Function triangulate_domain 

pub fn triangulate_domain(
    points: &[Point2],
    constraints: &[Constraint],
    rings: &[Ring],
) -> Result<Triangulation, TriangulationError>

Build a constrained Delaunay triangulation of the domain bounded by rings.

The result keeps exactly the triangles inside an outer ring and outside every hole (see the module documentation for the rule). The ring edges are constraints, as are constraints; the points that fall outside the domain are listed by Triangulation::outside_points.

Errors

Everything triangulate refuses, and TriangulationError::RingOutOfRange, TriangulationError::TooFewRingVertices, TriangulationError::RepeatedRingVertex, TriangulationError::FoldedRing, TriangulationError::MisnestedRing and TriangulationError::EmptyDomain (also for an empty ring list). Checks run in this order, ring by ring and vertex by vertex.