Base class for flow containers. Arranges child [Control] nodes vertically or horizontally in a left-to-right or top-to-bottom flow. A line is filled with [Control] nodes until no more fit on the same line, similar to text in an autowrapped label. Returns the current line count. The alignment of the container's children (must be one of [constant ALIGN_BEGIN], [constant ALIGN_CENTER] or [constant ALIGN_END]). Aligns children with the beginning of the container. Aligns children with the center of the container. Aligns children with the end of the container.