#1406: guides for an absolute child of an auto layout frame, and a test

crates/ui-egui/src/canvas/overlays.rs

@@ -419,7 +419,7 @@ fn transform_box(
 /// bottom likewise (the line is perpendicular to the edge it leaves). A centre constraint draws a
 /// short bar through the layer's middle — a horizontal one, a vertical one, or both (a cross when
 /// the layer is centred on both axes). Auto-layout frames ignore constraints, so no guides are
-/// drawn there.
+/// drawn there, except for a layer that ignores the auto layout (absolute position).
 fn constraint_lines(app: &FigApp, painter: &egui::Painter, doc: &Document, sel: &[NodeId]) {
     let s = stroke(accent(painter), 1.0);
     let line = |a: Pos2, b: Pos2| {
@@ -438,8 +438,9 @@ fn constraint_lines(app: &FigApp, painter: &egui::Painter, doc: &Document, sel:
         let Some(n) = doc.node(id) else { continue };
         let Some(parent_id) = n.parent else { continue };
         let Some(parent) = doc.node(parent_id) else { continue };
-        // Constraints bind a layer only to a non-auto-layout frame it sits inside.
-        if !parent.kind.is_frame_like() || parent.layout.is_some() {
+        // Constraints bind a layer only to a frame it sits inside: one without auto layout, or one
+        // whose auto layout the layer ignores (absolute position).
+        if !parent.kind.is_frame_like() || (parent.layout.is_some() && !n.child_layout.absolute) {
             continue;
         }
         let nw = doc.world_transform(id);

crates/ui-egui/src/canvas_fixes_tests.rs

@@ -162,3 +162,27 @@ fn the_pencil_previews_its_stroke_in_its_colour_and_weight() {
     let w = preview(&flat(&u.frame_output(vec![egui::Event::PointerMoved(p)]).shapes)).expect("still previewing");
     assert!((w - 1.0).abs() < 0.01, "at least a point: {w}");
 }
+
+#[test]
+fn a_selected_layer_shows_its_constraint_guides_in_its_frame() {
+    // A child pinned left (the default) in a frame without auto layout: a dashed guide runs from its
+    // left-edge midpoint to the frame's left edge. An auto layout frame places its children itself,
+    // so only a child that ignores the auto layout (absolute) shows one there.
+    let mut s = Session::new();
+    let f = id(&s.execute("frame.create", &json!({"x": 0, "y": 0, "width": 200, "height": 120})).unwrap());
+    let c = id(&s.execute("node.create", &json!({"type": "rectangle", "x": 80, "y": 40, "width": 40, "height": 40, "parent": f})).unwrap());
+    s.execute("select.set", &json!({"ids": [c]})).unwrap();
+    let mut u = Ui::new(s);
+    let guide = |u: &mut Ui| {
+        let shapes = flat(&u.frame_output(vec![]).shapes);
+        let doc = u.app.session.doc().unwrap();
+        let (fb, cb) = (doc.world_bounds(f).unwrap(), doc.world_bounds(c).unwrap());
+        let y = cb.center().y;
+        dashes_along(&shapes, u.app.to_screen(fb.x0, y), u.app.to_screen(cb.x0, y))
+    };
+    assert!(guide(&mut u) > 0, "a left constraint draws a dashed guide to the frame's left edge");
+    u.app.run("node.set", json!({"id": f, "props": {"layout": "horizontal", "padding": 40}}));
+    assert_eq!(guide(&mut u), 0, "auto layout places the child: no constraint guide");
+    u.app.run("node.set", json!({"id": c, "props": {"absolute": true}}));
+    assert!(guide(&mut u) > 0, "an absolute child is pinned by its constraints again");
+}