This article is from the Mac Programming FAQ, by Jon Watte firstname.lastname@example.org with numerous contributions by others.
Because there is always some overhead involved in calling QuickDraw;
you have the trap dispatcher, clipping checks, and checking whether the
CopyBits call is being recorded in a PICT handle (if you called
If you can't live with this, look at 4.8 below, but PLEASE try and make
CopyBits work, and retain the CopyBits code in your application, so
users with special monitors (accellerator cards, PowerBook color
screens, Radius Pivot screens) can still play your game. (non-game
applications don't need more speed than CopyBits can give at its max.