Function TestVehicleBuildProbability

src/newgrf_engine.cpp:1251–1258

* Test for vehicle build probability type. * @param v Vehicle whose build probability to test. * @param type Build probability type to test for. * @returns True or false depending on the probability result, or std::nullopt if the callback failed. */

 * @returns True or false depending on the probability result, or std::nullopt if the callback failed.
 */
std::optional<bool> TestVehicleBuildProbability(Vehicle *v, EngineID engine, BuildProbabilityType type)
{
	uint16_t p = GetVehicleCallback(CBID_VEHICLE_BUILD_PROBABILITY, to_underlying(type), 0, engine, v);
	if (p == CALLBACK_FAILED) return std::nullopt;

	const uint16_t PROBABILITY_RANGE = 100;
	return p + RandomRange(PROBABILITY_RANGE) >= PROBABILITY_RANGE;
}

static void DoTriggerVehicleRandomisation(Vehicle *v, VehicleRandomTrigger trigger, uint16_t base_random_bits, bool first)
{