Inside Macintosh: Imaging With QuickDraw /

Chapter 6 - Offscreen Graphics Worlds / Offscreen Graphics Worlds Reference

Routines / Creating, Altering, and Disposing of Offscreen Graphics Worlds

NewTempScreenBuffer

The NewGWorld function uses the NewTempScreenBuffer function to create an offscreen PixMap record and allocate temporary memory for the base address of its pixel image; applications generally don't need to use NewTempScreenBuffer.

FUNCTION NewTempScreenBuffer (globalRect: Rect; 
                             purgeable: Boolean; 
                             VAR gdh: GDHandle; 
                             VAR offscreenPixMap: PixMapHandle):
                             QDErr;

globalRect

The boundary rectangle, in global coordinates, for the offscreen pixel map.

purgeable

A value of TRUE to make the memory block for the offscreen pixel map purgeable, or a value of FALSE to make it unpurgeable.

gdh

The handle to the GDevice record for the graphics device with the greatest pixel depth among all graphics devices whose boundary rectangles intersect the rectangle specified in the globalRect parameter.

offscreenPixMap

A handle to the new offscreen PixMap record.

DESCRIPTION

The NewTempScreenBuffer function performs the same functions as NewScreenBuffer except that it creates the base address for the offscreen pixel image in temporary memory. When an application passes it the useTempMem flag, the NewGWorld function uses NewTempScreenBuffer instead of NewScreenBuffer.

SPECIAL CONSIDERATIONS

The NewTempScreenBuffer function may move or purge memory blocks in the application heap. Your application should not call this function at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the NewTempScreenBuffer function are

Trap macro	Selector
_QDExtensions	$000E0015