D8 language tweaks for better output between interface and content language

D8_translation_language_direction_tweaks

/**
 * Some simple modifications that can help when dealing with an admin/interface language
 * and a content language that have different directions (dir: ltr or rtl)
 *
 * Snippet to get current language of content.
 * \Drupal::languageManager()->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)
 *
 * Snippet to get current language of interface. This should be set to the users admin preference.
 * \Drupal::languageManager()->getCurrentLanguage(LanguageInterface::TYPE_INTERFACE)
 *
 * Can use getDirection(), getID(), and getName() for specific info about the langauge.
 */
 
/**
 * Implements hook_editor_js_settings_alter
 */
function MYMODULE_editor_js_settings_alter(array &$settings) {
  // Gets the direction of the content langauge.
  $direction = \Drupal::languageManager()
    ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)
    ->getDirection();

  // Set the language direction for ckeditor formatted text areas.
  foreach ($settings['editor']['formats'] as $name => $value) {
    $settings['editor']['formats'][$name]['editorSettings']['contentsLangDirection'] = $direction;
  }
}

/**
 * Implements hook_preprocess_input().
 */
function MYMODULE_preprocess_input(&$vars) {
  if (isset($vars['attributes']['id'])) {
    // Gets the direction of the content langauge.
    $direction = \Drupal::languageManager()
      ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)
      ->getDirection();
    
    // sets the direction for menu description form field
    if ($vars['attributes']['id'] == 'edit-menu-description') {
      $vars['attributes']['dir'] = $direction;
    }
    
    // sets the direction for the menu title form field
    if ($vars['attributes']['id'] == 'edit-menu-title') {
      $vars['attributes']['dir'] = $direction;
    }
  }
}

/**
 * Implements hook_preprocess_textarea().
 */
function MYMODULE_preprocess_textarea(&$vars) {
  $direction = \Drupal::languageManager()
    ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)
    ->getDirection();

  // If dealing with an Attribute object, use the setAttribute method.
  // Sometimes the attributes are already set as an array, sometimes
  // they are an attribute object. Be ready my friends.
  if ($vars['element']['#parents'][0] == 'body') {
    $vars['attributes']->setAttribute('dir', $direction);
  }
}
/**
 * Implements hook_preprocess_html().
 */
function MYMODULE_preprocess_html(&$vars) {
  $direction = \Drupal::languageManager()
    ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT)
    ->getDirection();

  // If you want the output to follow the direction of the content language,
  // regardless of the interface langauge direction. Helpful in making RTL language
  // pages look more appropriate, but still allow the favored admin language on 
  // the toolbar and tabs
  if (!\Drupal::service('router.admin_context')->isAdminRoute()) {
    $vars['html_attributes']['dir'] = $direction;
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 *
 * Alters the node edit form.
 */
function MYMODULE_form_node_page_edit_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
  
  // This is good to modify those fields whose content entry would make more sense to set to the direction
  // of the contents language. Like, on an arabic content page with an english interface, you probably 
  // don't need the user author field to be rtl, nor do you need the revision comments field.
  // Set the individual fields you think will best work with the content language direction.
  
  $content_language = \Drupal::languageManager()->getCurrentLanguage(LanguageInterface::TYPE_CONTENT);
  $direction = $content_language->getDirection();

  // This will alter the language direction of the title textfield
  foreach ($form['title']['widget'] as $key => $value) {
    if (is_numeric($key)) {
      $form['title']['widget'][$key]['value']['#attributes']['dir'] = $direction;
    }
  }

  // Textarea field language direction alteration example.
  // This will modify the dir of a body field, without a ckeditor
  foreach ($form['body']['widget'] as $key => $value) {
    if (is_numeric($key)) {
      $form['body']['widget'][$key]['#attributes']['dir'] = $direction;
    }
  }

  // Example for modifying direction of a link field.
  foreach ($form['LINK_FIELD_NAME']['widget'] as $key => $value) {
    if (is_numeric($key)) {
      $form['field_related_links']['widget'][$key]['uri']['#attributes']['dir'] = $direction;
      $form['field_related_links']['widget'][$key]['title']['#attributes']['dir'] = $direction;
    }
  }
}