This example is extremely contrived, of course it's going to be a nightmare in C. GUI latency probably has little to do with the overhead of objC message sending and more to do with tuning how things respond for UX purposes. For instance it's well known among gamers that on OSX the mouse has acceleration which makes it smother but less responsive in gaming. I wouldn't be surprised if this carried over to scrolling, animations, etc.

> If I were forced to write an OS X app in plain C, there would be plenty of macro usage around objc_msgSend

You will have re-invented the early versions of Objective C which were all done in the preprocessor :)