Calculates the union of two regions.

void UnionRgn (
     srcRgnA, 
     srcRgnB, 
     dstRgn
);

Parameter descriptions

srcRgnA

A handle to the first of two regions whose union is to be determined.

srcRgnB

A handle to the second of two regions whose union is to be determined.

dstRgn

On return, a handle to the region holding the resulting union area. If both regions are empty, UnionRgn sets the destination to the empty region defined by the rectangle (0,0,0,0).

The UnionRgn function does not create the destination region; you must have already allocated memory for it by using the NewRgn function.

The destination region may be one of the source regions, if desired.

DISCUSSION

The UnionRgn procedure calculates the union of the two regions whose handles you pass in the srcRgnA and srcRgnB parameters, and it places the union in the region whose handle you pass in the dstRgn parameter. If both regions are empty, UnionRgn sets the destination to the empty region defined by the rectangle (0,0,0,0).

The UnionRgn procedure does not create the destination region; you must have already allocated memory for it by using the NewRgn function.

The destination region may be one of the source regions, if desired.

SPECIAL CONSIDERATIONS

The UnionRgn function may temporarily use heap space that’s twice the size of the two input regions.

The UnionRgn 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)