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