anchor.diff:    /// target no longer triggers the auto scroll. This callback will be called
     /// in between each scroll.
     final VoidCallback? onScrollViewScrolled;
  -
  -  /// The velocity scalar per pixel over scroll.
  -  ///
  -  /// How the velocity scale with the over scroll distance. The auto scroll
  -  /// velocity = <distance of overscroll> * velocityScalar.
  -  final double velocityScalar;
   
     late Rect _dragTargetRelatedToScrollOrigin;
   
  
positive.code: ///
  /// The scroll velocity is controlled by the [velocityScalar]:
  ///
  /// velocity = <distance of overscroll> * [velocityScalar].
  class _EdgeDraggingAutoScroller {
    /// Creates a auto scroller that scrolls the [scrollable].
    _EdgeDraggingAutoScroller(this.scrollable, {this.onScrollViewScrolled, this.velocityScalar = _kDefaultAutoScrollVelocityScalar});
  
    // An eyeball value
    static const double _kDefaultAutoScrollVelocityScalar = 7;
  
negative.code:       _scrolling = false;
        return;
      }
      final Duration duration = Duration(milliseconds: (1000 / _kDefaultAutoScrollVelocityScalar).round());
      await scrollable.position.animateTo(
        newOffset,
        duration: duration,
  