userScrollDirection property

The direction in which the user is attempting to scroll, relative to the axisDirection and growthDirection.

For example, if growthDirection is GrowthDirection.reverse and axisDirection is AxisDirection.down, then a ScrollDirection.forward means that the user is scrolling up, in the positive scrollOffset direction.

If the user is not scrolling, this will return ScrollDirection.idle even if there is (for example) a ScrollActivity currently animating the position.

This is used by some slivers to determine how to react to a change in scroll offset. For example, RenderSliverFloatingPersistentHeader will only expand a floating app bar when the userScrollDirection is in the positive scroll offset direction.