Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 3 - QuickDraw Drawing / QuickDraw Drawing Reference

Routines / Creating and Managing Regions

RectInRgn

To determine whether a rectangle intersects a region, use the RectInRgn function.

FUNCTION RectInRgn (r:\xDDRect; rgn:\xDDRgnHandle):\xDDBoolean;

r

The rectangle to check for intersection.

rgn

A handle to the region to check.

DESCRIPTION

The RectInRgn function checks whether the rectangle specified in the r parameter intersects the region whose handle you pass in the rgn parameter. The RectInRgn function returns TRUE if the intersection encloses at least 1 bit or FALSE if it does not.

SPECIAL CONSIDERATIONS

The RectInRgn function sometimes returns TRUE when the rectangle merely intersects the region's bounding rectangle. If you need to know exactly whether a given rectangle intersects the actual region, you can use the RectRgn procedure (described on page 3-88) to set the rectangle to a region, and call SectRgn (described on page 3-90) to see whether the two regions intersect. If the result of SectRgn is an empty region, then the rectangle doesn't intersect the region.