SetEmptyRgn

Clear (discard ) a region's definition

#include <Quickdraw.h> Quickdraw

void SetEmptyRgn(theRgn );

RgnHandle theRgn ; handle of region to clear

SetEmptyRgn function destroys the structure of a region by disposing of any

region data in the Region structure, and setting its rgnBBox rectangle to

(0,0)(0,0).

theRgn is the handle of an existing region.

Notes: Any data accumulated via OpenRgn, or any of the mathematical

region-defining operations (such as FrameRect, LineTo, et.al.) is

destroyed by this call.

Unlike DisposeRgn (which eliminates the handle's master pointer as well

as the data), SetEmptyRgn retains the master pointer (so the region

handle remains valid), but disposes of all region definition data except for

the 10-byte Region structure.

The rgnBBox field of the Region is set to the empty rectangle (0,0)(,0,0).

The same effect can be obtained via:

SetRectRgn( theRgn, 0,0,0,0 );

Use the EmptyRgn function to find out is a region is already empty.

Referenced by (4):