in 04 - Layout/02 - Layout Components.js [22:39]
render() {
var children = this.prerendered;
var positionedChildren = [];
var y = 0;
for (var i = 0; i < children.length; i++) {
// This child is an opaque black box whose props cannot be inspected,
// nor cloned. It can only be rendered once. Rendering it twice results
// in a conflict, at least until we support painting the same stateful
// component in many different places (e.g. SVG's <use />)
var child = children[i];
positionedChildren.push(
<Positioner key={child.key} x={0} y={y}>{child}</Positioner>
);
// We can use it to inspect the child's reverse context though.
y += child.result.layoutHeight;
}
return <Fragment>{positionedChildren}</Fragment>;
}