Inside Macintosh: Apple Game Sprockets Guide /

Chapter 2 - DrawSprocket / DrawSprocket Reference

DrawSprocket Functions / Using Alternate Buffers

DSpAltBuffer_GetCGrafPtr

Use the DSpAltBuffer_GetCGrafPtr function to get the drawing area for an alternate buffer.

OSStatus DSpAltBuffer_GetCGrafPtr (
DSpAltBufferReference inAltBuffer,
DSpBufferKind inBufferKind,
CGrafPtr *outCGrafPtr);

inAltBuffer

A reference to an alternate buffer.

inBufferKind

The kind of buffer. Currently the only supported buffer kind is kDSpBufferKind_Normal.

outCGrafPtr

On exit, the graphics pointer associated with an alternate buffer.

function result

A result code.

DESCRIPTION

You pass the DSpAltBuffer_GetCGrafPtr function a reference to an alternate buffer in the inAltBuffer parameter and the kind of buffer in the inBufferKind parameter. The function returns a graphics pointer in the outCGrafPtr parameter. The pointer may then be used to image into the alternate buffer. After you have imaged into the alternate buffer, remember to invalidate the rectangles that you have worked in using the DSpAltBuffer_InvalRect function (page 2-65).

CALLING RESTRICTIONS

Do not call this function during an interrupt.