Fullscreen GZDoom 2.1.1 x64 only renders top left quarter of

[problemo]

I have an old laptop running GZDoom 2.1.1 x64. When win7's "Use visual styles on windows and buttons" (system > advanced system settings > performance) is enabled, GZDoom in fullscreen only renders the top left corner. Windowed mode works fine, renders everything. Tested wads were DOOM2 and Brutal Doom.

When ingame, Toggling Fullscreen=true mysteriously makes it work again. Setting gzdoom.exe to dedicated graphics card or switching desktop scaling from 120% to 100% does nothing, "Disable display scaling on high DPI" on Compatibility options is greyed out. Btw it's running win7 64bit with Windows Classic theme.

[Gez]

Is it the same as this?

[Guest]

Slightly different, the mouse isn't stuck, click it once and it behaves normally, as if the GZdoom window was simply shrunk to the top left quarter.

The cursor changes to the Doom pointer inside the rendered area and various Windows pointers when outside. Clicking works too, just that the view is restricted to the top left corner. There's also a black box rendered in the center of the screen below the Doom window, around the same size as the rendered Doom screen.

Pressing Alt+Enter twice restores the fullscreen functionality, rendering everything instead of just the top left quarter.

The "Disable visual themes" option in Properties is greyed out, maybe win7 Home Premium doesn't let me or something.