fix(aria/menu): add expansion delay

src/aria/menu/menu.spec.ts

@@ -18,8 +18,9 @@ describe('Standalone Menu Pattern', () => {
     fixture.detectChanges();
   };
 
-  const mouseover = (element: Element) => {
+  const mouseover = async (element: Element) => {
     element.dispatchEvent(new MouseEvent('mouseover', {bubbles: true}));
+    await new Promise(resolve => setTimeout(resolve, 0));
     fixture.detectChanges();
   };
 
@@ -309,9 +310,9 @@ describe('Standalone Menu Pattern', () => {
       expect(document.activeElement).toBe(berries);
     });
 
-    it('should open submenu on mouseover', () => {
+    it('should open submenu on mouseover', async () => {
       const berries = getItem('Berries');
-      mouseover(berries!);
+      await mouseover(berries!);
       expect(isSubmenuExpanded()).toBe(true);
     });
 
@@ -385,11 +386,11 @@ describe('Standalone Menu Pattern', () => {
       externalElement.remove();
     });
 
-    it('should close an unfocused submenu on mouse out', () => {
+    it('should close an unfocused submenu on mouse out', async () => {
       const berries = getItem('Berries');
       const submenu = getSubmenu();
 
-      mouseover(berries!);
+      await mouseover(berries!);
       expect(isSubmenuExpanded()).toBe(true);
 
       mouseout(berries!);
@@ -398,11 +399,11 @@ describe('Standalone Menu Pattern', () => {
       expect(isSubmenuExpanded()).toBe(false);
     });
 
-    it('should not close an unfocused submenu on mouse out if the parent menu is hovered', () => {
+    it('should not close an unfocused submenu on mouse out if the parent menu is hovered', async () => {
       const berries = getItem('Berries');
       const submenu = getSubmenu();
 
-      mouseover(berries!);
+      await mouseover(berries!);
       expect(isSubmenuExpanded()).toBe(true);
 
       mouseout(berries!);
@@ -944,12 +945,12 @@ describe('Menu Bar Pattern', () => {
 
 @Component({
   template: `
-<div ngMenu (onSelect)="onSelect($event)">
+<div ngMenu [expansionDelay]="0" (onSelect)="onSelect($event)">
   <div ngMenuItem value='Apple' searchTerm='Apple'>Apple</div>
   <div ngMenuItem value='Banana' searchTerm='Banana'>Banana</div>
   <div ngMenuItem value='Berries' searchTerm='Berries' [submenu]="berriesMenu">Berries</div>
 
-  <div ngMenu #berriesMenu="ngMenu">
+  <div ngMenu [expansionDelay]="0" #berriesMenu="ngMenu">
     <div ngMenuItem value='Blueberry' searchTerm='Blueberry'>Blueberry</div>
     <div ngMenuItem value='Blackberry' searchTerm='Blackberry'>Blackberry</div>
     <div ngMenuItem value='Strawberry' searchTerm='Strawberry'>Strawberry</div>
@@ -968,12 +969,12 @@ class StandaloneMenuExample {
   template: `
 <button ngMenuTrigger [menu]="menu">Open menu</button>
 
-<div ngMenu #menu="ngMenu">
+<div ngMenu [expansionDelay]="0" #menu="ngMenu">
   <div ngMenuItem value='Apple' searchTerm='Apple'>Apple</div>
   <div ngMenuItem value='Banana' searchTerm='Banana'>Banana</div>
   <div ngMenuItem value='Berries' searchTerm='Berries' [submenu]="berriesMenu">Berries</div>
 
-  <div ngMenu #berriesMenu="ngMenu">
+  <div ngMenu [expansionDelay]="0" #berriesMenu="ngMenu">
     <div ngMenuItem value='Blueberry' searchTerm='Blueberry'>Blueberry</div>
     <div ngMenuItem value='Blackberry' searchTerm='Blackberry'>Blackberry</div>
     <div ngMenuItem value='Strawberry' searchTerm='Strawberry'>Strawberry</div>
@@ -992,22 +993,22 @@ class MenuTriggerExample {}
   <div ngMenuItem value='File' searchTerm='File'>File</div>
   <div ngMenuItem value='Edit' searchTerm='Edit' [submenu]="editMenu">Edit</div>
 
-  <div ngMenu #editMenu="ngMenu">
+  <div ngMenu [expansionDelay]="0" #editMenu="ngMenu">
     <div ngMenuItem value='Undo' searchTerm='Undo'>Undo</div>
     <div ngMenuItem value='Redo' searchTerm='Redo'>Redo</div>
   </div>
 
   <div ngMenuItem [submenu]="viewMenu" value='View' searchTerm='View'>View</div>
 
-  <div ngMenu #viewMenu="ngMenu">
+  <div ngMenu [expansionDelay]="0" #viewMenu="ngMenu">
     <div ngMenuItem value='Zoom In' searchTerm='Zoom In'>Zoom In</div>
     <div ngMenuItem value='Zoom Out' searchTerm='Zoom Out'>Zoom Out</div>
     <div ngMenuItem value='Full Screen' searchTerm='Full Screen'>Full Screen</div>
   </div>
 
   <div ngMenuItem [submenu]="helpMenu" value='Help' searchTerm='Help'>Help</div>
 
-  <div ngMenu #helpMenu="ngMenu">
+  <div ngMenu [expansionDelay]="0" #helpMenu="ngMenu">
     <div ngMenuItem value='Documentation' searchTerm='Documentation'>Documentation</div>
     <div ngMenuItem value='About' searchTerm='About'>About</div>
   </div>

src/aria/menu/menu.ts

@@ -176,6 +176,9 @@ export class Menu<V> {
   /** A callback function triggered when a menu item is selected. */
   onSelect = output<V>();
 
+  /** The delay in milliseconds before expanding sub-menus on hover. */
+  readonly expansionDelay = input<number>(150); // Arbitrarily chosen.
+
   constructor() {
     this._pattern = new MenuPattern({
       ...this,
@@ -214,7 +217,7 @@ export class Menu<V> {
 
     afterRenderEffect(() => {
       if (!this._pattern.hasBeenFocused()) {
-        this._pattern.setDefaultState();
+        untracked(() => this._pattern.setDefaultState());
       }
     });
   }

src/aria/private/menu/menu.spec.ts

@@ -105,6 +105,7 @@ function getMenuPattern(
     orientation: signal('vertical'),
     selectionMode: signal('explicit'),
     element: signal(document.createElement('div')),
+    expansionDelay: signal(0),
   });
 
   items.set(
@@ -347,9 +348,10 @@ describe('Standalone Menu Pattern', () => {
       expect(submenu.isVisible()).toBe(false);
     });
 
-    it('should open submenu on mouseover', () => {
+    it('should open submenu on mouseover', async () => {
       const menuItem = menu.inputs.items()[0];
       menu.onMouseOver({target: menuItem.element()} as unknown as MouseEvent);
+      await new Promise(resolve => setTimeout(resolve, 0));
       expect(submenu.isVisible()).toBe(true);
     });
 
@@ -385,29 +387,34 @@ describe('Standalone Menu Pattern', () => {
       expect(submenu.isVisible()).toBe(false);
     });
 
-    it('should close a submenu on focus out', () => {
+    it('should close a submenu on focus out', async () => {
       const parentMenuItem = menu.inputs.items()[0];
       menu.onMouseOver({target: parentMenuItem.element()} as unknown as MouseEvent);
+      await new Promise(resolve => setTimeout(resolve, 0));
       expect(submenu.isVisible()).toBe(true);
       expect(submenu.isFocused()).toBe(false);
 
       submenu.onFocusOut(new FocusEvent('focusout', {relatedTarget: document.body}));
       expect(submenu.isVisible()).toBe(false);
     });
 
-    it('should close an unfocused submenu on mouse out', () => {
+    it('should close an unfocused submenu on mouse out', async () => {
       menu.onMouseOver({target: menu.inputs.items()[0].element()} as unknown as MouseEvent);
+      await new Promise(resolve => setTimeout(resolve, 0));
       expect(submenu.isVisible()).toBe(true);
 
       submenu.onMouseOut({relatedTarget: document.body} as unknown as MouseEvent);
+      await new Promise(resolve => setTimeout(resolve, 0));
       expect(submenu.isVisible()).toBe(false);
     });
 
-    it('should not close an unfocused submenu on mouse out if the parent menu is hovered', () => {
+    it('should not close an unfocused submenu on mouse out if the parent menu is hovered', async () => {
       const parentMenuItem = menu.inputs.items()[0];
       menu.onMouseOver({target: parentMenuItem.element()} as unknown as MouseEvent);
+      await new Promise(resolve => setTimeout(resolve, 0));
       expect(submenu.isVisible()).toBe(true);
       submenu.onMouseOut({relatedTarget: parentMenuItem.element()} as unknown as MouseEvent);
+      await new Promise(resolve => setTimeout(resolve, 0));
       expect(submenu.isVisible()).toBe(true);
     });
   });

src/aria/private/menu/menu.ts

@@ -40,6 +40,9 @@ export interface MenuInputs<V>
 
   /** The text direction of the menu bar. */
   textDirection: SignalLike<'ltr' | 'rtl'>;
+
+  /** The delay in milliseconds before expanding sub-menus on hover. */
+  expansionDelay: SignalLike<number>;
 }
 
 /** The inputs for the MenuTriggerPattern class. */
@@ -83,6 +86,12 @@ export class MenuPattern<V> {
   /** Whether the menu has received focus. */
   hasBeenFocused = signal(false);
 
+  /** Timeout used to open sub-menus on hover. */
+  _openTimeout: any;
+
+  /** Timeout used to close sub-menus on hover out. */
+  _closeTimeout: any;
+
   /** Whether the menu should be focused on mouse over. */
   shouldFocus = computed(() => {
     const root = this.root();
@@ -185,23 +194,55 @@ export class MenuPattern<V> {
       return;
     }
 
+    const parent = this.inputs.parent();
     const activeItem = this?.inputs.activeItem();
 
+    if (parent instanceof MenuItemPattern) {
+      const grandparent = parent.inputs.parent();
+      if (grandparent instanceof MenuPattern) {
+        grandparent._clearTimeouts();
+        grandparent.listBehavior.goto(parent, {focusElement: false});
+      }
+    }
+
     if (activeItem && activeItem !== item) {
-      activeItem.close();
+      this._closeItem(activeItem);
     }
 
-    if (item.expanded() && item.submenu()?.inputs.activeItem()) {
-      item.submenu()?.inputs.activeItem()?.close();
-      item.submenu()?.listBehavior.unfocus();
+    if (item.expanded()) {
+      this._clearCloseTimeout();
     }
 
-    item.open();
+    this._openItem(item);
     this.listBehavior.goto(item, {focusElement: this.shouldFocus()});
   }
 
+  /** Closes the specified menu item after a delay. */
+  private _closeItem(item: MenuItemPattern<V>) {
+    this._clearOpenTimeout();
+
+    if (!this._closeTimeout) {
+      this._closeTimeout = setTimeout(() => {
+        item.close();
+        this._closeTimeout = undefined;
+      }, this.inputs.expansionDelay());
+    }
+  }
+
+  /** Opens the specified menu item after a delay. */
+  private _openItem(item: MenuItemPattern<V>) {
+    this._clearOpenTimeout();
+
+    this._openTimeout = setTimeout(() => {
+      item.open();
+      this._openTimeout = undefined;
+    }, this.inputs.expansionDelay());
+  }
+
   /** Handles mouseout events for the menu. */
   onMouseOut(event: MouseEvent) {
+    this._clearOpenTimeout();
+
     if (this.isFocused()) {
       return;
     }
@@ -370,6 +411,28 @@ export class MenuPattern<V> {
       root.inputs.activeItem()?.close({refocus: true});
     }
   }
+
+  /** Clears any open or close timeouts for sub-menus. */
+  _clearTimeouts() {
+    this._clearOpenTimeout();
+    this._clearCloseTimeout();
+  }
+
+  /** Clears the open timeout. */
+  _clearOpenTimeout() {
+    if (this._openTimeout) {
+      clearTimeout(this._openTimeout);
+      this._openTimeout = undefined;
+    }
+  }
+
+  /** Clears the close timeout. */
+  _clearCloseTimeout() {
+    if (this._closeTimeout) {
+      clearTimeout(this._closeTimeout);
+      this._closeTimeout = undefined;
+    }
+  }
 }
 
 /** The menubar ui pattern class. */
@@ -685,6 +748,12 @@ export class MenuItemPattern<V> implements ListItem<V> {
       menuitem?._expanded.set(false);
       menuitem?.inputs.parent()?.listBehavior.unfocus();
       menuitems = menuitems.concat(menuitem?.submenu()?.inputs.items() ?? []);
+
+      const parent = menuitem?.inputs.parent();
+
+      if (parent instanceof MenuPattern) {
+        parent._clearTimeouts();
+      }
     }
   }
 }