DPMS on and off

dpms_onoff.cpp

// c++     -lX11 -L/usr/lib/arm-linux-gnueabihf/libX11.so.6  -lXext dpms_onoff.cpp -o dpms_onoff
// stolen pieces from  http://www.karlrunge.com/x11vnc/blockdpy.c 
// and also https://github.com/danfuzz/xscreensaver/blob/master/driver/dpms.c 
//expected behaviour: turns the screen off then on twice, but actually only does it once

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <memory.h>
#include <unistd.h>

extern "C" {
        #include <X11/Xlib.h>
        #include <X11/Xproto.h>
        #include <X11/extensions/dpms.h>

}

Display *dpy = NULL;
CARD16 standby, suspend, off;

int main(int argc, const char **argv)
{
            dpy = XOpenDisplay(NULL);
            if (! dpy) {
                fprintf(stderr, "XOpenDisplay failed.\n");
                exit(1);
            }

            CARD16 state;
            BOOL onoff = False;

            DPMSInfo(dpy, &state, &onoff);
            fprintf(stdout, "STATE %i\n",state);

//turn screen off
            CARD16 desired = DPMSModeOff;
            DPMSForceLevel(dpy, desired);
            usleep(1000*1000);

            DPMSInfo(dpy, &state, &onoff);
            fprintf(stdout, "STATE %i\n",state);

//turn screen on
            desired = DPMSModeOn;
            DPMSForceLevel(dpy, desired);
            usleep(1000*1000);

            DPMSInfo(dpy, &state, &onoff);
            fprintf(stdout, "STATE %i\n",state);

//turn screen off
            desired = DPMSModeOff;
            DPMSForceLevel(dpy, desired);
            usleep(1000*1000);
            //XSync (dpy, False);

            DPMSInfo(dpy, &state, &onoff);
            fprintf(stdout, "STATE %i\n",state);

//turn screen on
            desired = DPMSModeOn;
            DPMSForceLevel(dpy, desired);
            usleep(1000*1000);

            DPMSInfo(dpy, &state, &onoff);
            fprintf(stdout, "STATE %i\n",state);

   return 0;
}