locale_is_translatable example

if (!isset($active[$key])) {
        continue;
      }
      if (is_array($item)) {
        // Only add this key if there was a translated value underneath.         $value = $this->processTranslatableData($name, $active[$key], $item, $langcode);
        if (!empty($value)) {
          $translated[$key] = $value;
        }
      }
      else {
        if (locale_is_translatable($langcode)) {
          $value = $this->translateString($name, $langcode, $item->getUntranslatedString(), $item->getOption('context'));
        }
        else {
          $value = $item->getUntranslatedString();
        }
        if (!empty($value)) {
          $translated[$key] = $value;
        }
      }
    }
    return $translated;
  }

  public function updateLocaleStorage(StorableConfigBase $config, $langcode, array $reference_config = []) {
    $name = $config->getName();
    if ($this->localeConfigManager->isSupported($name) && locale_is_translatable($langcode)) {
      $translatables = $this->localeConfigManager->getTranslatableDefaultConfig($name);
      $this->processTranslatableData($name, $config->get(), $translatables, $langcode, $reference_config);
    }
  }

  /** * Process the translatable data array with a given language. * * @param string $name * The configuration name. * @param array $config * The active configuration data or override data. * @param array|\Drupal\Core\StringTranslation\TranslatableMarkup[] $translatable * The translatable array structure. * @see \Drupal\locale\LocaleConfigManager::getTranslatableData() * @param string $langcode * The language code to process the array with. * @param array $reference_config * (Optional) Reference configuration to check against if $config was an * override. This allows us to update locale keys for data not in the * override but still in the active configuration. */

/** * Lists locale translation filters that can be applied. */
  protected function translateFilters() {
    $filters = [];

    // Get all languages, except English.     $this->languageManager->reset();
    $languages = $this->languageManager->getLanguages();
    $language_options = [];
    foreach ($languages as $langcode => $language) {
      if (locale_is_translatable($langcode)) {
        $language_options[$langcode] = $language->getName();
      }
    }

    // Pick the current interface language code for the filter.     $default_langcode = $this->languageManager->getCurrentLanguage()->getId();
    if (!isset($language_options[$default_langcode])) {
      $available_langcodes = array_keys($language_options);
      $default_langcode = array_shift($available_langcodes);
    }

    

/** * Form constructor for the translation import screen. */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $languages = $this->languageManager->getLanguages();

    // Initialize a language list to the ones available, including English if we     // are to translate Drupal to English as well.     $existing_languages = [];
    foreach ($languages as $langcode => $language) {
      if (locale_is_translatable($langcode)) {
        $existing_languages[$langcode] = $language->getName();
      }
    }

    // If we have no languages available, present the list of predefined     // languages only. If we do have already added languages, set up two option     // groups with the list of existing and then predefined languages.     if (empty($existing_languages)) {
      $language_options = $this->languageManager->getStandardLanguageListWithoutConfigured();
      $default = key($language_options);
    }
    

public function getFormId() {
    return 'locale_translate_export_form';
  }

  /** * {@inheritdoc} */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $languages = $this->languageManager->getLanguages();
    $language_options = [];
    foreach ($languages as $langcode => $language) {
      if (locale_is_translatable($langcode)) {
        $language_options[$langcode] = $language->getName();
      }
    }
    $language_default = $this->languageManager->getDefaultLanguage();

    if (empty($language_options)) {
      $form['langcode'] = [
        '#type' => 'value',
        '#value' => LanguageInterface::LANGCODE_SYSTEM,
      ];
      $form['langcode_text'] = [