Boolean: a point at a boundary curve's end is that end, whatever its parameter (text cuts, #391) (#1195)

A point within the point tolerance of a boundary curve's end is that end in the boolean, whatever its parameter, so text cuts no longer leave unmatched sliver vertices (#391). Robustness goldens re-recorded for seeds 0, 34, 39, 41 and 57 with reasons.

vendor/README.md

@@ -17,6 +17,10 @@ Changes:
 - `transversal/integrate/mod.rs`: the result's shells and faces keep the order of the shell
   they come from (truck's connected components followed hash order of face addresses, so a
   boolean's faces came out in a different order on every run).
+- `transversal/loops_store/mod.rs`: a point at an end of a boundary curve (within the point
+  tolerance) is that end, whatever its parameter: a polyline's parameter counts segments, so
+  an intersection curve ending 2e-7 mm from another's end could read as inside it, cut it
+  into a sliver with a vertex of its own, and leave the result's shell open (#391).
 - `transversal/loops_store/mod.rs`: an intersection edge added to a face at a vertex that more
   than one wire visits (several curves end on it: the touching point of two equal cylinders) goes
   into the corner that holds its direction, swept counterclockwise about the face's normal from

vendor/truck-shapeops/src/transversal/loops_store/mod.rs

@@ -158,7 +158,7 @@ impl ParameterKind {
     }
 }
 
-impl<P: Copy, C: Clone> Loops<P, C> {
+impl<P: Copy + Tolerance, C: Clone> Loops<P, C> {
     fn search_parameter(&self, pt: P) -> Option<(usize, usize, ParameterKind)>
     where C: BoundedCurve<Point = P> + SearchParameter<D1, Point = P> {
         self.iter()
@@ -167,7 +167,18 @@ impl<P: Copy, C: Clone> Loops<P, C> {
             .find_map(|(i, j, edge)| {
                 let curve = edge.curve();
                 curve.search_parameter(pt, None, 1).and_then(|t| {
-                    let kind = ParameterKind::try_new(t, curve.range_tuple())?;
+                    // SolidCraft: a point at an end of the curve is that end, however far its
+                    // parameter is from the end's. The parameter alone is no distance: on a
+                    // polyline it counts segments, and an intersection curve ending 2e-7 mm from
+                    // another's end (two walls of a glyph meeting a face) read 1.4e-6 before it,
+                    // so it was cut into a sliver and the result's shell never closed (#391).
+                    let kind = if pt.near(&curve.front()) {
+                        ParameterKind::Front
+                    } else if pt.near(&curve.back()) {
+                        ParameterKind::Back
+                    } else {
+                        ParameterKind::try_new(t, curve.range_tuple())?
+                    };
                     Some((i, j, kind))
                 })
             })