public function render()
    {
        if (!$this->visible) {
            return;
        }

        parent::render();

        if ($this->title !== null) {
            $label_tag = new SwatHtmlTag('label');
            $label_tag->for = $this->id . '_radio_button_' . $this->value;
            $label_tag->setContent($this->title, $this->content_type);
            $label_tag->open();
        }

        $radio_button_tag = new SwatHtmlTag('input');
        $radio_button_tag->type = 'radio';
        $radio_button_tag->name = $this->id;
        $radio_button_tag->id = $this->id . '_radio_button_' . $this->value;
        $radio_button_tag->value = $this->value;
        if (!$this->sensitive) {
            $radio_button_tag->disabled = 'disabled';
        }

        $view = $this->getFirstAncestor('SwatView');
        if ($view !== null) {
            $selection = $view->getSelection($this);
            if ($selection->contains($this->value)) {
                $radio_button_tag->checked = 'checked';
            }
        }

        echo '<span class="swat-radio-wrapper">';
        $radio_button_tag->display();
        echo '<span class="swat-radio-shim"></span>';
        echo '</span>';

        if ($this->title !== null) {
            $label_tag->displayContent();
            $label_tag->close();
        }
    }