Tracerestrict: Add reverse at PBS signal sub-action

src/lang/extra/english.txt

@@ -1025,6 +1025,8 @@ STR_TRACE_RESTRICT_TRAIN_STATUS_REQUIRES_SERVICE                :requires servic
 STR_TRACE_RESTRICT_TRAIN_STATUS_STOPPING_AT_STATION_WAYPOINT    :stopping at station/waypoint
 STR_TRACE_RESTRICT_REVERSE_SIG                                  :Reverse behind signal
 STR_TRACE_RESTRICT_REVERSE_SIG_CANCEL                           :Cancel reverse behind signal
+STR_TRACE_RESTRICT_REVERSE_AT_SIG                               :Reverse at PBS signal
+STR_TRACE_RESTRICT_REVERSE_AT_SIG_CANCEL                        :Cancel reverse at PBS signal
 STR_TRACE_RESTRICT_SET_SPEED_RESTRICTION                        :Restrict train speed to: {VELOCITY}
 STR_TRACE_RESTRICT_REMOVE_SPEED_RESTRICTION                     :Remove train speed restriction
 STR_TRACE_RESTRICT_TRAIN_NOT_STUCK                              :Train is not stuck, do not show news reports about waiting at this PBS signal

src/sl/extended_ver_sl.cpp

@@ -80,7 +80,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_TRACE_RESTRICT_OWNER,             XSCF_NULL,                1,   1, "tracerestrict_owner",              nullptr, nullptr, nullptr          },
 	{ XSLFI_TRACE_RESTRICT_ORDRCND,           XSCF_NULL,                4,   4, "tracerestrict_order_cond",         nullptr, nullptr, nullptr          },
 	{ XSLFI_TRACE_RESTRICT_STATUSCND,         XSCF_NULL,                2,   2, "tracerestrict_status_cond",        nullptr, nullptr, nullptr          },
-	{ XSLFI_TRACE_RESTRICT_REVERSE,           XSCF_NULL,                1,   1, "tracerestrict_reverse",            nullptr, nullptr, nullptr          },
+	{ XSLFI_TRACE_RESTRICT_REVERSE,           XSCF_NULL,                2,   2, "tracerestrict_reverse",            nullptr, nullptr, nullptr          },
 	{ XSLFI_TRACE_RESTRICT_NEWSCTRL,          XSCF_NULL,                1,   1, "tracerestrict_newsctrl",           nullptr, nullptr, nullptr          },
 	{ XSLFI_TRACE_RESTRICT_COUNTER,           XSCF_NULL,                1,   1, "tracerestrict_counter",            nullptr, nullptr, "TRRC"           },
 	{ XSLFI_TRACE_RESTRICT_TIMEDATE,          XSCF_NULL,                2,   2, "tracerestrict_timedate",           nullptr, nullptr, nullptr          },

src/table/newgrf_debug_data.h

@@ -2279,6 +2279,7 @@ class NIHTraceRestrict : public NIHelper {
 		CA(RESERVE_THROUGH_ALWAYS)
 		CA(CMB_SIGNAL_MODE_CTRL)
 		CA(ORDER_CONDITIONALS)
+		CA(REVERSE_AT)
 #undef CA
 		output.print("");
 

src/tracerestrict.cpp

@@ -804,6 +804,13 @@ void TraceRestrictProgram::Execute(const Train* v, const TraceRestrictProgramInp
 							case TRRVF_CANCEL_REVERSE_BEHIND:
 								out.flags &= ~TRPRF_REVERSE_BEHIND;
 								break;
+
+							case TRRVF_REVERSE_AT:
+								out.flags |= TRPRF_REVERSE_AT;
+								break;
+
+							case TRRVF_CANCEL_REVERSE_AT:
+								out.flags &= ~TRPRF_REVERSE_AT;
 								break;
 
 							default:
@@ -1410,6 +1417,14 @@ CommandCost TraceRestrictProgram::Validate(const std::vector<TraceRestrictItem>
 							if (condstack.empty()) actions_used_flags &= ~TRPAUF_REVERSE_BEHIND;
 							break;
 
+						case TRRVF_REVERSE_AT:
+							actions_used_flags |= TRPAUF_REVERSE_AT;
+							break;
+
+						case TRRVF_CANCEL_REVERSE_AT:
+							if (condstack.empty()) actions_used_flags &= ~TRPAUF_REVERSE_AT;
+							break;
+
 						default:
 							return unknown_instruction();
 					}

src/tracerestrict.h

@@ -174,7 +174,7 @@ enum TraceRestrictItemType : uint8_t {
 	TRIT_COND_RESERVATION_THROUGH = 32,   ///< Test if train reservation passes through tile
 
 	TRIT_COND_END                 = 48,   ///< End (exclusive) of conditional item types, note that this has the same value as TRIT_REVERSE
-	TRIT_REVERSE                  = 48,   ///< Reverse behind signal
+	TRIT_REVERSE                  = 48,   ///< Reverse behind/at signal
 	TRIT_SPEED_RESTRICTION        = 49,   ///< Speed restriction
 	TRIT_NEWS_CONTROL             = 50,   ///< News control
 	TRIT_COUNTER                  = 51,   ///< Change counter value
@@ -312,6 +312,8 @@ enum TraceRestrictWaitAtPbsValueField : uint8_t {
 enum TraceRestrictReverseValueField : uint8_t {
 	TRRVF_REVERSE_BEHIND               = 0,       ///< Reverse behind signal
 	TRRVF_CANCEL_REVERSE_BEHIND        = 1,       ///< Cancel reverse behind signal
+	TRRVF_REVERSE_AT                   = 2,       ///< Reverse at PBS signal
+	TRRVF_CANCEL_REVERSE_AT            = 3,       ///< Cancel reverse at PBS signal
 };
 
 /**
@@ -448,6 +450,7 @@ enum TraceRestrictProgramResultFlags : uint16_t {
 	TRPRF_RM_SPEED_ADAPT_EXEMPT   = 1 << 10, ///< Remove speed adaptation exemption
 	TRPRF_SIGNAL_MODE_NORMAL      = 1 << 11, ///< Combined normal/shunt signal mode control: normal
 	TRPRF_SIGNAL_MODE_SHUNT       = 1 << 12, ///< Combined normal/shunt signal mode control: shunt
+	TRPRF_REVERSE_AT              = 1 << 13, ///< Reverse at PBS signal is set
 };
 DECLARE_ENUM_AS_BIT_SET(TraceRestrictProgramResultFlags)
 
@@ -476,6 +479,7 @@ enum TraceRestrictProgramActionsUsedFlags : uint32_t {
 	TRPAUF_RESERVE_THROUGH_ALWAYS = 1 << 17, ///< Reserve through action is unconditionally set
 	TRPAUF_CMB_SIGNAL_MODE_CTRL   = 1 << 18, ///< Combined normal/shunt signal mode control
 	TRPAUF_ORDER_CONDITIONALS     = 1 << 19, ///< Order conditionals are present
+	TRPAUF_REVERSE_AT             = 1 << 20, ///< Reverse at signal
 };
 DECLARE_ENUM_AS_BIT_SET(TraceRestrictProgramActionsUsedFlags)
 

src/tracerestrict_gui.cpp

@@ -335,10 +335,14 @@ static const TraceRestrictDropDownListSet _train_status_value = {
 static const StringID _reverse_value_str[] = {
 	STR_TRACE_RESTRICT_REVERSE_SIG,
 	STR_TRACE_RESTRICT_REVERSE_SIG_CANCEL,
+	STR_TRACE_RESTRICT_REVERSE_AT_SIG,
+	STR_TRACE_RESTRICT_REVERSE_AT_SIG_CANCEL,
 };
 static const uint _reverse_value_val[] = {
 	TRRVF_REVERSE_BEHIND,
 	TRRVF_CANCEL_REVERSE_BEHIND,
+	TRRVF_REVERSE_AT,
+	TRRVF_CANCEL_REVERSE_AT,
 };
 
 /** value drop down list for reverse types strings and values */
@@ -1614,6 +1618,14 @@ static void DrawInstructionString(const TraceRestrictProgram *prog, TraceRestric
 						instruction_string = STR_TRACE_RESTRICT_REVERSE_SIG_CANCEL;
 						break;
 
+					case TRRVF_REVERSE_AT:
+						instruction_string = STR_TRACE_RESTRICT_REVERSE_AT_SIG;
+						break;
+
+					case TRRVF_CANCEL_REVERSE_AT:
+						instruction_string = STR_TRACE_RESTRICT_REVERSE_AT_SIG_CANCEL;
+						break;
+
 					default:
 						NOT_REACHED();
 						break;

src/train.h

@@ -86,6 +86,7 @@ void FreeTrainTrackReservation(Train *v, TileIndex origin = INVALID_TILE, Trackd
 enum TryPathReserveResultFlags {
 	TPRRF_NONE                  = 0,      ///< No flags
 	TPRRF_RESERVATION_OK        = 0x01,   ///< Reservation OK
+	TPRRF_REVERSE_AT_SIGNAL     = 0x02,   ///< Reverse at signal
 };
 DECLARE_ENUM_AS_BIT_SET(TryPathReserveResultFlags)
 

src/train_cmd.cpp

@@ -84,6 +84,7 @@ DECLARE_ENUM_AS_BIT_SET(ChooseTrainTrackFlags)
 enum ChooseTrainTrackResultFlags {
 	CTTRF_NONE                  = 0,      ///< No flags
 	CTTRF_RESERVATION_MADE      = 0x01,   ///< A reservation was made
+	CTTRF_REVERSE_AT_SIGNAL     = 0x02,   ///< Reverse at signal
 };
 DECLARE_ENUM_AS_BIT_SET(ChooseTrainTrackResultFlags)
 
@@ -4329,12 +4330,12 @@ static void TryLongReserveChooseTrainTrack(Train *v, TileIndex tile, Trackdir td
 						long_reserve = (out.flags & TRPRF_LONG_RESERVE);
 					}
 					if (!long_reserve) return;
-					if (prog != nullptr && prog->actions_used_flags & (TRPAUF_WAIT_AT_PBS | TRPAUF_SLOT_ACQUIRE)) {
+					if (prog != nullptr && prog->actions_used_flags & (TRPAUF_WAIT_AT_PBS | TRPAUF_SLOT_ACQUIRE | TRPAUF_REVERSE_AT)) {
 						TraceRestrictProgramResult out;
 						TraceRestrictProgramInput input(exit_tile, exit_td, nullptr, nullptr);
 						input.permitted_slot_operations = TRPISP_ACQUIRE;
 						prog->Execute(v, input, out);
-						if (out.flags & TRPRF_WAIT_AT_PBS) {
+						if (out.flags & (TRPRF_WAIT_AT_PBS | TRPRF_REVERSE_AT)) {
 							return;
 						}
 					}
@@ -4436,7 +4437,7 @@ static ChooseTrainTrackResult ChooseTrainTrack(Train *v, TileIndex tile, DiagDir
 		if (track != INVALID_TRACK && HasPbsSignalOnTrackdir(tile, TrackEnterdirToTrackdir(track, enterdir)) && !IsNoEntrySignal(tile, track)) {
 			if (IsRestrictedSignal(tile) && v->force_proceed != TFP_SIGNAL) {
 				const TraceRestrictProgram *prog = GetExistingTraceRestrictProgram(tile, track);
-				if (prog != nullptr && prog->actions_used_flags & (TRPAUF_WAIT_AT_PBS | TRPAUF_SLOT_ACQUIRE | TRPAUF_TRAIN_NOT_STUCK)) {
+				if (prog != nullptr && prog->actions_used_flags & (TRPAUF_WAIT_AT_PBS | TRPAUF_SLOT_ACQUIRE | TRPAUF_TRAIN_NOT_STUCK | TRPAUF_REVERSE_AT)) {
 					TraceRestrictProgramResult out;
 					TraceRestrictProgramInput input(tile, TrackEnterdirToTrackdir(track, enterdir), nullptr, nullptr);
 					input.permitted_slot_operations = TRPISP_ACQUIRE;
@@ -4444,7 +4445,10 @@ static ChooseTrainTrackResult ChooseTrainTrack(Train *v, TileIndex tile, DiagDir
 					if (out.flags & TRPRF_TRAIN_NOT_STUCK && !(v->track & TRACK_BIT_WORMHOLE) && !(v->track == TRACK_BIT_DEPOT)) {
 						v->wait_counter = 0;
 					}
-					if (out.flags & TRPRF_WAIT_AT_PBS) {
+					if (out.flags & TRPRF_REVERSE_AT) {
+						result_flags |= CTTRF_REVERSE_AT_SIGNAL;
+					}
+					if (out.flags & (TRPRF_WAIT_AT_PBS | TRPRF_REVERSE_AT)) {
 						if (mark_stuck) MarkTrainAsStuck(v, true);
 						return { track, result_flags };
 					}
@@ -4672,7 +4676,7 @@ static ChooseTrainTrackResult ChooseTrainTrack(Train *v, TileIndex tile, DiagDir
  * @param first_tile_okay True if no path should be reserved if the current tile is a safe position.
  * @return Result flags.
  */
-TryPathReserveResultFlags TryPathReserveResultFlags(Train *v, bool mark_as_stuck, bool first_tile_okay)
+TryPathReserveResultFlags TryPathReserveWithResultFlags(Train *v, bool mark_as_stuck, bool first_tile_okay)
 {
 	dbg_assert(v->IsFrontEngine());
 
@@ -4767,16 +4771,20 @@ TryPathReserveResultFlags TryPathReserveResultFlags(Train *v, bool mark_as_stuck
 
 	if (Rail90DegTurnDisallowedTilesFromDiagDir(origin.tile, new_tile, exitdir)) reachable &= ~TrackCrossesTracks(TrackdirToTrack(origin.trackdir));
 
-	bool res_made = false;
+	TryPathReserveResultFlags result_flags = TPRRF_NONE;
 	if (reachable != TRACK_BIT_NONE) {
 		ChooseTrainTrackResult result = ChooseTrainTrack(v, new_tile, exitdir, reachable, CTTF_FORCE_RES | (mark_as_stuck ? CTTF_MARK_STUCK : CTTF_NONE));
-		if (result.ctt_flags & CTTRF_RESERVATION_MADE) res_made = true;
+		if (result.ctt_flags & CTTRF_RESERVATION_MADE) {
+			result_flags |= TPRRF_RESERVATION_OK;
+		} else if (result.ctt_flags & CTTRF_REVERSE_AT_SIGNAL) {
+			result_flags |= TPRRF_REVERSE_AT_SIGNAL;
+		}
 	}
 
-	if (!res_made) {
+	if ((result_flags & TPRRF_RESERVATION_OK) == 0) {
 		/* Free the depot reservation as well. */
 		if (v->track == TRACK_BIT_DEPOT && v->tile == origin.tile) SetDepotReservation(v->tile, false);
-		return false;
+		return result_flags;
 	}
 
 	if (HasBit(v->flags, VRF_TRAIN_STUCK)) {
@@ -4785,7 +4793,7 @@ TryPathReserveResultFlags TryPathReserveResultFlags(Train *v, bool mark_as_stuck
 	}
 	ClrBit(v->flags, VRF_TRAIN_STUCK);
 	if (_settings_game.vehicle.train_braking_model == TBM_REALISTIC) FillTrainReservationLookAhead(v);
-	return true;
+	return result_flags;
 }
 
 
@@ -5679,10 +5687,13 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 				if (!CheckCompatibleRail(v, gp.new_tile, enterdir)) goto invalid_rail;
 
 				TrackBits chosen_track;
+				bool reverse_at_signal = false;
 				if (prev == nullptr) {
 					/* Currently the locomotive is active. Determine which one of the
 					 * available tracks to choose */
-					chosen_track = TrackToTrackBits(ChooseTrainTrack(v, gp.new_tile, enterdir, bits, CTTF_MARK_STUCK | CTTF_NON_LOOKAHEAD).track);
+					ChooseTrainTrackResult result = ChooseTrainTrack(v, gp.new_tile, enterdir, bits, CTTF_MARK_STUCK | CTTF_NON_LOOKAHEAD);
+					chosen_track = TrackToTrackBits(result.track);
+					reverse_at_signal = (result.ctt_flags & CTTRF_REVERSE_AT_SIGNAL);
 					dbg_assert_msg_tile(chosen_track & (bits | GetReservedTrackbits(gp.new_tile)), gp.new_tile, "0x%X, 0x%X, 0x%X", chosen_track, bits, GetReservedTrackbits(gp.new_tile));
 
 					if (v->force_proceed != TFP_NONE && IsPlainRailTile(gp.new_tile) && HasSignals(gp.new_tile)) {
@@ -5706,6 +5717,11 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 						/* In front of a red signal */
 						Trackdir i = FindFirstTrackdir(trackdirbits);
 
+						if (reverse_at_signal) {
+							ClrBit(v->flags, VRF_TRAIN_STUCK);
+							goto reverse_train_direction;
+						}
+
 						/* Don't handle stuck trains here. */
 						if (HasBit(v->flags, VRF_TRAIN_STUCK)) return false;
 
@@ -6706,9 +6722,10 @@ static bool TrainLocoHandler(Train *v, bool mode)
 		bool turn_around = v->wait_counter % (_settings_game.pf.wait_for_pbs_path * DAY_TICKS) == 0 && _settings_game.pf.reverse_at_signals;
 
 		if (!turn_around && v->wait_counter % _settings_game.pf.path_backoff_interval != 0 && v->force_proceed == TFP_NONE) return true;
-		if (!TryPathReserve(v)) {
+		TryPathReserveResultFlags path_result = TryPathReserveWithResultFlags(v);
+		if ((path_result & TPRRF_RESERVATION_OK) == 0) {
 			/* Still stuck. */
-			if (turn_around) ReverseTrainDirection(v);
+			if (turn_around || (path_result & TPRRF_REVERSE_AT_SIGNAL)) ReverseTrainDirection(v);
 
 			if (HasBit(v->flags, VRF_TRAIN_STUCK) && v->wait_counter > 2 * _settings_game.pf.wait_for_pbs_path * DAY_TICKS) {
 				/* Show message to player. */