Feature: Allow building depots by drag and drop and joining them if they have the same transport type.

src/dock_gui.cpp

@@ -167,7 +167,9 @@ struct BuildDocksToolbarWindow : Window {
 				break;
 
 			case WID_DT_DEPOT: // Build depot button
-				if (HandlePlacePushButton(this, WID_DT_DEPOT, SPR_CURSOR_SHIP_DEPOT, HT_RECT)) ShowBuildDocksDepotPicker(this);
+				if (HandlePlacePushButton(this, widget, SPR_CURSOR_SHIP_DEPOT, HT_RECT)) {
+					ShowBuildDocksDepotPicker(this);
+				}
 				break;
 
 			case WID_DT_STATION: // Build station button
@@ -207,9 +209,16 @@ struct BuildDocksToolbarWindow : Window {
 				PlaceProc_DemolishArea(tile);
 				break;
 
-			case WID_DT_DEPOT: // Build depot button
+			case WID_DT_DEPOT: { // Build depot button
-				Command<CMD_BUILD_SHIP_DEPOT>::Post(STR_ERROR_CAN_T_BUILD_SHIP_DEPOT, CcBuildDocks, tile, _ship_depot_direction);
+				CloseWindowById(WC_SELECT_DEPOT, VEH_SHIP);
+
+				ViewportPlaceMethod vpm = _ship_depot_direction != AXIS_X ? VPM_LIMITED_X_FIXED_Y : VPM_LIMITED_Y_FIXED_X;
+				VpSetPlaceSizingLimit(_settings_game.depot.depot_spread);
+				VpStartPlaceSizing(tile, vpm, DDSP_BUILD_DEPOT);
+				/* Select tiles now to prevent selection from flickering. */
+				VpSelectTilesWithMethod(pt.x, pt.y, vpm);
 				break;
+			}
 
 			case WID_DT_STATION: { // Build station button
 				/* Determine the watery part of the dock. */
@@ -263,6 +272,15 @@ struct BuildDocksToolbarWindow : Window {
 				case DDSP_CREATE_RIVER:
 					Command<CMD_BUILD_CANAL>::Post(STR_ERROR_CAN_T_PLACE_RIVERS, CcPlaySound_CONSTRUCTION_WATER, end_tile, start_tile, WATER_CLASS_RIVER, _ctrl_pressed);
 					break;
+				case DDSP_BUILD_DEPOT: {
+					bool adjacent = _ctrl_pressed;
+					auto proc = [=](DepotID join_to) -> bool {
+						return Command<CMD_BUILD_SHIP_DEPOT>::Post(STR_ERROR_CAN_T_BUILD_SHIP_DEPOT, CcBuildDocks, start_tile, _ship_depot_direction, adjacent, join_to, end_tile);
+					};
+
+					ShowSelectDepotIfNeeded(TileArea(start_tile, end_tile), proc, VEH_SHIP);
+					break;
+				}
 
 				default: break;
 			}
@@ -520,10 +538,13 @@ struct BuildDocksDepotWindow : public PickerWindowBase {
 private:
 	static void UpdateDocksDirection()
 	{
+		VpSetPlaceFixedSize(2);
 		if (_ship_depot_direction != AXIS_X) {
 			SetTileSelectSize(1, 2);
+			_thd.select_method = VPM_LIMITED_X_FIXED_Y;
 		} else {
 			SetTileSelectSize(2, 1);
+			_thd.select_method = VPM_LIMITED_Y_FIXED_X;
 		}
 	}
 
@@ -538,6 +559,7 @@ public:
 	void Close([[maybe_unused]] int data = 0) override
 	{
 		CloseWindowById(WC_SELECT_DEPOT, VEH_SHIP);
+		VpResetFixedSize();
 		this->PickerWindowBase::Close();
 	}
 

src/rail_cmd.cpp

@@ -952,22 +952,32 @@ CommandCost CmdRemoveRailroadTrack(DoCommandFlag flags, TileIndex end_tile, Tile
 /**
  * Build a train depot
  * @param flags operation to perform
- * @param tile position of the train depot
+ * @param tile first position of the train depot
  * @param railtype rail type
  * @param dir entrance direction
+ * @param adjacent allow adjacent depots
+ * @param join_to depot to join to
+ * @param end_tile end tile of the area to be built
  * @return the cost of this operation or an error
  *
  * @todo When checking for the tile slope,
  * distinguish between "Flat land required" and "land sloped in wrong direction"
  */
-CommandCost CmdBuildTrainDepot(DoCommandFlag flags, TileIndex tile, RailType railtype, DiagDirection dir)
+CommandCost CmdBuildTrainDepot(DoCommandFlag flags, TileIndex tile, RailType railtype, DiagDirection dir, bool adjacent, DepotID join_to, TileIndex end_tile)
 {
 	/* check railtype and valid direction for depot (0 through 3), 4 in total */
 	if (!ValParamRailType(railtype) || !IsValidDiagDirection(dir)) return CMD_ERROR;
 
-	Slope tileh = GetTileSlope(tile);
-
 	CommandCost cost(EXPENSES_CONSTRUCTION);
+	TileArea ta(tile, end_tile);
+	Depot *depot = nullptr;
+
+	/* Create a new depot or find a depot to join to. */
+	CommandCost ret = FindJoiningDepot(ta, VEH_TRAIN, join_to, depot, adjacent, flags);
+	if (ret.Failed()) return ret;
+
+	uint8_t num_new_depot_tiles = 0;
+	uint8_t num_rotated_depot_tiles = 0;
 
 	/* Prohibit construction if
 	 * The tile is non-flat AND
@@ -975,58 +985,59 @@ CommandCost CmdBuildTrainDepot(DoCommandFlag flags, TileIndex tile, RailType rai
 	 * 2) the tile is steep i.e. spans two height levels
 	 * 3) the exit points in the wrong direction
 	 */
+	for (Tile t : ta) {
+		if (IsBridgeAbove(t)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
 
-	if (tileh != SLOPE_FLAT) {
+		Slope tileh = GetTileSlope(t);
-		if (!_settings_game.construction.build_on_slopes || !CanBuildDepotByTileh(dir, tileh)) {
+		if (tileh != SLOPE_FLAT) {
-			return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+			if (!_settings_game.construction.build_on_slopes ||
+					!CanBuildDepotByTileh(dir, tileh)) {
+				return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+			}
+			cost.AddCost(_price[PR_BUILD_FOUNDATION]);
+		}
+
+		/* Check whether a depot tile exists and it needs to be rotated. */
+		if (IsRailDepotTile(t) && GetDepotIndex(t) == join_to && railtype == GetRailType(t)) {
+			if (dir == GetRailDepotDirection(t)) continue;
+
+			ret = EnsureNoVehicleOnGround(t);
+			if (ret.Failed()) return ret;
+
+			num_rotated_depot_tiles++;
+			if (flags & DC_EXEC) {
+				SetRailDepotExitDirection(t, dir);
+			}
+		} else {
+			cost.AddCost(Command<CMD_LANDSCAPE_CLEAR>::Do(flags, t));
+			if (cost.Failed()) return cost;
+
+			num_new_depot_tiles++;
+			if (flags & DC_EXEC) {
+				MakeRailDepot(t, _current_company, depot->index, dir, railtype);
+				MarkTileDirtyByTile(t);
+			}
+		}
+
+		if (flags & DC_EXEC) {
+			AddSideToSignalBuffer(t, INVALID_DIAGDIR, _current_company);
+			YapfNotifyTrackLayoutChange(t, DiagDirToDiagTrack(dir));
+			MarkTileDirtyByTile(t);
 		}
-		cost.AddCost(_price[PR_BUILD_FOUNDATION]);
 	}
 
-	/* Allow the user to rotate the depot instead of having to destroy it and build it again */
+	if (num_new_depot_tiles + num_rotated_depot_tiles == 0) return CommandCost();
-	bool rotate_existing_depot = false;
-	if (IsRailDepotTile(tile) && railtype == GetRailType(tile)) {
-		CommandCost ret = CheckTileOwnership(tile);
-		if (ret.Failed()) return ret;
 
-		if (dir == GetRailDepotDirection(tile)) return CommandCost();
+	cost.AddCost(_price[PR_BUILD_DEPOT_TRAIN] * (num_new_depot_tiles + num_rotated_depot_tiles));
-
+	cost.AddCost(RailBuildCost(railtype) * (num_new_depot_tiles + num_rotated_depot_tiles));
-		ret = EnsureNoVehicleOnGround(tile);
-		if (ret.Failed()) return ret;
-
-		rotate_existing_depot = true;
-	}
-
-	if (!rotate_existing_depot) {
-		cost.AddCost(Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile));
-		if (cost.Failed()) return cost;
-
-		if (IsBridgeAbove(tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
-
-		if (!Depot::CanAllocateItem()) return CMD_ERROR;
-	}
 
 	if (flags & DC_EXEC) {
-		if (rotate_existing_depot) {
+		Company::Get(_current_company)->infrastructure.rail[railtype] += num_new_depot_tiles;
-			SetRailDepotExitDirection(tile, dir);
+		DirtyCompanyInfrastructureWindows(_current_company);
-		} else {
+		depot->AfterAddRemove(ta, true);
-			Depot *d = new Depot(tile, VEH_TRAIN, _current_company);
+		if (join_to == NEW_DEPOT) MakeDefaultName(depot);
-			d->build_date = TimerGameCalendar::date;
-
-			MakeRailDepot(tile, _current_company, d->index, dir, railtype);
-			MakeDefaultName(d);
-
-			Company::Get(_current_company)->infrastructure.rail[railtype]++;
-			DirtyCompanyInfrastructureWindows(_current_company);
-		}
-
-		MarkTileDirtyByTile(tile);
-		AddSideToSignalBuffer(tile, INVALID_DIAGDIR, _current_company);
-		YapfNotifyTrackLayoutChange(tile, DiagDirToDiagTrack(dir));
 	}
 
-	cost.AddCost(_price[PR_BUILD_DEPOT_TRAIN]);
-	cost.AddCost(RailBuildCost(railtype));
 	return cost;
 }
 
@@ -1558,6 +1569,7 @@ CommandCost CmdConvertRail(DoCommandFlag flags, TileIndex tile, TileIndex area_s
 	if (area_start >= Map::Size()) return CMD_ERROR;
 
 	TrainList affected_trains;
+	std::vector<DepotID> affected_depots;
 
 	CommandCost cost(EXPENSES_CONSTRUCTION);
 	CommandCost error = CommandCost(STR_ERROR_NO_SUITABLE_RAILROAD_TRACK); // by default, there is no track to convert.
@@ -1653,11 +1665,11 @@ CommandCost CmdConvertRail(DoCommandFlag flags, TileIndex tile, TileIndex area_s
 							/* notify YAPF about the track layout change */
 							YapfNotifyTrackLayoutChange(tile, GetRailDepotTrack(tile));
 
-							/* Update build vehicle window related to this depot */
+							if (find(affected_depots.begin(), affected_depots.end(), (tile)) == affected_depots.end()) {
-							DepotID depot_id = GetDepotIndex(tile);
+								affected_depots.push_back(GetDepotIndex(tile));
-							InvalidateWindowData(WC_VEHICLE_DEPOT, depot_id);
+							}
-							InvalidateWindowData(WC_BUILD_VEHICLE, depot_id);
 						}
+
 						found_convertible_track = true;
 						cost.AddCost(RailConvertCost(type, totype));
 						break;
@@ -1755,6 +1767,13 @@ CommandCost CmdConvertRail(DoCommandFlag flags, TileIndex tile, TileIndex area_s
 	}
 
 	if (flags & DC_EXEC) {
+		/* Update affected depots. */
+		for (auto &depot_tile : affected_depots) {
+			Depot *dep = Depot::Get(depot_tile);
+			dep->RescanDepotTiles();
+			InvalidateWindowData(WC_VEHICLE_DEPOT, dep->index);
+		}
+
 		/* Railtype changed, update trains as when entering different track */
 		for (Train *v : affected_trains) {
 			v->ConsistChanged(CCF_TRACK);
@@ -1775,9 +1794,11 @@ static CommandCost RemoveTrainDepot(TileIndex tile, DoCommandFlag flags)
 	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
-		/* read variables before the depot is removed */
+		Depot *depot = Depot::GetByTile(tile);
+		Company *c = Company::GetIfValid(depot->owner);
+		assert(c != nullptr);
+
 		DiagDirection dir = GetRailDepotDirection(tile);
-		Owner owner = GetTileOwner(tile);
 		Train *v = nullptr;
 
 		if (HasDepotReservation(tile)) {
@@ -1785,14 +1806,17 @@ static CommandCost RemoveTrainDepot(TileIndex tile, DoCommandFlag flags)
 			if (v != nullptr) FreeTrainTrackReservation(v);
 		}
 
-		Company::Get(owner)->infrastructure.rail[GetRailType(tile)]--;
+		c->infrastructure.rail[GetRailType(tile)]--;
-		DirtyCompanyInfrastructureWindows(owner);
+		DirtyCompanyInfrastructureWindows(c->index);
 
-		delete Depot::GetByTile(tile);
 		DoClearSquare(tile);
-		AddSideToSignalBuffer(tile, dir, owner);
+
+		AddSideToSignalBuffer(tile, dir, c->index);
+
 		YapfNotifyTrackLayoutChange(tile, DiagDirToDiagTrack(dir));
 		if (v != nullptr) TryPathReserve(v, true);
+
+		depot->AfterAddRemove(TileArea(tile), false);
 	}
 
 	return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_DEPOT_TRAIN]);

src/rail_cmd.h

@@ -19,7 +19,7 @@ CommandCost CmdBuildRailroadTrack(DoCommandFlag flags, TileIndex end_tile, TileI
 CommandCost CmdRemoveRailroadTrack(DoCommandFlag flags, TileIndex end_tile, TileIndex start_tile, Track track);
 CommandCost CmdBuildSingleRail(DoCommandFlag flags, TileIndex tile, RailType railtype, Track track, bool auto_remove_signals);
 CommandCost CmdRemoveSingleRail(DoCommandFlag flags, TileIndex tile, Track track);
-CommandCost CmdBuildTrainDepot(DoCommandFlag flags, TileIndex tile, RailType railtype, DiagDirection dir);
+CommandCost CmdBuildTrainDepot(DoCommandFlag flags, TileIndex tile, RailType railtype, DiagDirection dir, bool adjacent, DepotID depot_id, TileIndex end_tile);
 CommandCost CmdBuildSingleSignal(DoCommandFlag flags, TileIndex tile, Track track, SignalType sigtype, SignalVariant sigvar, bool convert_signal, bool skip_existing_signals, bool ctrl_pressed, SignalType cycle_start, SignalType cycle_stop, uint8_t num_dir_cycle, uint8_t signals_copy);
 CommandCost CmdRemoveSingleSignal(DoCommandFlag flags, TileIndex tile, Track track);
 CommandCost CmdConvertRail(DoCommandFlag flags, TileIndex tile, TileIndex area_start, RailType totype, bool diagonal);
@@ -40,6 +40,6 @@ DEF_CMD_TRAIT(CMD_REMOVE_SIGNAL_TRACK,   CmdRemoveSignalTrack,   CMD_AUTO,
 CommandCallback CcPlaySound_CONSTRUCTION_RAIL;
 CommandCallback CcStation;
 CommandCallback CcBuildRailTunnel;
-void CcRailDepot(Commands cmd, const CommandCost &result, TileIndex tile, RailType rt, DiagDirection dir);
+void CcRailDepot(Commands cmd, const CommandCost &result, TileIndex tile, RailType rt, DiagDirection dir, bool adjacent, DepotID join_to, TileIndex end_tile);
 
 #endif /* RAIL_CMD_H */

src/rail_gui.cpp

@@ -117,7 +117,7 @@ static void GenericPlaceRail(TileIndex tile, Track track)
  */
 static void PlaceExtraDepotRail(TileIndex tile, DiagDirection dir, Track track)
 {
-	if (GetRailTileType(tile) == RAIL_TILE_DEPOT) return;
+	if (IsRailDepot(tile)) return;
 	if (GetRailTileType(tile) == RAIL_TILE_SIGNALS && !_settings_client.gui.auto_remove_signals) return;
 	if ((GetTrackBits(tile) & DiagdirReachesTracks(dir)) == 0) return;
 
@@ -138,24 +138,26 @@ static const DiagDirection _place_depot_extra_dir[12] = {
 	DIAGDIR_NW, DIAGDIR_NE, DIAGDIR_NW, DIAGDIR_NE,
 };
 
-void CcRailDepot(Commands, const CommandCost &result, TileIndex tile, RailType, DiagDirection dir)
+void CcRailDepot(Commands, const CommandCost &result, TileIndex start_tile, RailType, DiagDirection dir, bool, DepotID, TileIndex end_tile)
 {
 	if (result.Failed()) return;
 
-	if (_settings_client.sound.confirm) SndPlayTileFx(SND_20_CONSTRUCTION_RAIL, tile);
+	if (_settings_client.sound.confirm) SndPlayTileFx(SND_20_CONSTRUCTION_RAIL, start_tile);
 	if (!_settings_client.gui.persistent_buildingtools) ResetObjectToPlace();
 
-	tile += TileOffsByDiagDir(dir);
+	TileArea ta(start_tile, end_tile);
+	for (TileIndex t : ta) {
+		TileIndex tile = t + TileOffsByDiagDir(dir);
 
-	if (IsTileType(tile, MP_RAILWAY)) {
+		if (IsTileType(tile, MP_RAILWAY)) {
-		PlaceExtraDepotRail(tile, _place_depot_extra_dir[dir], _place_depot_extra_track[dir]);
+			PlaceExtraDepotRail(tile, _place_depot_extra_dir[dir], _place_depot_extra_track[dir]);
 
-		/* Don't place the rail straight out of the depot of there is another depot across from it. */
+			Tile double_depot_tile = tile + TileOffsByDiagDir(dir);
-		Tile double_depot_tile = tile + TileOffsByDiagDir(dir);
+			bool is_double_depot = IsValidTile(double_depot_tile) && IsRailDepotTile(double_depot_tile);
-		bool is_double_depot = IsValidTile(double_depot_tile) && IsRailDepotTile(double_depot_tile);
+			if (!is_double_depot) PlaceExtraDepotRail(tile, _place_depot_extra_dir[dir + 4], _place_depot_extra_track[dir + 4]);
-		if (!is_double_depot) PlaceExtraDepotRail(tile, _place_depot_extra_dir[dir + 4], _place_depot_extra_track[dir + 4]);
 
-		PlaceExtraDepotRail(tile, _place_depot_extra_dir[dir + 8], _place_depot_extra_track[dir + 8]);
+			PlaceExtraDepotRail(tile, _place_depot_extra_dir[dir + 8], _place_depot_extra_track[dir + 8]);
+		}
 	}
 }
 
@@ -690,9 +692,14 @@ struct BuildRailToolbarWindow : Window {
 				PlaceProc_DemolishArea(tile);
 				break;
 
-			case WID_RAT_BUILD_DEPOT:
+			case WID_RAT_BUILD_DEPOT: {
-				Command<CMD_BUILD_TRAIN_DEPOT>::Post(STR_ERROR_CAN_T_BUILD_TRAIN_DEPOT, CcRailDepot, tile, _cur_railtype, _build_depot_direction);
+				CloseWindowById(WC_SELECT_DEPOT, VEH_TRAIN);
+
+				ViewportPlaceMethod vpm = (DiagDirToAxis(_build_depot_direction) == 0) ? VPM_X_LIMITED : VPM_Y_LIMITED;
+				VpStartPlaceSizing(tile, vpm, DDSP_BUILD_DEPOT);
+				VpSetPlaceSizingLimit(_settings_game.depot.depot_spread);
 				break;
+			}
 
 			case WID_RAT_BUILD_WAYPOINT:
 				PlaceRail_Waypoint(tile);
@@ -788,6 +795,17 @@ struct BuildRailToolbarWindow : Window {
 						}
 					}
 					break;
+
+				case DDSP_BUILD_DEPOT: {
+					bool adjacent = _ctrl_pressed;
+
+					auto proc = [=](DepotID join_to) -> bool {
+						return Command<CMD_BUILD_TRAIN_DEPOT>::Post(STR_ERROR_CAN_T_BUILD_TRAIN_DEPOT, CcRailDepot, start_tile, _cur_railtype, _build_depot_direction, adjacent, join_to, end_tile);
+					};
+
+					ShowSelectDepotIfNeeded(TileArea(start_tile, end_tile), proc, VEH_TRAIN);
+					break;
+				}
 			}
 		}
 	}

src/road_cmd.cpp

@@ -1141,66 +1141,79 @@ std::tuple<CommandCost, Money> CmdRemoveLongRoad(DoCommandFlag flags, TileIndex
  * @param flags operation to perform
  * @param rt road type
  * @param dir entrance direction
+ * @param adjacent allow adjacent depots
+ * @param depot_id depot to join to
+ * @param end_tile end tile of the depot to be built
  * @return the cost of this operation or an error
  *
  * @todo When checking for the tile slope,
  * distinguish between "Flat land required" and "land sloped in wrong direction"
  */
-CommandCost CmdBuildRoadDepot(DoCommandFlag flags, TileIndex tile, RoadType rt, DiagDirection dir)
+CommandCost CmdBuildRoadDepot(DoCommandFlag flags, TileIndex tile, RoadType rt, DiagDirection dir, bool adjacent, DepotID join_to, TileIndex end_tile)
 {
 	if (!ValParamRoadType(rt) || !IsValidDiagDirection(dir)) return CMD_ERROR;
 
+	TileArea ta(tile, end_tile);
+	assert(ta.w == 1 || ta.h == 1);
+
+	/* Create a new depot or find a depot to join to. */
+	Depot *depot = nullptr;
+	CommandCost ret = FindJoiningDepot(ta, VEH_ROAD, join_to, depot, adjacent, flags);
+	if (ret.Failed()) return ret;
+
+	uint8_t num_new_depot_tiles = 0;
+	uint8_t num_rotated_depot_tiles = 0;
+
 	CommandCost cost(EXPENSES_CONSTRUCTION);
+	for (Tile t : ta) {
+		if (IsBridgeAbove(t)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
 
-	Slope tileh = GetTileSlope(tile);
+		Slope tileh = GetTileSlope(t);
-	if (tileh != SLOPE_FLAT) {
+		if (tileh != SLOPE_FLAT) {
-		if (!_settings_game.construction.build_on_slopes || !CanBuildDepotByTileh(dir, tileh)) {
+			if (!_settings_game.construction.build_on_slopes || !CanBuildDepotByTileh(dir, tileh)) {
-			return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+				return_cmd_error(STR_ERROR_FLAT_LAND_REQUIRED);
+			}
+			cost.AddCost(_price[PR_BUILD_FOUNDATION]);
+		}
+
+		/* Check whether a depot tile exists and it needs to be rotated. */
+		if (IsRoadDepotTile(t) &&
+				GetDepotIndex(t) == join_to &&
+				(HasRoadTypeTram(t) ? rt == GetRoadTypeTram(t) : rt == GetRoadTypeRoad(t))) {
+			if (dir == GetRoadDepotDirection(t)) continue;
+
+			ret = EnsureNoVehicleOnGround(t);
+			if (ret.Failed()) return ret;
+
+			num_rotated_depot_tiles++;
+			if (flags & DC_EXEC) {
+				SetRoadDepotExitDirection(t, dir);
+				MarkTileDirtyByTile(t);
+			}
+
+		} else {
+			cost.AddCost(Command<CMD_LANDSCAPE_CLEAR>::Do(flags, t));
+			if (cost.Failed()) return cost;
+
+			num_new_depot_tiles++;
+			if (flags & DC_EXEC) {
+				MakeRoadDepot(t, _current_company, depot->index, dir, rt);
+				MarkTileDirtyByTile(t);
+			}
 		}
-		cost.AddCost(_price[PR_BUILD_FOUNDATION]);
 	}
 
-	/* Allow the user to rotate the depot instead of having to destroy it and build it again */
+	if (num_new_depot_tiles + num_rotated_depot_tiles == 0) return CommandCost();
-	bool rotate_existing_depot = false;
-	if (IsRoadDepotTile(tile) && (HasRoadTypeTram(tile) ? rt == GetRoadTypeTram(tile) : rt == GetRoadTypeRoad(tile)))
-	{
-		CommandCost ret = CheckTileOwnership(tile);
-		if (ret.Failed()) return ret;
-
-		if (dir == GetRoadDepotDirection(tile)) return CommandCost();
-
-		ret = EnsureNoVehicleOnGround(tile);
-		if (ret.Failed()) return ret;
-
-		rotate_existing_depot = true;
-	}
-
-	if (!rotate_existing_depot) {
-		cost.AddCost(Command<CMD_LANDSCAPE_CLEAR>::Do(flags, tile));
-		if (cost.Failed()) return cost;
-
-		if (IsBridgeAbove(tile)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
-
-		if (!Depot::CanAllocateItem()) return CMD_ERROR;
-	}
 
 	if (flags & DC_EXEC) {
-		if (rotate_existing_depot) {
+		/* A road depot has two road bits. */
-			SetRoadDepotExitDirection(tile, dir);
+		UpdateCompanyRoadInfrastructure(rt, _current_company, num_new_depot_tiles * ROAD_DEPOT_TRACKBIT_FACTOR);
-		} else {
-			Depot *dep = new Depot(tile, VEH_ROAD, _current_company);
-			dep->build_date = TimerGameCalendar::date;
-			MakeRoadDepot(tile, _current_company, dep->index, dir, rt);
-			MakeDefaultName(dep);
 
-			/* A road depot has two road bits. */
+		depot->AfterAddRemove(ta, true);
-			UpdateCompanyRoadInfrastructure(rt, _current_company, ROAD_DEPOT_TRACKBIT_FACTOR);
+		if (join_to == NEW_DEPOT) MakeDefaultName(depot);
-		}
-
-		MarkTileDirtyByTile(tile);
 	}
 
-	cost.AddCost(_price[PR_BUILD_DEPOT_ROAD]);
+	cost.AddCost(_price[PR_BUILD_DEPOT_ROAD] * (num_new_depot_tiles + num_rotated_depot_tiles));
 	return cost;
 }
 
@@ -1215,7 +1228,8 @@ static CommandCost RemoveRoadDepot(TileIndex tile, DoCommandFlag flags)
 	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
-		Company *c = Company::GetIfValid(GetTileOwner(tile));
+		Depot *depot = Depot::GetByTile(tile);
+		Company *c = Company::GetIfValid(depot->owner);
 		if (c != nullptr) {
 			/* A road depot has two road bits. */
 			RoadType rt = GetRoadTypeRoad(tile);
@@ -1224,8 +1238,8 @@ static CommandCost RemoveRoadDepot(TileIndex tile, DoCommandFlag flags)
 			DirtyCompanyInfrastructureWindows(c->index);
 		}
 
-		delete Depot::GetByTile(tile);
 		DoClearSquare(tile);
+		depot->AfterAddRemove(TileArea(tile), false);
 	}
 
 	return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_DEPOT_ROAD]);

src/road_cmd.h

@@ -13,6 +13,7 @@
 #include "direction_type.h"
 #include "road_type.h"
 #include "command_type.h"
+#include "depot_type.h"
 
 enum RoadStopClassID : uint16_t;
 
@@ -22,7 +23,7 @@ void UpdateNearestTownForRoadTiles(bool invalidate);
 CommandCost CmdBuildLongRoad(DoCommandFlag flags, TileIndex end_tile, TileIndex start_tile, RoadType rt, Axis axis, DisallowedRoadDirections drd, bool start_half, bool end_half, bool is_ai);
 std::tuple<CommandCost, Money> CmdRemoveLongRoad(DoCommandFlag flags, TileIndex end_tile, TileIndex start_tile, RoadType rt, Axis axis, bool start_half, bool end_half);
 CommandCost CmdBuildRoad(DoCommandFlag flags, TileIndex tile, RoadBits pieces, RoadType rt, DisallowedRoadDirections toggle_drd, TownID town_id);
-CommandCost CmdBuildRoadDepot(DoCommandFlag flags, TileIndex tile, RoadType rt, DiagDirection dir);
+CommandCost CmdBuildRoadDepot(DoCommandFlag flags, TileIndex tile, RoadType rt, DiagDirection dir, bool adjacent, DepotID join_to, TileIndex end_tile);
 CommandCost CmdConvertRoad(DoCommandFlag flags, TileIndex tile, TileIndex area_start, RoadType to_type);
 
 DEF_CMD_TRAIT(CMD_BUILD_LONG_ROAD,  CmdBuildLongRoad,  CMD_AUTO | CMD_NO_WATER | CMD_DEITY, CMDT_LANDSCAPE_CONSTRUCTION)
@@ -33,7 +34,7 @@ DEF_CMD_TRAIT(CMD_CONVERT_ROAD,     CmdConvertRoad,    0,
 
 CommandCallback CcPlaySound_CONSTRUCTION_OTHER;
 CommandCallback CcBuildRoadTunnel;
-void CcRoadDepot(Commands cmd, const CommandCost &result, TileIndex tile, RoadType rt, DiagDirection dir);
+void CcRoadDepot(Commands cmd, const CommandCost &result, TileIndex start_tile, RoadType rt, DiagDirection dir, bool adjacent, DepotID join_to, TileIndex end_tile);
 void CcRoadStop(Commands cmd, const CommandCost &result, TileIndex tile, uint8_t width, uint8_t length, RoadStopType, bool is_drive_through, DiagDirection dir, RoadType, RoadStopClassID spec_class, uint16_t spec_index, StationID, bool);
 
 #endif /* ROAD_CMD_H */

src/road_gui.cpp

@@ -171,13 +171,17 @@ void ConnectRoadToStructure(TileIndex tile, DiagDirection direction)
 	}
 }
 
-void CcRoadDepot(Commands, const CommandCost &result, TileIndex tile, RoadType, DiagDirection dir)
+void CcRoadDepot(Commands, const CommandCost &result, TileIndex start_tile, RoadType, DiagDirection dir, bool, DepotID, TileIndex end_tile)
 {
 	if (result.Failed()) return;
 
-	if (_settings_client.sound.confirm) SndPlayTileFx(SND_1F_CONSTRUCTION_OTHER, tile);
+	if (_settings_client.sound.confirm) SndPlayTileFx(SND_1F_CONSTRUCTION_OTHER, start_tile);
 	if (!_settings_client.gui.persistent_buildingtools) ResetObjectToPlace();
-	ConnectRoadToStructure(tile, dir);
+
+	TileArea ta(start_tile, end_tile);
+	for (TileIndex tile : ta) {
+		ConnectRoadToStructure(tile, dir);
+	}
 }
 
 /**
@@ -638,8 +642,10 @@ struct BuildRoadToolbarWindow : Window {
 				break;
 
 			case WID_ROT_DEPOT:
-				Command<CMD_BUILD_ROAD_DEPOT>::Post(this->rti->strings.err_depot, CcRoadDepot,
+				CloseWindowById(WC_SELECT_DEPOT, VEH_ROAD);
-						tile, _cur_roadtype, _road_depot_orientation);
+
+				VpSetPlaceSizingLimit(_settings_game.depot.depot_spread);
+				VpStartPlaceSizing(tile, (DiagDirToAxis(_road_depot_orientation) == 0) ? VPM_X_LIMITED : VPM_Y_LIMITED, DDSP_BUILD_DEPOT);
 				break;
 
 			case WID_ROT_BUILD_WAYPOINT:
@@ -810,6 +816,18 @@ struct BuildRoadToolbarWindow : Window {
 					}
 					break;
 
+				case DDSP_BUILD_DEPOT: {
+					bool adjacent = _ctrl_pressed;
+					StringID error_string = this->rti->strings.err_depot;
+
+					auto proc = [=](DepotID join_to) -> bool {
+						return Command<CMD_BUILD_ROAD_DEPOT>::Post(error_string, CcRoadDepot, start_tile, _cur_roadtype, _road_depot_orientation, adjacent, join_to, end_tile);
+					};
+
+					ShowSelectDepotIfNeeded(TileArea(start_tile, end_tile), proc, VEH_ROAD);
+					break;
+				}
+
 				case DDSP_CONVERT_ROAD:
 					Command<CMD_CONVERT_ROAD>::Post(rti->strings.err_convert_road, CcPlaySound_CONSTRUCTION_OTHER, end_tile, start_tile, _cur_roadtype);
 					break;

src/roadveh_cmd.cpp

@@ -37,6 +37,7 @@
 #include "framerate_type.h"
 #include "roadveh_cmd.h"
 #include "road_cmd.h"
+#include "depot_base.h"
 
 #include "table/strings.h"
 
@@ -250,6 +251,41 @@ void RoadVehUpdateCache(RoadVehicle *v, bool same_length)
 	v->vcache.cached_max_speed = (max_speed != 0) ? max_speed * 4 : RoadVehInfo(v->engine_type)->max_speed;
 }
 
+/**
+ * Find an adequate tile for placing an engine.
+ * @param[in,out] tile A tile of the depot.
+ * @param e Engine to be built.
+ * @param flags Flags of the command.
+ * @return CommandCost() or an error message if the depot is not appropriate.
+ */
+CommandCost FindDepotTileForPlacingEngine(TileIndex &tile, const Engine *e, DoCommandFlag flags)
+{
+	assert(IsRoadDepotTile(tile));
+
+	Depot *dep = Depot:: GetByTile(tile);
+
+	/* Check that the vehicle can drive on some tile of the depot */
+	RoadType rt = e->u.road.roadtype;
+	const RoadTypeInfo *rti = GetRoadTypeInfo(rt);
+	if ((dep->r_types.road_types & rti->powered_roadtypes) == 0) return_cmd_error(STR_ERROR_DEPOT_WRONG_DEPOT_TYPE);
+
+	/* Use same tile if possible when replacing. */
+	if (flags & DC_AUTOREPLACE) {
+		/* Use same tile if possible when replacing. */
+		if (HasTileAnyRoadType(tile, rti->powered_roadtypes)) return CommandCost();
+	}
+
+	tile = INVALID_TILE;
+	for (auto &depot_tile : dep->depot_tiles) {
+		if (!HasTileAnyRoadType(depot_tile, rti->powered_roadtypes)) continue;
+		tile = depot_tile;
+		break;
+	}
+
+	assert(tile != INVALID_TILE);
+	return CommandCost();
+}
+
 /**
  * Build a road vehicle.
  * @param flags    type of operation.
@@ -260,10 +296,12 @@ void RoadVehUpdateCache(RoadVehicle *v, bool same_length)
  */
 CommandCost CmdBuildRoadVehicle(DoCommandFlag flags, TileIndex tile, const Engine *e, Vehicle **ret)
 {
-	/* Check that the vehicle can drive on the road in question */
+	assert(IsRoadDepotTile(tile));
 	RoadType rt = e->u.road.roadtype;
 	const RoadTypeInfo *rti = GetRoadTypeInfo(rt);
-	if (!HasTileAnyRoadType(tile, rti->powered_roadtypes)) return_cmd_error(STR_ERROR_DEPOT_WRONG_DEPOT_TYPE);
+
+	CommandCost check = FindDepotTileForPlacingEngine(tile, e, flags);
+	if (check.Failed()) return check;
 
 	if (flags & DC_EXEC) {
 		const RoadVehicleInfo *rvi = &e->u.road;

src/script/api/script_marine.cpp

@@ -83,7 +83,7 @@
 	EnforcePrecondition(false, ::IsValidTile(front));
 	EnforcePrecondition(false, (::TileX(front) == ::TileX(tile)) != (::TileY(front) == ::TileY(tile)));
 
-	return ScriptObject::Command<CMD_BUILD_SHIP_DEPOT>::Do(tile, ::TileX(front) == ::TileX(tile) ? AXIS_Y : AXIS_X);
+	return ScriptObject::Command<CMD_BUILD_SHIP_DEPOT>::Do(tile, ::TileX(front) == ::TileX(tile) ? AXIS_Y : AXIS_X, false, INVALID_DEPOT, tile);
 }
 
 /* static */ bool ScriptMarine::BuildDock(TileIndex tile, StationID station_id)

src/script/api/script_rail.cpp

@@ -145,7 +145,7 @@
 
 	DiagDirection entrance_dir = (::TileX(tile) == ::TileX(front)) ? (::TileY(tile) < ::TileY(front) ? DIAGDIR_SE : DIAGDIR_NW) : (::TileX(tile) < ::TileX(front) ? DIAGDIR_SW : DIAGDIR_NE);
 
-	return ScriptObject::Command<CMD_BUILD_TRAIN_DEPOT>::Do(tile, (::RailType)ScriptObject::GetRailType(), entrance_dir);
+	return ScriptObject::Command<CMD_BUILD_TRAIN_DEPOT>::Do(tile, (::RailType)ScriptObject::GetRailType(), entrance_dir, false, INVALID_DEPOT, tile);
 }
 
 /* static */ bool ScriptRail::BuildRailStation(TileIndex tile, RailTrack direction, SQInteger num_platforms, SQInteger platform_length, StationID station_id)

src/script/api/script_road.cpp

@@ -535,7 +535,7 @@ static bool NeighbourHasReachableRoad(::RoadType rt, TileIndex start_tile, DiagD
 
 	DiagDirection entrance_dir = (::TileX(tile) == ::TileX(front)) ? (::TileY(tile) < ::TileY(front) ? DIAGDIR_SE : DIAGDIR_NW) : (::TileX(tile) < ::TileX(front) ? DIAGDIR_SW : DIAGDIR_NE);
 
-	return ScriptObject::Command<CMD_BUILD_ROAD_DEPOT>::Do(tile, ScriptObject::GetRoadType(), entrance_dir);
+	return ScriptObject::Command<CMD_BUILD_ROAD_DEPOT>::Do(tile, ScriptObject::GetRoadType(), entrance_dir, false, INVALID_DEPOT, tile);
 }
 
 /* static */ bool ScriptRoad::_BuildRoadStationInternal(TileIndex tile, TileIndex front, RoadVehicleType road_veh_type, bool drive_through, StationID station_id)

src/train_gui.cpp

@@ -15,6 +15,7 @@
 #include "vehicle_func.h"
 #include "zoom_func.h"
 #include "train_cmd.h"
+#include "depot_map.h"
 
 #include "table/strings.h"
 
@@ -29,11 +30,12 @@
 void CcBuildWagon(Commands, const CommandCost &result, VehicleID new_veh_id, uint, uint16_t, CargoArray, TileIndex tile, EngineID, bool, CargoID, ClientID)
 {
 	if (result.Failed()) return;
+	DepotID depot_id = GetDepotIndex(tile);
 
 	/* find a locomotive in the depot. */
 	const Vehicle *found = nullptr;
 	for (const Train *t : Train::Iterate()) {
-		if (t->IsFrontEngine() && t->tile == tile && t->IsStoppedInDepot()) {
+		if (t->IsFrontEngine() && t->IsStoppedInDepot() && GetDepotIndex(t->tile) == depot_id) {
 			if (found != nullptr) return; // must be exactly one.
 			found = t;
 		}

src/viewport.cpp

@@ -1013,7 +1013,7 @@ DepotID _viewport_highlight_depot = INVALID_DEPOT; ///< Currently selected depot
 static TileHighlightType GetTileHighlightType(TileIndex t)
 {
 	if (_viewport_highlight_depot != INVALID_DEPOT) {
-		if (IsDepotTile(t) && GetDepotIndex(t) == _viewport_highlight_depot) return THT_WHITE;
+		if (IsDepotTile(t) && GetDepotIndex(t) == _viewport_highlight_depot) return THT_BLUE;
 	}
 
 	if (_viewport_highlight_station != nullptr) {

src/viewport_type.h

@@ -122,6 +122,7 @@ enum ViewportDragDropSelectionProcess {
 	DDSP_PLANT_TREES,          ///< Plant trees
 	DDSP_BUILD_BRIDGE,         ///< Bridge placement
 	DDSP_BUILD_OBJECT,         ///< Build an object
+	DDSP_BUILD_DEPOT,          ///< Depot placement
 
 	/* Rail specific actions */
 	DDSP_PLACE_RAIL,           ///< Rail placement

src/water_cmd.cpp

@@ -94,66 +94,75 @@ static void MarkCanalsAndRiversAroundDirty(TileIndex tile)
 /**
  * Build a ship depot.
  * @param flags type of operation
- * @param tile tile where ship depot is built
+ * @param tile first tile where ship depot is built
  * @param axis depot orientation (Axis)
+ * @param adjacent allow adjacent depots
+ * @param join_to depot to join to
+ * @param end_tile end tile of area to be built
  * @return the cost of this operation or an error
  */
-CommandCost CmdBuildShipDepot(DoCommandFlag flags, TileIndex tile, Axis axis)
+CommandCost CmdBuildShipDepot(DoCommandFlag flags, TileIndex tile, Axis axis, bool adjacent, DepotID join_to, TileIndex end_tile)
 {
 	if (!IsValidAxis(axis)) return CMD_ERROR;
 	TileIndex tile2 = tile + (axis == AXIS_X ? TileDiffXY(1, 0) : TileDiffXY(0, 1));
 
-	if (!HasTileWaterGround(tile) || !HasTileWaterGround(tile2)) {
+	TileArea complete_area(tile, end_tile);
-		return_cmd_error(STR_ERROR_MUST_BE_BUILT_ON_WATER);
+	complete_area.Add(tile2);
-	}
+	assert(complete_area.w == 2 || complete_area.h == 2);
 
-	if (IsBridgeAbove(tile) || IsBridgeAbove(tile2)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+	TileArea northern_tiles(complete_area.tile);
+	northern_tiles.Add(complete_area.tile + (axis == AXIS_X ? TileDiffXY(0, complete_area.h - 1) : TileDiffXY(complete_area.w - 1, 0)));
 
-	if (!IsTileFlat(tile) || !IsTileFlat(tile2)) {
+	/* Create a new depot or find a depot to join to. */
-		/* Prevent depots on rapids */
+	Depot *depot = nullptr;
-		return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
+	CommandCost ret = FindJoiningDepot(complete_area, VEH_SHIP, join_to, depot, adjacent, flags);
-	}
-
-	if (!Depot::CanAllocateItem()) return CMD_ERROR;
-
-	WaterClass wc1 = GetWaterClass(tile);
-	WaterClass wc2 = GetWaterClass(tile2);
-	CommandCost cost = CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_DEPOT_SHIP]);
-
-	bool add_cost = !IsWaterTile(tile);
-	CommandCost ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags | DC_AUTO, tile);
 	if (ret.Failed()) return ret;
-	if (add_cost) {
+
-		cost.AddCost(ret);
+	/* Get the cost of building all the ship depots. */
-	}
+	CommandCost cost = CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_DEPOT_SHIP] * northern_tiles.w * northern_tiles.h);
-	add_cost = !IsWaterTile(tile2);
+
-	ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags | DC_AUTO, tile2);
+	/* Update infrastructure counts after the tile clears earlier.
-	if (ret.Failed()) return ret;
+	 * Clearing object tiles may result in water tiles which are already accounted for in the water infrastructure total.
-	if (add_cost) {
+	 * See: MakeWaterKeepingClass() */
-		cost.AddCost(ret);
+	uint new_water_infra = 0;
+
+	for (TileIndex t : complete_area) {
+		/* Build water depots in water valid tiles... */
+		if (!IsValidTile(t) || !HasTileWaterGround(t)) return_cmd_error(STR_ERROR_MUST_BE_BUILT_ON_WATER);
+
+		/* ... with no bridges above... */
+		if (IsBridgeAbove(t)) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
+
+		/* ... and preventing depots on rapids. */
+		if (!IsTileFlat(t)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
+
+		/* Keep original water class before clearing tile. */
+		WaterClass wc = GetWaterClass(t);
+
+		/* Clear the tile. */
+		bool add_cost = !IsWaterTile(t);
+		CommandCost ret = Command<CMD_LANDSCAPE_CLEAR>::Do(flags | DC_AUTO, t);
+		if (ret.Failed()) return ret;
+		if (add_cost) cost.AddCost(ret);
+
+		if (wc == WATER_CLASS_CANAL && !(HasTileWaterClass(t) && GetWaterClass(t) == WATER_CLASS_CANAL && IsTileOwner(t, _current_company))) new_water_infra++;
+
+		if (flags & DC_EXEC) {
+			DepotPart dp = northern_tiles.Contains(t) ? DEPOT_PART_NORTH : DEPOT_PART_SOUTH;
+			MakeShipDepot(t,  _current_company, depot->index, dp, axis, wc);
+			CheckForDockingTile(t);
+			MarkTileDirtyByTile(t);
+		}
 	}
 
 	if (flags & DC_EXEC) {
-		Depot *depot = new Depot(tile, VEH_SHIP, _current_company);
+		Company::Get(_current_company)->infrastructure.water += new_water_infra +
-		depot->build_date = TimerGameCalendar::date;
+				complete_area.w * complete_area.h * LOCK_DEPOT_TILE_FACTOR;
-
-		uint new_water_infra = 2 * LOCK_DEPOT_TILE_FACTOR;
-		/* Update infrastructure counts after the tile clears earlier.
-		 * Clearing object tiles may result in water tiles which are already accounted for in the water infrastructure total.
-		 * See: MakeWaterKeepingClass() */
-		if (wc1 == WATER_CLASS_CANAL && !(HasTileWaterClass(tile) && GetWaterClass(tile) == WATER_CLASS_CANAL && IsTileOwner(tile, _current_company))) new_water_infra++;
-		if (wc2 == WATER_CLASS_CANAL && !(HasTileWaterClass(tile2) && GetWaterClass(tile2) == WATER_CLASS_CANAL && IsTileOwner(tile2, _current_company))) new_water_infra++;
-
-		Company::Get(_current_company)->infrastructure.water += new_water_infra;
 		DirtyCompanyInfrastructureWindows(_current_company);
 
-		MakeShipDepot(tile,  _current_company, depot->index, DEPOT_PART_NORTH, axis, wc1);
-		MakeShipDepot(tile2, _current_company, depot->index, DEPOT_PART_SOUTH, axis, wc2);
-		CheckForDockingTile(tile);
-		CheckForDockingTile(tile2);
-		MarkTileDirtyByTile(tile);
-		MarkTileDirtyByTile(tile2);
 		MakeDefaultName(depot);
+		depot->AfterAddRemove(complete_area, true);
+		if (join_to == NEW_DEPOT) MakeDefaultName(depot);
 	}
 
 	return cost;
@@ -275,9 +284,8 @@ static CommandCost RemoveShipDepot(TileIndex tile, DoCommandFlag flags)
 	bool do_clear = (flags & DC_FORCE_CLEAR_TILE) != 0;
 
 	if (flags & DC_EXEC) {
-		delete Depot::GetByTile(tile);
+		Depot *depot = Depot::GetByTile(tile);
-
+		Company *c = Company::GetIfValid(depot->owner);
-		Company *c = Company::GetIfValid(GetTileOwner(tile));
 		if (c != nullptr) {
 			c->infrastructure.water -= 2 * LOCK_DEPOT_TILE_FACTOR;
 			if (do_clear && GetWaterClass(tile) == WATER_CLASS_CANAL) c->infrastructure.water--;
@@ -286,6 +294,8 @@ static CommandCost RemoveShipDepot(TileIndex tile, DoCommandFlag flags)
 
 		if (!do_clear) MakeWaterKeepingClass(tile,  GetTileOwner(tile));
 		MakeWaterKeepingClass(tile2, GetTileOwner(tile2));
+
+		depot->AfterAddRemove(TileArea(tile, tile2), false);
 	}
 
 	return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_DEPOT_SHIP]);

src/water_cmd.h

@@ -13,7 +13,7 @@
 #include "command_type.h"
 #include "water_map.h"
 
-CommandCost CmdBuildShipDepot(DoCommandFlag flags, TileIndex tile, Axis axis);
+CommandCost CmdBuildShipDepot(DoCommandFlag flags, TileIndex tile, Axis axis, bool adjacent, DepotID depot_id, TileIndex end_tile);
 CommandCost CmdBuildCanal(DoCommandFlag flags, TileIndex tile, TileIndex start_tile, WaterClass wc, bool diagonal);
 CommandCost CmdBuildLock(DoCommandFlag flags, TileIndex tile);