Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 3 - QuickDraw Drawing / QuickDraw Drawing Reference

Routines / Creating and Managing Polygons

OffsetPoly

To move a polygon, use the OffsetPoly procedure.

PROCEDURE OffsetPoly (poly:\xDDPolyHandle; dh,dv:\xDDInteger);

poly

A handle to a polygon to move.

dh

The horizontal distance to move the polygon.

dv

The vertical distance to move the polygon.

DESCRIPTION

The OffsetPoly procedure moves the polygon whose handle you pass in the poly parameter by adding the value you specify in the dh parameter to the horizontal coordinates of its points, and by adding the value you specify in the dv parameter to the vertical coordinates of all points of its region boundary. If the values of dh and dv are positive, the movement is to the right and down; if either is negative, the corresponding movement is in the opposite direction. The region retains its size and shape. This doesn't affect the screen unless you subsequently call a routine to draw the region.

Note

OffsetPoly is an especially efficient operation, because the data defining a polygon is stored relative to the first point of the polygon and so isn't actually changed by OffsetPoly.