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

If using NSScreen is an option, you could do something like this in OSX 10.7:

NSRect framePixels = [screen convertRectToBacking:[screen frame]];

where framePixels.size is your display's pixel resolution and screen is a pointer to NSScreen. For example, this code would print the pixel resolution of all active displays to console:

for (NSScreen* screen in [NSScreen screens])
{
    NSRect framePixels = [screen convertRectToBacking:[screen frame]];
    NSLog(@"framePixels: (%f, %f)", framePixels.size.width, framePixels.size.height);
}