Bug 480976

SUMMARY
System Settings→Desktop Effects→Window Open/Close Animation has three options. The "Scale" option allows the user to change the open/close scale in its menu. The scale is 0.8 by default (i.e. opening / closing animation happens within the bounds of the animated object: shrink to 0.8 of original size when closing, expand from 0.8 of target size when opening) and is limited to no more than 9.99. This scale feature affects how the Task Switcher appears / disappears.

When using the Task Switcher when the close scale is set to more than 1.0, graphical artefacts start appearing on the screen once the close animation has finished. The larger the number, the bigger and more obvious the artefacts are. The artefacts seem to be remnants of the animation that are still being drawn to the screen, and they seem to only ever appear in areas of the screen that the Task Switcher did NOT fill when it was open. They can be cleared by running the mouse over them, opening the start menu over them, or going into the desktop overview with Meta+Tab. They seem to flicker / respond to changes drawn to other windows (see them flashing as the timer updates in the attached video, for instance).

STEPS TO REPRODUCE
1. In Desktop Effects, set the Window Open/Close Animation to "Scale"
2. Open the "Scale" options and set "Window close scale" to more than 1.0 (3.0+ will be more obvious)
3. Select Apply and then OK in the "Scale" options.
4. Use the Task Switcher with Alt+Tab.

OBSERVED RESULT
On releasing Alt+Tab, parts of the Task Switcher's close animation continue to be drawn to the screen. They flicker and are not the same each time they appear, but are reproducible.

EXPECTED RESULT
The close animation ends cleanly.

SOFTWARE/OS VERSIONS
KDE Neon Testing
Wayland
KDE Plasma Version: 6.0.0
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.1

ADDITIONAL INFORMATION
Laptop GPU: Mesa Intel HD Graphics 3000