Tests: nested clip groups in isolation mode and Direct Selection drags

- isolation_reaches_hidden_art_only_for_the_isolated_clip_group: with the
  outer clip group isolated, clicks and marquees take the art its own mask
  hides, while an inner clip group's mask still clips that group's art;
  isolating the inner group or its art reaches the inner hidden art.
- isolation_lets_direct_selection_take_the_art_a_clip_group_hides now
  continues the press with a drag on the same tool and checks the Move
  step and its preview, for Direct Selection and Group Selection.

crates/doc/src/hit/tests.rs

@@ -533,6 +533,56 @@ fn isolation_reaches_the_art_a_clipping_mask_hides() {
     }
 }
 
+/// #3748, nested clip groups: with the outer clip group isolated, a click or a marquee takes
+/// the art its own mask hides, while the mask of a clip group inside it still limits that
+/// group's art. With the inner clip group isolated, or its art, the inner mask does not.
+#[test]
+fn isolation_reaches_hidden_art_only_for_the_isolated_clip_group() {
+    let mut d = Document::new(300.0, 200.0);
+    let l = d.layers[0].id;
+    let (outer, outer_clip, outer_art, inner, inner_clip, inner_art) =
+        (d.alloc_id(), d.alloc_id(), d.alloc_id(), d.alloc_id(), d.alloc_id(), d.alloc_id());
+    let mask = |id, r| {
+        let mut path = Node::path(id, shapes::rectangle(r), Appearance::basic(Paint::None, Paint::None, 0.0));
+        if let NodeKind::Path { clipping, .. } = &mut path.kind {
+            *clipping = true;
+        }
+        Arc::new(path)
+    };
+    let art = |id, r| Arc::new(Node::path(id, shapes::rectangle(r), Appearance::default_art()));
+    let inner_group = Node::new(
+        inner,
+        NodeKind::Group {
+            children: vec![mask(inner_clip, Rect::new(60.0, 60.0, 120.0, 120.0)), art(inner_art, Rect::new(40.0, 40.0, 160.0, 160.0))],
+            clip: true,
+        },
+    );
+    let children =
+        vec![mask(outer_clip, Rect::new(20.0, 20.0, 180.0, 180.0)), art(outer_art, Rect::new(190.0, 20.0, 260.0, 180.0)), Arc::new(inner_group)];
+    d.insert(Some(l), 0, Node::new(outer, NodeKind::Group { children, clip: true })).unwrap();
+    // `outer_hidden` is outside the outer mask, on the outer group's own art; `inner_hidden` is
+    // inside the outer mask and outside the inner one, on the inner group's art.
+    let (outer_hidden, inner_hidden, shown) = (Point::new(220.0, 100.0), Point::new(150.0, 100.0), Point::new(90.0, 90.0));
+    let leaf = |p, scope| hit_test(&d, p, HitOptions { scope, ..SELECTING }).map(|h| h.leaf);
+    assert_eq!((leaf(outer_hidden, None), leaf(inner_hidden, None)), (None, None), "not isolated");
+    assert_eq!(leaf(outer_hidden, Some(outer)), Some(outer_art), "outer isolated: its own hidden art");
+    assert_eq!(leaf(inner_hidden, Some(outer)), None, "outer isolated: the inner mask still clips");
+    let h = hit_test(&d, shown, HitOptions { scope: Some(outer), ..SELECTING });
+    assert_eq!(h.map(|h| (h.leaf, h.top_object(Some(outer)))), Some((inner_art, inner)), "outer isolated: shown art");
+    assert_eq!(leaf(inner_hidden, Some(inner)), Some(inner_art), "inner isolated");
+    assert_eq!(leaf(outer_hidden, Some(inner)), None, "inner isolated: the outer group's art");
+    assert_eq!(leaf(inner_hidden, Some(inner_art)), Some(inner_art), "the inner art isolated");
+    // These marquees cross the right edge of the outer art (outside the outer mask) and of the
+    // inner art (inside the outer mask, outside the inner one).
+    let (outer_edge, inner_edge) = (Rect::new(255.0, 95.0, 265.0, 105.0), Rect::new(155.0, 95.0, 165.0, 105.0));
+    assert_eq!(marquee(&d, outer_edge, Some(outer), false), vec![outer_art]);
+    assert!(marquee(&d, inner_edge, Some(outer), false).is_empty());
+    assert!(marquee(&d, inner_edge, Some(outer), true).is_empty());
+    assert_eq!(marquee(&d, inner_edge, Some(inner), false), vec![inner_art]);
+    assert!(marquee(&d, inner_edge, None, false).is_empty());
+    assert!(marquee(&d, outer_edge, None, false).is_empty());
+}
+
 /// Art in a sublayer is an object of its own: a click or a marquee takes it, not the
 /// sublayer; hidden, locked and template sublayers block both.
 #[test]

crates/tools/src/direct/tests.rs

@@ -129,16 +129,25 @@ fn a_press_on_a_clipping_path_takes_its_segment_over_the_art() {
 }
 
 /// #3748: in isolation mode Direct Selection and Group Selection take the art that the
-/// isolated clip group hides outside its mask; outside isolation mode a press there does not.
+/// isolated clip group hides outside its mask, and a drag from there moves it; outside
+/// isolation mode a press there does not take it.
 #[test]
 fn isolation_lets_direct_selection_take_the_art_a_clip_group_hides() {
     let (d, g, _, art) = doc_with_masked_square();
     let (s, p) = (Selection::default(), paint());
+    let mut picked = Selection::default();
+    picked.add(art);
     let names = |actions: &[Action]| actions.iter().any(|a| matches!(a, Action::Exec(_, v) if v["id"] == json!(art.0) || v["ids"] == json!([art.0])));
     for group in [false, true] {
         let isolated = ToolContext { isolation: Some(g), ..cx(&d, &s, &p) };
-        let a = DirectSelectionTool::new(group).pointer(&isolated, &PointerEvent::new(PointerKind::Down, 530.0, 450.0));
+        let mut t = DirectSelectionTool::new(group);
+        let a = t.pointer(&isolated, &PointerEvent::new(PointerKind::Down, 530.0, 450.0));
         assert!(names(&a), "group {group}: {a:?}");
+        // The press selected the art: the drag that follows moves it.
+        let isolated = ToolContext { isolation: Some(g), ..cx(&d, &picked, &p) };
+        let a = t.pointer(&isolated, &PointerEvent::new(PointerKind::Drag, 510.0, 470.0));
+        assert!(a.iter().any(|a| matches!(a, Action::Begin(n) if n == "Move")), "group {group}: {a:?}");
+        assert!(a.iter().any(|a| matches!(a, Action::Preview(..))), "group {group}: {a:?}");
         let a = DirectSelectionTool::new(group).pointer(&cx(&d, &s, &p), &PointerEvent::new(PointerKind::Down, 530.0, 450.0));
         assert!(!names(&a), "group {group}, not isolated: {a:?}");
     }