Menus: a pointer coming back into the window over another title switches menus (#1290)

crates/ui-egui/src/menus/bar.rs

@@ -14,6 +14,12 @@ fn browse_menu_id() -> egui::Id {
     egui::Id::unique("menu-bar-browse")
 }
 
+/// The id under which [`menu_bar`] remembers where it last saw the pointer (`None`: outside the
+/// window).
+fn last_pointer_id() -> egui::Id {
+    egui::Id::unique("menu-bar-last-pointer")
+}
+
 /// Draw the in-window menu bar (the engine's AE menu tree).
 ///
 /// The titles open on the press, not the release (native menu bars): while one is held the menus
@@ -34,6 +40,12 @@ pub fn menu_bar(app: &mut EffectcraftApp, ui: &mut egui::Ui) {
     if ctx.data(|d| d.get_temp(browse_menu_id())).unwrap_or(false) {
         nav.set_browsing();
     }
+    // Whether the pointer has moved since the last frame. Kept by position rather than egui's
+    // `delta`, which is zero for the first position after the pointer comes back into the window:
+    // coming back in over another title must switch to it too (#1290).
+    let pointer = ctx.pointer_hover_pos();
+    let last = ctx.data_mut(|d| std::mem::replace(d.get_temp_mut_or(last_pointer_id(), None), pointer));
+    let moved = pointer.is_some() && pointer != last;
     let mut drawn = 0;
     ui.horizontal_centered(|ui| {
         ui.add_space(6.0);
@@ -53,7 +65,6 @@ pub fn menu_bar(app: &mut EffectcraftApp, ui: &mut egui::Ui) {
                 // then happened somewhere else), and toggle the menu. Hovering another title
                 // switches to it once the pointer has moved: merely resting there must not take a
                 // keyboard-driven menu over.
-                let moved = ctx.input(|i| i.pointer.delta() != egui::Vec2::ZERO);
                 // With the button down elsewhere nothing is hovered, so the title under the
                 // pointer takes the highlight by hand: the hover-switch to it shows, one frame
                 // later like egui's own hover (the open title keeps its open look).

crates/ui-egui/tests/it/ui_menus.rs

@@ -418,3 +418,18 @@ fn a_resting_pointer_does_not_override_the_arrow_keys() {
     assert!(shown(&h, "Keyboard Shortcuts"), "Right opened Edit with the pointer still on File");
     assert!(!shown(&h, "Open Project"));
 }
+
+/// Leaving the window keeps the menu open, and coming back in over another title switches to it
+/// (#1290): egui reports no pointer movement for that first position.
+#[test]
+fn pointer_reentering_over_another_title_switches_menus() {
+    let mut h = harness();
+    let (file, edit) = (rect(&h, "menu.File"), rect(&h, "menu.Edit"));
+    click_at(&mut h, file.center());
+    h.input_mut().events.push(Event::PointerGone);
+    h.run_steps(2);
+    assert!(shown(&h, "Open Project"), "leaving the window kept File open");
+    move_to(&mut h, edit.center());
+    assert!(shown(&h, "Keyboard Shortcuts"), "coming back over Edit opened it");
+    assert!(!shown(&h, "Open Project"), "and closed File");
+}