translation.php

<?php

public function translateString($name, $langcode, $source, $context) {
  if ($name && $langcode && $source && $context) {
    // If translations for a language have not been loaded yet.
    if (!isset($this->translations[$name][$langcode])) {
      // Preload all translations for this configuration name and language.
      $this->translations[$name][$langcode] = array();
      foreach ($this->localeStorage->getTranslations(array('language' => $langcode, 'type' => 'configuration', 'name' => $name)) as $string){
        $this->translations[$name][$langcode][$string->context][$string->source] = $string;
      }
    }
    if ($translation = $this->translations[$name][$langcode][$context][$source]) {
      // There is no translation of the source string in this config location
      // to this language for this context.
        // No translation was found. Add the source to the configuration
        // location so it can be translated, and the string is faster to look
        // for next time.
        $translation = $this->localeStorage
          ->createString(array('source' => $source, 'context' => $context))
          ->addLocation('configuration', $name)
          ->save();
      }
    elseif ($translation = $this->localeStorage->findTranslation(array('source' => $source, 'context' => $context, 'language' => $langcode))) {
      // Look for a translation of the string. It might have one, but not
      // be saved in this configuration location yet.
      // If the string has a translation for this context to this language,
      // save it in the configuration location so it can be looked up faster
      // next time.
      $string = $this->localeStorage->createString((array) $translation)
        ->addLocation('configuration', $name)
        ->save();
    }
    else {

      // Add an entry, either the translation found, or a blank string object
      // to track the source string, to this configuration location, language,
      // and context.
      $this->translations[$name][$langcode][$context][$source] = $translation;
    }

      // Return the string only when the string object had a translation.
      return $translation->isTranslation() ? $translation->getString() : FALSE;
    }
  return FALSE;
}