While I was experimenting with animation, I had to make a few basic prototypes for a layout system and see how they intertwine. Here's the API in conjunction with React:
var MyComp = React.createClass({
  registerLayoutValues: function() {
    return {
      self: {
        width: 30,
        left: (get('parent', 'width') - get('self', 'width')) / 2 // Center.
 }