(svn r19319) -Codechange: EnsureNoVehicleOnGround() returns a CommandCost.

10 files changed, 109 insertions, 42 deletions

diff --git a/src/disaster_cmd.cpp b/src/disaster_cmd.cpp
index 6ff1ed1ba..d2f34f2cc 100644
--- a/src/disaster_cmd.cpp
+++ b/src/disaster_cmd.cpp
@@ -67,7 +67,7 @@ enum DisasterSubType {
 
 static void DisasterClearSquare(TileIndex tile)
 {
-	if (!EnsureNoVehicleOnGround(tile)) return;
+	if (EnsureNoVehicleOnGround(tile).Failed()) return;
 
 	switch (GetTileType(tile)) {
 		case MP_RAILWAY:
diff --git a/src/industry_cmd.cpp b/src/industry_cmd.cpp
index 0ebe23c9a..66686ee9f 100644
--- a/src/industry_cmd.cpp
+++ b/src/industry_cmd.cpp
@@ -1337,7 +1337,9 @@ static CommandCost CheckIfIndustryTilesAreFree(TileIndex tile, const IndustryTil
 				return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
 			}
 		} else {
-			if (!EnsureNoVehicleOnGround(cur_tile)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
+			CommandCost ret = EnsureNoVehicleOnGround(cur_tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 			if (MayHaveBridgeAbove(cur_tile) && IsBridgeAbove(cur_tile)) return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
 
 			const IndustryTileSpec *its = GetIndustryTileSpec(gfx);
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
index 86e0fbbc7..eb29fef07 100644
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -416,7 +416,7 @@ CommandCost CmdBuildSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 			break;
 		}
 
-		case MP_ROAD:
+		case MP_ROAD: {
 #define M(x) (1 << (x))
 			/* Level crossings may only be built on these slopes */
 			if (!HasBit(M(SLOPE_SEN) | M(SLOPE_ENW) | M(SLOPE_NWS) | M(SLOPE_NS) | M(SLOPE_WSE) | M(SLOPE_EW) | M(SLOPE_FLAT), tileh)) {
@@ -424,7 +424,9 @@ CommandCost CmdBuildSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 			}
 #undef M
 
-			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+			CommandCost ret = EnsureNoVehicleOnGround(tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 
 			if (IsNormalRoad(tile)) {
 				if (HasRoadWorks(tile)) return_cmd_error(STR_ERROR_ROAD_WORKS_IN_PROGRESS);
@@ -463,6 +465,7 @@ CommandCost CmdBuildSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 				return_cmd_error(STR_ERROR_ALREADY_BUILT);
 			}
 			/* FALLTHROUGH */
+		}
 
 		default: {
 			/* Will there be flat water on the lower halftile? */
@@ -528,10 +531,14 @@ CommandCost CmdRemoveSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1,
 		case MP_ROAD: {
 			if (!IsLevelCrossing(tile) ||
 					GetCrossingRailBits(tile) != trackbit ||
-					(_current_company != OWNER_WATER && !CheckTileOwnership(tile)) ||
-					(!(flags & DC_BANKRUPT) && !EnsureNoVehicleOnGround(tile))) {
+					(_current_company != OWNER_WATER && !CheckTileOwnership(tile))) {
 				return CMD_ERROR;
 			}
+			if (!(flags & DC_BANKRUPT)) {
+				CommandCost ret = EnsureNoVehicleOnGround(tile);
+				ret.SetGlobalErrorMessage();
+				if (ret.Failed()) return ret;
+			}
 
 			if (flags & DC_EXEC) {
 				if (HasReservedTracks(tile, trackbit)) {
@@ -1408,7 +1415,13 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 			/* Vehicle on the tile when not converting Rail <-> ElRail
 			 * Tunnels and bridges have special check later */
 			if (tt != MP_TUNNELBRIDGE) {
-				if (!IsCompatibleRail(type, totype) && !EnsureNoVehicleOnGround(tile)) continue;
+				if (!IsCompatibleRail(type, totype)) {
+					CommandCost ret = EnsureNoVehicleOnGround(tile);
+					if (ret.Failed()) {
+						ret.SetGlobalErrorMessage();
+						continue;
+					}
+				}
 				if (flags & DC_EXEC) { // we can safely convert, too
 					TrackBits reserved = GetReservedTrackbits(tile);
 					Track     track;
@@ -1524,8 +1537,9 @@ static CommandCost RemoveTrainDepot(TileIndex tile, DoCommandFlag flags)
 	if (!CheckTileOwnership(tile) && _current_company != OWNER_WATER)
 		return CMD_ERROR;
 
-	if (!EnsureNoVehicleOnGround(tile))
-		return CMD_ERROR;
+	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		/* read variables before the depot is removed */
@@ -1581,7 +1595,9 @@ static CommandCost ClearTile_Track(TileIndex tile, DoCommandFlag flags)
 
 			/* when bankrupting, don't make water dirty, there could be a ship on lower halftile */
 			if (water_ground && !(flags & DC_BANKRUPT)) {
-				if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+				CommandCost ret = EnsureNoVehicleOnGround(tile);
+				ret.SetGlobalErrorMessage();
+				if (ret.Failed()) return ret;
 
 				/* The track was removed, and left a coast tile. Now also clear the water. */
 				if (flags & DC_EXEC) DoClearSquare(tile);
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
index 7ee64c795..0f6cc1581 100644
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -183,14 +183,19 @@ static CommandCost RemoveRoad(TileIndex tile, DoCommandFlag flags, RoadBits piec
 	if (!HasBit(rts, rt)) return CMD_ERROR;
 
 	switch (GetTileType(tile)) {
-		case MP_ROAD:
-			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
-			break;
+		case MP_ROAD: {
+			CommandCost ret = EnsureNoVehicleOnGround(tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
+		} break;
 
-		case MP_STATION:
+		case MP_STATION: {
 			if (!IsDriveThroughStopTile(tile)) return CMD_ERROR;
-			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
-			break;
+
+			CommandCost ret = EnsureNoVehicleOnGround(tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
+		} break;
 
 		case MP_TUNNELBRIDGE: {
 			if (GetTunnelBridgeTransportType(tile) != TRANSPORT_ROAD) return CMD_ERROR;
@@ -493,7 +498,9 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 							Owner owner = GetRoadOwner(tile, ROADTYPE_ROAD);
 							if (owner != OWNER_NONE && !CheckOwnership(owner, tile)) return CMD_ERROR;
 
-							if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+							CommandCost ret = EnsureNoVehicleOnGround(tile);
+							ret.SetGlobalErrorMessage();
+							if (ret.Failed()) return ret;
 
 							/* Ignore half built tiles */
 							if ((flags & DC_EXEC) && rt != ROADTYPE_TRAM && IsStraightRoad(existing)) {
@@ -549,7 +556,9 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 				default: goto do_clear;
 			}
 
-			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+			CommandCost ret = EnsureNoVehicleOnGround(tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 
 			if (flags & DC_EXEC) {
 				Track railtrack = AxisToTrack(OtherAxis(roaddir));
@@ -627,7 +636,11 @@ do_clear:;
 		}
 	}
 
-	if (!tile_cleared && !EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+	if (!tile_cleared) {
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
+	}
 
 	cost.AddCost(CountBits(pieces) * _price[PR_BUILD_ROAD]);
 	if (!tile_cleared && IsTileType(tile, MP_TUNNELBRIDGE)) {
@@ -900,7 +913,9 @@ static CommandCost RemoveRoadDepot(TileIndex tile, DoCommandFlag flags)
 {
 	if (!CheckTileOwnership(tile) && _current_company != OWNER_WATER) return CMD_ERROR;
 
-	if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		delete Depot::GetByTile(tile);
@@ -1358,7 +1373,7 @@ static void TileLoop_Road(TileIndex tile)
 			if (t->road_build_months != 0 &&
 					(DistanceManhattan(t->xy, tile) < 8 || grp != HZB_TOWN_EDGE) &&
 					IsNormalRoad(tile) && !HasAtMostOneBit(GetAllRoadBits(tile))) {
-				if (GetFoundationSlope(tile, NULL) == SLOPE_FLAT && EnsureNoVehicleOnGround(tile) && Chance16(1, 40)) {
+				if (GetFoundationSlope(tile, NULL) == SLOPE_FLAT && EnsureNoVehicleOnGround(tile).Succeeded() && Chance16(1, 40)) {
 					StartRoadWorks(tile);
 
 					SndPlayTileFx(SND_21_JACKHAMMER, tile);
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
index 51072e4c9..45fa5ce06 100644
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -671,7 +671,9 @@ CommandCost CheckBuildableTile(TileIndex tile, uint invalid_dirs, int &allowed_z
 		return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
 	}
 
-	if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	uint z;
 	Slope tileh = GetTileSlope(tile, &z);
@@ -1362,7 +1364,11 @@ CommandCost RemoveFromRailBaseStation(TileArea ta, SmallVector<T *, 4> &affected
 		if (!HasStationTileRail(tile)) continue;
 
 		/* If there is a vehicle on ground, do not allow to remove (flood) the tile */
-		if (!EnsureNoVehicleOnGround(tile)) continue;
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		if (ret.Failed()) {
+			ret.SetGlobalErrorMessage();
+			continue;
+		}
 
 		/* Check ownership of station */
 		T *st = T::GetByTile(tile);
@@ -1526,7 +1532,9 @@ CommandCost RemoveRailStation(T *st, DoCommandFlag flags)
 		/* for nonuniform stations, only remove tiles that are actually train station tiles */
 		if (!st->TileBelongsToRailStation(tile)) continue;
 
-		if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 
 		cost.AddCost(_price[PR_CLEAR_STATION_RAIL]);
 		if (flags & DC_EXEC) {
@@ -1832,7 +1840,9 @@ static CommandCost RemoveRoadStop(TileIndex tile, DoCommandFlag flags)
 		/* remove the 'going through road stop' status from all vehicles on that tile */
 		if (flags & DC_EXEC) FindVehicleOnPos(tile, NULL, &ClearRoadStopStatusEnum);
 	} else {
-		if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 	}
 
 	if (flags & DC_EXEC) {
@@ -2234,7 +2244,9 @@ static CommandCost RemoveAirport(TileIndex tile, DoCommandFlag flags)
 	TILE_AREA_LOOP(tile_cur, st->airport) {
 		if (!st->TileBelongsToAirport(tile_cur)) continue;
 
-		if (!EnsureNoVehicleOnGround(tile_cur)) return CMD_ERROR;
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 
 		cost.AddCost(_price[PR_CLEAR_STATION_AIRPORT]);
 
@@ -2432,8 +2444,10 @@ static CommandCost RemoveDock(TileIndex tile, DoCommandFlag flags)
 	TileIndex tile1 = st->dock_tile;
 	TileIndex tile2 = tile1 + TileOffsByDiagDir(GetDockDirection(tile1));
 
-	if (!EnsureNoVehicleOnGround(tile1)) return CMD_ERROR;
-	if (!EnsureNoVehicleOnGround(tile2)) return CMD_ERROR;
+	CommandCost ret = EnsureNoVehicleOnGround(tile1);
+	if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile2);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		DoClearSquare(tile1);
diff --git a/src/unmovable_cmd.cpp b/src/unmovable_cmd.cpp
index 55fe0a4c5..039a0162f 100644
--- a/src/unmovable_cmd.cpp
+++ b/src/unmovable_cmd.cpp
@@ -177,7 +177,9 @@ CommandCost CmdSellLandArea(TileIndex tile, DoCommandFlag flags, uint32 p1, uint
 	if (!IsOwnedLandTile(tile)) return CMD_ERROR;
 	if (!CheckTileOwnership(tile) && _current_company != OWNER_WATER) return CMD_ERROR;
 
-	if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) DoClearSquare(tile);
 
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index bba6a5219..05df6ad9f 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -408,9 +408,9 @@ static Vehicle *EnsureNoVehicleProcZ(Vehicle *v, void *data)
 
 /* Ensure there is no vehicle at the ground at the given position.
  * @param tile Position to examine.
- * @return A vehicle has been found.
+ * @return Succeeded command (ground is free) or failed command (a vehicle is found).
  */
-bool EnsureNoVehicleOnGround(TileIndex tile)
+CommandCost EnsureNoVehicleOnGround(TileIndex tile)
 {
 	byte z = GetTileMaxZ(tile);
 
@@ -419,8 +419,8 @@ bool EnsureNoVehicleOnGround(TileIndex tile)
 	 * Such a message does not affect MP synchronisation.
 	 */
 	Vehicle *v = VehicleFromPos(tile, &z, &EnsureNoVehicleProcZ, true);
-	if (v != NULL) _error_message = STR_ERROR_TRAIN_IN_THE_WAY + v->type;
-	return v == NULL;
+	if (v != NULL) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
+	return CommandCost();
 }
 
 /** Procedure called for every vehicle found in tunnel/bridge in the hash map */
diff --git a/src/vehicle_func.h b/src/vehicle_func.h
index 82b465478..e1e2e2d55 100644
--- a/src/vehicle_func.h
+++ b/src/vehicle_func.h
@@ -156,7 +156,7 @@ static inline uint32 GetCmdSendToDepot(const BaseVehicle *v)
 	return GetCmdSendToDepot(v->type);
 }
 
-bool EnsureNoVehicleOnGround(TileIndex tile);
+CommandCost EnsureNoVehicleOnGround(TileIndex tile);
 void StopAllVehicles();
 
 extern VehicleID _vehicle_id_ctr_day;
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
index 8074abe19..01c25157f 100644
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -174,7 +174,10 @@ static CommandCost RemoveShipDepot(TileIndex tile, DoCommandFlag flags)
 
 	/* do not check for ship on tile when company goes bankrupt */
 	if (!(flags & DC_BANKRUPT)) {
-		if (!EnsureNoVehicleOnGround(tile) || !EnsureNoVehicleOnGround(tile2)) return CMD_ERROR;
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile2);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
 	}
 
 	if (flags & DC_EXEC) {
@@ -244,8 +247,11 @@ static CommandCost RemoveShiplift(TileIndex tile, DoCommandFlag flags)
 	if (!CheckTileOwnership(tile) && GetTileOwner(tile) != OWNER_NONE) return CMD_ERROR;
 
 	/* make sure no vehicle is on the tile. */
-	if (!EnsureNoVehicleOnGround(tile) || !EnsureNoVehicleOnGround(tile + delta) || !EnsureNoVehicleOnGround(tile - delta))
-		return CMD_ERROR;
+	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile + delta);
+	if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile - delta);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	if (flags & DC_EXEC) {
 		DoClearSquare(tile);
@@ -341,7 +347,7 @@ CommandCost CmdBuildCanal(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 static CommandCost ClearTile_Water(TileIndex tile, DoCommandFlag flags)
 {
 	switch (GetWaterTileType(tile)) {
-		case WATER_TILE_CLEAR:
+		case WATER_TILE_CLEAR: {
 			if (flags & DC_NO_WATER) return_cmd_error(STR_ERROR_CAN_T_BUILD_ON_WATER);
 
 			/* Make sure freeform edges are allowed or it's not an edge tile. */
@@ -351,7 +357,9 @@ static CommandCost ClearTile_Water(TileIndex tile, DoCommandFlag flags)
 			}
 
 			/* Make sure no vehicle is on the tile */
-			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+			CommandCost ret = EnsureNoVehicleOnGround(tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 
 			if (GetTileOwner(tile) != OWNER_WATER && GetTileOwner(tile) != OWNER_NONE && !CheckTileOwnership(tile)) return CMD_ERROR;
 
@@ -360,12 +368,15 @@ static CommandCost ClearTile_Water(TileIndex tile, DoCommandFlag flags)
 				MarkCanalsAndRiversAroundDirty(tile);
 			}
 			return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_WATER]);
+		}
 
 		case WATER_TILE_COAST: {
 			Slope slope = GetTileSlope(tile, NULL);
 
 			/* Make sure no vehicle is on the tile */
-			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+			CommandCost ret = EnsureNoVehicleOnGround(tile);
+			ret.SetGlobalErrorMessage();
+			if (ret.Failed()) return ret;
 
 			if (flags & DC_EXEC) {
 				DoClearSquare(tile);
diff --git a/src/waypoint_cmd.cpp b/src/waypoint_cmd.cpp
index 413d7be66..7be4a6ce4 100644
--- a/src/waypoint_cmd.cpp
+++ b/src/waypoint_cmd.cpp
@@ -179,7 +179,10 @@ static CommandCost IsValidTileForWaypoint(TileIndex tile, Axis axis, StationID *
 
 	Owner owner = GetTileOwner(tile);
 	if (!CheckOwnership(owner)) return CMD_ERROR;
-	if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+
+	CommandCost ret = EnsureNoVehicleOnGround(tile);
+	ret.SetGlobalErrorMessage();
+	if (ret.Failed()) return ret;
 
 	Slope tileh = GetTileSlope(tile, NULL);
 	if (tileh != SLOPE_FLAT &&
@@ -390,7 +393,11 @@ CommandCost RemoveBuoy(TileIndex tile, DoCommandFlag flags)
 
 	if (HasStationInUse(wp->index, INVALID_COMPANY)) return_cmd_error(STR_ERROR_BUOY_IS_IN_USE);
 	/* remove the buoy if there is a ship on tile when company goes bankrupt... */
-	if (!(flags & DC_BANKRUPT) && !EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+	if (!(flags & DC_BANKRUPT)) {
+		CommandCost ret = EnsureNoVehicleOnGround(tile);
+		ret.SetGlobalErrorMessage();
+		if (ret.Failed()) return ret;
+	}
 
 	if (flags & DC_EXEC) {
 		wp->facilities &= ~FACIL_DOCK;