Converting between Cocoa and Carbon coordinates?

Question

I am looking for a robust (I mean working in all multi-munitor configuration) algo to convert a cocoa point/rect to carbon equivalent and the reverse operation.

I've googled but was unable to find something which work properly.

Thanks in advance for your help.

Regards,

Answer 1

After several iterations I got to the following category on NSScreen:

+ (NSScreen*) screenWithPoint: (NSPoint) p
{
    for (NSScreen *candidate in [NSScreen screens])
        if (NSPointInRect(p, [candidate frame]))
            return candidate;
    return nil;
}

+ (NSScreen*) screenWithMenuBar
{
    return [self screenWithPoint:NSZeroPoint];
}

+ (float) menuScreenHeight
{
    return NSMaxY([[self screenWithMenuBar] frame]);
}

+ (CGPoint) carbonPointFrom: (NSPoint) cocoaPoint
{
    return CGPointMake(cocoaPoint.x, [self menuScreenHeight] - cocoaPoint.y);
}

+ (NSPoint) cocoaPointFrom: (CGPoint) carbonPoint
{
    return NSMakePoint(carbonPoint.x, [self menuScreenHeight] - carbonPoint.y);
}

This works fine even with multiple displays.

Answer 2

The posted code from Apple's code from UIElementInspector turn out to be buggy, in that it doesn't account for the origin of a non-main screen. The fixed (and refactored) code looks like this:

+ (CGPoint)carbonScreenPointFromCocoaScreenPoint:(NSPoint)cocoaPoint {
  NSScreen* foundScreen = nil;
  NSRect screenFrame;
  for (NSScreen* screen in [NSScreen screens]) {
    screenFrame = [screen frame];
    if (NSPointInRect(cocoaPoint, screenFrame)) {
      foundScreen = screen;
      break;
    }
  }
  if (! foundScreen) return CGPointMake(0.0, 0.0);
  return CGPointMake(cocoaPoint.x, 
    screenFrame.origin.y + screenFrame.size.height - cocoaPoint.y);
}