Function GrowTownAtRoad

src/town_cmd.cpp:1793–1874

* Try to grow a town at a given road tile. * @param t The town to grow. * @param tile The road tile to try growing from. * @return true if we successfully expanded the town. */

 * @return true if we successfully expanded the town.
 */
static bool GrowTownAtRoad(Town *t, TileIndex tile, TownExpandModes modes)
{
	/* Special case.
	 * @see GrowTownInTile Check the else if
	 */
	DiagDirection target_dir = DIAGDIR_END; // The direction in which we want to extend the town

	assert(tile < Map::Size());

	/* Number of times to search.
	 * Better roads, 2X2 and 3X3 grid grow quite fast so we give
	 * them a little handicap. */
	int iterations;
	switch (t->layout) {
		case TL_BETTER_ROADS:
			iterations = 10 + t->cache.num_houses * 2 / 9;
			break;

		case TL_3X3_GRID:
		case TL_2X2_GRID:
			iterations = 10 + t->cache.num_houses * 1 / 9;
			break;

		default:
			iterations = 10 + t->cache.num_houses * 4 / 9;
			break;
	}

	do {
		RoadBits cur_rb = GetTownRoadBits(tile); // The RoadBits of the current tile

		/* Try to grow the town from this point */
		switch (GrowTownInTile(&tile, cur_rb, target_dir, t, modes)) {
			case TownGrowthResult::Succeed:
				return true;
			case TownGrowthResult::SearchStopped:
				iterations = 0;
				break;
			default:
				break;
		};

		/* Exclude the source position from the bitmask
		 * and return if no more road blocks available */
		if (IsValidDiagDirection(target_dir)) cur_rb &= ~DiagDirToRoadBits(ReverseDiagDir(target_dir));
		if (cur_rb == ROAD_NONE) return false;

		if (IsTileType(tile, MP_TUNNELBRIDGE)) {
			/* Only build in the direction away from the tunnel or bridge. */
			target_dir = ReverseDiagDir(GetTunnelBridgeDirection(tile));
		} else {
			/* Select a random bit from the blockmask, walk a step
			 * and continue the search from there. */
			do {
				if (cur_rb == ROAD_NONE) return false;
				RoadBits target_bits;
				do {
					target_dir = RandomDiagDir();