anchor.diff:    }
   
     void _snapToPosition(SnappingPosition snappingPosition) {
  +    widget.onSnapStart?.call(_currentPosition, snappingPosition);
       _animateToPosition(snappingPosition);
       _lastSnappingPosition = snappingPosition;
     }
  
positive.code:     this.controller,
      this.onSheetMoved,
      this.onSnapCompleted,
    })  : assert(snappingPositions.isNotEmpty),
          super(key: key);
  
  
negative.code:   final Function(double position)? onSheetMoved;
    final Function(double position, SnappingPosition snappingPosition)?
        onSnapCompleted;
  
    /// This is called when a snapping animation starts
    final Function(double position, SnappingPosition snappingPosition)?
        onSnapStart;
  
    SnappingSheet({
      Key? key,
  