anchor.diff:    bool get _isAtSnapSize {
       return extent.snapSizes.any(
         (double snapSize) {
  -        return (extent.currentExtent - snapSize).abs() <= extent.pixelsToExtent(physics.tolerance.distance);
  +        return (extent.currentSize - snapSize).abs() <= extent.pixelsToSize(physics.tolerance.distance);
         },
       );
     }
  
positive.code:       builder: (BuildContext context, BoxConstraints constraints) {
          _extent.availablePixels = widget.maxChildSize * constraints.biggest.height;
          final Widget sheet = FractionallySizedBox(
            heightFactor: _extent.currentExtent,
            alignment: Alignment.bottomCenter,
            child: widget.builder(context, _scrollController),
          );
  
negative.code:   void initState() {
      super.initState();
      _extent = _DraggableSheetExtent(
        minSize: widget.minChildSize,
        maxSize: widget.maxChildSize,
        snap: widget.snap,
        snapSizes: _impliedSnapSizes(),
        initialSize: widget.initialChildSize,
        onSizeChanged: _setSize,
      );
      _scrollController = _DraggableScrollableSheetScrollController(extent: _extent);
    }
  