A region is an area in a viewport. In Objective Views, regions are typically used to track the exact portions of the viewport that a component is drawing in. Regions are used to detect if a component has been hit by the mouse, and also to invalidate the proper areas of the viewport for drawing.
Figure 78 – Region class hierarchy
A region is just a collection of polygons. When the region of a component is calculated, the polygons of the individual drawing areas are calculated and assembled in the CODRgn object. Curves are approximated as polygons. The bounding rectangle of a component is calculated from the region and can be retrieved from the CODRgn object.
Polygon regions are the individual polygons that comprise a CODRgn object. Typically, there is one polygon region for each primitive component that is part of a composite.