test: a shortened viewport menu scrolls and picks the scrolled row

The context menu can now be cut short by its popup's configure and
scroll. Drive that through the designer's own wheel hook and press
path: three notches move three rows, and the press runs the row drawn
under the pointer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

 src/main.rs | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/src/main.rs b/src/main.rs
index 225ec77..85630ef 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1893,6 +1893,48 @@ mod tests {
         context_menu::hide();
     }
 
+    /// A viewport menu the compositor cut short (the popup's configure lands
+    /// it through `context_menu::place`) scrolls under the designer's own
+    /// wheel hook, and a press afterwards runs the row DRAWN under the
+    /// pointer — the scrolled one, not the one at that offset unscrolled.
+    #[test]
+    fn a_shortened_viewport_menu_scrolls_and_picks_the_scrolled_row() {
+        use crate::app::ViewportMenuAction as A;
+        use crate::window::{LocalPosition, WindowEvent};
+        use cce_ui::widget::{context_menu, ElementState, MouseButton, MouseScrollDelta};
+        let mut state = State::new(false);
+        state.cursor_x = 300.0;
+        state.cursor_y = 200.0;
+        state.open_viewport_context_menu();
+        let full = context_menu::CONTEXT_MENU.with(|m| m.borrow().content_h);
+        context_menu::place(300.0, 0.0, full * 0.5);
+
+        // Over the first row, which is Frame All — an action, not a slider.
+        state.cursor_x = context_menu::x() + 20.0;
+        state.cursor_y = context_menu::row_y(0) + context_menu::ROW_H * 0.5;
+        assert_eq!(state.viewport_menu_actions[0], A::FrameAll);
+        state.handle_event(&WindowEvent::CursorMoved {
+            position: LocalPosition { x: state.cursor_x as f64, y: state.cursor_y as f64 },
+        });
+        state.handle_event(&WindowEvent::MouseWheel { delta: MouseScrollDelta::LineDelta(0.0, -3.0) });
+        let scroll = context_menu::CONTEXT_MENU.with(|m| m.borrow().scroll);
+        assert_eq!(scroll, 3.0 * context_menu::ROW_H, "three notches down, three rows");
+        assert!(state.viewport_menu_open(), "scrolling keeps the menu up");
+
+        // The row now under the pointer is row 3; pressing it runs row 3's
+        // action. Pick a row whose effect is visible: a toggle.
+        let row = context_menu::row_at(state.cursor_x, state.cursor_y).expect("a row under the pointer");
+        assert_eq!(row, 3);
+        let A::Command(id) = state.viewport_menu_actions[row] else {
+            panic!("row 3 should be a toggle command, is {:?}", state.viewport_menu_actions[row]);
+        };
+        let before = state.command_toggle_state(id);
+        state.handle_event(&WindowEvent::MouseInput { state: ElementState::Pressed, button: MouseButton::Left });
+        state.handle_event(&WindowEvent::MouseInput { state: ElementState::Released, button: MouseButton::Left });
+        assert_ne!(state.command_toggle_state(id), before, "the scrolled row ran");
+        context_menu::hide();
+    }
+
     /// Point Size is a viewport-menu slider over the palette row's 0–0.1,
     /// and it re-sizes what it feeds without re-evaluating anything: the
     /// Selected-Group markers are rebuilt from their KEPT members at Point