Menus: hover intent for submenus; panels occlude; flip left

Panels occlude the rows under them. A submenu without room on the
right opens on the left of its row. A submenu opens after the pointer
rests 150 ms; a row crossed toward an open submenu waits 300 ms.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/menus/tests/aim.rs

@@ -0,0 +1,167 @@
+//! Hover intent: delayed submenus, the aim triangle, flips, occlusion.
+
+use gpui::{
+    Bounds, Context, FocusHandle, IntoElement, Modifiers, MouseButton, ParentElement, Pixels,
+    Render, Styled, TestAppContext, VisualTestContext, Window, div, point, px, size,
+};
+
+use super::settle;
+use crate::{
+    menus::{ContextMenu, Menu, MenuItem, aim},
+    primitives::FocusScope,
+    theme::Theme,
+};
+
+/// A region whose context menu has two submenus and a plain row.
+struct Region {
+    root: FocusHandle,
+}
+
+impl Render for Region {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let insert = Menu::new()
+            .item(MenuItem::new("Row above"))
+            .item(MenuItem::new("Row below"))
+            .item(MenuItem::new("Column left"));
+        let delete = Menu::new()
+            .item(MenuItem::new("Delete row"))
+            .item(MenuItem::new("Delete column"));
+        let menu = Menu::new()
+            .item(MenuItem::submenu("Insert", insert))
+            .item(MenuItem::submenu("Delete", delete))
+            .item(MenuItem::new("Plain"));
+        FocusScope::new(&self.root).size_full().child(
+            ContextMenu::new("region", menu)
+                .size_full()
+                .child(div().size_full()),
+        )
+    }
+}
+
+/// A region in a window `width` wide, its menu opened at `x`.
+fn region(width: f32, x: f32, cx: &mut TestAppContext) -> &mut VisualTestContext {
+    cx.update(|cx| {
+        Theme::init(cx);
+        crate::forms::bind_keys(cx);
+    });
+    let (_, cx) = cx.add_window_view(|_, cx| Region {
+        root: cx.focus_handle(),
+    });
+    cx.simulate_resize(size(px(width), px(600.0)));
+    settle(cx);
+    let at = point(px(x), px(20.0));
+    cx.simulate_mouse_move(at, None, Modifiers::none());
+    cx.simulate_mouse_down(at, MouseButton::Right, Modifiers::none());
+    cx.simulate_mouse_up(at, MouseButton::Right, Modifiers::none());
+    settle(cx);
+    cx
+}
+
+fn bounds(name: &str, cx: &mut VisualTestContext) -> Option<Bounds<Pixels>> {
+    cx.debug_bounds(Box::leak(name.to_string().into_boxed_str()))
+}
+
+fn row(label: &str, cx: &mut VisualTestContext) -> Bounds<Pixels> {
+    bounds(&format!("menu-row-{label}"), cx).expect("the row is drawn")
+}
+
+fn shown(label: &str, cx: &mut VisualTestContext) -> bool {
+    bounds(&format!("menu-row-{label}"), cx).is_some()
+}
+
+fn move_to(at: gpui::Point<Pixels>, cx: &mut VisualTestContext) {
+    cx.simulate_mouse_move(at, None, Modifiers::none());
+    settle(cx);
+}
+
+fn wait(time: std::time::Duration, cx: &mut VisualTestContext) {
+    cx.executor().advance_clock(time);
+    settle(cx);
+}
+
+/// Opens Insert's submenu by resting on it.
+fn rest_on_insert(cx: &mut VisualTestContext) {
+    move_to(row("Insert", cx).center(), cx);
+    wait(aim::OPEN, cx);
+    assert!(shown("Row above", cx), "Insert's submenu opened");
+}
+
+#[gpui::test]
+fn a_submenu_opens_after_the_pointer_rests(cx: &mut TestAppContext) {
+    let cx = region(1000.0, 40.0, cx);
+    move_to(row("Insert", cx).center(), cx);
+    assert!(!shown("Row above", cx), "not yet");
+    wait(aim::OPEN, cx);
+    assert!(shown("Row above", cx));
+}
+
+#[gpui::test]
+fn aiming_at_the_submenu_holds_it_across_rows(cx: &mut TestAppContext) {
+    let cx = region(1000.0, 40.0, cx);
+    rest_on_insert(cx);
+    let delete = row("Delete", cx);
+    move_to(point(delete.right() - px(16.0), delete.center().y), cx);
+    assert!(
+        shown("Row above", cx),
+        "crossing Delete keeps Insert's submenu"
+    );
+    wait(aim::HOLD / 2, cx);
+    assert!(shown("Row above", cx));
+    move_to(row("Row below", cx).center(), cx);
+    wait(aim::HOLD, cx);
+    assert!(shown("Row above", cx), "the submenu was reached");
+    assert!(!shown("Delete row", cx));
+}
+
+#[gpui::test]
+fn resting_on_a_crossed_row_switches_after_the_hold(cx: &mut TestAppContext) {
+    let cx = region(1000.0, 40.0, cx);
+    rest_on_insert(cx);
+    let delete = row("Delete", cx);
+    move_to(point(delete.right() - px(16.0), delete.center().y), cx);
+    wait(aim::HOLD, cx);
+    assert!(shown("Delete row", cx), "Delete's submenu replaced it");
+    assert!(!shown("Row above", cx));
+}
+
+#[gpui::test]
+fn moving_away_from_the_submenu_switches_at_once(cx: &mut TestAppContext) {
+    let cx = region(1000.0, 40.0, cx);
+    rest_on_insert(cx);
+    let insert = row("Insert", cx).center();
+    move_to(point(insert.x, row("Delete", cx).center().y), cx);
+    assert!(!shown("Row above", cx), "straight down left Insert");
+    wait(aim::OPEN, cx);
+    assert!(shown("Delete row", cx));
+}
+
+#[gpui::test]
+fn a_submenu_without_room_on_the_right_opens_on_the_left(cx: &mut TestAppContext) {
+    let cx = region(800.0, 790.0, cx);
+    rest_on_insert(cx);
+    let parent = bounds("menu-panel-0", cx).expect("the menu");
+    let sub = bounds("menu-panel-1", cx).expect("the submenu");
+    // It meets the row's edge, as on the right, sliding in.
+    let edge = row("Insert", cx).left() + crate::motion::NUDGE;
+    assert!(sub.left() < parent.left(), "{sub:?} left of {parent:?}");
+    assert!(sub.right() <= edge, "{sub:?} leaves the rows of {parent:?}");
+}
+
+#[gpui::test]
+fn rows_under_a_submenu_take_no_hover(cx: &mut TestAppContext) {
+    let cx = region(320.0, 10.0, cx);
+    rest_on_insert(cx);
+    let (plain, sub) = (
+        row("Plain", cx),
+        bounds("menu-panel-1", cx).expect("submenu"),
+    );
+    assert!(sub.left() < plain.right(), "the submenu covers the menu");
+    let under = point((sub.left() + plain.right()) / 2.0, plain.center().y);
+    assert!(sub.contains(&under), "the point is on the submenu");
+    move_to(under, cx);
+    wait(aim::HOLD + aim::OPEN, cx);
+    assert!(
+        shown("Row above", cx),
+        "Plain under the submenu stayed unmarked"
+    );
+}