anchor.diff:    //final VM.Matrix4 _pMatrix = new VM.Matrix4.identity();
     bool clearColorBuffer = true;
     bool clearDepthBuffer = true;
  +  int viewPortX = 0;
  +  int viewPortY = 0;
     List<DrawStats> stats = null;
     final Camera _camera;
     final Perspective _perspective;
  
positive.code:     }
    }
  
    void _UpdatePerspective() {
      VM.setPerspectiveMatrix(
          _mat, fov * Math.PI / 180.0, width / height, near, far);
      //m.setFrom(_mat);
  
negative.code:     _lastFov_ = fov;
      //LogInfo(
      //    "New perspective: ${perspar.width} ${perspar.height} ${perspar.fov}");
      UpdatePerspective();
    }
  
    void Adjust(HTML.CanvasElement canvas) {
  