anchor.diff:    double _scaleX = 1.0;
     double _scaleY = 1.0;
   
  +  double _skewX = 0.0;
  +  double _skewY = 0.0;
  +
     /// The visibility of this node and its children.
     bool visible = true;
   
  
positive.code:   void set position(Point position) {
      assert(position != null);
      _position = position;
      invalidateTransformMatrix();
    }
  
  
negative.code:                0.0, 0.0, 1.0, 0.0,
                _position.x, _position.y, 0.0, 1.0);
  
      if (_skewX != 0.0 || _skewY != 0.0) {
        // Needs skew transform
        Matrix4 skew = new Matrix4(1.0, math.tan(radians(_skewX)), 0.0, 0.0,
                                   math.tan(radians(_skewY)), 1.0, 0.0, 0.0,
                                   0.0, 0.0, 1.0, 0.0,
                                   0.0, 0.0, 0.0, 1.0);
        matrix.multiply(skew);
      }
  
      return matrix;
    }
  
  