GitLab

Test module with usage attached -> compose_dialog.zip

Install and hit /admin/iefstyle_form_test

Callback usage to open:

$response = new AjaxResponse();
$response->addCommand(new InsertCommand(null, $form['parent_container']));
$response->addCommand(new ComposeOpenModalDialog('#child-container', 'Modal Title', ['width' => '800', 'appendTo' => '#parent-container']));
return $response;

Callback usage to close:

$response = new AjaxResponse();
$response->addCommand(new CloseDialogCommand('#child-container'));
$response->addCommand(new InsertCommand(null, $form['parent_container']));
return $response;