Function ShipTestUpDownOnLock

src/ship_cmd.cpp:566–584

* Test if a ship is in the centre of a lock and should move up or down. * @param v Ship being tested. * @return 0 if ship is not moving in lock, or -1 to move down, 1 to move up. */

 * @return 0 if ship is not moving in lock, or -1 to move down, 1 to move up.
 */
static int ShipTestUpDownOnLock(const Ship *v)
{
	/* Suitable tile? */
	if (!IsTileType(v->tile, MP_WATER) || !IsLock(v->tile) || GetLockPart(v->tile) != LockPart::Middle) return 0;

	/* Must be at the centre of the lock */
	if ((v->x_pos & 0xF) != 8 || (v->y_pos & 0xF) != 8) return 0;

	DiagDirection diagdir = GetInclinedSlopeDirection(GetTileSlope(v->tile));
	assert(IsValidDiagDirection(diagdir));

	if (DirToDiagDir(v->direction) == diagdir) {
		/* Move up */
		return (v->z_pos < GetTileMaxZ(v->tile) * (int)TILE_HEIGHT) ? 1 : 0;
	} else {
		/* Move down */
		return (v->z_pos > GetTileZ(v->tile) * (int)TILE_HEIGHT) ? -1 : 0;
	}
}

/**
 * Test and move a ship up or down in a lock.