GEOS SDK TechDocs|
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2.10 Drawing Bitmaps | 
2.12 Regions GrDrawPath(), GrFillPath()
GrDrawPath()
draws a path using the current line attributes.
GrFillPath()
fills a path using the current area attributes.
GrFillPath()
can fill the path using either an odd/even or winding fill rule. If the path is to be filled using the winding fill rule, the path must have been defined so that the segments forming the border of each region go around the region so that the interior of the region is to the left. That is, on convex parts of the border, edges should be in the counterclockwise direction. On concave parts of the border edges should go clockwise. For an illustration of a path following this rule, see the figure above. The fill rule is specified by means of a
RegionFillRule
value, which may be one of
ODD_EVEN or
WINDING.
When you define a path by combining two other paths, the result might not be exactly what you would expect.
GEOS SDK TechDocs|
| 2.10 Drawing Bitmaps | 2.12 Regions 