Walk a PolygonPath's command stream and yield one PathAnchor per
on-curve point. Adjacent C/Q control points are attached as
controlIn/controlOut. Subpath boundaries (M after a previous M or Z)
start fresh — the new M's anchor has no controlIn from a Z.
Walk a PolygonPath's command stream and yield one
PathAnchorper on-curve point. Adjacent C/Q control points are attached ascontrolIn/controlOut. Subpath boundaries (M after a previous M or Z) start fresh — the new M's anchor has nocontrolInfrom a Z.