Let the box of another layer's points win over a region of the active one

With points selected only on another edited layer, a press inside the
combined box over an unselected filled region of the active layer picked
the region instead of dragging the box. Other layers' selections now count
in the same priority check; a press on an already selected region still
drags the regions.

crates/engine/src/vectoredit/pointer.rs

@@ -428,11 +428,11 @@ impl Session {
     }
 
     /// The region of the active layer a press at `ev` would take (Move tool, `h` the network's part
-    /// there). Inside the transform box around points selected in their own right, the box keeps
-    /// its drag unless the region is already selected.
+    /// there). Inside the transform box around points selected in their own right (in any edited
+    /// layer), the box keeps its drag unless the region is already selected.
     fn region_under(doc: &Document, ve: &VectorEdit, h: Option<VHit>, ev: &PointerEvent) -> Option<usize> {
         let r = region_hit(doc, ve, ev.p(), ev.zoom)?;
-        let own = !ve.shown_vertices().is_empty() || !ve.segments.is_empty();
+        let own = !ve.shown_vertices().is_empty() || !ve.segments.is_empty() || ve.others_selected();
         let in_box = !ev.shift && own && transform::box_hit(doc, ve, h, ev.p(), ev.zoom) == Some(BoxHit::Inside);
         (!in_box || ve.regions.contains(&r)).then_some(r)
     }

crates/engine/src/vectoredit/transform_tests.rs

@@ -397,3 +397,32 @@ fn inside_the_box_of_several_layers_drags_and_a_click_clears_them_all() {
     click(&mut s, 150.0, 50.0);
     assert!(ve(&s).parts().iter().all(|p| p.vertices.is_empty()), "a click inside clears every layer's points");
 }
+
+#[test]
+fn inside_the_box_of_another_layer_drags_over_a_region_of_the_active_one() {
+    // `b`'s points selected, `a` (a filled 300 square around `b`) active with nothing selected:
+    // the press at the box's centre lands on `a`'s region too.
+    let mut s = Session::new();
+    let mut square = |x: f64, size: f64| {
+        crate::params::id_of(&ex(&mut s, "shape.rectangle", json!({"x": x, "y": x, "width": size, "height": size}))["id"]).unwrap()
+    };
+    let (a, b) = (square(0.0, 300.0), square(100.0, 50.0));
+    ex(&mut s, "view.snapGeometry", json!({"on": false}));
+    ex(&mut s, "view.snapObjects", json!({"on": false}));
+    ex(&mut s, "view.snapPixel", json!({"on": false}));
+    ex(&mut s, "vector.edit.begin", json!({"ids": [a, b]}));
+    ex(&mut s, "vector.edit.select", json!({"id": b, "vertices": [0, 1, 2, 3]}));
+    ex(&mut s, "vector.edit.select", json!({"id": a, "add": true}));
+    let doc = s.doc().unwrap().clone();
+    let e = ve(&s);
+    assert!(e.id == a && e.vertices.is_empty() && e.others_selected());
+    assert!(hit_any(&doc, &e, pt(125.0, 125.0), 6.0).is_none());
+    assert!(regions::region_hit(&doc, &e, pt(125.0, 125.0), 1.0).is_some(), "a region of the active layer under the press");
+    assert_eq!(box_hit(&doc, &e, None, pt(125.0, 125.0), 1.0), Some(BoxHit::Inside));
+    let before: Vec<Point> = (0..4).map(|v| page_pt(&s, b, v)).collect();
+    drag(&mut s, (125.0, 125.0), (145.0, 135.0));
+    assert!(ve(&s).regions.is_empty(), "the region isn't selected");
+    for (v, p) in before.iter().enumerate() {
+        assert!(near(page_pt(&s, b, v), *p + Vec2::new(20.0, 10.0)), "point {v} of b moves along");
+    }
+}