Created attachment 167472 [details]
Example of this bug in a maximized app

SUMMARY
Whenever the floating panel "de-floats" while running on a screen resolution of 2256x1504 with 150% fractional scaling, a small sliver of the desktop's wallpaper can be seen at the bottom right of the display. This can be especially distracting in fullscreen apps, such as games or letterboxed video.

STEPS TO REPRODUCE
1. Set screen resolution to 2256x1504 (if possible. I'm not sure if this can be done in a VM, in which case try using a Framework Laptop or Microsoft Surface Laptop)
2. Set scale factor to 150%
3. Restart KDE Plasma (for good measure)
4. Run an app maximized or in fullscreen (for instance, Firefox or a Steam game)

OBSERVED RESULT
A small sliver of the desktop wallpaper can be seen of the bottom right of the screen

EXPECTED RESULT
The panel defloats without showing any of the wallpaper

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE Tumbleweed 20240317
(available in About System)
KDE Plasma Version: 6.0.2
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2

ADDITIONAL INFORMATION
Strangely I notice this only seems to happen under the following conditions (though there may be more):
1. An app is fullscreened. The reason why this is odd is because if you don't open any fullscreen apps, maximized windows will actually display properly. But after one fullscreen window has been opened (and later closed, doesn't matter), maximized windows have this effect.
2. Displays are switched.

Also, this actually even affects the screen locker, which is slightly funny, but I guess it kinda makes sense?