Bug 106026

The "first fit" algorithm for polygons, http://hansmuller-webkit.blogspot.com/2012/08/revised-algorithm-for-finding-first.html, depends on temporary "offset" edges. Offset edges can be defined simply, as a pair of vertices. The existing ExclusionPolygonEdge struct similarly manages a pair of vertices however its implemention, and some of its operations, are specific to the ExclusionPolygon class. ExclusionPolygonEdge manages a pair of indices into an ExclusionPolygon's array of vertices and provides operations for moving forwards and backwards in the polygon's vertex chain. Both edge types will have some operations in common. For example: bool overlapsRect(const FloatRect&) const; bool intersection(const VertexPair&, FloatPoint&) const; An absract VertexPair class would enable this. The ExclusionPolygonEdge struct should become a class and inherit from VertexPair.