QuickTime 3 Reference
This section describes functions that apply to all derived media handler components.
There is a minor change to the MediaIdle function that is related to the new media handler support for partial screen redrawing.
From time to time, your derived media handler component may determine that only a portion of the available drawing area needs to be redrawn. You can signal that condition to the base media handler component by setting the mPartialDraw flag to 1 in the flags your component returns to the Movie Toolbox from your MediaIdle function. You return these flags using the flagsOut parameter.
Whenever you set this flag to 1, the Movie Toolbox calls your component's MediaGetDrawingRgn function in order to determine the portion of the image that needs to be redrawn.
As an example, consider a full-screen animation. Only rarely is the entire image in motion. Typically, only a small portion of the screen image moves. By using partial redrawing, you can significantly improve the playback performance of such a movie.
See also: MediaInvalidateRegion and MediaGetDrawingRgn.