G11: Join tool connects endpoints near scrub line ends

Squashed from #4272 onto main.

crates/engine/src/cmd/draw2.rs

@@ -1497,6 +1497,7 @@ fn join_scrub(s: &mut Session, p: &Value) -> Result<Value> {
             .min_by(|a, b| a.1.total_cmp(&b.1))
             .map_or(0.0, |x| x.0)
     };
+    let (first_pt, last_pt) = (pts.first().copied(), pts.last().copied());
     let mut ends: Vec<(f64, NodeId, usize, bool, Point)> = vec![];
     for id in target_paths(&st.doc, &st.selection, poly_bounds(&pts, tol)) {
         let (pd, _) = path_of(&st.doc, id)?;
@@ -1505,9 +1506,20 @@ fn join_scrub(s: &mut Session, p: &Value) -> Result<Value> {
                 continue;
             }
             for (start, a) in [(true, sp.anchors[0].p), (false, sp.anchors[sp.anchors.len() - 1].p)] {
-                if dist_to_polyline(&pts, a) <= tol {
-                    ends.push((order(a), id, si, start, a));
+                let on_scrub = dist_to_polyline(&pts, a) <= tol;
+                let near_start = first_pt.is_some_and(|p| a.distance(p) <= tol);
+                let near_end = last_pt.is_some_and(|p| a.distance(p) <= tol);
+                if !on_scrub && !near_start && !near_end {
+                    continue;
                 }
+                let ord = if on_scrub {
+                    order(a)
+                } else if near_start && (!near_end || first_pt.is_some_and(|p| a.distance(p) <= a.distance(last_pt.unwrap_or(p)))) {
+                    -1.0
+                } else {
+                    1e30
+                };
+                ends.push((ord, id, si, start, a));
             }
         }
     }

crates/engine/src/tests_draw2.rs

@@ -944,6 +944,21 @@ fn join_tool_joins_two_lines() {
     assert_eq!(p.subpaths[0].anchors[2].p, Point::new(300.0, 150.0));
 }
 
+/// #2899: a scrub from one open end toward the other joins them when the line passes near the
+/// endpoints, not only when it crosses them.
+#[test]
+fn join_tool_joins_endpoints_near_the_scrub_ends() {
+    let mut s = session();
+    let a = line(&mut s, 100.0, 100.0, 200.0, 100.0);
+    line(&mut s, 205.0, 100.0, 300.0, 150.0);
+    s.execute("select.none", &json!({})).unwrap();
+    drag(&mut s, "join", &[(198.0, 92.0), (207.0, 92.0)], Mods::default());
+    assert_eq!(paths(&s).len(), 1);
+    let p = path(&s, a);
+    assert_eq!(p.anchor_count(), 3);
+    assert_eq!(p.subpaths[0].anchors[1].p, Point::new(202.5, 100.0));
+}
+
 #[test]
 fn line_family_tools_draw_and_click_asks_dialog() {
     let mut s = session();