Resolution changer for Mac OSX

setgetscreenres.m

// http://apple.stackexchange.com/questions/139548/changing-display-resolution-on-retina-machines-while-in-command-line-mode
/*
 * COMPILE:
 *    c++ setgetscreenres.m -framework ApplicationServices -o setgetscreenres
 * USE:
 *    setgetscreenres 2048 1280  # 1440 900
 */

#include <ApplicationServices/ApplicationServices.h>

bool MyDisplaySwitchToMode (CGDirectDisplayID display, CFDictionaryRef mode);

int main (int argc, const char * argv[])
{
  int h;                          // horizontal resolution
  int v;                          // vertical resolution
  CFDictionaryRef switchMode;     // mode to switch to
  CGDirectDisplayID mainDisplay;  // ID of main display

  CFDictionaryRef CGDisplayCurrentMode(CGDirectDisplayID display);

  if (argc == 1) {
    CGRect screenFrame = CGDisplayBounds(kCGDirectMainDisplay);
    CGSize screenSize  = screenFrame.size;
    printf("%g %g\n", screenSize.width, screenSize.height);
    return 0;
  }
  if (argc != 3 || !(h = atoi(argv[1])) || !(v = atoi(argv[2])) ) {
    fprintf(stderr, "ERROR: Use %s horres vertres\n", argv[0]);
    return -1;
  }

  mainDisplay = CGMainDisplayID();

  switchMode = CGDisplayBestModeForParameters(mainDisplay, 32, h, v, NULL);

  if (! MyDisplaySwitchToMode(mainDisplay, switchMode)) {
    fprintf(stderr, "Error changing resolution to %d %d\n", h, v);
    return 1;
  }

  return 0;
}

bool MyDisplaySwitchToMode (CGDirectDisplayID display, CFDictionaryRef mode)
{
  CGDisplayConfigRef config;
  if (CGBeginDisplayConfiguration(&config) == kCGErrorSuccess) {
    CGConfigureDisplayMode(config, display, mode);
    CGCompleteDisplayConfiguration(config, kCGConfigureForSession );
    return true;
  }
  return false;
}