sclass FlexibleRateTimer implements AutoCloseable {
  Runnable action;
  double hertz;
  double timestamp;
  transient DoLater doLater;
  transient new Flag started;
  transient volatile bool disposed;
  
  *() {}
  *(double *hertz, Runnable *action) {}
  
  void start {
    if (!started.raise()) ret;
    _kaboom();
  }
  
  void _kaboom {
    if (disposed) ret;
    dispose doLater;
    if (timestamp == 0) timestamp = sysNow();
    timestamp += 1000/hertz;
    doLater = new DoLater(iround(timestamp), r {
      pcallF(action);
      _kaboom();
    });
    doLater.enable();
  }
  
  void cancel { close(); }
  
  public void close {
    set disposed;
    dispose doLater;
  }
}