Function CanRoadContinueIntoNextTile

src/town_cmd.cpp:1266–1300

* Checks if a town road can be continued into the next tile. * Road vehicle stations, bridges, and tunnels are fine, as long as they are facing the right direction. * * @param t The current town * @param tile The tile where the road would be built * @param road_dir The direction of the road * @return true if the road can be continued, else false */

 * @return true if the road can be continued, else false
 */
static bool CanRoadContinueIntoNextTile(const Town *t, const TileIndex tile, const DiagDirection road_dir)
{
	const TileIndexDiff delta = TileOffsByDiagDir(road_dir); // +1 tile in the direction of the road
	TileIndex next_tile = tile + delta; // The tile beyond which must be connectable to the target tile
	RoadBits rcmd = DiagDirToRoadBits(ReverseDiagDir(road_dir));
	RoadType rt = GetTownRoadType();

	/* Before we try anything, make sure the tile is on the map and not the void. */
	if (!IsValidTile(next_tile)) return false;

	/* If the next tile is a bridge or tunnel, allow if it's continuing in the same direction. */
	if (IsTileType(next_tile, MP_TUNNELBRIDGE)) {
		return GetTunnelBridgeTransportType(next_tile) == TRANSPORT_ROAD && GetTunnelBridgeDirection(next_tile) == road_dir;
	}

	/* If the next tile is a station, allow if it's a road station facing the proper direction. Otherwise return false. */
	if (IsTileType(next_tile, MP_STATION)) {
		/* If the next tile is a road station, allow if it can be entered by the new tunnel/bridge, otherwise disallow. */
		if (IsDriveThroughStopTile(next_tile)) return GetDriveThroughStopAxis(next_tile) == DiagDirToAxis(road_dir);
		if (IsBayRoadStopTile(next_tile)) return GetBayRoadStopDir(next_tile) == ReverseDiagDir(road_dir);
		return false;
	}

	/* If the next tile is a road depot, allow if it's facing the right way. */
	if (IsTileType(next_tile, MP_ROAD)) {
		return IsRoadDepot(next_tile) && GetRoadDepotDirection(next_tile) == ReverseDiagDir(road_dir);
	}

	/* If the next tile is a railroad track, check if towns are allowed to build level crossings.
	 * If level crossing are not allowed, reject the construction. Else allow DoCommand to determine if the rail track is buildable. */
	if (IsTileType(next_tile, MP_RAILWAY) && !_settings_game.economy.allow_town_level_crossings) return false;

	/* If a road tile can be built, the construction is allowed. */
	return Command<CMD_BUILD_ROAD>::Do({DoCommandFlag::Auto, DoCommandFlag::NoWater}, next_tile, rcmd, rt, DRD_NONE, t->index).Succeeded();
}

/**
 * Grows the town with a bridge.