Function CanFollowRoad

src/town_cmd.cpp:1751–1785

* Checks whether a road can be followed or is a dead end, that can not be extended to the next tile. * This only checks trivial but often cases. * @param tile Start tile for road. * @param dir Direction for road to follow or build. * @return true If road is or can be connected in the specified direction. */

 * @return true If road is or can be connected in the specified direction.
 */
static bool CanFollowRoad(TileIndex tile, DiagDirection dir, TownExpandModes modes)
{
	TileIndex target_tile = tile + TileOffsByDiagDir(dir);
	if (!IsValidTile(target_tile)) return false;
	if (HasTileWaterGround(target_tile)) return false;

	RoadBits target_rb = GetTownRoadBits(target_tile);
	if (TownAllowedToBuildRoads(modes)) {
		/* Check whether a road connection exists or can be build. */
		switch (GetTileType(target_tile)) {
			case MP_ROAD:
				return target_rb != ROAD_NONE;

			case MP_STATION:
				return IsDriveThroughStopTile(target_tile);

			case MP_TUNNELBRIDGE:
				return GetTunnelBridgeTransportType(target_tile) == TRANSPORT_ROAD;

			case MP_HOUSE:
			case MP_INDUSTRY:
			case MP_OBJECT:
				return false;

			default:
				/* Checked for void and water earlier */
				return true;
		}
	} else {
		/* Check whether a road connection already exists,
		 * and it leads somewhere else. */
		RoadBits back_rb = DiagDirToRoadBits(ReverseDiagDir(dir));
		return (target_rb & back_rb) != 0 && (target_rb & ~back_rb) != 0;
	}
}

/**
 * Try to grow a town at a given road tile.