UIBehaviour Components Overview

While not exactly performant, uGUI has always been quite extensible. By deriving from UIBehaviour, you gain several callbacks that uGUI will call while it is traversing the GameObject tree. You have to also implements a desired interface : ILayoutController, ILayoutSelfController, ILayoutGroup, ILayoutIgnorer so that your custom component take an appropriate role plugging into the layout system.

The layout script is nothing more than continuously setting RectTransform values, but thanks to DrivenRectTransformTracker, the RectTransform UI properly greyed out and looks like the values are really controlled by the component. The tracker helps telling the editor that values changed this way does not count as dirtying the scene too.

So Notch Solution use this to control the RectTransform such that its content area is safe, not outside of safe area and not occluded by any cutouts.