Base class for box containers. Arranges child [Control] nodes vertically or horizontally, and rearranges them automatically when their minimum size changes. $DOCS_URL/tutorials/ui/gui_containers.html Adds a [Control] node to the box as a spacer. If [param begin] is [code]true[/code], it will insert the [Control] node in front of all other children. The alignment of the container's children (must be one of [constant ALIGNMENT_BEGIN], [constant ALIGNMENT_CENTER], or [constant ALIGNMENT_END]). If [code]true[/code], the [BoxContainer] will arrange its children vertically, rather than horizontally. Can't be changed when using [HBoxContainer] and [VBoxContainer]. The child controls will be arranged at the beginning of the container, i.e. top if orientation is vertical, left if orientation is horizontal (right for RTL layout). The child controls will be centered in the container. The child controls will be arranged at the end of the container, i.e. bottom if orientation is vertical, right if orientation is horizontal (left for RTL layout). The space between the [BoxContainer]'s elements, in pixels.