Directs a custom video compositor object to cancel or finish all pending video composition requests.
- iOS 7.0+
- macOS 10.9+
- Mac Catalyst 13.0+Beta
- tvOS 9.0+
Upon receiving this message, a custom video compositor must block until it has either cancelled all pending frame requests, and called the
finish method for each of them. If cancellation is not possible, the method must block until it has finished processing of all the frames and called the
finish(with method for each of them.