objective c - 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 screen on a Retina MacBook Pro, I would expect to fetch the native pixel dimensions using

size_t pixelWidth = CGDisplayPixelsWide(directDisplayID);
size_t pixelHeight = CGDisplayPixelsHigh(directDisplayID);

However, these calls only return the dimensions of the currently selected mode. If I change screen resolution I get back different values. I was looking to get back 2880 x 1800 on a 15" rMBP.

How do I fetch the native pixel dimensions of a Retina MacBook Pro screen?

Answer 1

I think the best approach is to enumerate all of the display modes (including the 1x modes) and find the biggest 1x mode's dimensions.

You would use CGDisplayCopyAllDisplayModes() and pass a dictionary with the key kCGDisplayShowDuplicateLowResolutionModes mapped to kCFBooleanTrue as the options to get all of the modes. You can test that CGDisplayModeGetPixelWidth() is equal to CGDisplayModeGetWidth() to determine which are 1x.