Base class for box containers. Arranges child controls vertically or horizontally, and rearranges the controls automatically when their minimum size changes. $DOCS_URL/tutorials/ui/gui_containers.html Adds a control to the box as a spacer. If [code]true[/code], [code]begin[/code] will insert the spacer control in front of other children. 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.