FutureBuilder<List<House>>(
          future: fetchHouseList(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return CircularProgressIndicator();
            }

            if (snapshot.hasError) {
              return Icon(Icons.error);
            }

            final houses = snapshot.data;

            return Stack(
              children: houses
                  .map(
                    (house) => Positioned(
                      left: house.x,
                      top: house.y,
                      child: ContextMenuRegion(
                        ...
                      ),
                    ),
                  )
                  .toList(),
            );
          },
        )