Don't use self.path in HalfEdgeGeom

This prepares for moving the path to `CurveGeom`.

crates/fj-core/src/algorithms/approx/edge.rs

@@ -30,7 +30,14 @@ impl Approx for (&Handle<HalfEdge>, &Handle<Surface>) {
         let tolerance = tolerance.into();
 
         let start_position_surface =
-            geometry.of_half_edge(half_edge).start_position();
+            geometry.of_half_edge(half_edge).start_position(
+                &geometry
+                    .of_curve(half_edge.curve())
+                    .unwrap()
+                    .local_on(surface)
+                    .unwrap()
+                    .path,
+            );
         let start_position =
             match cache.start_position.get(half_edge.start_vertex()) {
                 Some(position) => position,

crates/fj-core/src/geometry/half_edge.rs

@@ -47,12 +47,12 @@ impl HalfEdgeGeom {
     }
 
     /// Compute the surface position where the half-edge starts
-    pub fn start_position(&self) -> Point<2> {
+    pub fn start_position(&self, path: &SurfacePath) -> Point<2> {
         // Computing the surface position from the curve position is fine.
         // `HalfEdge` "owns" its start position. There is no competing code that
         // could compute the surface position from slightly different data.
 
         let [start, _] = self.boundary.inner;
-        self.path.point_from_path_coords(start)
+        path.point_from_path_coords(start)
     }
 }

crates/fj-core/src/operations/split/face.rs

@@ -105,8 +105,26 @@ impl SplitFace for Shell {
         let dividing_half_edge_a_to_d = {
             let half_edge = HalfEdge::line_segment(
                 [
-                    core.layers.geometry.of_half_edge(&b).start_position(),
+                    core.layers.geometry.of_half_edge(&b).start_position(
-                    core.layers.geometry.of_half_edge(&d).start_position(),
+                        &core
+                            .layers
+                            .geometry
+                            .of_curve(b.curve())
+                            .unwrap()
+                            .local_on(face.surface())
+                            .unwrap()
+                            .path,
+                    ),
+                    core.layers.geometry.of_half_edge(&d).start_position(
+                        &core
+                            .layers
+                            .geometry
+                            .of_curve(d.curve())
+                            .unwrap()
+                            .local_on(face.surface())
+                            .unwrap()
+                            .path,
+                    ),
                 ],
                 None,
                 face.surface().clone(),

crates/fj-core/src/topology/objects/cycle.rs

@@ -31,7 +31,11 @@ impl Cycle {
     /// Please note that this is not *the* winding of the cycle, only one of the
     /// two possible windings, depending on the direction you look at the
     /// surface that the cycle is defined on from.
-    pub fn winding(&self, geometry: &Geometry, _: &Handle<Surface>) -> Winding {
+    pub fn winding(
+        &self,
+        geometry: &Geometry,
+        surface: &Handle<Surface>,
+    ) -> Winding {
         // The cycle could be made up of one or two circles. If that is the
         // case, the winding of the cycle is determined by the winding of the
         // first circle.
@@ -70,7 +74,14 @@ impl Cycle {
 
         for (a, b) in self.half_edges().pairs() {
             let [a, b] = [a, b].map(|half_edge| {
-                geometry.of_half_edge(half_edge).start_position()
+                geometry.of_half_edge(half_edge).start_position(
+                    &geometry
+                        .of_curve(half_edge.curve())
+                        .unwrap()
+                        .local_on(surface)
+                        .unwrap()
+                        .path,
+                )
             });
 
             sum += (b.u - a.u) * (b.v + a.v);

crates/fj-core/src/validate/solid.rs

@@ -106,13 +106,23 @@ impl SolidValidationError {
                     .flat_map(|cycle| cycle.half_edges().iter().cloned())
                     .zip(repeat(face.surface()))
             })
-            .map(|(h, s)| {
+            .filter_map(|(h, s)| {
-                (
+                let Some(local_curve_geometry) =
+                    geometry.of_curve(h.curve()).unwrap().local_on(s)
+                else {
+                    // If the curve geometry has no local definition,
+                    // there's nothing we can check.
+                    return None;
+                };
+
+                Some((
                     geometry.of_surface(s).point_from_surface_coords(
-                        geometry.of_half_edge(&h).start_position(),
+                        geometry
+                            .of_half_edge(&h)
+                            .start_position(&local_curve_geometry.path),
                     ),
                     h.start_vertex().clone(),
-                )
+                ))
             })
             .collect();
 

crates/fj-core/src/validation/checks/curve_geometry_mismatch.rs

@@ -201,6 +201,9 @@ mod tests {
         )
         .is_err());
 
+        // Ignore remaining validation errors.
+        let _ = core.layers.validation.take_errors();
+
         Ok(())
     }
 }

crates/fj-core/src/validation/checks/half_edge_connection.rs

@@ -93,7 +93,7 @@ fn check_region<'r>(
 
 fn check_cycle<'r>(
     cycle: &'r Cycle,
-    _: &'r Handle<Surface>,
+    surface: &'r Handle<Surface>,
     geometry: &'r Geometry,
     config: &'r ValidationConfig,
 ) -> impl Iterator<Item = AdjacentHalfEdgesNotConnected> + 'r {
@@ -105,8 +105,18 @@ fn check_cycle<'r>(
                 .path
                 .point_from_path_coords(end)
         };
-        let start_pos_of_second_half_edge =
+
-            geometry.of_half_edge(second).start_position();
+        let Some(local_curve_geometry) =
+            geometry.of_curve(second.curve()).unwrap().local_on(surface)
+        else {
+            // If the curve geometry is not defined for our local surface,
+            // there's nothing we can check.
+            return None;
+        };
+
+        let start_pos_of_second_half_edge = geometry
+            .of_half_edge(second)
+            .start_position(&local_curve_geometry.path);
 
         let distance_between_positions = (end_pos_of_first_half_edge
             - start_pos_of_second_half_edge)