Subtracts one region from another.

void DiffRgn (
     srcRgnA, 
     srcRgnB, 
     dstRgn
);

Parameter descriptions

srcRgnA

A handle to the region to subtract from.

srcRgnB

A handle to the region to subtract.

dstRgn

On return, a handle to the region holding the resulting area. If the first source region is empty, DiffRgn sets the destination to the empty region defined by the rectangle (0,0,0,0).

The DiffRgn 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 DiffRgn procedure subtracts the region whose handle you pass in the srcRgnB parameter from the region whose handle you pass in the srcRgnA parameter and places the difference in the region whose handle you pass in the dstRgn parameter. If the first source region is empty, DiffRgn sets the destination to the empty region defined by the rectangle (0,0,0,0).

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

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)