@erik Depending on the details, I believe this is being addressed. I think this is something the Traverse people want, and they're big contributors to winit. Also, Mads Marquart (another winit contributor) is working on objc2 and there's a strong sense of migrating toward that.

Keep in mind though, there are a lot of constraints coming from the platforms themselves in terms of what you can, can not, and must do on the UI thread, especially if you want it to be actually safe.