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

The library X11 working only with unix-like OS, so it is a not cross-platform solution.

A full code

#include 

#include 

int
main(const int argc, const char *argv[])
{

    Display *display;
    Screen *screen;

    // open a display
    display = XOpenDisplay(NULL);

    // return the number of available screens
    int count_screens = ScreenCount(display);

    printf("Total count screens: %d\n", count_screens);


    for (int i = 0; i < count_screens; ++i) {
        screen = ScreenOfDisplay(display, i);
        printf("\tScreen %d: %dX%d\n", i + 1, screen->width, screen->height);
    }

    // close the display
    XCloseDisplay(display);

   return 0;
}

A compilation

gcc -o setup setup.c -std=c11 `pkg-config --cflags --libs x11`

A result (actual for my computer)

Total count screens: 1
    Screen 1: 1366X768

Based on:

1. https://tronche.com/gui/x/xlib/display/opening.html
2. https://tronche.com/gui/x/xlib/display/display-macros.html
3. https://tronche.com/gui/x/xlib/display/screen-information.html
4. https://stackoverflow.com/a/1829747/6003870