Function check_winding 

pub fn check_winding(
    points: &ExactPoints,
    arrangement: &Arrangement,
    rings: &[TracedRing],
    regions: &[TracedRegion],
    budget: &mut PairBudget,
    options: &ExecutionOptions,
) -> GeomResult<()>

Refuse a class that winds more than once at some point.

Every point has winding 0 or 1 for the class when each outer ring lies in as many outer rings as holes of the class, and each hole in one more outer ring than holes. Counts each ring’s containment in every other ring whose box can hold it; each decided containment counts against budget.