class Link

class Link extends PrerenderBase {

  /**
   * {@inheritdoc}
   */
  public static function preRenderElement(Element $element) {
    // Injects the icon into the title (the only way this is possible).
    if ($icon = & $element->getProperty('icon')) {
      $title = $element->getProperty('title');

      // Handle #icon_only.
      if ($element->getProperty('icon_only')) {
        if ($attribute_title = $element->getAttribute('title', '')) {
          $title .= ' - ' . $attribute_title;
        }
        $element
        ->setAttribute('title', $title)
          ->addClass('icon-only')
          ->setProperty('title', $icon);
        if (Bootstrap::getTheme()->getSetting('tooltip_enabled')) {
          $element->setAttribute('data-toggle', 'tooltip');
        }
        return;
      }

      // Handle #icon_position.
      $position = $element->getProperty('icon_position', 'before');

      // Render #icon and trim it (so it doesn't add underlines in whitespace).
      $rendered_icon = trim(Element::create($icon)->renderPlain());

      // Default position is before.
      $markup = "[email protected]";
      if ($position === 'after') {
        $markup = "@title$rendered_icon";
      }

      // Replace the title and set an icon position class.
      $element
      ->setProperty('title', new FormattableMarkup($markup, ['@title' => $title]))
        ->addClass("icon-$position");
    }
  }

}