From 093c87d08a59605b0a7567cd2d686797e5718b78 Mon Sep 17 00:00:00 2001
From: Books <sabaksa11@gmail.com>
Date: Sun, 11 Oct 2026 03:57:13 +1100
Subject: [PATCH] DIMANGULAR: accept polyline segments (fixes #10) (#15)

Picking a side of a rectangle or a PLINE segment was rejected with
"Select a line or an arc." because only LINE and ARC entities were
accepted. The picked object is now resolved to the segment under the
cursor: straight polyline segments work like lines and arc segments
like arcs.
---
 crates/engine/src/cmd/annotate.rs       | 23 +++++++++++++++++------
 crates/engine/src/cmd/annotate_tests.rs | 25 +++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/crates/engine/src/cmd/annotate.rs b/crates/engine/src/cmd/annotate.rs
index a925085..ee09c34 100644
--- a/crates/engine/src/cmd/annotate.rs
+++ b/crates/engine/src/cmd/annotate.rs
@@ -760,6 +760,19 @@ fn pick_at(s: &Session, p: Vec2) -> Option<Handle> {
     crate::select::pick(s.doc().ok()?, &s.space(), p, ap)
 }
 
+/// The straight or curved piece of `h` picked at `p`: a line, an arc, or the polyline segment nearest `p`.
+fn segment_at(s: &Session, h: Handle, p: Vec2) -> Option<Segment> {
+    match &s.doc().ok()?.entity(h)?.kind {
+        EntityKind::Line(l) => Some(Segment::Line(cadcraft_geom::Line::new(l.a.xy(), l.b.xy()))),
+        EntityKind::Arc(a) => Some(Segment::Arc { arc: cadcraft_geom::Arc::new(a.center.xy(), a.radius, a.start, a.end), ccw: true }),
+        EntityKind::LwPolyline(pl) => cadcraft_geom::Polyline { vertices: pl.vertices.clone(), closed: pl.closed }
+            .segments()
+            .into_iter()
+            .min_by(|x, y| x.closest(p).dist(p).total_cmp(&y.closest(p).dist(p))),
+        _ => None,
+    }
+}
+
 struct LinearM {
     aligned: bool,
     pts: Vec<Vec2>,
@@ -1003,15 +1016,13 @@ impl Interactive for AngularM {
                     s.echo("*Invalid selection*");
                     return Ok(Step::Continue);
                 };
-                let kind = s.doc()?.entity(h).map(|e| e.kind.clone());
-                match kind {
-                    Some(EntityKind::Arc(a)) if self.first.is_none() => {
-                        let g = cadcraft_geom::Arc::new(a.center.xy(), a.radius, a.start, a.end);
+                match segment_at(s, h, p) {
+                    Some(Segment::Arc { arc: g, .. }) if self.first.is_none() => {
                         self.arc = Some((g.center, g.start_point(), g.end_point()));
                     }
-                    Some(EntityKind::Line(l)) => {
+                    Some(Segment::Line(l)) => {
                         self.handles.push(h);
-                        let seg = (l.a.xy(), l.b.xy());
+                        let seg = (l.a, l.b);
                         if self.first.is_none() {
                             self.first = Some(seg);
                         } else {
diff --git a/crates/engine/src/cmd/annotate_tests.rs b/crates/engine/src/cmd/annotate_tests.rs
index f644acd..02a117b 100644
--- a/crates/engine/src/cmd/annotate_tests.rs
+++ b/crates/engine/src/cmd/annotate_tests.rs
@@ -143,6 +143,31 @@ fn angular_between_lines_follows_rotation() {
     assert_eq!(cadcraft_render::dimension_in(s.doc().unwrap(), &dim(&s, d)).value, "45°");
 }
 
+#[test]
+fn interactive_angular_picks_polyline_segments() {
+    // Rectangle sides are polyline segments, not lines (issue #10).
+    let mut s = Session::new();
+    s.cmdline("rectang 0,0 10,5").unwrap();
+    s.cmdline("dimangular").unwrap();
+    s.cmdline("5,0").unwrap();
+    s.cmdline("0,2").unwrap();
+    s.cmdline("2,2").unwrap();
+    assert!(s.running.is_none());
+    let d = s.last_dim.unwrap();
+    assert_eq!(cadcraft_render::dimension_in(s.doc().unwrap(), &dim(&s, d)).value, "90°");
+    // A polyline arc segment works like an arc.
+    s.cmdline("pline 20,0 30,0 a 30,10").unwrap();
+    s.cmdline("").unwrap();
+    s.cmdline("dimangular").unwrap();
+    let (cx, cy) = (30.0 + 5.0 * std::f64::consts::FRAC_1_SQRT_2, 5.0 - 5.0 * std::f64::consts::FRAC_1_SQRT_2);
+    s.cmdline(&format!("{cx},{cy}")).unwrap();
+    s.cmdline("40,5").unwrap();
+    assert!(s.running.is_none());
+    let d2 = s.last_dim.unwrap();
+    assert_ne!(d, d2);
+    assert_eq!(cadcraft_render::dimension_in(s.doc().unwrap(), &dim(&s, d2)).value, "180°");
+}
+
 #[test]
 fn erase_disassociate_and_reassociate() {
     let mut s = Session::new();