gistfile1.js

function WidgetParentStdMod () {
  Y.before(this._initParentStdMod, this, 'renderUI');

  Y.before(function () {
    console.log('halt?');
    return new Y.Do.Halt('ParentStdMod halted this');
  }, this, '_renderChildren');

  Y.after(this._renderChildrenAfterSync, this, 'syncUI');
}

WidgetParentStdMod.ATTRS = {
  childrenContainer : {
    value : Y.WidgetStdMod.BODY
  }
};

WidgetParentStdMod.prototype = {
  _initParentStdMod : function () {
    var c = this.get('childrenContainer'),
      renderTo;

    if (c == Y.WidgetStdMod.BODY) {
      renderTo = this.bodyNode;
    } else if (c == Y.WidgetStdMod.HEADER) {
      renderTo = this.headerNode;
    } else if (c == Y.WidgetStdMod.FOOTER) {
      renderTo = this.footerNode;
    }

    this._childrenContainer = renderTo || this.get('contentBox');
  }, 

  _renderChildrenAfterSync : function () {
    this.each(Y.bind(function (child) {
      child.render(this._childrenContainer);
    }, this));
  }
};

var Container = Y.Base.create('container', Y.Widget, [Y.WidgetStdMod, Y.WidgetParent, WidgetParentStdMod]);
var ChildContainer = Y.Base.create('child-container', Y.Widget, [Y.WidgetStdMod, Y.WidgetChild]);

var myContainer = new Container({
  defaultChildType : ChildContainer,
  children : [
    {width: 400, height: 400, headerContent : "foo", bodyContent : 'bar', footerContent : 'baz', fillHeight : Y.WidgetStdMod.BODY},
  ],
  width: 800,
  height : 600,
  boundingBox : '#contents',
  headerContent : 'header',
  bodyContent : 'foo',
  footerContent: 'footer',
  fillHeight : Y.WidgetStdMod.BODY,
  render : true
});