(svn r24246) -Add [FS#5052-ish]: [NewGRF] Variable with the current max speed for vehicles.

src/aircraft.h

@@ -76,6 +76,7 @@ struct Aircraft FINAL : public SpecializedVehicle<Aircraft, VEH_AIRCRAFT> {
 	int GetDisplaySpeed() const    { return this->cur_speed; }
 	int GetDisplayMaxSpeed() const { return this->vcache.cached_max_speed; }
 	int GetSpeedOldUnits() const   { return this->vcache.cached_max_speed * 10 / 128; }
+	int GetCurrentMaxSpeed() const { return this->GetSpeedOldUnits(); }
 	Money GetRunningCost() const;
 	bool IsInDepot() const { return (this->vehstatus & VS_HIDDEN) != 0 && IsHangarTile(this->tile); }
 	bool Tick();

src/newgrf_engine.cpp

@@ -619,6 +619,10 @@ static uint32 VehicleGetVariable(Vehicle *v, const ResolverObject *object, byte
 		case 0x4B: // Long date of last service
 			return v->date_of_last_service;
 
+		case 0x4C: // Current maximum speed in NewGRF units
+			if (!v->IsPrimaryVehicle()) return 0;
+			return v->GetCurrentMaxSpeed();
+
 		/* Variables which use the parameter */
 		case 0x60: // Count consist's engine ID occurance
 			if (v->type != VEH_TRAIN) return v->GetEngine()->grf_prop.local_id == parameter ? 1 : 0;

src/ship.h

@@ -37,6 +37,7 @@ struct Ship FINAL : public SpecializedVehicle<Ship, VEH_SHIP> {
 	SpriteID GetImage(Direction direction, EngineImageType image_type) const;
 	int GetDisplaySpeed() const { return this->cur_speed / 2; }
 	int GetDisplayMaxSpeed() const { return this->vcache.cached_max_speed / 2; }
+	int GetCurrentMaxSpeed() const { return min(this->vcache.cached_max_speed, this->current_order.max_speed * 2); }
 	Money GetRunningCost() const;
 	bool IsInDepot() const { return this->state == TRACK_BIT_DEPOT; }
 	bool Tick();

src/train_cmd.cpp

@@ -369,6 +369,8 @@ int Train::GetCurveSpeedLimit() const
  */
 int Train::GetCurrentMaxSpeed() const
 {
+	if (_settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) return min(this->gcache.cached_max_track_speed, this->current_order.max_speed);
+
 	int max_speed = this->tcache.cached_max_curve_speed;
 	assert(max_speed == this->GetCurveSpeedLimit());
 

src/vehicle_base.h

@@ -398,6 +398,12 @@ public:
 	 */
 	virtual int GetDisplayMaxSpeed() const { return 0; }
 
+	/**
+	 * Calculates the maximum speed of the vehicle under its current conditions.
+	 * @return Current maximum speed in native units.
+	 */
+	virtual int GetCurrentMaxSpeed() const { return 0; }
+
 	/**
 	 * Gets the running cost of a vehicle
 	 * @return the vehicle's running cost