How FrameRgn works
Posted on 2001-07-22
Rects :array of TRect;
Points :array of TPoint;
Rects is an array of rectangles that is filled indirectly by GetRegionData (and stored in the same order as they were found in the RGNDATA structure).
Points is an ordered array of points I will use to draw an outline of the region. (This array will be identical to the array of points you would pass into CreatePolyPolygonRgn, if you were to create the region that way)
I can't use FrameRgn for two reasons:
1. FrameRgn really isn't very powerful. I want to draw marching ants and FrameRgn apparently only draws solid lines.
2. I am not using the region for the purposes of directly drawing to a device context.
I would like to know the algorithm FrameRgn uses to draw the outline of a region, so I can convert Rects to Points.