Triangulation issue: Zebra about manifold

[elalish]

Still digging into what's wrong with this one, but I can see why it's a tough customer:

Amazingly this is not self-intersecting. However, this is also a great example of why the even-odd fill rule is such a disaster. Strictly positive fill rule would have made a much more sensible polygon.

[elalish]

@pca006132 Unfortunately minimize_testcase fails for this polygon - it returns a single inverted triangle, but as far as I can tell there's nothing with incorrect winding in the whole thing. I'd guess it's getting confused by the touching vertices.

[pca006132]

Make sense, that code was assuming non-intersecting (touching) polygons. Should try to make it more general one day...