static File userDesktopDir() {
  File f = toFile(loadTextFile(userDesktopDirPointerFile()));
  if (f == null) {
    final new Var<File> v;
    selectDir("Please select your desktop directory", userDir("Desktop"), voidfunc(File f) { v.set(f); });
    ret waitForVarToBeNotNull(v, 100);
  }
}