[Algorithms] Special cases of Weiler-Atherton

[Andrzej B. <bor...@gm...>]

I am writing Weiler-Atherton algorithm. I can't find full description of
this.
My source trial is on bitbucket on aborucki/weileratherton, this is unclear
of brute_force_intersections() function because I am moving form
brute-force to Bentley-Ottmann sweep line intersections.
I have two main rountines:
brute_force_intersections(): inserting points of intersections
unionWalk - walk over lists and make union two polygons.
In unionWalk are special cases: vertex of one polygon touch vertex second
polygon etc
Where can I find detail description of this algorithm?