case top_to_bottom: return "top_to_bottom";
case bottom_to_top: return "bottom_to_top";
case left_to_right: return "left_to_right";
case right_to_left: return "right_to_left";
case top_to_bottom: return "top_to_bottom";
case bottom_to_top: return "bottom_to_top";
case left_to_right: return "left_to_right";
case right_to_left: return "right_to_left";