A curve-/spline-fit heavy polyline stores both the fitted curve points
(vertex flag 8 / 1) and the spline-frame control points (flag 16),
which only SPLFRAME is meant to show. Chaining every stored vertex
drew spokes from the curve to the control frame — stray points on the
curve and, on wide polylines, a blobbed band (#408). drawn_vertices2d
now drops the control points whenever fit data is present (falling
back to the stored vertices when it is not) and feeds the wire, the
wide-band fills and the tapered band alike, so snapping no longer
lands on frame points either.
Co-Authored-By: Claude Fable 5 <[email protected]>