Toggle primary display using XRandr

toggle-primary.c

/*
  Copyright 2012, Jarkko Oranen

  Redistribution, modification and use in any form is permitted 
  Use at your own risk. I will take no responsibility.
*/

// gcc -std=c99 -lXrandr toggle_primary.c -o toggle-primary

#include <X11/Xlib.h>
#include <X11/extensions/Xrandr.h>


Display* dpy = NULL;
Window root = 0;

int main(int argc, char** argv) {

    dpy = XOpenDisplay(NULL);
    root = DefaultRootWindow(dpy);
   
    XRRScreenResources* res = XRRGetScreenResources(dpy, root);
    int num_connected = 0;
    RROutput connected[res->noutput]; 
    for (int i = 0; i < res->noutput; i++) {
        XRROutputInfo* oinfo = XRRGetOutputInfo(dpy, res, res->outputs[i]);
        if (oinfo->connection == RR_Connected) {
            connected[num_connected] = res->outputs[i];
            num_connected++;
        }  
        
        XRRFreeOutputInfo(oinfo);
    }
    
    if (num_connected <= 1) {
       goto exit;
    } 
    
    for (int i = 0; i < num_connected; i++) {
        if (XRRGetOutputPrimary(dpy, root) == connected[i]) {
            XRRSetOutputPrimary(dpy, root, connected[(i+1) % num_connected]);
            break;
        }
    }

exit:    
    XSync(dpy, 1);
    XCloseDisplay(dpy);
    return 0;    
         
}