function delegateRenderBy(DecorateViewModel $parentView, $rootPassedToNext = null)
    {
        if ($rootPassedToNext === null)
            // first segment of list do not pass nextRoot
            $rootPassedToNext = $parentView;

        $this->myRoot   = $rootPassedToNext;
        $this->nextRoot = $parentView;


        if (null ===  $callback = $this->delegateRenderBy )
            return;

        // DO_LEAST_PHPVER_SUPPORT 5.4 closure bindto
        if ($callback instanceof \Closure && version_compare(phpversion(), '5.4.0') > 0) {
            $callback = \Closure::bind(
                $callback
                , $this->_view
                , get_class($this)
            );
        }

        call_user_func($callback, $parentView, $parentView->parent(), $this);
    }