/**
* {@inheritdoc}
*/
public static function processElement(Element $element, FormStateInterface $form_state, array &$complete_form)
{
$dropbuttons = Element::create();
foreach ($element->children(TRUE) as $key => $child) {
if ($dropbutton = $child->getProperty('dropbutton')) {
// If there is no dropbutton for this button group yet, create one.
if (!isset($dropbuttons->{$dropbutton})) {
$dropbuttons->{$dropbutton} = ['#type' => 'dropbutton'];
}
$dropbuttons[$dropbutton]['#links'][$key] = $child->getArray();
// Remove original child from the element so it's not rendered twice.
$child->setProperty('printed', TRUE);
}
}
$element->exchangeArray($dropbuttons->getArray() + $element->getArray());
}
