Created attachment 162573 [details]
Deformed window geometry after leaving fullscreen

To reproduce this bug we need a 3rd party window manager app, to place windows to the left / right / top / bottom because MacOs doesn't provide commands to place windows on-screen,  at least not on my Os (macos 10.14.6)

STEPS TO REPRODUCE

1. to start, open Krita in window mode (not fullscreen ) and make Kritas window smaller, but change window boundaries manually 
2. Now use any window manager app and change kritas window boundaries to cover the whole monitor size (not fullscreen )
3. Enter full-screen with krita
4. Exit from fullscreen mode in krita
5. Result : kritas window geometry will contract
6. Now let's try to resolve the bug;  so let's change kritas window boundaries manually to cover the monitor (not fullscreen )
7. Enter fullscreen in krita and then, exit  from fullscreen 
8. Result: krita will keep its window aspect ratio and behave normally (no contraction, as seen in my attachments )

OBSERVED RESULT
With window manager apps, Krita isn't able to detect its real window geometry. Krita seems to read window geometry from some setting instead to detect the real window size on-screen

EXPECTED RESULT
Please add some code to check and keep window geometry as it is after leaving full-screen mode, so this bug gets trapped. This bug annoyed me for years and I found the solution just today. Because of this behavior I couldn't use fullscreen mode all this time. 

SOFTWARE/OS VERSIONS
macOS: 10.14.6
Qt Version:

ADDITIONAL INFORMATION
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