Since 7b28c6d17c7da278307756cfcd0da830e5d39baf, we directly use `NtUserGetClientRect` to get the size of the GL target windows. But that returns an empty rect for minimized windows, and attempting to set a zero size on a CGL context in `-[WineOpenGLContext wine_updateBackingSize:]` causes a Metal assertion. You can see this by minimizing e.g. Geometry Dash or Garry's Mod.
We could just not call wine_updateBackingSize if we find a zero dimension for the window, but I think we want to attempt to keep the backing size correct. Perhaps there's a better way to get the client rect of a minimized window than the un-AdjustWindowRect approach I'm using here? If the window is minimized fullscreen, `get_win_data(hwnd)->rects.client` is (-32000, -32000) - (-32000, -32000).
-- v2: winemac.drv: Never set a zero backing size for a GL context.