The pre-existing swatch name-clash test is a negated conjunction that clippy 1.95 flags as nonminimal_bool, which stopped cargo xtask ci before this PR's crates were checked. Rewrite it as the equivalent disjunction; no behaviour change.
Profile samples added inside a flattened chord used the chord's direction for their normal, so a zoomed outline jogged at every flatten vertex. Keep the source segment that drew each flattened piece and ask it for the exact tangent at added samples; fit runs with coordinate-wise Fritsch-Carlson tangents. Adds a regression test and records the change in the parity evidence.
When a constant profile's half-width reaches the local radius of curvature, the smooth inner offset crosses the centre and the non-zero fill leaves a hole. Cut through the centre at those samples; the cut is inside the painted stroke. Varying profiles keep the offset because their crossings can be real caustics, where a cut would show as a slit. Regression test: a radius-5 circle with a 30 pt stroke contains its centre.
Offset smooth points along the curve's normal instead of the flattened polyline's miter (w/cos), which spiked the edge at every sample on tight curves. Fit runs with chord-length Catmull-Rom tangents so a short sample cannot flatten the long segment beside it, and add a coarse wide-circle regression test.
A width profile's sides now run as a cubic Hermite curve through the
points, its slope at each one the weighted harmonic mean of the secants
either side (Fritsch-Carlson). That is C1 continuous and monotone
between points, so it never overshoots them, a width change eases in and
out instead of making a corner, and moving one point only reshapes the
two segments beside it. The ends are flat; two points at one t are still
a step.
The outline samples the curve along the path (densify subdivides each
profile segment) so the smooth width draws on straight runs too, and a
flat profile keeps its old straight pieces.
Hit testing now counts every segment near enough to reach the point, as
the wider side of a farther one can paint past the nearest; gradient
strips reach over projecting dash caps. Tests updated for the new
sampled widths; new tests cover smoothing, monotonicity, locality and
steps.
Adam