code: private static boolean hasSync(Screen screen)
      {
          final Config config = screen.getConfig();
          final Resolution output = config.getOutput();
          return config.isWindowed() && output.getRate() > 0;
      }
docs: Check if screen has sync locked.
  
  @param screen The screen reference.
  @return <code>true</code> if sync enabled, <code>false</code> else.