Change: Path signals now show green on junction-less tracks by default (#12857)

src/pathfinder/yapf/yapf_rail.cpp

@@ -57,6 +57,8 @@ private:
 	Trackdir  m_res_fail_td;      ///< The trackdir where the reservation failed
 	TileIndex m_origin_tile;      ///< Tile our reservation will originate from
 
+	std::vector<std::pair<TileIndex, Trackdir>> m_signals_set_to_red; ///< List of signals turned red during a path reservation.
+
 	bool FindSafePositionProc(TileIndex tile, Trackdir td)
 	{
 		if (IsSafeWaitingPosition(Yapf().GetVehicle(), tile, td, true, !TrackFollower::Allow90degTurns())) {
@@ -88,8 +90,9 @@ private:
 	/** Try to reserve a single track/platform. */
 	bool ReserveSingleTrack(TileIndex tile, Trackdir td)
 	{
+		Trackdir rev_td = ReverseTrackdir(td);
 		if (IsRailStationTile(tile)) {
-			if (!ReserveRailStationPlatform(tile, TrackdirToExitdir(ReverseTrackdir(td)))) {
+			if (!ReserveRailStationPlatform(tile, TrackdirToExitdir(rev_td))) {
 				/* Platform could not be reserved, undo. */
 				m_res_fail_tile = tile;
 				m_res_fail_td = td;
@@ -101,6 +104,13 @@ private:
 				m_res_fail_td = td;
 				return false;
 			}
+
+			/* Green path signal opposing the path? Turn to red. */
+			if (HasPbsSignalOnTrackdir(tile, rev_td) && GetSignalStateByTrackdir(tile, rev_td) == SIGNAL_STATE_GREEN) {
+				m_signals_set_to_red.emplace_back(tile, rev_td);
+				SetSignalStateByTrackdir(tile, rev_td, SIGNAL_STATE_RED);
+				MarkTileDirtyByTile(tile);
+			}
 		}
 
 		return tile != m_res_dest || td != m_res_dest_td;
@@ -159,6 +169,7 @@ public:
 		/* Don't bother if the target is reserved. */
 		if (!IsWaitingPositionFree(Yapf().GetVehicle(), m_res_dest, m_res_dest_td)) return false;
 
+		m_signals_set_to_red.clear();
 		for (Node *node = m_res_node; node->m_parent != nullptr; node = node->m_parent) {
 			node->IterateTiles(Yapf().GetVehicle(), Yapf(), *this, &CYapfReserveTrack<Types>::ReserveSingleTrack);
 			if (m_res_fail_tile != INVALID_TILE) {
@@ -171,6 +182,11 @@ public:
 					fail_node->IterateTiles(Yapf().GetVehicle(), Yapf(), *this, &CYapfReserveTrack<Types>::UnreserveSingleTrack);
 				} while (fail_node != node && (fail_node = fail_node->m_parent) != nullptr);
 
+				/* Re-instate green path signals we turned to red. */
+				for (auto [sig_tile, td] : m_signals_set_to_red) {
+					SetSignalStateByTrackdir(sig_tile, td, SIGNAL_STATE_GREEN);
+				}
+
 				return false;
 			}
 		}

src/signal.cpp

@@ -15,6 +15,7 @@
 #include "viewport_func.h"
 #include "train.h"
 #include "company_base.h"
+#include "pbs.h"
 
 #include "safeguards.h"
 
@@ -251,6 +252,9 @@ enum SigFlags {
 	SF_GREEN2 = 1 << 4, ///< two or more green exits found
 	SF_FULL   = 1 << 5, ///< some of buffers was full, do not continue
 	SF_PBS    = 1 << 6, ///< pbs signal found
+	SF_SPLIT  = 1 << 7, ///< track merge/split found
+	SF_ENTER  = 1 << 8, ///< signal entering the block found
+	SF_ENTER2 = 1 << 9, ///< two or more signals entering the block found
 };
 
 DECLARE_ENUM_AS_BIT_SET(SigFlags)
@@ -305,6 +309,9 @@ static SigFlags ExploreSegment(Owner owner)
 					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags |= SF_TRAIN;
 				}
 
+				/* Is this a track merge or split? */
+				if (!HasAtMostOneBit(tracks)) flags |= SF_SPLIT;
+
 				if (HasSignals(tile)) { // there is exactly one track - not zero, because there is exit from this tile
 					Track track = TrackBitsToTrack(tracks_masked); // mask TRACK_BIT_X and Y too
 					if (HasSignalOnTrack(tile, track)) { // now check whole track, not trackdir
@@ -315,11 +322,11 @@ static SigFlags ExploreSegment(Owner owner)
 						 * ANY conventional signal in REVERSE direction
 						 * (if it is a presignal EXIT and it changes, it will be added to 'to-be-done' set later) */
 						if (HasSignalOnTrackdir(tile, reversedir)) {
-							if (IsPbsSignal(sig)) {
+							if (IsPbsSignal(sig)) flags |= SF_PBS;
-								flags |= SF_PBS;
+							if (flags & SF_ENTER) flags |= SF_ENTER2;
-							} else if (!_tbuset.Add(tile, reversedir)) {
+							flags |= SF_ENTER;
-								return flags | SF_FULL;
+
-							}
+							if (!_tbuset.Add(tile, reversedir)) return flags | SF_FULL;
 						}
 						if (HasSignalOnTrackdir(tile, trackdir) && !IsOnewaySignal(tile, track)) flags |= SF_PBS;
 
@@ -411,13 +418,20 @@ static void UpdateSignalsAroundSegment(SigFlags flags)
 	while (_tbuset.Get(&tile, &trackdir)) {
 		assert(HasSignalOnTrackdir(tile, trackdir));
 
-		SignalType sig = GetSignalType(tile, TrackdirToTrack(trackdir));
+		Track track = TrackdirToTrack(trackdir);
+		SignalType sig = GetSignalType(tile, track);
 		SignalState newstate = SIGNAL_STATE_GREEN;
 
+		/* Signal state of reserved path signals is handled by the reserve/unreserve process. */
+		if (IsPbsSignal(sig) && (GetRailReservationTrackBits(tile) & TrackToTrackBits(track)) != TRACK_BIT_NONE) continue;
+
 		/* determine whether the new state is red */
 		if (flags & SF_TRAIN) {
 			/* train in the segment */
 			newstate = SIGNAL_STATE_RED;
+		} else if (IsPbsSignal(sig) && (flags & (SF_SPLIT | SF_ENTER2))) {
+			/* Turn path signals red if the segment has a junction or more than one way in. */
+			newstate = SIGNAL_STATE_RED;
 		} else {
 			/* is it a bidir combo? - then do not count its other signal direction as exit */
 			if (sig == SIGTYPE_COMBO && HasSignalOnTrackdir(tile, ReverseTrackdir(trackdir))) {

src/train_cmd.cpp

@@ -2430,6 +2430,9 @@ void FreeTrainTrackReservation(const Train *v)
 					SetSignalStateByTrackdir(tile, td, SIGNAL_STATE_RED);
 					MarkTileDirtyByTile(tile);
 				}
+			} else if (HasPbsSignalOnTrackdir(tile, ReverseTrackdir(td))) {
+				/* Reservation passes an opposing path signal. Mark signal for update to re-establish the proper default state. */
+				AddSideToSignalBuffer(tile, TrackdirToExitdir(ReverseTrackdir(td)), v->owner);
 			} else if (HasSignalOnTrackdir(tile, ReverseTrackdir(td)) && IsOnewaySignal(tile, TrackdirToTrack(td))) {
 				break;
 			}
@@ -2440,6 +2443,8 @@ void FreeTrainTrackReservation(const Train *v)
 
 		free_tile = true;
 	}
+
+	UpdateSignalsInBuffer();
 }
 
 static const uint8_t _initial_tile_subcoord[6][4][3] = {
@@ -2481,6 +2486,8 @@ static PBSTileInfo ExtendTrainReservation(const Train *v, TrackBits *new_tracks,
 
 	CFollowTrackRail ft(v);
 
+	std::vector<std::pair<TileIndex, Trackdir>> signals_set_to_red;
+
 	TileIndex tile = origin.tile;
 	Trackdir  cur_td = origin.trackdir;
 	while (ft.Follow(tile, cur_td)) {
@@ -2518,14 +2525,28 @@ static PBSTileInfo ExtendTrainReservation(const Train *v, TrackBits *new_tracks,
 		tile = ft.m_new_tile;
 		cur_td = FindFirstTrackdir(ft.m_new_td_bits);
 
+		Trackdir rev_td = ReverseTrackdir(cur_td);
 		if (IsSafeWaitingPosition(v, tile, cur_td, true, _settings_game.pf.forbid_90_deg)) {
 			bool wp_free = IsWaitingPositionFree(v, tile, cur_td, _settings_game.pf.forbid_90_deg);
 			if (!(wp_free && TryReserveRailTrack(tile, TrackdirToTrack(cur_td)))) break;
+			/* Green path signal opposing the path? Turn to red. */
+			if (HasPbsSignalOnTrackdir(tile, rev_td) && GetSignalStateByTrackdir(tile, rev_td) == SIGNAL_STATE_GREEN) {
+				signals_set_to_red.emplace_back(tile, rev_td);
+				SetSignalStateByTrackdir(tile, rev_td, SIGNAL_STATE_RED);
+				MarkTileDirtyByTile(tile);
+			}
 			/* Safe position is all good, path valid and okay. */
 			return PBSTileInfo(tile, cur_td, true);
 		}
 
 		if (!TryReserveRailTrack(tile, TrackdirToTrack(cur_td))) break;
+
+		/* Green path signal opposing the path? Turn to red. */
+		if (HasPbsSignalOnTrackdir(tile, rev_td) && GetSignalStateByTrackdir(tile, rev_td) == SIGNAL_STATE_GREEN) {
+			signals_set_to_red.emplace_back(tile, rev_td);
+			SetSignalStateByTrackdir(tile, rev_td, SIGNAL_STATE_RED);
+			MarkTileDirtyByTile(tile);
+		}
 	}
 
 	if (ft.m_err == CFollowTrackRail::EC_OWNER || ft.m_err == CFollowTrackRail::EC_NO_WAY) {
@@ -2553,6 +2574,11 @@ static PBSTileInfo ExtendTrainReservation(const Train *v, TrackBits *new_tracks,
 		UnreserveRailTrack(tile, TrackdirToTrack(cur_td));
 	}
 
+	/* Re-instate green signals we turned to red. */
+	for (auto [sig_tile, td] : signals_set_to_red) {
+		SetSignalStateByTrackdir(sig_tile, td, SIGNAL_STATE_GREEN);
+	}
+
 	/* Path invalid. */
 	return PBSTileInfo();
 }