Join the selected end points of two paths with Ctrl+J

Fixes #4163

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/path.rs

@@ -467,6 +467,9 @@ fn join(s: &mut Session, p: &Value) -> Result<Value> {
             if a == b {
                 return Err(bad(C, "join two different paths"));
             }
+            let st = s.doc()?;
+            let picked_a = st.selection.anchors.get(&a).cloned().unwrap_or_default();
+            let picked_b = st.selection.anchors.get(&b).cloned().unwrap_or_default();
             s.edit("Join", |d, sel| {
                 let pb = d.node(b).and_then(|n| n.path_data()).cloned().ok_or(EngineError::NoNode(b))?;
                 let pa = path_mut(d, a)?;
@@ -481,8 +484,24 @@ fn join(s: &mut Session, p: &Value) -> Result<Value> {
                 // The ends asked for, else the closest pair.
                 let cands =
                     [(xl.distance(yf), false, false), (xl.distance(yl), false, true), (xf.distance(yf), true, false), (xf.distance(yl), true, true)];
-                let (rx, ry) =
-                    ends.unwrap_or_else(|| cands.into_iter().min_by(|p, q| p.0.total_cmp(&q.0)).map_or((false, false), |(_, rx, ry)| (rx, ry)));
+                // Direct-selected end points decide which ends meet, before the closest pair does.
+                let end_of = |picked: &std::collections::BTreeSet<(usize, usize)>, si: usize, len: usize| {
+                    let last_ix = len.checked_sub(1)?;
+                    let first = picked.contains(&(si, 0));
+                    let last = picked.contains(&(si, last_ix));
+                    match (first, last) {
+                        (true, false) => Some(true),
+                        (false, true) => Some(false),
+                        _ => None,
+                    }
+                };
+                let by_selection = match (end_of(&picked_a, sa, x.anchors.len()), end_of(&picked_b, sb, y.anchors.len())) {
+                    (Some(fa), Some(fb)) => Some((fa, !fb)),
+                    _ => None,
+                };
+                let (rx, ry) = ends
+                    .or(by_selection)
+                    .unwrap_or_else(|| cands.into_iter().min_by(|p, q| p.0.total_cmp(&q.0)).map_or((false, false), |(_, rx, ry)| (rx, ry)));
                 if rx {
                     x.reverse();
                 }

crates/engine/src/tests_draw2.rs

@@ -2188,6 +2188,20 @@ fn join_takes_the_paths_and_the_ends_to_join() {
     }
 }
 
+/// Without `ends`, the end points picked with the direct selection are the ones joined.
+#[test]
+fn join_uses_the_selected_end_points() {
+    let mut s = session();
+    let a = line(&mut s, 0.0, 0.0, 100.0, 0.0);
+    let b = line(&mut s, 110.0, 0.0, 200.0, 0.0);
+    s.execute("select.all", &json!({})).unwrap();
+    s.execute("select.anchors", &json!({"id": a.0, "anchors": [[0, 0]], "mode": "add"})).unwrap();
+    s.execute("select.anchors", &json!({"id": b.0, "anchors": [[0, 1]], "mode": "add"})).unwrap();
+    s.execute("path.join", &json!({})).unwrap();
+    let pts: Vec<(f64, f64)> = path(&s, a).subpaths[0].anchors.iter().map(|x| (x.p.x, x.p.y)).collect();
+    assert_eq!(pts, [(100.0, 0.0), (0.0, 0.0), (200.0, 0.0), (110.0, 0.0)]);
+}
+
 /// `path.join {to}` makes the joined anchor a corner or smooth point.
 #[test]
 fn join_to_corner_or_smooth_sets_the_merged_anchor() {