title: QFileDialog dynamic translation
body: <p>This question has <a href="https://stackoverflow.com/questions/8906944/qfiledialog-localization">unfortunately been asked before</a> but I'm going insane here.
  In my Qt Application the user is able to dynamically change the language which works perfect for all my own translations. It does not work for my calls to QFileDialog. The respective code:</p>
  
  <pre><code>void myapp::change_language(std::string&amp; lang_str){
      // my own translations works
      qApp-&gt;removeTranslator(&amp;this-&gt;app_lang);
      this-&gt;app_lang.load(QString::fromStdString(lang_str));
      qApp-&gt;installTranslator(&amp;this-&gt;app_lang);
  
      // system translations, works not for qfiledialog
      qApp-&gt;removeTranslator(&amp;this-&gt;app_lang_qt);
      bool test = this-&gt;app_lang_qt.load("qt_fr.qm"); // returns true
      qApp-&gt;installTranslator(&amp;this-&gt;app_lang_qt);
  }
  </code></pre>
  
  <p>And</p>
  
  <pre><code>void myapp::changeEvent(QEvent* event){
      if(event-&gt;type() == QEvent::LanguageChange){
          this-&gt;ui.retranslateUi(this);
      }
      QMainWindow::changeEvent(event);
  }
  </code></pre>
  
  <p>With</p>
  
  <pre><code>QTranslator app_lang;
  QTranslator app_lang_qt;
  </code></pre>
  
  <p>The fixed string "qt_fr.qm" is just for testing purpose because french is easily detectable.</p>
  
  <p>What I want is to change the language in static calls to QFileDialog and QMessageBox but the language is only changed in QMessageBox, not in QFileDialog. For both classes I'm only calling the static members to that can't be the issue. I also tried to install this translator in the main.cpp with the same results.</p>