anchor.diff:          break;
       }
   
  +    _visibleArea = new Rect.fromLTRB(-offsetX / scaleX,
  +                                     -offsetY / scaleY,
  +                                     systemWidth + offsetX / scaleX,
  +                                     systemHeight + offsetY / scaleY);
  +
       _transformMatrix.translate(offsetX, offsetY);
       _transformMatrix.scale(scaleX, scaleY);
  -
  -    return _transformMatrix;
     }
   
     void _invalidateTransformMatrix() {
  +    _visibleArea = null;
       _transformMatrix = null;
       _rootNode._invalidateToBoxTransformMatrix();
     }
  
positive.code: 
    Rect _visibleArea;
  
    Rect get visibleArea => _visibleArea;
  
    // Setup
  
  
negative.code: 
      // Add new references
      _addSpriteBoxReference(_rootNode);
      markNeedsLayout();
    }
  
    // Tracking of frame rate and updates
  