public function submission_empty($submission) {
        $allempty = true;

        foreach ($this->submissionplugins as $plugin) {
            if ($plugin->is_enabled() && $plugin->is_visible()) {
                if (!$allempty || !$plugin->is_empty($submission)) {
                    $allempty = false;
                }
            }
        }
        return $allempty;
    }