(svn r19369) -Codechange: EnsureNoTrainOnTrackBits() returns a CommandCost now.

src/rail_cmd.cpp

@@ -155,7 +155,9 @@ static const byte _track_sloped_sprites[14] = {
 static bool EnsureNoTrainOnTrack(TileIndex tile, Track track)
 {
 	TrackBits rail_bits = TrackToTrackBits(track);
-	return EnsureNoTrainOnTrackBits(tile, rail_bits);
+	CommandCost ret = EnsureNoTrainOnTrackBits(tile, rail_bits);
+	ret.SetGlobalErrorMessage();
+	return ret.Succeeded();
 }
 
 /** Check that the new track bits may be built.

src/signal.cpp

@@ -301,7 +301,8 @@ static SigFlags ExploreSegment(Owner owner)
 
 				if (tracks == TRACK_BIT_HORZ || tracks == TRACK_BIT_VERT) { // there is exactly one incidating track, no need to check
 					tracks = tracks_masked;
-					if (!(flags & SF_TRAIN) && !EnsureNoTrainOnTrackBits(tile, tracks)) flags |= SF_TRAIN;
+					/* If no train detected yet, and there is not no train -> there is a train -> set the flag */
+					if (!(flags & SF_TRAIN) && EnsureNoTrainOnTrackBits(tile, tracks).Failed()) flags |= SF_TRAIN;
 				} else {
 					if (tracks_masked == TRACK_BIT_NONE) continue; // no incidating track
 					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;

src/vehicle.cpp

@@ -472,15 +472,15 @@ static Vehicle *EnsureNoTrainOnTrackProc(Vehicle *v, void *data)
  * @param track_bits The track bits.
  * @return \c true if no train that interacts, is found. \c false if a train is found.
  */
-bool EnsureNoTrainOnTrackBits(TileIndex tile, TrackBits track_bits)
+CommandCost EnsureNoTrainOnTrackBits(TileIndex tile, TrackBits track_bits)
 {
 	/* Value v is not safe in MP games, however, it is used to generate a local
 	 * error message only (which may be different for different machines).
 	 * Such a message does not affect MP synchronisation.
 	 */
 	Vehicle *v = VehicleFromPos(tile, &track_bits, &EnsureNoTrainOnTrackProc, 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();
 }
 
 static void UpdateNewVehiclePosHash(Vehicle *v, bool remove)

src/vehicle_func.h

@@ -158,7 +158,7 @@ static inline uint32 GetCmdSendToDepot(const BaseVehicle *v)
 }
 
 CommandCost EnsureNoVehicleOnGround(TileIndex tile);
-bool EnsureNoTrainOnTrackBits(TileIndex tile, TrackBits track_bits);
+CommandCost EnsureNoTrainOnTrackBits(TileIndex tile, TrackBits track_bits);
 void StopAllVehicles();
 
 extern VehicleID _vehicle_id_ctr_day;