Method focusFirstItem

src/material/menu/menu.ts:397–419

* Focus the first item in the menu. * @param origin Action from which the focus originated. Used to set the correct styling.

(origin: FocusOrigin = 'program')

   * @param origin Action from which the focus originated. Used to set the correct styling.
   */
  focusFirstItem(origin: FocusOrigin = 'program'): void {
    // Wait for `afterNextRender` to ensure iOS VoiceOver screen reader focuses the first item (#24735).
    this._firstItemFocusRef?.destroy();
    this._firstItemFocusRef = afterNextRender(
      () => {
        const menuPanel = this._resolvePanel();

        // If an item in the menuPanel is already focused, avoid overriding the focus.
        if (!menuPanel || !menuPanel.contains(document.activeElement)) {
          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 menuPanel panel so keyboard events like Escape still work. Also this will
          // give _some_ feedback to screen readers.
          if (!manager.activeItem && menuPanel) {
            menuPanel.focus();
          }
        }
      },
      {injector: this._injector},
    );
  }

  /**
   * Resets the active item in the menu. This is used when the menu is opened, allowing