Detect any key press, including modifier keys, on OS X

Question

I need to detect all the keys that the user presses. Using -keyDown: I can get most key presses (alphanumeric, function keys, arrows, space bar, escape, return)

Answer 1

Try it:

[NSEvent addLocalMonitorForEventsMatchingMask:NSKeyDownMask|NSFlagsChangedMask handler:^NSEvent *(NSEvent *incomingEvent) {
    if (incomingEvent.type == NSFlagsChanged && (incomingEvent.modifierFlags & NSDeviceIndependentModifierFlagsMask)) {
        NSLog(@"modifier key down");
    } else if (incomingEvent.type == NSKeyDown) {
        NSLog(@"other key down");
    }

    return incomingEvent;
}];