Method _handleFocusOut

src/cdk/listbox/listbox.ts:828–840

* Called when the focus leaves an element in the listbox. * @param event The focusout event

(event: FocusEvent)

   * @param event The focusout event
   */
  protected _handleFocusOut(event: FocusEvent) {
    // Some browsers (e.g. Chrome and Firefox) trigger the focusout event when the user returns back to the document.
    // To prevent losing the active option in this case, we store it in `_previousActiveOption` and restore it on the window `blur` event
    // This ensures that the `activeItem` matches the actual focused element when the user returns to the document.
    this._previousActiveOption = this.listKeyManager.activeItem;

    const otherElement = event.relatedTarget as Element;
    if (this.element !== otherElement && !this.element.contains(otherElement)) {
      this._onTouched();
      this._hasFocus = false;
      this._setNextFocusToSelectedOption();
    }
  }

  /** Get the id of the active option if active descendant is being used. */
  protected _getAriaActiveDescendant(): string | null | undefined {