fix: apply point constraints to sketch preselection

crates/ui-egui/src/lib.rs

@@ -545,6 +545,13 @@ impl SolveApp {
             self.last_command = Some((spec.id.to_string(), spec.label.to_string()));
         }
         if let Some(mut t) = tools::Tool::for_command(id) {
+            if let Some(params) = tools::constraint_preselection(id, &self.session.selection) {
+                if self.run(id, params).is_ok() {
+                    let _ = self.session.execute("select.clear", &json!({}));
+                    self.set_status("Constraint applied", false);
+                }
+                return;
+            }
             // Curve-pair constraints can consume an exact preselection. Leave ambiguous
             // selections to the ordinary pick tool; never silently constrain a subset.
             if matches!(

crates/ui-egui/src/tools.rs

@@ -323,6 +323,41 @@ fn run_shape(app: &mut SolveApp, t: &Tool) -> Result<Vec<String>, String> {
     Ok(result["curves"].as_array().into_iter().flatten().filter_map(|c| c.as_str().map(str::to_string)).collect())
 }
 
+/// Only consume a complete, unambiguous selection; command validation owns geometry.
+pub(crate) fn constraint_preselection(command: &str, selection: &[solvecraft_engine::Sel]) -> Option<Value> {
+    use solvecraft_engine::Sel::{SketchCurve, SketchPoint};
+    match (command, selection) {
+        ("sketch.constraint.coincident", [a, b]) => {
+            let entity = |s: &solvecraft_engine::Sel| match s {
+                SketchPoint { id } | SketchCurve { id } => Some(id.clone()),
+                _ => None,
+            };
+            let (a, b) = (entity(a)?, entity(b)?);
+            (a != b).then(|| json!({"a":a,"b":b}))
+        }
+        (
+            "sketch.constraint.midpoint",
+            [SketchPoint { id: point }, SketchCurve { id: line }] | [SketchCurve { id: line }, SketchPoint { id: point }],
+        ) => Some(json!({"point":point,"line":line})),
+        ("sketch.constraint.symmetry", [a, b, c]) => {
+            let mut points = Vec::new();
+            let mut lines = Vec::new();
+            for entity in [a, b, c] {
+                match entity {
+                    SketchPoint { id } => points.push(id),
+                    SketchCurve { id } => lines.push(id),
+                    _ => return None,
+                }
+            }
+            match (points.as_slice(), lines.as_slice()) {
+                ([a, b], [line]) if a != b => Some(json!({"a":a,"b":b,"line":line})),
+                _ => None,
+            }
+        }
+        _ => None,
+    }
+}
+
 fn run_pick(app: &mut SolveApp, t: &Tool) {
     let k = &t.picks;
     let params = match t.cmd {

crates/ui-egui/tests/point_constraint_preselection.rs

@@ -0,0 +1,88 @@
+use serde_json::json;
+use solvecraft_engine::{Sel, sketch::ConstraintKind};
+use solvecraft_ui_egui::scenario::Harness;
+
+fn setup() -> Harness {
+    let mut h = Harness::new();
+    h.app.run("sketch.create", json!({"plane":"XY"})).unwrap();
+    h.app.run("sketch.line", json!({"points":[[10,10],[30,10]],"infer":false,"connect":false})).unwrap();
+    h.app.run("sketch.point", json!({"point":[20,20],"id":"a"})).unwrap();
+    h.app.run("sketch.point", json!({"point":[25,30],"id":"b"})).unwrap();
+    h.call("ui.view", json!({"view":"top"}));
+    h
+}
+
+#[test]
+fn clicked_point_constraint_preselection_applies_and_undoes_once() {
+    for (command, picks) in [
+        ("coincident", vec![[20, 20], [25, 30]]),
+        ("coincident", vec![[20, 20], [20, 10]]),
+        ("coincident", vec![[20, 10], [20, 20]]),
+        ("midpoint", vec![[20, 20], [20, 10]]),
+        ("midpoint", vec![[20, 10], [20, 20]]),
+        ("symmetry", vec![[20, 10], [20, 20], [25, 30]]),
+        ("symmetry", vec![[20, 20], [20, 10], [25, 30]]),
+    ] {
+        let mut h = setup();
+        for (index, pick) in picks.iter().enumerate() {
+            h.step(&json!({"click":{"sketch":pick},"shift":index>0})).unwrap();
+        }
+        assert_eq!(h.app.session.selection.len(), picks.len(), "{command}");
+        let before = h.app.session.doc.to_json();
+        let undo = h.app.session.undo.len();
+        h.step(&json!({"start":format!("sketch.constraint.{command}")})).unwrap();
+        assert!(!h.app.status.as_ref().is_some_and(|(_, _, error)| *error), "{command}: {:?}", h.app.status);
+        assert!(h.app.tool.is_none());
+        assert!(h.app.session.selection.is_empty());
+        assert_eq!(h.app.session.undo.len(), undo + 1);
+        let state = h.app.session.world_state();
+        let sk = &state.sketch(h.app.session.active_sketch.unwrap()).unwrap().sketch;
+        assert!(sk.constraints.iter().any(|c| match command {
+            "coincident" => matches!(c.kind, ConstraintKind::Coincident { .. } | ConstraintKind::PointOnCurve { .. }),
+            "midpoint" => matches!(c.kind, ConstraintKind::Midpoint { .. }),
+            _ => matches!(c.kind, ConstraintKind::Symmetric { .. }),
+        }));
+        let point = |id| sk.point(sk.resolve_point(id).unwrap()).unwrap();
+        let a = point("a");
+        let b = point("b");
+        let start = point("l1.start");
+        let end = point("l1.end");
+        let axis = (end - start).normalized().unwrap();
+        match command {
+            "midpoint" => assert!(a.dist((start + end) * 0.5) < 1e-6),
+            "symmetry" => {
+                assert!(((a + b) * 0.5 - start).cross(axis).abs() < 1e-6);
+                assert!((b - a).dot(axis).abs() < 1e-6);
+            }
+            _ if picks.contains(&[20, 10]) => assert!((a - start).cross(axis).abs() < 1e-6),
+            _ => assert!(a.dist(b) < 1e-6),
+        }
+        let after = h.app.session.doc.to_json();
+        h.app.run("edit.undo", json!({})).unwrap();
+        assert_eq!(h.app.session.doc.to_json(), before);
+        h.app.run("edit.redo", json!({})).unwrap();
+        assert_eq!(h.app.session.doc.to_json(), after);
+    }
+}
+
+#[test]
+fn rejected_and_ambiguous_preselection_preserve_document_and_selection() {
+    let mut h = setup();
+    h.app.run("sketch.constraint.fix", json!({"entities":["a","b"]})).unwrap();
+    h.app.session.selection = vec![Sel::SketchPoint { id: "a".into() }, Sel::SketchPoint { id: "b".into() }];
+    let selection = h.app.session.selection.clone();
+    let before = h.app.session.doc.to_json();
+    let undo = h.app.session.undo.len();
+    h.step(&json!({"start":"sketch.constraint.coincident"})).unwrap();
+    assert!(h.app.status.as_ref().is_some_and(|(_, _, error)| *error));
+    assert_eq!(h.app.session.selection, selection);
+    assert_eq!(h.app.session.doc.to_json(), before);
+    assert_eq!(h.app.session.undo.len(), undo);
+    for command in ["coincident", "midpoint", "symmetry"] {
+        h.app.session.selection = vec![Sel::SketchPoint { id: "a".into() }];
+        h.step(&json!({"start":format!("sketch.constraint.{command}")})).unwrap();
+        assert!(h.app.tool.as_ref().unwrap().picks.is_empty());
+        assert_eq!(h.app.session.selection.len(), 1);
+        assert_eq!(h.app.session.doc.to_json(), before);
+    }
+}

docs/book/src/guide/sketching.md

@@ -94,7 +94,12 @@ aligned, horizontal, vertical, radius, diameter and angle dimensions. Each is a
 For Parallel, Perpendicular, Equal, Tangent, Concentric and Collinear, select exactly two
 sketch curves (Shift-click to add the second) and choose the constraint to apply it immediately.
 You can also start the constraint first and then pick its curves. An incomplete or mixed
-selection starts that pick workflow; a rejected constraint keeps the selection for correction.
+selection leaves the tool ready for ordinary picking.
+
+Coincident accepts an exact selection of two points or a point and a curve. Midpoint
+accepts one point and one line, in either selection order. Symmetry accepts two distinct
+points and one symmetry line, regardless of where the line occurs in the selection.
+Successful constraints clear the selection; rejected constraints preserve it.
 
 Under-constrained geometry is blue and fully constrained geometry turns dark, and the status
 shows the remaining degrees of freedom. A constraint or dimension that would over-constrain the