Function DoTriggerVehicleRandomisation

src/newgrf_engine.cpp:1260–1319

}

static void DoTriggerVehicleRandomisation(Vehicle *v, VehicleRandomTrigger trigger, uint16_t base_random_bits, bool first)
{
	/* We can't trigger a non-existent vehicle... */
	assert(v != nullptr);

	VehicleResolverObject object(v->engine_type, v, VehicleResolverObject::WO_CACHED, false, CBID_RANDOM_TRIGGER);
	v->waiting_random_triggers.Set(trigger); // store now for var 5F
	object.SetWaitingRandomTriggers(v->waiting_random_triggers);

	object.ResolveRerandomisation();

	/* Store remaining triggers. */
	v->waiting_random_triggers.Reset(object.GetUsedRandomTriggers());

	/* Rerandomise bits. Scopes other than SELF are invalid for rerandomisation. For bug-to-bug-compatibility with TTDP we ignore the scope. */
	uint16_t new_random_bits = Random();
	uint32_t reseed = object.GetReseedSum();
	v->random_bits &= ~reseed;
	v->random_bits |= (first ? new_random_bits : base_random_bits) & reseed;

	switch (trigger) {
		case VehicleRandomTrigger::NewCargo:
			/* All vehicles in chain get ANY_NEW_CARGO trigger now.
			 * So we call it for the first one and they will recurse.
			 * Indexing part of vehicle random bits needs to be
			 * same for all triggered vehicles in the chain (to get
			 * all the random-cargo wagons carry the same cargo,
			 * i.e.), so we give them all the NEW_CARGO triggered
			 * vehicle's portion of random bits. */
			assert(first);
			DoTriggerVehicleRandomisation(v->First(), VehicleRandomTrigger::AnyNewCargo, new_random_bits, false);
			break;

		case VehicleRandomTrigger::Depot:
			/* We now trigger the next vehicle in chain recursively.
			 * The random bits portions may be different for each
			 * vehicle in chain. */
			if (v->Next() != nullptr) DoTriggerVehicleRandomisation(v->Next(), trigger, 0, true);
			break;

		case VehicleRandomTrigger::Empty:
			/* We now trigger the next vehicle in chain
			 * recursively.  The random bits portions must be same
			 * for each vehicle in chain, so we give them all
			 * first chained vehicle's portion of random bits. */
			if (v->Next() != nullptr) DoTriggerVehicleRandomisation(v->Next(), trigger, first ? new_random_bits : base_random_bits, false);
			break;

		case VehicleRandomTrigger::AnyNewCargo:
			/* Now pass the trigger recursively to the next vehicle
			 * in chain. */
			assert(!first);
			if (v->Next() != nullptr) DoTriggerVehicleRandomisation(v->Next(), trigger, base_random_bits, false);
			break;

		case VehicleRandomTrigger::Callback32:
			/* Do not do any recursion */
			break;