add list

crates/core/tests/scroll_area.rs

@@ -94,3 +94,57 @@ fn the_thumb_paints_when_the_content_overflows() {
     // 30 rows × 20px in a 200px viewport: the thumb has something to report.
     assert!(handle.max_offset().y > px(0.));
 }
+
+/// The gallery's exact shell: a window-filling root, a window-filling scroll
+/// area over padded flex-column content that towers past the viewport.
+struct GalleryShell {
+    scroll: ScrollHandle,
+}
+
+impl Render for GalleryShell {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        div().size_full().child(
+            ScrollArea::new("gallery-scroll")
+                .handle(self.scroll.clone())
+                .size_full()
+                .child(
+                    div()
+                        .p_6()
+                        .flex()
+                        .flex_col()
+                        .gap_5()
+                        .children((0..12).map(|section| {
+                            div()
+                                .h(px(220.))
+                                .child(SharedString::from(format!("section {section}")))
+                        })),
+                ),
+        )
+    }
+}
+
+#[test]
+fn a_gallery_style_window_fill_scroll_area_scrolls_tall_flex_content() {
+    let mut cx = TestAppContext::single();
+    cx.update(Theme::init);
+    let handle = ScrollHandle::new();
+    let handle_for_view = handle.clone();
+    let window = cx.add_window(move |_, _| GalleryShell {
+        scroll: handle_for_view,
+    });
+    let mut visual = VisualTestContext::from_window(window.into(), &cx);
+    visual.update(|window, cx| {
+        window.draw(cx).clear(cx);
+    });
+
+    // 12 sections × 220px + padding towers past the window; a wheel event
+    // over the middle of the viewport must scroll the root area.
+    visual.simulate_event(ScrollEvent {
+        position: point(px(300.), px(300.)),
+        delta: ScrollDelta::Pixels(point(px(0.), px(-60.))),
+        modifiers: Modifiers::default(),
+        ..Default::default()
+    });
+    assert_eq!(handle.offset().y, px(-60.));
+    assert!(handle.max_offset().y > px(1000.));
+}