How to query X11 display resolution?

Question

It seems like an simple problem, but I can\'t find the answer: How do you query (via X11) what monitors exist and their resolutions?

Answer 1

If Xinerama is in use, try XineramaQueryScreens. Otherwise, you may be able to assume a single screen and use (X)WidthOfScreen/(X)HeightOfScreen.

(Also see the other answer. It's remotely possible someone is using the old X screen model where your screens are :x.0, :x.1, etc.)