SetClip

Set clipping region of active GrafPort

#include <Quickdraw.h> Quickdraw

void SetClip(newClipRgn );

RgnHandle newClipRgn ; handle to desired clipping region

SetClip copies the specified region to the current GrafPort's clipRgn. All

drawing on the port will be clipped to this area.

newClipRgn is a handle to a Region, expressed in local coordinates.

Notes: The data describing newClipRgn is copied, so changing the original later

will have no effect. The RgnHandle in GrafPort.clipRgn stays the same, but

the master pointer is changed to point to the duplicated Region structure.

Using the clipping region can simplify many operations. For instance, one

way to draw a half-circle is to set the clipping region to cover half the area

where the circle will be drawn, then draw a full circle. Another example:

set the clipping region to the shape of an oval, then as you draw lines

through the oval, only the pixels inside are affected:

To avoid subsequent redrawing errors, you may want to change the clip

region temporarily:

RgnHandle saveRgn, myRgn;

saveRgn = NewRgn();

GetClip( saveRgn );

SetClip( myRgn ); [TOKEN:12074] or ClipRect( &anyRect ) */

... draw zoom stuff ...

SetClip( saveRgn );

DisposeRgn( saveRgn );

All drawing to a GrafPort is clipped to the intersection of the port's

portBits.bounds, portRect, visRgn, and clipRgn. Initially, the clipRgn of a

GrafPort covers a large rectangle: (-32768,-32768) (32767,32767),

so it has no effect until you set it to a smaller value via this function.

The ClipRect function is a quick way to set the clipping region to a

rectangular area.

The OpenPicture and DrawPicture functions may malfunction unless

you make the clip region smaller than its arbitrarily-large initial setting.

Referenced by (26):