anchor.diff:  
     double _xRadius;
     double get xRadius => _xRadius;
  -  void set xRadius (double value) {
  -    assert(value != null);
  -    if (_xRadius == value)
  -      return;
  -    _xRadius = value;
  +  void set xRadius (double newXRadius) {
  +    assert(newXRadius != null);
  +    if (_xRadius == newXRadius)
  +      return;
  +    _xRadius = newXRadius;
       markNeedsPaint();
     }
   
     double _yRadius;
     double get yRadius => _yRadius;
  -  void set yRadius (double value) {
  -    assert(value != null);
  -    if (_yRadius == value)
  -      return;
  -    _yRadius = value;
  +  void set yRadius (double newYRadius) {
  +    assert(newYRadius != null);
  +    if (_yRadius == newYRadius)
  +      return;
  +    _yRadius = newYRadius;
       markNeedsPaint();
     }
   
  
positive.code: 
    Matrix4 _transform;
  
    void set transform(Matrix4 value) {
      assert(value != null);
      if (_transform == value)
        return;
      _transform = new Matrix4.copy(value);
      markNeedsPaint();
    }
  
  
negative.code: 
    double _opacity;
    double get opacity => _opacity;
    void set opacity (double newOpacity) {
      assert(newOpacity != null);
      assert(newOpacity >= 0.0 && newOpacity <= 1.0);
      if (_opacity == newOpacity)
        return;
      _opacity = newOpacity;
      markNeedsPaint();
    }
  
  