How to programmatically determine native pixel resolution of Retina MacBook Pro screen on OS X?

Question

Given a CGDirectDisplayID returned from

CGError error = CGGetActiveDisplayList(8, directDisplayIDs, &displayCount);

for the built-in s

Answer 1

CGDisplayModeGetIOFlags can tell you some information of the display. The native resolutions have kDisplayModeNativeFlag set. The following will set ns to be the native resolution of the current screen of the window win.

CGDirectDisplayID sid = ((NSNumber *)[win.screen.deviceDescription
    objectForKey:@"NSScreenNumber"]).unsignedIntegerValue;
CFArrayRef ms = CGDisplayCopyAllDisplayModes(sid, NULL);
CFIndex n = CFArrayGetCount(ms);
NSSize ns;
for(int i = 0; i < n; ++i){
    CGDisplayModeRef m = (CGDisplayModeRef)CFArrayGetValueAtIndex(ms, i);
    if(CGDisplayModeGetIOFlags(m) & kDisplayModeNativeFlag){
        ns.width = CGDisplayModeGetPixelWidth(m);
        ns.height = CGDisplayModeGetPixelHeight(m);
        break;
    }
}
CFRelease(ms);