anchor.diff:  class LeaveBehindDemoState extends State<LeaveBehindDemo> {
     static final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
     DismissDirection _dismissDirection = DismissDirection.horizontal;
  +  bool _confirmDismiss = true;
     List<LeaveBehindItem> leaveBehindItems;
   
     void initListItems() {
  
positive.code:     @required this.onArchive,
      @required this.onDelete,
      @required this.dismissDirection,
    }) : super(key: key);
  
    final LeaveBehindItem item;
    final DismissDirection dismissDirection;
    final void Function(LeaveBehindItem) onArchive;
    final void Function(LeaveBehindItem) onDelete;
  
    void _handleArchive() {
      onArchive(item);
  
negative.code:                 checked: _dismissDirection == DismissDirection.startToEnd,
                  child: const Text('Only swipe right'),
                ),
                CheckedPopupMenuItem<LeaveBehindDemoAction>(
                  value: LeaveBehindDemoAction.confirmDismiss,
                  checked: _confirmDismiss,
                  child: const Text('Confirm dismiss'),
                ),
              ],
            ),
          ],
  