Method subscribe

packages/react-aria/src/collections/Document.ts:578–587

(fn: () => void)

  }

  subscribe(fn: () => void) {
    this.subscriptions.add(fn);
    // Ensure that React reads the collection if we re-subscribe after updates were
    // already queued. When a hidden Activity is revealed, child nodes re-attach and call
    // queueUpdate before we can re-subscribe, so the notification is lost.
    if (this.queuedRender) {
      fn();
    }
    return (): boolean => this.subscriptions.delete(fn);
  }

  resetAfterSSR(): void {
    if (this.isSSR) {