static new LatestAppearance<S> thingsOnScreen_newestFirst_latestAppearance;
static Lock thingsOnScreen_newestFirst_lock = lock();

static L<S> thingsOnScreen_newestFirst() {
  Set<S> things = thingsOnScreen();
  lock thingsOnScreen_newestFirst_lock;
  ret thingsOnScreen_newestFirst_latestAppearance.recordAndSort(things);
}