pub fn arc_ring_signed_area(ring: &ArcRing) -> ScalarExpand description
Signed area of a bulge-encoded ring; positive when counter-clockwise.
The polygon shoelace over the vertices plus each arc’s circular-segment term, so a ring whose shape is decided by its arcs is classified by its actual geometry rather than by its chords. A crescent thin enough that its chord polygon winds the other way would otherwise be misread.