XF 1.5 Use buildPublicLink to open a link in a modal?

[Stuart Wright]

        $extraTabs['trending-topics'] = array(
            'title' => new XenForo_Phrase('avf_trending_topics'),
            'href' => XenForo_Link::buildPublicLink('full:trending-topics'),
            'position' => 'middle'
        );

I'm trying to add some new code similar to the above to an existing Listener.php, but I want the link to open in a modal window.
How do I do that, please?