public function addPopup($popup = null, $icon = 'caret square down')
    {
        if (!$this->app) {
            throw new Exception('Columns\'s popup need to have a layout.');
        }

        $popup = $this->app->add($popup ? $popup : 'Popup')->setHoverable();

        $this->setHeaderPopup($popup, $icon);

        return $popup;
    }