sketch(fix): preserve rectangle constraints through fillets (#1543)

Thanks @Karl-VonRichter for the fix.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

crates/engine/src/cmd/sketch_corner_tests.rs

@@ -102,6 +102,67 @@ fn driven_by(s: &Session, name: &str) -> Vec<String> {
     sk(s).constraints.iter().filter(|c| c.param.as_deref() == Some(name)).map(|c| c.id.clone()).collect()
 }
 
+#[test]
+fn fully_defined_rectangles_keep_their_size_when_all_corners_are_filleted() {
+    for center in [false, true] {
+        for square in [false, true] {
+            let mut s = new_sketch();
+            let height = if square { 40.0 } else { 20.0 };
+            let r = if center {
+                run(&mut s, "sketch.rectangle.center", json!({"center": [0, 0], "corner": [20, height / 2.0]}))
+            } else {
+                run(&mut s, "sketch.rectangle.two_point", json!({"p0": [0, 0], "p1": [40, height]}))
+            };
+            let anchor = if center { "p5" } else { "p1" };
+            run(&mut s, "sketch.constraint.coincident", json!({"a": anchor, "b": "origin"}));
+            let width = run(&mut s, "sketch.dimension", json!({"entities": ["l1"], "value": 40}));
+            if square {
+                run(&mut s, "sketch.constraint.equal", json!({"a": "l1", "b": "l2"}));
+            } else {
+                run(&mut s, "sketch.dimension", json!({"entities": ["l2"], "value": height}));
+            }
+            let info = run(&mut s, "sketch.inspect", json!({}));
+            assert_eq!(info["dof"], 0, "{info}");
+            let points: Vec<Value> = ["bottom_left", "bottom_right", "top_right", "top_left"].iter().map(|name| r["corners"][name].clone()).collect();
+            for (i, point) in points.iter().enumerate() {
+                let f = run(&mut s, "sketch.fillet", json!({"point": point, "radius": 3}));
+                assert_eq!(f["sketch"]["solved"], true, "center={center}, square={square}: {f}");
+                assert_eq!(f["sketch"]["dof"], 0, "center={center}, square={square}: {f}");
+                let expected = 40.0 * height - (i + 1) as f64 * (9.0 - std::f64::consts::PI * 9.0 / 4.0);
+                assert!((area(&s) - expected).abs() < 1e-5, "corner={i}, center={center}, square={square}: {} != {expected}", area(&s));
+            }
+            let expected = 40.0 * height - 4.0 * (9.0 - std::f64::consts::PI * 9.0 / 4.0);
+            assert!((area(&s) - expected).abs() < 1e-5, "center={center}, square={square}: {} != {expected}", area(&s));
+            run(&mut s, "parameters.change", json!({"name": width["param"], "expression": "50 mm"}));
+            assert!(solved(&s));
+            let expected = 50.0 * if square { 50.0 } else { height } - 4.0 * (9.0 - std::f64::consts::PI * 9.0 / 4.0);
+            assert!((area(&s) - expected).abs() < 1e-5, "center={center}, square={square}: {} != {expected}", area(&s));
+            let id = s.active_sketch.unwrap();
+            let saved = solidcraft_doc::Document::from_json(&s.doc.to_json()).unwrap();
+            assert_eq!(saved.sketch(id).unwrap(), s.doc.sketch(id).unwrap());
+            run(&mut s, "edit.undo", json!({}));
+            run(&mut s, "edit.redo", json!({}));
+            assert!((area(&s) - expected).abs() < 1e-5);
+        }
+    }
+}
+
+#[test]
+fn filleting_a_side_keeps_its_original_midpoint() {
+    let mut s = new_sketch();
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0": [-20, 0], "p1": [20, 30]}));
+    run(&mut s, "sketch.constraint.midpoint", json!({"point": "origin", "line": "l1"}));
+    run(&mut s, "sketch.dimension", json!({"entities": ["l1"], "value": 40}));
+    run(&mut s, "sketch.dimension", json!({"entities": ["l2"], "value": 30}));
+    for point in ["p1", "p2"] {
+        let f = run(&mut s, "sketch.fillet", json!({"point": point, "radius": 3}));
+        assert_eq!(f["sketch"]["solved"], true, "{f}");
+        assert_eq!(f["sketch"]["dof"], 0, "{f}");
+        let (lo, hi) = sk(&s).bounds().unwrap();
+        assert!((lo.x + 20.0).abs() < 1e-6 && (hi.x - 20.0).abs() < 1e-6, "{lo:?} {hi:?}");
+    }
+}
+
 /// The spout of a basin: a vertical riser and a horizontal top, the top's length dimensioned
 /// to the corner and the corner's height dimensioned from the origin. Filleting the corner used
 /// to drop the height and leave the length on the shortened straight part, so the top came out

crates/engine/src/cmd/sketch_modify.rs

@@ -569,6 +569,44 @@ fn reattach(sk: &mut Sketch, l: usize, corner: usize, np: usize) {
     }
 }
 
+/// Equal lengths and midpoints describe the original side, not its shortened tangent
+/// segment. Keep that side as construction geometry sharing the original corner points.
+/// Later corner cuts retain those points through `keep_corner`, so this also works when
+/// the other end is rounded in a separate command.
+fn keep_side_relations(sk: &mut Sketch, line: usize) -> Result<Vec<String>> {
+    let affected = |k: &ConstraintKind| {
+        matches!(*k, ConstraintKind::Equal { a, b } if a == line || b == line) || matches!(*k, ConstraintKind::Midpoint { l, .. } if l == line)
+    };
+    if !sk.constraints.iter().any(|k| affected(&k.kind)) {
+        return Ok(Vec::new());
+    }
+    let Some(CurveKind::Line { a, b }) = sk.curves.get(line).map(|c| c.kind.clone()) else { return Ok(Vec::new()) };
+    let support = sk.add_line_pts(a, b, None)?;
+    if let Some(c) = sk.curves.get_mut(support) {
+        c.construction = true;
+    }
+    let mut moved = Vec::new();
+    for k in &mut sk.constraints {
+        if !affected(&k.kind) {
+            continue;
+        }
+        match &mut k.kind {
+            ConstraintKind::Equal { a, b } => {
+                if *a == line {
+                    *a = support;
+                }
+                if *b == line {
+                    *b = support;
+                }
+            }
+            ConstraintKind::Midpoint { l, .. } => *l = support,
+            _ => {}
+        }
+        moved.push(k.id.clone());
+    }
+    Ok(moved)
+}
+
 /// What became of a rounded or cut corner's point: kept as a virtual sharp corner (its id),
 /// and the constraints and dimensions that now measure to it.
 #[derive(Default)]
@@ -642,9 +680,14 @@ fn cut_corner(
     let v = (pb - pc).normalized().ok_or_else(|| bad(cmd, "degenerate line"))?;
     let ta = sk.add_point(pc + u * da, None)?;
     let tb = sk.add_point(pc + v * db, None)?;
+    let mut moved = keep_side_relations(sk, la)?;
+    moved.extend(keep_side_relations(sk, lb)?);
     reattach(sk, la, c, ta);
     reattach(sk, lb, c, tb);
-    let kept = keep_corner(sk, c, [(la, ta), (lb, tb)])?;
+    let mut kept = keep_corner(sk, c, [(la, ta), (lb, tb)])?;
+    if let Some(k) = &mut kept {
+        k.moved.extend(moved);
+    }
     let removed = kept.is_none();
     if removed {
         sk.remove_points(&[c]);

crates/ui-egui/src/sketch_corner_ui_tests.rs

@@ -378,6 +378,34 @@ fn a_fillet_rounds_every_picked_corner_to_one_radius() {
     assert!((ss.profiles[0].area - (1200.0 - 3.0 * 25.0 * (1.0 - std::f64::consts::PI / 4.0))).abs() < 1e-6, "{}", ss.profiles[0].area);
 }
 
+#[test]
+fn fully_constrained_center_rectangle_corners_can_be_picked_and_filleted() {
+    let mut h = crate::scenario::Harness::new();
+    h.app.run("sketch.create", json!({"plane":"XY"})).unwrap();
+    h.app.run("sketch.rectangle.center", json!({"center":[0,0],"corner":[20,15]})).unwrap();
+    h.app.run("sketch.constraint.coincident", json!({"a":"p5","b":"origin"})).unwrap();
+    h.app.run("sketch.dimension", json!({"entities":["l1"],"value":40})).unwrap();
+    h.app.run("sketch.dimension", json!({"entities":["l2"],"value":30})).unwrap();
+    h.frames(2);
+    h.step(&json!({"start":"sketch.fillet"})).unwrap();
+    h.frames(2);
+    for corner in [[-20, -15, 0], [20, -15, 0], [20, 15, 0], [-20, 15, 0]] {
+        h.step(&json!({"click":{"world":corner}})).unwrap();
+        h.frames(2);
+    }
+    assert_eq!(h.app.dialog.as_ref().map(|d| d.inputs[0].items.len()), Some(4));
+    set_size(&mut h.app, "3");
+    apply(&mut h);
+    assert!(h.app.dialog.is_none(), "{:?}", h.app.status);
+    let info = h.app.run("sketch.inspect", json!({})).unwrap();
+    assert_eq!(info["dof"], 0, "{info}");
+    assert_eq!(info["status"], "solved", "{info}");
+    let st = h.app.session.world_state();
+    let ss = st.sketch(h.app.session.active_sketch.unwrap()).unwrap();
+    assert_eq!(ss.sketch.curves.iter().filter(|c| matches!(c.kind, CurveKind::Arc { .. })).count(), 4);
+    assert!((ss.profiles[0].area - (1200.0 - 36.0 * (1.0 - std::f64::consts::PI / 4.0))).abs() < 1e-6);
+}
+
 #[test]
 fn ordinary_drawing_keeps_origin_snap_and_real_origin_corners_work() {
     let mut h = crate::scenario::Harness::new();

crates/ui-egui/src/sketch_tools.rs

@@ -460,17 +460,18 @@ fn sketch_entity(app: &SolveApp, hits: &[Hit]) -> Option<(String, bool)> {
 }
 
 /// The two editable curves that meet at sketch point `pi`, in curve order, which is the order
-/// the corner commands resolve them in from a `point` parameter. None unless exactly two meet
-/// there and each is one the command can work on: a line always, an arc only for a fillet.
+/// the corner commands resolve them in from a `point` parameter. Construction curves are
+/// ignored when more than two meet. Each side must be a line, or an arc for a fillet.
 pub(crate) fn corner_curves(sk: &solidcraft_engine::sketch::Sketch, pi: usize, arcs_ok: bool) -> Option<(usize, usize)> {
     use solidcraft_engine::sketch::CurveKind;
-    let curves: Vec<_> = sk
-        .curves
-        .iter()
-        .enumerate()
-        .filter(|(ci, c)| !sk.is_linked_curve(*ci) && c.kind.ends().is_some_and(|(a, b)| a == pi || b == pi))
-        .take(3)
-        .collect();
+    let candidates =
+        sk.curves.iter().enumerate().filter(|(ci, c)| !sk.is_linked_curve(*ci) && c.kind.ends().is_some_and(|(a, b)| a == pi || b == pi));
+    let mut curves: Vec<_> = candidates.clone().take(3).collect();
+    // Center rectangles have construction diagonals at their corners. Match the engine's
+    // corner selection: when more than two curves meet, use the profile sides.
+    if curves.len() > 2 {
+        curves = candidates.filter(|(_, c)| !c.construction).take(3).collect();
+    }
     if curves.iter().any(|(_, c)| !matches!(c.kind, CurveKind::Line { .. }) && !(arcs_ok && matches!(c.kind, CurveKind::Arc { .. }))) {
         return None;
     }