fix(material/menu): focus the first item when opening menu on iOS VoiceOver

When opening the menu using the iOS VoiceOver screen reader, focus the first item in the menu.
Previously, the first menu item would focus on other screen readers like desktop VoiceOver but
not with iOS VoiceOver.

Waiting until `onStable` seems to fix this.

Fixes #24735

Author: zarend

src/material-experimental/mdc-menu/menu.spec.ts

@@ -1151,6 +1151,7 @@ describe('MDC-based MatMenu', () => {
     fixture.detectChanges();
 
     fixture.componentInstance.trigger.menuOpened.subscribe(() => {
+      flush();
       (document.querySelectorAll('.mat-mdc-menu-panel [mat-menu-item]')[3] as HTMLElement).focus();
     });
     fixture.componentInstance.trigger.openMenu();

src/material/menu/menu.spec.ts

@@ -1147,6 +1147,7 @@ describe('MatMenu', () => {
     fixture.detectChanges();
 
     fixture.componentInstance.trigger.menuOpened.subscribe(() => {
+      flush();
       (document.querySelectorAll('.mat-menu-panel [mat-menu-item]')[3] as HTMLElement).focus();
     });
     fixture.componentInstance.trigger.openMenu();

src/material/menu/menu.ts

@@ -391,42 +391,32 @@ export class _MatMenuBase
    * @param origin Action from which the focus originated. Used to set the correct styling.
    */
   focusFirstItem(origin: FocusOrigin = 'program'): void {
-    // When the content is rendered lazily, it takes a bit before the items are inside the DOM.
-    if (this.lazyContent) {
-      this._ngZone.onStable.pipe(take(1)).subscribe(() => this._focusFirstItem(origin));
-    } else {
-      this._focusFirstItem(origin);
-    }
-  }
-
-  /**
-   * Actual implementation that focuses the first item. Needs to be separated
-   * out so we don't repeat the same logic in the public `focusFirstItem` method.
-   */
-  private _focusFirstItem(origin: FocusOrigin) {
-    const manager = this._keyManager;
+    // Wait for `onStable` to ensure iOS VoiceOver screen reader focuses the first item (#24735).
+    this._ngZone.onStable.pipe(take(1)).subscribe(() => {
+      const manager = this._keyManager;
 
-    manager.setFocusOrigin(origin).setFirstItemActive();
-
-    // If there's no active item at this point, it means that all the items are disabled.
-    // Move focus to the menu panel so keyboard events like Escape still work. Also this will
-    // give _some_ feedback to screen readers.
-    if (!manager.activeItem && this._directDescendantItems.length) {
-      let element = this._directDescendantItems.first!._getHostElement().parentElement;
-
-      // Because the `mat-menu` is at the DOM insertion point, not inside the overlay, we don't
-      // have a nice way of getting a hold of the menu panel. We can't use a `ViewChild` either
-      // because the panel is inside an `ng-template`. We work around it by starting from one of
-      // the items and walking up the DOM.
-      while (element) {
-        if (element.getAttribute('role') === 'menu') {
-          element.focus();
-          break;
-        } else {
-          element = element.parentElement;
+      manager.setFocusOrigin(origin).setFirstItemActive();
+
+      // If there's no active item at this point, it means that all the items are disabled.
+      // Move focus to the menu panel so keyboard events like Escape still work. Also this will
+      // give _some_ feedback to screen readers.
+      if (!manager.activeItem && this._directDescendantItems.length) {
+        let element = this._directDescendantItems.first!._getHostElement().parentElement;
+
+        // Because the `mat-menu` is at the DOM insertion point, not inside the overlay, we don't
+        // have a nice way of getting a hold of the menu panel. We can't use a `ViewChild` either
+        // because the panel is inside an `ng-template`. We work around it by starting from one of
+        // the items and walking up the DOM.
+        while (element) {
+          if (element.getAttribute('role') === 'menu') {
+            element.focus();
+            break;
+          } else {
+            element = element.parentElement;
+          }
         }
       }
-    }
+    });
   }
 
   /**