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

For modern X servers, there's also the XRandR extension, which provides the most up-to-date model of multi screen layout information, including overlapping screens and dynamic screen changes.

Documentation of it is available in the XRandR 1.3.1 Protocol spec and the libXrandr man page.