anchor.diff:    @override
     void initState() {
       controller = PhotoViewController();
  +    controller
  +      ..scale = defScale
  +      ..scaleState = PhotoViewScaleState.zooming;
       // TODO: implement initState
       super.initState();
     }
  
positive.code:   _ControllerExampleState createState() => _ControllerExampleState();
  }
  
  double min = pi * -2;
  double max = pi * 2;
  
  class _ControllerExampleState extends State<ControllerExample> {
    PhotoViewController controller;
  
negative.code:           )),
      );
    }
  
    Widget _streamBuild(BuildContext context, AsyncSnapshot snapshot) {
      if (snapshot.hasError || !snapshot.hasData) {
        return Container();
      }
      final PhotoViewControllerValue value = snapshot.data;
      return Column(
        children: <Widget>[
          Text(
            "Rotation ${value.rotation}",
            style: TextStyle(color: Colors.white),
          ),
          SliderTheme(
              data: SliderTheme.of(context).copyWith(
                  activeTrackColor: Colors.orange, thumbColor: Colors.orange),
              child: Slider(
                  value: value.rotation.clamp(min, max),
                  min: min,
                  max: max,
                  onChanged: (double newRotation) {
                    controller.rotation = newRotation;
                    controller.scaleState = PhotoViewScaleState.zooming;
                  })),
          Text(
            "Scale ${value.scale}",
            style: TextStyle(color: Colors.white),
          ),
          SliderTheme(
              data: SliderTheme.of(context).copyWith(
                  activeTrackColor: Colors.orange, thumbColor: Colors.orange),
              child: Slider(
                  value: value.scale.clamp(minScale, maxScale),
                  min: minScale,
                  max: maxScale,
                  onChanged: (double newScale) {
                    controller.scale = newScale;
                    controller.scaleState = PhotoViewScaleState.zooming;
                  })),
        ],
      );
    }
  }
  