message: Initialize mMouseTilePosition to invalid value
  This prevents highlighting of the map corner when a new map first loads,
  and before the mouse is positioned over the detail map.
diff: @@ -105,7 +105,7 @@ private:
  int mEdgeLength = 0;
  - MapCoordinate mMouseTilePosition{};
  + MapCoordinate mMouseTilePosition{{-1, -1}, 0};
  NAS2D::Point<int> mMousePixelPosition;
  NAS2D::Point<int> mOriginTilePosition; // Top tile of detail view diamond, or top left corner of minimap view box
  