anchor.diff:    /// @param name
     /// @param this.program
     /// @param unis
  -  Scene(String name, this.program, [List<UniformGroup> unis = null])
  +  Scene(String name, this.program, [List<UniformGroup> unis])
         : uniforms = unis == null ? <UniformGroup>[] : unis,
           super(name);
   
     void add(Node n) {
  -    assert( n != null);
  +    assert(n != null);
       nodes.add(n);
     }
   
  -   void remove(Node n) {
  +  void remove(Node n) {
       nodes.remove(n);
     }
   
  -   void removeAll() {
  +  void removeAll() {
       nodes.clear();
  -   }
  +  }
   }
   
   void drawRecursively(RenderProgram prog, Node node, final VM.Matrix4 parent,
  
positive.code:   int viewPortW = 0;
    int viewPortH = 0;
  
    RenderPhase(String name, this._cgl, [this._framebuffer = null])
        : super(name) {
      if (_framebuffer == null) _framebuffer = new Framebuffer.Screen(_cgl);
    }
  
  
negative.code:   }
  
    void add(Scene s) {
      assert(s != null);
      _scenes.add(s);
    }
  
    void Draw([List<DrawStats> stats]) {
      _framebuffer.Activate(
          _clear_mode, viewPortX, viewPortY, viewPortW, viewPortH);
  
  