Ignore repeated initial sketch points while drawing

ROADMAP.md

@@ -63,6 +63,9 @@ headline counts in-scope tabs only and lists the deferred ones separately.
 
 ## Dimensioning and error reporting
 
+- Repeating the initial point of a planar multi-point sketch drawing tool is neutral: the tool
+  waits for a distinct point without a degenerate-shape error or history entry. Typed input
+  and programmatic commands retain their validation.
 - Single-line and rectangle-side dimensioning supports selecting a line or its two endpoints.
   Type a value and press Enter to commit one undo step; rejected values remain editable and
   cancellation leaves the sketch unchanged. Fit keeps geometry clear of the Sketch Palette

crates/ui-egui/src/sketch_neutral_click_tests.rs

@@ -0,0 +1,44 @@
+use crate::scenario::Harness;
+use serde_json::json;
+
+#[test]
+fn repeated_first_point_is_neutral_and_drawing_can_continue() {
+    for (command, rest) in [
+        ("sketch.rectangle.two_point", vec![[10, 5, 0]]),
+        ("sketch.rectangle.center", vec![[10, 5, 0]]),
+        ("sketch.rectangle.three_point", vec![[10, 0, 0], [10, 5, 0]]),
+        ("sketch.circle.center", vec![[5, 0, 0]]),
+        ("sketch.circle.three_point", vec![[10, 0, 0], [5, 5, 0]]),
+        ("sketch.line", vec![[10, 5, 0]]),
+        ("sketch.polygon.inscribed", vec![[10, 5, 0]]),
+        ("sketch.slot.center_to_center", vec![[10, 0, 0], [10, 3, 0]]),
+    ] {
+        let mut h = Harness::new();
+        h.app.run("sketch.create", json!({"plane":"XY"})).unwrap();
+        h.app.cam.distance = 50.0;
+        h.step(&json!({"start":command})).unwrap();
+        let before = h.app.session.doc.to_json();
+        let undo = h.app.session.undo.len();
+        let p = h.call("ui.at", json!({"sketch":[0,0]}))["result"].clone();
+        h.call("ui.click", json!({"x":p[0],"y":p[1],"double":true}));
+        assert!(!h.app.status.as_ref().is_some_and(|s| s.2), "{command}: {:?}", h.app.status);
+        assert_eq!(h.app.tool.as_ref().unwrap().pts.len(), 1, "{command}");
+        assert_eq!(h.app.session.doc.to_json(), before);
+        assert_eq!(h.app.session.undo.len(), undo);
+        for point in rest {
+            h.step(&json!({"move":{"world":point}})).unwrap();
+            if command == "sketch.slot.center_to_center" {
+                // The live width editor is placed at the cursor; Enter accepts it.
+                h.step(&json!({"key":"Enter"})).unwrap();
+            } else {
+                h.step(&json!({"click":{"world":point}})).unwrap();
+            }
+        }
+        assert!(!h.app.status.as_ref().is_some_and(|s| s.2), "{command}: {:?}", h.app.status);
+        let state = h.app.session.world_state();
+        assert!(!state.sketches[0].sketch.curves.is_empty(), "{command}: {:?}; {:?}", h.app.tool, h.app.status);
+        assert_eq!(h.app.session.undo.len(), undo + 1, "{command}");
+        h.app.run("edit.undo", json!({})).unwrap();
+        assert_eq!(h.app.session.doc.to_json(), before, "{command}");
+    }
+}

crates/ui-egui/src/tools.rs

@@ -12,6 +12,10 @@ use crate::viewport::{Hit, Proj, pick, sketch_point_at};
 #[path = "sketch_display_preview_tests.rs"]
 mod display_preview_tests;
 
+#[cfg(test)]
+#[path = "sketch_neutral_click_tests.rs"]
+mod neutral_click_tests;
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Kind {
     /// Click points; `n` points complete the shape (0 = chain until finished).
@@ -144,12 +148,18 @@ pub fn on_click(app: &mut SolveApp, proj: &Proj, pos: Pos2) {
         return;
     }
     match tool.kind {
-        Kind::Draw(_) => {
+        Kind::Draw(n) => {
             if let Some(mut p) = sketch_point_at(app, proj, pos) {
                 // Typed values win over the cursor; lines snap to horizontal/vertical.
                 if tool.dims.iter().any(|b| b.locked) || (tool.cmd == "sketch.line" && p.1.is_none()) {
                     p = (crate::sketch_dims::effective(app, &tool, p.0), None);
                 }
+                // A repeated initial point supplies no extent. Keep waiting rather than
+                // attempting a degenerate shape; explicit typed values still validate.
+                if n != 1 && tool.pts.len() == 1 && tool.pts.first().is_some_and(|first| first.0 == p.0) && !tool.dims.iter().any(|b| b.locked) {
+                    app.tool = Some(tool);
+                    return;
+                }
                 app.tool = Some(tool);
                 place(app, p);
                 return;