Provide the basic form which calls through to subforms. If overridden, it is best to call through to the parent, or to at least make sure all of the functions in this form are called.
Overrides FilterPluginBase::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
parent::buildOptionsForm($form, $form_state);
$this->view
->initStyle();
// Allow to choose all fields as possible
if ($this->view->style_plugin
->usesFields()) {
$options = array();
foreach ($this->view->display_handler
->getHandlers('field') as $name => $field) {
$options[$name] = $field
->adminLabel(TRUE);
}
if ($options) {
$form['fields'] = array(
'#type' => 'select',
'#title' => t('Choose fields to combine for filtering'),
'#description' => t("This filter doesn't work for very special field handlers."),
'#multiple' => TRUE,
'#options' => $options,
'#default_value' => $this->options['fields'],
);
}
else {
form_set_error('', t('You have to add some fields to be able to use this filter.'));
}
}
}