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.)

Answer 2

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

A full code

#include <stdio.h>

#include <X11/Xlib.h>

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

Answer 3

Python

import os
from Xlib import X, display
d = display.Display()
s = d.screen().root
output = os.popen("xrandr --listmonitors | grep '*' | awk {'print $4'}").read().splitlines()
num_sc = s.xinerama_get_screen_count().screen_count
width = s.get_geometry().width
height = s.get_geometry().height
print("Total count screens: %s" % num_sc)
for i in range(num_sc):
    print("\tScreen %s(%s): %sX%s" % (i, output[i], width, height))

Bash

$ xrandr --listmonitors
$ xrandr
$ xrandr | grep '*' | awk {'print $1'}

Answer 4

Clean xrandr output for imagemagick use

$ xrandr |grep \* |awk '{print $1}'

Results here in:

1920x1080

Answer 5

Check out display macros and screen macros from the Xlib manual.

Specifically:

• From the first link: ScreenCount(), ScreenOfDisplay()
• From the second link: WidthOfScreen(), HeightOfScreen()

Answer 6

This might be helpfull for cli and scripting

xwininfo -root

But xRandR might be more accurate, especially, when there is multiple monitor environment:

xrandr