Fix speed reduction after critical breakdowns.

Previous code set vcache.cached_max_speed directly (and incorrectly),
which did not survive across save/load or network joins.
Instead add a struct Train field to store the number
of critical breakdowns since last service and do the speed reduction
properly in Train::ConsistChanged.
Slightly tweak algorithm for speed reduction.

src/saveload/vehicle_sl.cpp

@@ -726,6 +726,7 @@ const SaveLoad *GetVehicleDescription(VehicleType vt)
 		SLE_CONDNULL(2, 2, 19),
 		 SLE_CONDVAR(Train, gv_flags,            SLE_UINT16,                 139, SL_MAX_VERSION),
 		SLE_CONDNULL(11, 2, 143), // old reserved space
+		 SLE_CONDVAR(Train, critical_breakdown_count, SLE_UINT8,           SL_IB, SL_MAX_VERSION),
 
 		     SLE_END()
 	};

src/settings_type.h

@@ -462,7 +462,7 @@ struct VehicleSettings {
 	byte   extend_vehicle_life;              ///< extend vehicle life by this many years
 	byte   road_side;                        ///< the side of the road vehicles drive on
 	uint8  plane_crashes;                    ///< number of plane crashes, 0 = none, 1 = reduced, 2 = normal
-	bool   improved_breakdowns;		 ///< different types, chances and serverities of breakdowns
+	bool   improved_breakdowns;              ///< different types, chances and severities of breakdowns
 };
 
 /** Settings related to the economy. */

src/train.h

@@ -106,6 +106,7 @@ struct Train FINAL : public GroundVehicle<Train, VEH_TRAIN> {
 	TrackBitsByte track;
 	TrainForceProceedingByte force_proceed;
 	RailTypeByte railtype;
+	byte critical_breakdown_count; ///< Counter for the number of critical breakdowns since last service
 	RailTypes compatible_railtypes;
 
 	/** Ticks waiting in front of a signal, ticks being stuck or a counter for forced proceeding through signals. */

src/train_cmd.cpp

@@ -191,6 +191,12 @@ void Train::ConsistChanged(ConsistChangeFlags allowed_changes)
 		u->tcache.user_def_data = GetVehicleProperty(u, PROP_TRAIN_USER_DATA, u->tcache.user_def_data);
 		this->InvalidateNewGRFCache();
 		u->InvalidateNewGRFCache();
+
+		if (!u->IsArticulatedPart()) {
+			if (u->IsEngine() || u->IsMultiheaded()) {
+				this->tcache.cached_num_engines++;
+			}
+		}
 	}
 
 	for (Train *u = this; u != NULL; u = u->Next()) {
@@ -233,13 +239,13 @@ void Train::ConsistChanged(ConsistChangeFlags allowed_changes)
 			/* max speed is the minimum of the speed limits of all vehicles in the consist */
 			if ((rvi_u->railveh_type != RAILVEH_WAGON || _settings_game.vehicle.wagon_speed_limits) && !UsesWagonOverride(u)) {
 				uint16 speed = GetVehicleProperty(u, PROP_TRAIN_SPEED, rvi_u->max_speed);
-				if (HasBit(u->flags, VRF_NEED_REPAIR)) speed = u->vcache.cached_max_speed;
+				if (HasBit(u->flags, VRF_NEED_REPAIR) && this->IsFrontEngine()) {
+					for (uint i = 0; i < u->critical_breakdown_count; i++) {
+						speed = min(speed - (speed / (this->tcache.cached_num_engines + 2)) + 1, speed);
+					}
+				}
 				if (speed != 0) max_speed = min(speed, max_speed);
 			}
-
-			if (u->IsEngine() || u-> IsMultiheaded()) {
-				this->tcache.cached_num_engines++;
-			}
 		}
 
 		uint16 new_cap = e_u->DetermineCapacity(u);

src/vehicle.cpp

@@ -104,6 +104,7 @@ void VehicleServiceInDepot(Vehicle *v)
 		if (v->Next() != NULL) VehicleServiceInDepot(v->Next());
 		if (!(Train::From(v)->IsEngine()) && !(Train::From(v)->IsRearDualheaded())) return;
 		ClrBit(Train::From(v)->flags,VRF_NEED_REPAIR);
+		Train::From(v)->critical_breakdown_count = 0;
 		const RailVehicleInfo *rvi = &e->u.rail;
 		v->vcache.cached_max_speed = rvi->max_speed;
 		if (Train::From(v)->IsFrontEngine()) {
@@ -1352,17 +1353,12 @@ bool Vehicle::HandleBreakdown()
 							}
 							/* Max Speed reduction*/
 							if (_settings_game.vehicle.improved_breakdowns) {
-								const Engine *e = Engine::Get(this->engine_type);
-								const RailVehicleInfo *rvi = &e->u.rail;
-								if (!HasBit(Train::From(this)->flags,VRF_NEED_REPAIR)) {
-									if (rvi->max_speed > this->vcache.cached_max_speed) {
-										this->vcache.cached_max_speed = rvi->max_speed;
-									}
+								if (!HasBit(Train::From(this)->flags, VRF_NEED_REPAIR)) {
+									SetBit(Train::From(this)->flags, VRF_NEED_REPAIR);
+									Train::From(this)->critical_breakdown_count = 1;
+								} else if (Train::From(this)->critical_breakdown_count != 255) {
+									Train::From(this)->critical_breakdown_count++;
 								}
-								uint16 target_max_speed = min(this->vcache.cached_max_speed -
-										(this->vcache.cached_max_speed >> 1) / Train::From(this->First())->tcache.cached_num_engines + 1, this->vcache.cached_max_speed);
-								this->vcache.cached_max_speed = max(target_max_speed, min<uint16>(rvi->max_speed / 4, 28));
-								SetBit(Train::From(this)->flags, VRF_NEED_REPAIR);
 								Train::From(this->First())->ConsistChanged(CCF_TRACK);
 							}
 						/* FALL THROUGH */