
This image (linked due to size) shows how GZDoom looks when maximized in windowed mode. That black bar at the top doesn't bother me so much, as it's always done that. (The game resolution is 1280x800, screen is 1280x1024). When maximixed, the image always renders pinned to the lower left corner.
Except with the new mouse-controlled menu. My pointer (which you can't see in that picture) is pointing at New Game, however because everything is rendered lower than expected, GZDoom thinks i'm pointing at Game Files. (You can see how it's the same distance.)
Seems like the best thing here would be to force it to render the window in the top left of the window's client area...
Spoiler: System Specs