Obtains a pointer to an offscreen pixel map.

Ptr GetPixBaseAddr (
    PixMapHandle pm
);

Parameter descriptions

pm

A handle to an offscreen pixel map. To get a handle to an offscreen pixel map, use the GetGWorldPixMap function.

function result

A 32-bit pointer to the beginning of a pixel image. If the offscreen buffer has been purged, GetPixBaseAddr returns NULL.

DISCUSSION

The baseAddr field of the PixMap structure for an offscreen graphics world contains a handle instead of a pointer, which is what the baseAddr field for an onscreen pixel map contains. You must use the GetPixBaseAddr function to obtain a pointer to the PixMap structure for an offscreen graphics world.

Your application should never directly access the baseAddr field of the PixMap structure for an offscreen graphics world; instead, always use GetPixBaseAddr. If your application is using 24-bit mode, use the PixMap32Bit function to determine whether a pixel map requires 32-bit addressing mode for access to its pixel image.

SPECIAL CONSIDERATIONS

Any QuickDraw functions that your application uses after calling GetPixBaseAddr may change the base address for the offscreen pixel image.

The GetPixBaseAddr function may move or purge memory blocks in the application heap; do not call this function at interrupt time.

AVAILABILITY

Supported in Carbon. Available in Carbon 1.0.2 and later when running Mac OS 8.1 or later.

© 2000 Apple Computer, Inc. (Last Updated 6/30/2000)