protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
        {
            if (this != Keyboard.FocusedElement)
            {
                base.OnGotKeyboardFocus(e);
                return;
            }

            // If there is no other child element getting focused as the focus
            // returned to the main window, then we need to explicitly set the
            // focus back onto the text canvas (or the start-up page, whichever
            // is currently on top).
            if (null != textEditorControl)
            {
                textEditorControl.SetFocusOnForegroundContent();
            }
        }