getting scroll position such as top or bottom with RectGetter

[pishguy]

with RectGetter widget we can detect visible items into ListView, for example:

List<int> getVisible() {
  var rect = RectGetter.getRectFromKey(listViewKey);
  var _items = <int>[];
  _keys.forEach((index, key) {
    var itemRect = RectGetter.getRectFromKey(key);
    if (itemRect != null && !(itemRect.top > rect.bottom || itemRect.bottom < rect.top)) _items.add(index);
  });

  return _items;
}

in this code i want to detect ListView scroll position achieve on top of list or bottom of list, maybe you guess this issue can be solve with ScrollController, but i check that and that have a bit problem and i can't resolve with that

now how can i get scroll position such as top or bottom with RectGetter?