Sketch: drawing infers tangent (from an arc end) and perpendicular (from a line end) constraints; profile finding prefilters crossings by bounding box (text and free-form sketches 30x faster); large-sketch solver tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/engine/src/cmd/sketch.rs

@@ -435,10 +435,17 @@ fn draw_line(s: &mut Session, p: &Value) -> Result<Value> {
             }
             if infer {
                 let d = b.pos() - a.pos();
-                if d.y.abs() <= d.len() * 1e-9 {
+                let axis = if d.y.abs() <= d.len() * 1e-9 {
                     cons.push(add_c(sk, ConstraintKind::Horizontal { l: c })?);
+                    true
                 } else if d.x.abs() <= d.len() * 1e-9 {
                     cons.push(add_c(sk, ConstraintKind::Vertical { l: c })?);
+                    true
+                } else {
+                    false
+                };
+                if let Some(k) = infer_at_start(sk, c, axis) {
+                    cons.push(add_c(sk, k)?);
                 }
             }
             curves.push(c);
@@ -449,6 +456,38 @@ fn draw_line(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(result((curves, cons), info))
 }
 
+/// A relation the new line `c` has with the curve it starts from (drawn exactly so): tangent
+/// to an arc, or perpendicular to a line (parallel continuations are left alone). `axis`: the
+/// line already got horizontal/vertical, so a perpendicular to an axis-aligned line would be
+/// redundant.
+fn infer_at_start(sk: &Sketch, c: usize, axis: bool) -> Option<ConstraintKind> {
+    let CurveKind::Line { a, b } = sk.curves.get(c)?.kind else { return None };
+    let (pa, pb) = (sk.point(a)?, sk.point(b)?);
+    let u = (pb - pa).normalized()?;
+    for (i, o) in sk.curves.iter().enumerate() {
+        if i == c || !o.kind.uses(a) {
+            continue;
+        }
+        match o.kind {
+            CurveKind::Arc { c: cc, .. } => {
+                let r = (pa - sk.point(cc)?).normalized()?;
+                if r.dot(u).abs() < 1e-9 {
+                    return Some(ConstraintKind::Tangent { a: i, b: c });
+                }
+            }
+            CurveKind::Line { a: oa, b: ob } => {
+                let v = (sk.point(ob)? - sk.point(oa)?).normalized()?;
+                let o_axis = v.x.abs() < 1e-9 || v.y.abs() < 1e-9;
+                if u.dot(v).abs() < 1e-9 && !(axis && o_axis) {
+                    return Some(ConstraintKind::Perpendicular { a: i, b: c });
+                }
+            }
+            _ => {}
+        }
+    }
+    None
+}
+
 /// Closed polygon of lines through new or referenced corner points.
 fn polygon_lines(sk: &mut Sketch, corners: &[Vec2]) -> Result<(Vec<usize>, Vec<usize>)> {
     let pts: Vec<usize> = corners.iter().map(|c| sk.add_point(*c, None)).collect::<std::result::Result<_, _>>()?;

crates/engine/src/cmd/sketch_constraints_tests.rs

@@ -133,3 +133,16 @@ fn auto_constrain_fully_constrains_a_rough_sketch() {
     assert!(s.active_sketch.is_none());
     assert!(r["added"].as_array().unwrap().len() >= 3, "{r}");
 }
+
+#[test]
+fn drawing_infers_tangent_and_perpendicular() {
+    let mut s = new_sketch();
+    let l1 = ids(&run(&mut s, "DrawPolyline", json!({"points": [[0, 0], [10, 10]], "infer": true}))["curves"])[0].clone();
+    let r = run(&mut s, "DrawPolyline", json!({"points": [format!("{l1}.end"), [20, 0]], "infer": true}));
+    assert_eq!(r["constraints"].as_array().unwrap().len(), 1, "{r}");
+    let a = ids(&run(&mut s, "ArcCenterTwoPoint", json!({"center": [50, 0], "start": [60, 0], "end": [50, 10]}))["curves"])[0].clone();
+    let r = run(&mut s, "DrawPolyline", json!({"points": [format!("{a}.end"), [30, 10]], "infer": true}));
+    let si = run(&mut s, "sketch.inspect", json!({}));
+    let names: Vec<&str> = si["constraints"].as_array().unwrap().iter().map(|c| c["name"].as_str().unwrap()).collect();
+    assert!(names.contains(&"Perpendicular") && names.contains(&"Tangent"), "{names:?} {r}");
+}