I think that's wrong now. Quartz and OpenGL are arguably as important as the other in modern Mac OS X
That's just at the lower levels, though. Cocoa programmers are more likely to write Quartz code than OpenGL code.
The compositor does use OpenGL to get data onto the GPU. That's not something you have to really be aware of at the Cocoa level, though. It could change at any time without breaking existing Quartz apps.
by Scott Stevenson — Sep 22
That's just at the lower levels, though. Cocoa programmers are more likely to write Quartz code than OpenGL code.
The compositor does use OpenGL to get data onto the GPU. That's not something you have to really be aware of at the Cocoa level, though. It could change at any time without breaking existing Quartz apps.