code: public static void bind (Layer layer, final Signal<Clock> update, final Slot<Clock> onUpdate,
                             final Signal<Clock> paint, final Slot<Clock> onPaint) {
      layer.state.connectNotify(new Slot<Layer.State>() {
        public void onEmit (Layer.State state) {
          _pcon = Closeable.Util.close(_pcon);
          _ucon = Closeable.Util.close(_ucon);
          if (state == Layer.State.ADDED) {
            _ucon = update.connect(onUpdate);
            _pcon = paint.connect(onPaint);
          }
        }
        private Closeable _ucon = Closeable.Util.NOOP, _pcon = Closeable.Util.NOOP;
      });
    }
docs: Automatically connects {@code onUpdate} to {@code update}, and {@code onPaint} to {@code
  paint} when {@code layer} is added to a scene graph, and disconnects them when {@code layer}
  is removed.