Historical map overlay with MapBox in Flutter

home_page.dart

 return SafeArea(
      child: Scaffold(
        body: Stack(
          children: [
            FlutterMap(
              ...
            ),
            Positioned(
              top: 0,
              right: 0,
              child: Container(height: 60.0, width: 60.0, child: _openPopupMenu()),
            ),
          ],
        ),
      ),
    );
  }