Fillet: refuse only crossed faces the round makes, not ones the body had (#1488) (#1517)

Thanks @erkexzcx.

crates/engine/src/tests/nudge_slivers.rs

@@ -0,0 +1,76 @@
+//! #1488: a loft joined into a slab, flush with the slab's outer face and its bottom, takes the
+//! boolean's last retry (the tool nudged a fraction of a micron). That leaves sliver faces
+//! along the flush faces, one of which reads as a face whose boundary crosses itself; every
+//! later round on the body was then refused for it ("the rounds would leave openings"), even
+//! one 36 mm away. A round is now refused only for crossed faces it makes.
+
+use serde_json::json;
+
+use super::run;
+use crate::Session;
+
+/// The issue's slab `width` thick with a window through it and the pleat loft joined into it.
+fn slab_with_pleat(width: f64) -> Session {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"corner": [-60, 0, 0], "length": 120, "width": width, "height": 95, "body_name": "Wall"}));
+    run(
+        &mut s,
+        "solid.box",
+        json!({"corner": [-24, -0.5, -1], "length": 48, "width": width + 1.0, "height": 91, "operation": "cut", "targets": ["Wall"]}),
+    );
+    run(&mut s, "sketch.create", json!({"plane": "XY", "name": "Bottom"}));
+    run(
+        &mut s,
+        "sketch.line",
+        json!({"closed": true, "infer": false, "connect": false, "points": [
+            [-26, 3], [-24.76384, 3], [-16.0568, 14.97217], [-8, 4.90117], [0, 14.90117], [8, 4.90117], [16.0568, 14.97217], [24.76384, 3], [26, 3],
+            [26, 0], [23.23616, 0], [15.9432, 10.02783], [8, 0.09883], [0, 10.09883], [-8, 0.09883], [-15.9432, 10.02783], [-23.23616, 0], [-26, 0]]}),
+    );
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "sketch.create", json!({"plane": "XY", "offset": 90.5, "name": "Top"}));
+    run(
+        &mut s,
+        "sketch.line",
+        json!({"closed": true, "infer": false, "connect": false, "points": [
+            [-26, 3], [-24, 3], [-16, 3], [-8, 3], [0, 3], [8, 3], [16, 3], [24, 3], [26, 3],
+            [26, 0], [24, 0], [16, 0], [8, 0], [0, 0], [-8, 0], [-16, 0], [-24, 0], [-26, 0]]}),
+    );
+    run(&mut s, "sketch.finish", json!({}));
+    run(
+        &mut s,
+        "solid.loft",
+        json!({"sections": [{"sketch": "Bottom"}, {"sketch": "Top"}], "operation": "join", "targets": ["Wall"], "name": "Pleat"}),
+    );
+    s
+}
+
+fn wall(s: &Session) -> solidcraft_kernel::Body {
+    s.model.state().body("Wall").map(|b| b.body.clone()).unwrap()
+}
+
+/// The R1 round on the slab's end edge at x = −60 works after the join, as it does on the 3 mm
+/// slab (and on the 3.5 mm one before the loft), and adds no crossed face of its own.
+#[test]
+fn a_round_far_from_the_joined_loft_works() {
+    for (width, pick) in [(3.5, [-60.0, 1.75, 95.0]), (3.0, [-60.0, 1.5, 95.0])] {
+        let mut s = slab_with_pleat(width);
+        let before = wall(&s);
+        let r = s.execute("solid.fillet", &json!({"body": "Wall", "edges": [pick], "radius": 1}));
+        assert!(r.is_ok(), "{width} mm: {r:?}");
+        let after = wall(&s);
+        assert_eq!(after.face_count(), before.face_count() + 1, "{width} mm: one round face");
+        assert_eq!(after.crossed_faces().unwrap(), before.crossed_faces().unwrap(), "{width} mm");
+        // The round lies along the picked edge: the end face's top corner is gone.
+        let m = solidcraft_kernel::measure(&after).unwrap();
+        assert!((m.bbox.min.x + 60.0).abs() < 1e-6 && (m.bbox.max.z - 95.0).abs() < 1e-6, "{width} mm: {:?}", m.bbox);
+    }
+}
+
+/// A round that does cross faces is still refused, joined loft or not (#871's check stands).
+#[test]
+fn rounds_that_overlap_are_still_refused() {
+    let mut s = slab_with_pleat(3.5);
+    // Both long top edges of the 3.5 mm slab with a radius over half its thickness.
+    let r = s.execute("solid.fillet", &json!({"body": "Wall", "edges": [[-40, 0, 95], [-40, 3.5, 95]], "radius": 2}));
+    assert!(r.is_err(), "{r:?}");
+}