Try to extend reservation when passing sighting distance of non-end signal

src/pbs.cpp

@@ -550,6 +550,8 @@ static PBSTileInfo FollowReservation(Owner o, RailTypes rts, TileIndex tile, Tra
 					/* Exit signal */
 					const int end_offset = start_offset + (TILE_SIZE * length) /* + ((DiagDirToDiagTrackBits(GetTunnelBridgeDirection(end)) & GetTunnelBridgeTrackBits(end)) ? 16 : 8)*/;
 					lookahead->AddSignal(signal_speed, end_offset, z);
+
+					lookahead->SetNextExtendPositionIfUnset();
 				} else {
 					update_z(tile, trackdir, false);
 					if (length > 1) {
@@ -591,6 +593,7 @@ static PBSTileInfo FollowReservation(Owner o, RailTypes rts, TileIndex tile, Tra
 					uint16 signal_speed = GetRailTypeInfo(rt)->max_speed;
 					if (signal_speed == 0 || (speed_restriction != 0 && speed_restriction < signal_speed)) signal_speed = speed_restriction;
 					lookahead->AddSignal(signal_speed, 0, z);
+					lookahead->SetNextExtendPositionIfUnset();
 				}
 			}
 
@@ -662,6 +665,18 @@ static Vehicle *FindTrainOnTrackEnum(Vehicle *v, void *data)
 	return nullptr;
 }
 
+void TrainReservationLookAhead::SetNextExtendPosition()
+{
+	int32 threshold = this->current_position + 24;
+	for (const TrainReservationLookAheadItem &item : this->items) {
+		if (item.type == TRLIT_SIGNAL && item.start > threshold) {
+			this->next_extend_position = item.start - 24;
+			return;
+		}
+	}
+	this->next_extend_position = this->current_position;
+}
+
 bool ValidateLookAhead(const Train *v)
 {
 	TileIndex tile = v->lookahead->reservation_end_tile;
@@ -846,6 +861,7 @@ void TryCreateLookAheadForTrainInTunnelBridge(Train *t)
 		t->lookahead->reservation_end_trackdir = GetTunnelBridgeEntranceTrackdir(t->tile);
 		t->lookahead->reservation_end_z = t->z_pos;
 		t->lookahead->current_position = 0;
+		t->lookahead->next_extend_position = 0;
 		t->lookahead->tunnel_bridge_reserved_tiles = DistanceManhattan(t->tile, TileVirtXY(t->x_pos, t->y_pos));
 		t->lookahead->reservation_end_position = GetTileMarginInFrontOfTrain(t);
 		t->lookahead->flags = 0;
@@ -874,6 +890,8 @@ void TryCreateLookAheadForTrainInTunnelBridge(Train *t)
 			/* Exit signal */
 			const int end_offset = TILE_SIZE * length;
 			t->lookahead->AddSignal(signal_speed, end_offset, z);
+
+			t->lookahead->SetNextExtendPositionIfUnset();
 		}
 
 		FillLookAheadCurveDataFromTrainPosition(t);
@@ -897,6 +915,7 @@ void FillTrainReservationLookAhead(Train *v)
 	if (v->lookahead == nullptr) {
 		v->lookahead.reset(new TrainReservationLookAhead());
 		v->lookahead->current_position = 0;
+		v->lookahead->next_extend_position = 0;
 
 		/* Special case, if called from TrainController,
 		 * v->tile, v->track and v->direction can be updated to the new tile,

src/pbs.h

@@ -83,6 +83,7 @@ struct TrainReservationLookAhead {
 	Trackdir  reservation_end_trackdir;   ///< The reserved trackdir on the end tile.
 	int32 current_position;               ///< Current position of the train on the reservation
 	int32 reservation_end_position;       ///< Position of the end of the reservation
+	int32 next_extend_position;           ///< Next position to try extending the reservation at the sighting distance of the next mid-reservation signal
 	int16 reservation_end_z;              ///< The z coordinate of the reservation end
 	int16 tunnel_bridge_reserved_tiles;   ///< How many tiles a reservation into the tunnel/bridge currently extends into the wormhole
 	uint16 flags;                         ///< Flags (TrainReservationLookAheadFlags)
@@ -131,6 +132,13 @@ struct TrainReservationLookAhead {
 		int end = this->RealEndPosition();
 		this->items.push_back({ end + offset, end + offset, z_pos, target_speed, TRLIT_CURVE_SPEED });
 	}
+
+	void SetNextExtendPosition();
+
+	void SetNextExtendPositionIfUnset()
+	{
+		if (this->next_extend_position <= this->current_position) this->SetNextExtendPosition();
+	}
 };
 
 /** Flags for FollowTrainReservation */
@@ -146,6 +154,8 @@ PBSTileInfo FollowTrainReservation(const Train *v, Vehicle **train_on_res = null
 void ApplyAvailableFreeTunnelBridgeTiles(TrainReservationLookAhead *lookahead, int free_tiles, TileIndex tile, TileIndex end);
 void TryCreateLookAheadForTrainInTunnelBridge(Train *t);
 void FillTrainReservationLookAhead(Train *v);
+void SetLookAheadNextExtendPosition(Train *v);
+void SetLookAheadNextExtendPositionIfUnset(Train *v);
 bool IsSafeWaitingPosition(const Train *v, TileIndex tile, Trackdir trackdir, bool include_line_end, bool forbid_90deg = false);
 bool IsWaitingPositionFree(const Train *v, TileIndex tile, Trackdir trackdir, bool forbid_90deg = false, PBSWaitingPositionRestrictedSignalInfo *restricted_signal_info = nullptr);
 

src/saveload/afterload.cpp

@@ -3934,6 +3934,14 @@ bool AfterLoadGame()
 		UpdateAllBlockSignals();
 	}
 
+	if (!SlXvIsFeaturePresent(XSLFI_REALISTIC_TRAIN_BRAKING, 5) && _settings_game.vehicle.train_braking_model == TBM_REALISTIC) {
+		for (Train *t : Train::Iterate()) {
+			if (t->lookahead != nullptr) {
+				t->lookahead->SetNextExtendPosition();
+			}
+		}
+	}
+
 	if (SlXvIsFeatureMissing(XSLFI_INFLATION_FIXED_DATES)) {
 		_settings_game.economy.inflation_fixed_dates = !IsSavegameVersionBefore(SLV_GS_INDUSTRY_CONTROL);
 	}

src/saveload/extended_ver_sl.cpp

@@ -147,7 +147,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_ANIMATED_TILE_EXTRA,    XSCF_NULL,                1,   1, "animated_tile_extra",       nullptr, nullptr, nullptr        },
 	{ XSLFI_NEWGRF_INFO_EXTRA,      XSCF_NULL,                1,   1, "newgrf_info_extra",         nullptr, nullptr, nullptr        },
 	{ XSLFI_INDUSTRY_CARGO_ADJ,     XSCF_IGNORABLE_UNKNOWN,   1,   1, "industry_cargo_adj",        nullptr, nullptr, nullptr        },
-	{ XSLFI_REALISTIC_TRAIN_BRAKING,XSCF_NULL,                4,   4, "realistic_train_braking",   nullptr, nullptr, "VLKA"         },
+	{ XSLFI_REALISTIC_TRAIN_BRAKING,XSCF_NULL,                5,   5, "realistic_train_braking",   nullptr, nullptr, "VLKA"         },
 	{ XSLFI_INFLATION_FIXED_DATES,  XSCF_IGNORABLE_ALL,       1,   1, "inflation_fixed_dates",     nullptr, nullptr, nullptr        },
 	{ XSLFI_WATER_FLOODING,         XSCF_NULL,                2,   2, "water_flooding",            nullptr, nullptr, nullptr        },
 	{ XSLFI_MORE_HOUSES,            XSCF_NULL,                2,   2, "more_houses",               nullptr, nullptr, nullptr        },

src/saveload/vehicle_sl.cpp

@@ -1390,6 +1390,7 @@ const SaveLoadTable GetVehicleLookAheadDescription()
 		     SLE_VAR(TrainReservationLookAhead, tunnel_bridge_reserved_tiles, SLE_INT16),
 		     SLE_VAR(TrainReservationLookAhead, flags,                        SLE_UINT16),
 		     SLE_VAR(TrainReservationLookAhead, speed_restriction,            SLE_UINT16),
+		SLE_CONDVAR_X(TrainReservationLookAhead, next_extend_position,        SLE_INT32,  SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_REALISTIC_TRAIN_BRAKING, 5)),
 	};
 
 	return _vehicle_look_ahead_desc;

src/table/newgrf_debug_data.h

@@ -209,7 +209,10 @@ class NIHVehicle : public NIHelper {
 					}
 				};
 
-				seprintf(buffer, lastof(buffer), "    Position: current: %d, z: %d, end: %d, remaining: %d", l.current_position, stats.z_pos, l.reservation_end_position, l.reservation_end_position - l.current_position);
+				b = buffer + seprintf(buffer, lastof(buffer), "    Position: current: %d, z: %d, end: %d, remaining: %d", l.current_position, stats.z_pos, l.reservation_end_position, l.reservation_end_position - l.current_position);
+				if (l.next_extend_position > l.current_position) {
+					b += seprintf(b, lastof(buffer), ", next extend position: %d (dist: %d)", l.next_extend_position, l.next_extend_position - l.current_position);
+				}
 				print(buffer);
 
 				b = buffer + seprintf(buffer, lastof(buffer), "    Reservation ends at %X (%u x %u), trackdir: %02X, z: %d",

src/train_cmd.cpp

@@ -975,6 +975,7 @@ static void AdvanceLookAheadPosition(Train *v)
 		const int32 old_position = v->lookahead->current_position;
 		v->lookahead->current_position = 0;
 		v->lookahead->reservation_end_position -= old_position;
+		v->lookahead->next_extend_position -= old_position;
 		for (TrainReservationLookAheadItem &item : v->lookahead->items) {
 			item.start -= old_position;
 			item.end -= old_position;
@@ -998,6 +999,11 @@ static void AdvanceLookAheadPosition(Train *v)
 		}
 		v->lookahead->items.pop_front();
 	}
+
+	if (v->lookahead->current_position == v->lookahead->next_extend_position) {
+		TryLongReserveChooseTrainTrackFromReservationEnd(v, true);
+		v->lookahead->SetNextExtendPositionIfUnset();
+	}
 }
 
 /**