GPU scaling issue with GroovyMAME

[oomek]

I encountered a strange issue with GM and GPU Scaling

In d3d mode scaling method is forced to Preserve Aspect Ratio.
In bgfx mode scaling method is forced to Full Panel.

I would like to use Full Panel in d3d, but GM seems to ignore what I select in Radeon Settings.
I think it has nothing to do with aspect ratios and internal MAME scaling. Because in slightly older drivers I could see the setting changing from Preserve Aspect Ratio back to Full Screen in Radeon Settings window right after exiting GM. My guess is that it has something to do with how GM is initiating fullscreen modes.

To reproduce the issue gm needs to be called on a 16:9 screen with:

-resolution 1280x1024@60 -video bgfx
(game will be stretched regardless of Scaling Mode)

-resolution 1280x1024@60 -video d3d
(game will be letterboxed regardless of Scaling Mode)

[oomek]

It seems to be directly tied to the DirectX version the app is launched in as I've managed to reproduce it in Valley Benchmark
DX9 letterbox
DX11 stretched

That's odd, any clues?

[oomek]

I have narrowed it down to Windows 10 Anniversary Edition Update. It has nothing to do with GM, so the topic can be closed or deleted. Bloody Microshit again...