anchor.diff:      this.gestureDetectorBehavior,
       this.tightMode,
       this.filterQuality,
  +    this.disableGestures,
     })  : child = null,
           childSize = null,
           assert(imageProvider != null);
   
  -  PhotoViewGalleryPageOptions.customChild({
  +  PhotoViewGalleryPageOptions.customChild( {
       @required this.child,
       this.childSize,
       this.heroAttributes,
  
positive.code:             tightMode: pageOption.tightMode,
              filterQuality: pageOption.filterQuality,
              basePosition: pageOption.basePosition,
            );
  
      return ClipRect(
  
negative.code:     this.gestureDetectorBehavior,
      this.tightMode,
      this.filterQuality,
      this.disableGestures,
    })  : imageProvider = null,
          assert(child != null);
  
  