Bug 511593

SUMMARY
Going from a maximized window to a non maximized window causes a very brief visual glitch. The window will be redrawn in its windowed size in the top left corner of the monitor on top of the currently drawn window, and this state will last for at least a frame (I saw it on a 60 hz recording of my 240 hz screen).

Important note : I have all relevant desktop effects disabled, and my global animation speed is instant.


STEPS TO REPRODUCE
1. Have animation speed to the "instant" speed, and relevant desktop effects disabled (I don't know them, since I disabled them every since I started using kde and never reenabled them.
2. Have a maximized window on a monitor.
3. Drag the window using the top bar to make it windowed.

OBSERVED RESULT
The window will be redrawn in its windowed size in the top left corner of the monitor on top of the currently drawn window, causing a visual glitch (a "flash").

EXPECTED RESULT
The window should jump to its windowed state without being redrawn this way, instantly.

SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux 
KDE Plasma Version: 6.5.1
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0

ADDITIONAL INFORMATION
I've never noticed this happening before upgrading to 6.5, so i'm pretty sure it's a new bug that appeared in 6.5.