Feature: Try to reuse a removed depot when placing a new one. (based on patch by adf88, #6328, #7051)

src/depot.cpp

@@ -65,6 +65,20 @@ Depot::~Depot()
 	InvalidateWindowData(WC_SELECT_DEPOT, this->veh_type);
 }
 
+/**
+ * Cancel deletion of this depot (reuse it).
+ * @param xy New location of the depot.
+ * @see Depot::IsInUse
+ * @see Depot::Disuse
+ */
+void Depot::Reuse(TileIndex xy)
+{
+	this->delete_ctr = 0;
+	this->xy = xy;
+	this->ta.tile = xy;
+	this->ta.h = this->ta.w = 1;
+}
+
 /**
  * Schedule deletion of this depot.
  *
@@ -73,6 +87,7 @@ Depot::~Depot()
  * placed again later without messing vehicle orders.
  *
  * @see Depot::IsInUse
+ * @see Depot::Reuse
  */
 void Depot::Disuse()
 {
@@ -112,13 +127,19 @@ CommandCost Depot::BeforeAddTiles(TileArea ta)
 {
 	assert(ta.tile != INVALID_TILE);
 
-	if (this->ta.tile != INVALID_TILE) {
+	if (this->ta.tile != INVALID_TILE && this->IsInUse()) {
 		/* Important when the old rect is completely inside the new rect, resp. the old one was empty. */
 		ta.Add(this->ta.tile);
 		ta.Add(TileAddXY(this->ta.tile, this->ta.w - 1, this->ta.h - 1));
 	}
 
-	if ((ta.w > _settings_game.depot.depot_spread) || (ta.h > _settings_game.depot.depot_spread)) {
+	/* A max depot spread of 1 for VEH_SHIP is a special case,
+	 * as ship depots consist of two tiles. */
+	if (this->veh_type == VEH_SHIP && _settings_game.depot.depot_spread == 1) {
+		/* (ta.w, ta.h) must be equal to (1, 2) or (2, 1).
+		 * This means that ta.w * ta.h must be equal to 2. */
+		if (ta.w * ta.h != 2) return_cmd_error(STR_ERROR_DEPOT_TOO_SPREAD_OUT);
+	} else if (std::max(ta.w, ta.h) > _settings_game.depot.depot_spread) {
 		return_cmd_error(STR_ERROR_DEPOT_TOO_SPREAD_OUT);
 	}
 	return CommandCost();
@@ -158,8 +179,13 @@ void Depot::AfterAddRemove(TileArea ta, bool adding)
 	} else {
 		assert(this->IsInUse());
 		this->Disuse();
+		TileIndex old_tile = this->xy;
+		this->RescanDepotTiles();
+		assert(this->depot_tiles.empty());
+		this->xy = old_tile;
 	}
 
+	InvalidateWindowData(WC_VEHICLE_DEPOT, this->index);
 	InvalidateWindowData(WC_SELECT_DEPOT, veh_type);
 }
 

src/depot_base.h

@@ -78,12 +78,14 @@ struct Depot : DepotPool::PoolItem<&_depot_pool> {
 	 * and the depot awaits to be deleted.
 	 * @return true iff still in use
 	 * @see Depot::Disuse
+	 * @see Depot::Reuse
 	 */
 	inline bool IsInUse() const
 	{
 		return this->delete_ctr == 0;
 	}
 
+	void Reuse(TileIndex xy);
 	void Disuse();
 
 	/* Check we can add some tiles to this depot. */

src/depot_cmd.cpp

@@ -77,6 +77,23 @@ CommandCost CmdRenameDepot(DoCommandFlag flags, DepotID depot_id, const std::str
 	return CommandCost();
 }
 
+/**
+ * Find a demolished depot close to a tile.
+ * @param ta Tile area to search for.
+ * @param type Depot type.
+ * @param cid Previous owner of the depot.
+ * @return The index of a demolished nearby depot, or INVALID_DEPOT if none.
+ */
+DepotID FindDeletedDepotCloseTo(TileArea ta, VehicleType type, CompanyID cid)
+{
+	for (Depot *depot : Depot::Iterate()) {
+		if (depot->IsInUse() || depot->veh_type != type || depot->owner != cid) continue;
+		if (ta.Contains(depot->xy)) return depot->index;
+	}
+
+	return INVALID_DEPOT;
+}
+
 void OnTick_Depot()
 {
 	if (_game_mode == GM_EDITOR) return;
@@ -128,6 +145,12 @@ CommandCost FindJoiningDepot(TileArea ta, VehicleType veh_type, DepotID &join_to
 			}
 		}
 
+		if (closest_depot == INVALID_DEPOT) {
+			/* Check for close unused depots. */
+			check_area.Expand(7); // total distance of 8
+			closest_depot = FindDeletedDepotCloseTo(check_area, veh_type, _current_company);
+		}
+
 		if (closest_depot != INVALID_DEPOT) {
 			assert(Depot::IsValidID(closest_depot));
 			depot = Depot::Get(closest_depot);
@@ -151,6 +174,7 @@ CommandCost FindJoiningDepot(TileArea ta, VehicleType veh_type, DepotID &join_to
 		depot = Depot::Get(join_to);
 		assert(depot->owner == _current_company);
 		assert(depot->veh_type == veh_type);
+		if (!depot->IsInUse() && (flags & DC_EXEC)) depot->Reuse(ta.tile);
 		return depot->BeforeAddTiles(ta);
 	}
 

src/depot_gui.cpp

@@ -1249,6 +1249,15 @@ static const Depot *FindDepotsNearby(TileArea ta, VehicleType veh_type, bool dis
 	TileIndex tile = TileAddByDir(andd.search_area.tile, DIR_N);
 	CircularTileSearch(&tile, max_dist, ta.w, ta.h, AddNearbyDepot, &andd);
 
+	/* Add reusable depots. */
+	ta.Expand(8);
+	for (Depot *d : Depot::Iterate()) {
+		if (d->IsInUse()) continue;
+		if (d->veh_type != veh_type || d->owner != _current_company) continue;
+		if (!ta.Contains(d->xy)) continue;
+		_depots_nearby_list.push_back(d->index);
+	}
+
 	return nullptr;
 }