Monitor X11 display activity and disable HDMI on inactivity (Raspberry Pi)

switchOff.c

//Install dependencies: sudo apt install libxss-dev
//Compile with: gcc -o switchOff switchOff.c -lXss -lX11
#include <X11/extensions/scrnsaver.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int main(void) {
    
    Display *dpy = NULL;
    while(!dpy) {
        dpy = XOpenDisplay(":0");
        usleep(1000 * 1000);
    }

    int on = 1;
    while(1) {
        XScreenSaverInfo *info = XScreenSaverAllocInfo();
        XScreenSaverQueryInfo(dpy, DefaultRootWindow(dpy), info);

        //Disable after 5 minutes
        if(info->idle >= 5 * 60 * 1000) {
            if(on) {
                printf("Off\n");
                system("/usr/bin/vcgencmd display_power 0");
                on = 0;
            }
        } else {
            if(!on) {
                printf("On\n");
                system("/usr/bin/vcgencmd display_power 1");
                on = 1;
            }
        }
        
        XFree(info);
        usleep(100 * 1000);
    }

    return(0);
}