Make Iris layout dependencies explicit

src/sense_tests.rs

@@ -73,9 +73,13 @@ fn a_button_over_a_list_scrolls_the_list_and_still_clicks() {
     let clicked = Rc::new(Cell::new(false));
     {
         let scrolled = scrolled.clone();
-        rsc.register_event(list_weak, CursorSense::Scroll, move |_ctx, _rsc| {
-            scrolled.set(true);
-        });
+        rsc.register_event(
+            list_weak,
+            CursorSense::Scroll(Axis::Y),
+            move |_ctx, _rsc| {
+                scrolled.set(true);
+            },
+        );
     }
     {
         let clicked = clicked.clone();
@@ -461,10 +465,10 @@ fn taking_the_pointer_cancels_everyone_else_tracking_the_press() {
         events: EventManager::default(),
     };
 
-    // The bystander *contains* the capturer, which is the real shape: a
-    // transcript's `LazySpan` and one row's own text both track the same
-    // press, and a `Stack`'s siblings would be on separate layers where
-    // only the topmost is dispatched to at all.
+    // The bystander contains the capturer on a lower visual layer: the
+    // shape of a vertical transcript scroller with a higher horizontal
+    // scroller inside one row. Both observe the undecided press, then only
+    // the recognizer matching its direction may consume it.
     let capturer = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
     let capturer_weak = capturer.weak();
     let bystander = rsc.ui.widgets.add_strong(Stack {
@@ -478,7 +482,7 @@ fn taking_the_pointer_cancels_everyone_else_tracking_the_press() {
         let capturer_saw = capturer_saw.clone();
         rsc.register_event(
             capturer_weak,
-            CursorSense::drag_senses(),
+            CursorSense::drag(Axis::X),
             move |ctx, _rsc| {
                 capturer_saw.set(capturer_saw.get() + 1);
                 if matches!(ctx.data.sense, CursorSense::Pressing(_)) {
@@ -493,7 +497,7 @@ fn taking_the_pointer_cancels_everyone_else_tracking_the_press() {
         let (cancelled, ended) = (cancelled.clone(), ended.clone());
         rsc.register_event(
             bystander_weak,
-            CursorSense::drag_senses(),
+            CursorSense::drag(Axis::Y),
             move |ctx, _rsc| match ctx.data.sense {
                 CursorSense::Cancel => cancelled.set(cancelled.get() + 1),
                 CursorSense::PressEnd(_) | CursorSense::Drop => ended.set(ended.get() + 1),
@@ -515,7 +519,7 @@ fn taking_the_pointer_cancels_everyone_else_tracking_the_press() {
     render.update(&root, &mut rsc);
     assert_eq!(cancelled.get(), 0, "nothing has captured yet");
 
-    let mut moved = cursor_at((50.0, 20.0).into());
+    let mut moved = cursor_at((80.0, 50.0).into());
     moved.buttons.left = ActivationState::On;
     render.run_sensors(&mut rsc, &mut state, moved, win);
     render.update(&root, &mut rsc);
@@ -590,6 +594,9 @@ fn a_drag_pans_whichever_nested_scroll_area_owns_its_axis() {
                 record.set(Some(id));
                 id
             })
+            // The horizontal area is visually above the vertical one, as
+            // it is when a raised transcript row contains sideways content.
+            .layer_offset(1)
             .scrollable(Axis::Y, Pin::Start)
             .add_strong(&mut rsc);
         let inner = seen.get().unwrap();