Function GeometrySingleton.clipPolygons2d
Clips polygon_a against polygon_b and returns an array of clipped polygons. This performs constant OPERATION_DIFFERENCE between polygons. Returns an empty array if polygon_b completely overlaps polygon_a.
If polygon_b is enclosed by polygon_a, returns an outer polygon (boundary) and inner polygon (hole) which could be distiguished by calling isPolygonClockwise.