anchor.diff:    /// Mirror to [PhotoView.enableRotation]
     final bool enableRotation;
   
  +  /// An index of the [PageView] inside [PhotoViewGallery]
  +  final int defaultPageIndex;
  +
     @override
     State<StatefulWidget> createState() {
       return _PhotoViewGalleryState();
  
positive.code:     this.onPageChanged,
      this.scaleStateChangedCallback,
      this.enableRotation = false,
    }) : super(key: key);
  
    /// A list of options to describe the items in the gallery
  
negative.code:     _controller = widget.pageController ?? PageController();
      _locked = false;
      super.initState();
      WidgetsBinding.instance.addPostFrameCallback((_) => _controller.jumpToPage(widget.defaultPageIndex) );
    }
  
    void scaleStateChangedCallback(PhotoViewScaleState scaleState) {
  