anchor.diff:        _startResizePerformance();
     }
   
  -  Point get _activeCardDragEndPoint {
  -    if (!_isActive)
  -      return Point.origin;
  -    assert(_size != null);
  -    double extent = _directionIsYAxis ? _size.height : _size.width;
  -    return new Point(_dragExtent.sign * extent * _kDismissCardThreshold, 0.0);
  -  }
  -
     bool get _isActive {
       return _size != null && (_dragUnderway || _fadePerformance.isAnimating);
     }
  
positive.code:         break;
      }
  
      if (oldDragExtent.sign != _dragExtent.sign)
        setState(() {}); // Rebuild to update the new drag endpoint.
      if (!_fadePerformance.isAnimating)
        _fadePerformance.progress = _dragExtent.abs() / (_size.width * _kDismissCardThreshold);
    }
  
negative.code:     if (!_isActive || _fadePerformance.isAnimating)
        return;
  
      setState(() {
        _dragUnderway = false;
        if (_fadePerformance.isCompleted) {
          _startResizePerformance();
        } else if (_isFlingGesture(velocity)) {
          double flingVelocity = _directionIsYAxis ? velocity.dy : velocity.dx;
          _dragExtent = flingVelocity.sign;
          _fadePerformance.fling(velocity: flingVelocity.abs() * _kFlingVelocityScale);
        } else {
          _fadePerformance.reverse();
        }
      });
    }
  
    void _handleSizeChanged(Size newSize) {
      setState(() {
        _size = new Size.copy(newSize);
      });
    }
  
    Point get _activeCardDragEndPoint {
      if (!_isActive)
        return Point.origin;
      assert(_size != null);
      double extent = _directionIsYAxis ? _size.height : _size.width;
      return new Point(_dragExtent.sign * extent * _kDismissCardThreshold, 0.0);
    }
  
    Widget build() {
  