When being forced to use Swift you have to use an Objective-C wrapper to be able to run C or C++ code. Why do you need to run C or C++ code? Because you use cross-platform libraries. So, you cannot use them anymore because on WatchOS. You are forced to write everything again in Swift without any advantage but wasting your time and introducing bugs. Therefore, being forced to use Swift is a killer! From a programmer's point of view there is simply no advantage at all to use Swift.

Theoretically, there is still a problem (depends how the queue works which is not clear to me): when the window closes, the view should also close. Then, the view's destructor should release the delegate which in turn should release the semaphore. BUT if the queue is still running (I do not know if this is possible), this will lead to a crash because the released semaphore is still used.