scrollUp method

Implementation

@override
void scrollUp(int pixels) {
  MenuViewState? view = findListenerOfExactType(MenuViewState);
  if (view == null) return;

  // already at top
  if (view.controller.offset == 0) return;

  var to = view.controller.offset - pixels;
  to = (to < 0) ? 0 : to;

  view.controller.jumpTo(to);
}