views_ui_standard_display_dropdown

views_ui_standard_display_dropdown(&$form, FormStateInterface $form_state, $section)

function views_ui_standard_display_dropdown(&$form, FormStateInterface $form_state, $section) {
  $view = $form_state->get('view');
  $display_id = $form_state->get('display_id');
  $executable = $view->getExecutable();
  $displays = $executable->displayHandlers;
  $current_display = $executable->display_handler;

  // @todo Move this to a separate function if it's needed on any forms that
  // don't have the display dropdown.
  $form['override'] = array(
    '#prefix' => '<div class="views-override clearfix form--inline views-offset-top" data-drupal-views-offset="top">',
    '#suffix' => '</div>',
    '#weight' => -1000,
    '#tree' => TRUE,
  );

  // Add the "2 of 3" progress indicator.
  if ($form_progress = $view->getFormProgress()) {
    $form['progress']['#markup'] = '<div id="views-progress-indicator" class="views-progress-indicator">' . t('@current of @total', array('@current' => $form_progress['current'], '@total' => $form_progress['total'])) . '</div>';
    $form['progress']['#weight'] = -1001;
  }

  // The dropdown should not be added when :
  // - this is the default display.
  // - there is no master shown and just one additional display (mostly page)
  //   and the current display is defaulted.
  if ($current_display->isDefaultDisplay() || ($current_display->isDefaulted($section) && !\Drupal::config('views.settings')->get('ui.show.master_display') && count($displays) <= 2)) {
    return;
  }

  // Determine whether any other displays have overrides for this section.
  $section_overrides = FALSE;
  $section_defaulted = $current_display->isDefaulted($section);
  foreach ($displays as $id => $display) {
    if ($id === 'default' || $id === $display_id) {
      continue;
    }
    if ($display && !$display->isDefaulted($section)) {
      $section_overrides = TRUE;
    }
  }

  $display_dropdown['default'] = ($section_overrides ? t('All displays (except overridden)') : t('All displays'));
  $display_dropdown[$display_id] = t('This @display_type (override)', array('@display_type' => $current_display->getPluginId()));
  // Only display the revert option if we are in a overridden section.
  if (!$section_defaulted) {
    $display_dropdown['default_revert'] = t('Revert to default');
  }

  $form['override']['dropdown'] = array(
    '#type' => 'select',
    '#title' => t('For'), // @TODO: Translators may need more context than this.
    '#options' => $display_dropdown,
  );
  if ($current_display->isDefaulted($section)) {
    $form['override']['dropdown']['#default_value'] = 'defaults';
  }
  else {
    $form['override']['dropdown']['#default_value'] = $display_id;
  }

}