>>>>> On Mon, 15 Apr 2013 18:48:29 +0900, YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp> said:

> On Mac, the "expose" handler is called in many situations than you
> might expect including outside the control of application code:
> e.g., creating a snapshot of the window image for icons or "Exposé"
> (http://support.apple.com/kb/HT2503).

Taking a snapshot inside the application itself is also useful.  The
Mac port uses it for animation effects such as fullscreen transition
and buffer switching triggered by touch-sensitive pointing devices,
for example.  It calls the "expose" handler behind the scenes when
creating the snapshot image.

				     YAMAMOTO Mitsuharu
				mituharu@math.s.chiba-u.ac.jp