transient sclass RSTOverQ implements Runnable {
  Runnable runnable;
  Q q = startQ();
  F0<AutoCloseable> enter; // optional ownership marker, e.g. for DynModules
  bool trigger, running;

  *(Runnable *runnable) {}
  *(Runnable *runnable, Q *q)  { assertNotNull(q); }
  *(Q q, Runnable runnable) { this(runnable, q); }

  void trigger() { go(); }
  synchronized void go() {
    if (trigger) ret;
    trigger = true;
    q.add(r _run);
  }
  public void run() { go(); }
  void get() { go(); } // so you can use the ! syntax
  
  synchronized bool running() { ret running; }
  
  void _run() {
    synchronized(this) {
      if (!trigger)
        ret;
      running = true;
      trigger = false;
    }

    try {
      temp callF(enter);
      pcallF(runnable);
    } finally {
      synchronized(this) {
        running = false;
      }
    }
  }
  
  synchronized bool triggered() { ret trigger; }
  
  void waitUntilDone {
    while (running()) sleep(1);
  }
  
  S stats() { ret renderVars(+trigger, +running, +q, +runnable); }
}

Began life as a copy of #1006319