OpenRgn

Begin recording a region shape

#include <Quickdraw.h> Quickdraw

void OpenRgn( );

OpenRgn hides the graphical pen for the current GrafPort and begins a

session of recording line-drawing and shape-framing calls. A subsequent call

to CloseRgn makes the region's shape available to the program.

Notes: Subsequent calls to Line, LineTo, FrameOval, FramePoly,

temporary buffer. When you next call CloseRgn, the outlines are joined,

creating a region definition. This definition can be used in drawing (such as

filling the region) and mathematical operations, such as shrinking or

expanding the region, obtaining the union or difference of two regions, etc.

See CloseRgn for an example of usage.

This automatically hides the pen so that subsequent drawing is not seen. As

with HidePen, it actually decrements the pnVis field of the current

GrafPort-if that field is greater than 0 (e.g., as after an unbalanced call to

ShowPen), the pen will remain visible. If you want the pen to be visible

while the region is open, you may call ShowPen while the region is open.

While the region is open, the rgnSave field of the current GrafPort

contains a pointer to the accumulating region shape data. If you want to

temporarily "turn off" region recording, you can save the current value of

rgnSave and set it to NIL. When you restore the previous value, recording

will resume. Also, the recording stops when the current GrafPort becomes

inactive (see SetPort) and resumes when it is reactivated.

Only one region or polygon (see OpenPoly) may be open at a time. You

should not attempt to "nest" these operations.

Referenced by (50):