Pressing a button while enter/space is pressed

[Federico Mena Quintero <federico ximian com>]

I wanted to hack GtkButton so that it would show itself as pressed
while the spacebar or Enter is being held down (and you could cancel
the press with Escape).

However, I have no clue of how to do that because if you hold down
those keys, you'll get a multitude of KeyPress and KeyRelease events.
How do I tell X to give me a single KeyRelease when the key is
actually released?

[RTFM is a valid answer if you give me the relevant section of the FM :) ]

  Federico