anchor.diff:  
     Rect _visibleArea;
   
  -  Rect get visibleArea => _visibleArea;
  +  Rect get visibleArea {
  +    if (_visibleArea == null) _calcTransformMatrix();
  +    return _visibleArea;
  +  }
   
     // Setup
   
  
positive.code: 
      // Add new references
      _addSpriteBoxReference(_rootNode);
    }
  
    // Tracking of frame rate and updates
  
negative.code:   ///     var matrix = mySpriteBox.transformMatrix;
    Matrix4 get transformMatrix {
      // Get cached matrix if available
      if (_transformMatrix == null) {
        _calcTransformMatrix();
      }
      return _transformMatrix;
    }
  
    void _calcTransformMatrix() {
      _transformMatrix = new Matrix4.identity();
  
      // Calculate matrix
  