Provide a form to edit options for this plugin.
Overrides ExposedFormPluginBase::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
parent::buildOptionsForm($form, $form_state);
$form['text_input_required'] = array(
'#type' => 'text_format',
'#title' => t('Text on demand'),
'#description' => t('Text to display instead of results until the user selects and applies an exposed filter.'),
'#default_value' => $this->options['text_input_required'],
'#format' => isset($this->options['text_input_required_format']) ? $this->options['text_input_required_format'] : filter_default_format(),
'#wysiwyg' => FALSE,
);
}