anchor.diff:    destroy(SvgSvgElement svg, SvgPanZoom spz);
   }
   
  -enum State {
  -  NONE, PAN
  -}
  +enum State { NONE, PAN }
   
   class SvgPanZoom {
     final SvgSvgElement _svg;
  
positive.code:       controlsEnabled = true;
      }
    }
  
  
    /// Unbind mouse events and free callbacks.
    destroy() {
  
negative.code:   /// Does not center image.
    void fit() {
      Rectangle viewBox = _viewport.viewBox;
      var newScale = math.min(_width / (viewBox.width - viewBox.left),
          _height / (viewBox.height - viewBox.top));
  
      _zoom(newScale, true);
    }
  