readMapData method
Reads data for an area defined by the tile in the upper left and the tile in the lower right corner. Precondition: upperLeft.tileX <= lowerRight.tileX && upperLeft.tileY <= lowerRight.tileY
@param upperLeft tile that defines the upper left corner of the requested area. @param lowerRight tile that defines the lower right corner of the requested area. @return map data for the tile.
Implementation
@override
Future<DatastoreReadResult> readMapData(Tile upperLeft, Tile lowerRight) async {
await _lateOpen();
return _readMapDataComplete(upperLeft, lowerRight, MapfileSelector.ALL);
}