Windows screenshots are blank when pressing PrintScreen in Fullscreen mode
Hmm. Obviously I don't know if this is rather a Windows issue than ADOM, but I've never noticed quite this problem before. Usually if PrintScreen doesn't work, the clipboard is simply empty, whereas in this case the clipboard is not empty.
When I press PrintScreen, I appear to get a blank image:
Using most websites and programs pastes a black image.
Using Paint.Net, it creates a larger-than-default completely transparent image (ie empty).
However, I was able to successfully take a screenshot using Steam's hotkey. (where Stream screenshots hard to use for inline forum posts)
PS: Actually, PSP also takes a completely black screenshot.
This happens with video players and other games too, it's related to how graphics rendering works. Print Screen can't capture everything, that's why Steam added the screenshot feature and programs like HyperSnap DX exist.
I experience this issue as well and want to see it fixed. But unfortunately it happens to other games in fullscreen as well so unlikely anything can be done for ADOM in particular.