There must be a problem with your event loop. WaitNextEvent/GetNextEvent should handle FKEYs for you. How do you know event handling is going on? The System 9 behaviour sounds like the event is queued but not read by your application. What are you using for the event mask? What about sleep time?

If this is just some cut down example code, it may well be missed. I can guarantee that the screen capture is not disabled by using the whole display as your window.

Ken