Method renderButton

/**
 * Render a button.
 *
 * @param   array  &$node  A toolbar node.
 *
 * @return  string
 *
 * @since   1.5
 * @throws  \Exception
 */
public function renderButton(&$node)
{
    // Get the button type.
    $type = $node[0];
    $button = $this->loadButtonType($type);
    // Check for error.
    if ($button === false) {
        throw new \UnexpectedValueException(Text::sprintf('JLIB_HTML_BUTTON_NOT_DEFINED', $type));
    }
    $button->setParent($this);
    return $button->render($node);
}