Function GetAircraftFlightLevel

src/aircraft_cmd.cpp:769–805

template <class T>
int GetAircraftFlightLevel(T *v, bool takeoff)
{
	/* Aircraft is in flight. We want to enforce it being somewhere
	 * between the minimum and the maximum allowed altitude. */
	int aircraft_min_altitude;
	int aircraft_max_altitude;
	GetAircraftFlightLevelBounds(v, &aircraft_min_altitude, &aircraft_max_altitude);
	int aircraft_middle_altitude = (aircraft_min_altitude + aircraft_max_altitude) / 2;

	/* If those assumptions would be violated, aircraft would behave fairly strange. */
	assert(aircraft_min_altitude < aircraft_middle_altitude);
	assert(aircraft_middle_altitude < aircraft_max_altitude);

	int z = v->z_pos;
	if (z < aircraft_min_altitude ||
			(HasBit(v->flags, VAF_IN_MIN_HEIGHT_CORRECTION) && z < aircraft_middle_altitude)) {
		/* Ascend. And don't fly into that mountain right ahead.
		 * And avoid our aircraft become a stairclimber, so if we start
		 * correcting altitude, then we stop correction not too early. */
		SetBit(v->flags, VAF_IN_MIN_HEIGHT_CORRECTION);
		z += takeoff ? 2 : 1;
	} else if (!takeoff && (z > aircraft_max_altitude ||
			(HasBit(v->flags, VAF_IN_MAX_HEIGHT_CORRECTION) && z > aircraft_middle_altitude))) {
		/* Descend lower. You are an aircraft, not an space ship.
		 * And again, don't stop correcting altitude too early. */
		SetBit(v->flags, VAF_IN_MAX_HEIGHT_CORRECTION);
		z--;
	} else if (HasBit(v->flags, VAF_IN_MIN_HEIGHT_CORRECTION) && z >= aircraft_middle_altitude) {
		/* Now, we have corrected altitude enough. */
		ClrBit(v->flags, VAF_IN_MIN_HEIGHT_CORRECTION);
	} else if (HasBit(v->flags, VAF_IN_MAX_HEIGHT_CORRECTION) && z <= aircraft_middle_altitude) {
		/* Now, we have corrected altitude enough. */
		ClrBit(v->flags, VAF_IN_MAX_HEIGHT_CORRECTION);
	}

	return z;
}

template int GetAircraftFlightLevel(DisasterVehicle *v, bool takeoff);
template int GetAircraftFlightLevel(Aircraft *v, bool takeoff);