

This issue appears to be directly tied to the DRM Direct Scanout optimization layer on AMD hardware under Wayland. Forcing the compositor to bypass direct scanout completely eliminates the geometry clipping and flashing.

STEPS TO REPRODUCE

    Set up a dual-monitor configuration with an AMD RX 580 GPU on Wayland.

    Configure the primary display in landscape mode (2560x1440) and the secondary display in portrait mode (1200x1600, 1.33x fractional scaling).

    Open several application windows across both displays.

    Trigger the "Present Windows" effect using Meta+W.

OBSERVED RESULT
The windows on the landscape monitor scale normally, but the secondary portrait display experiences rapid buffer flashing/flickering. The window previews on the portrait display are visually cut off, misaligned with the actual screen geometry, and unusable until the effect is dismissed.

EXPECTED RESULT
The Present Windows effect should cleanly and smoothly tile open windows across all displays simultaneously, respecting the vertical/horizontal boundaries and scaling factors of mixed-orientation layouts without flickering.

SOFTWARE/OS VERSIONS

    Operating System: CachyOS x86_64 (Kernel: Linux 7.0.12-1-cachyos)

    KDE Plasma Version: 6.7.0

    KDE Frameworks Version: 6.7.0

    Qt Version: 6.7.0

    Graphics Platform: Wayland

ADDITIONAL INFORMATION

    Hardware: Intel Xeon E5-2673 v4 | AMD Radeon RX 580 Series

    Monitor Setup: LG QHD (2560x1440 @ 144Hz, Landscape) + DELL 2007FP (1200x1600 @ 60Hz, Portrait, 1.33x Scaling)

    Workaround Identified: Adding KWIN_DRM_NO_DIRECT_SCANOUT=1 to /etc/environment and restarting the session completely resolves the bug. Present Windows functions flawlessly with this flag active, strongly pointing to an issue with how scene-drm handles coordinate scaling calculations for rotated buffers during direct scanout handoffs on Polaris/AMD open-source drivers.