Base interface to implement by componets that control the layout of RectTransforms.
If a component is driving its own RectTransform it should implement the interface ILayoutSelfController. If a component is driving the RectTransforms of its children, it should implement ILayoutGroup.
The layout system will first invoke SetLayoutHorizontal and then SetLayoutVertical.In the SetLayoutHorizontal call it is valid to call LayoutUtility.GetMinWidth, LayoutUtility.GetPreferredWidth, and LayoutUtility.GetFlexibleWidth on the RectTransform of itself or any of its children. In the SetLayoutVertical call it is valid to call LayoutUtility.GetMinHeight, LayoutUtility.GetPreferredHeight, and LayoutUtility.GetFlexibleHeight on the RectTransform of itself or any of its children.The component may use this information to determine the width and height to use for its own RectTransform or the RectTransforms of its children.| SetLayoutHorizontal | Callback invoked by the auto layout system which handles horizontal aspects of the layout. |
| SetLayoutVertical | Callback invoked by the auto layout system which handles vertical aspects of the layout. |