Pre-render callback: Attaches the dropbutton library and required markup.
function drupal_pre_render_dropbutton($element) {
$element['#attached']['library'][] = array(
'system',
'drupal.dropbutton',
);
$element['#attributes']['class'][] = 'dropbutton';
if (!isset($element['#theme_wrappers'])) {
$element['#theme_wrappers'] = array();
}
array_unshift($element['#theme_wrappers'], 'dropbutton_wrapper');
// Enable targeted theming of specific dropbuttons (e.g., 'operations' or
// 'operations__node').
if (isset($element['#subtype'])) {
$element['#theme'] .= '__' . $element['#subtype'];
}
return $element;
}