Inside Macintosh: Apple Game Sprockets Guide /

Chapter 2 - DrawSprocket / DrawSprocket Reference

DrawSprocket Functions / Using Alternate Buffers

DSpAltBuffer_InvalRect

You can use the DSpAltBuffer_InvalRect function to invalidate a rectangle in an alternate buffer.

OSStatus DSpAltBuffer_InvalRect (
DSpAltBufferReference inAltBuffer,
const Rect *inInvalidRect);

inAltBuffer

A reference to an alternate buffer.

inInvalidRect

A pointer to the rectangle to be invalidated.

function result

A result code.

DESCRIPTION

You would invalidate a rectangle in an alternate buffer in the following situations:

• Before calling DSpAltBuffer_RebuildTransparencyMask so as to rebuild only those sections of a transparency mask that have changed.
• To invalidate areas of an overlay or underlay you have changed so that the changes are transferred to the back buffer on the next DSpContext_SwapBuffers call.

You pass the DSpAltBuffer_InvalRect function a reference to an alternate buffer in the inAltBuffer parameter and a pointer to the rectangle to be invalidated in the inInvalidRect parameter.

CALLING RESTRICTIONS

Do not call this function during an interrupt.