protected function load_stealth_activity(navigation_node $coursenode, $modinfo) {
        if (empty($modinfo->cms[$this->page->cm->id])) {
            return null;
        }
        $cm = $modinfo->cms[$this->page->cm->id];
        if ($cm->icon) {
            $icon = new pix_icon($cm->icon, get_string('modulename', $cm->modname), $cm->iconcomponent);
        } else {
            $icon = new pix_icon('icon', get_string('modulename', $cm->modname), $cm->modname);
        }
        $url = $cm->url;
        $activitynode = $coursenode->add(format_string($cm->name), $url, navigation_node::TYPE_ACTIVITY, null, $cm->id, $icon);
        $activitynode->title(get_string('modulename', $cm->modname));
        $activitynode->hidden = (!$cm->visible);
        if (!$cm->is_visible_on_course_page()) {
            // Do not show any error here, let the page handle exception that activity is not visible for the current user.
            // Also there may be no exception at all in case when teacher is logged in as student.
            $activitynode->display = false;
        } else if (!$url) {
            // Don't show activities that don't have links!
            $activitynode->display = false;
        } else if (self::module_extends_navigation($cm->modname)) {
            $activitynode->nodetype = navigation_node::NODETYPE_BRANCH;
        }
        return $activitynode;
    }