Using SwiftUI Window/WindowGroup with TCA

[zachwaugh]

I'm wondering if anyone has good patterns for dealing with SwiftUI windows, specifically on macOS, but believe it applies equally to iOS as well. The standard SwiftUI template looks like this:

@main
struct SomeApp: App {
    let store: StoreOf<SomeAppReducer>
    
    var body: some Scene {
        WindowGroup {
            ContentView(store: store)
        }
    }
}

The problem is if you want to support multi-window, all those windows will just be sharing the same state. Windows can be open in a few ways, but they won't necessarily flow through the reducer like File > New Window or programmatically through openWindow() in the Environment, so I'm not sure how to setup some conditional state like I typically would when presenting a sheet. There's no way to programmatically control the presentation (that I'm aware of.)

Even for a single window, I don't want to load the state until it is shown, so I'm doing something like where I load/unload the state in onAppear/onDisappear:

Window("Welcome", id: "welcome") {
    ZStack {
        if let store = store.scope(state: \.welcome, action: \.welcome) {
            WelcomeView(store: store)
        } else {
            Color.clear
        }
    }
    .onAppear {
        store.send(.welcomeWindowOnAppear)
    }
    .onDisappear {
        store.send(.welcomeWindowOnDisappear)
    }
}

That seems to work, but doesn't feel great. For multi-window, I could do something similar with an array of IdentifiedArrayOf<MainWindow.State>, but I don't know how to uniquely identify each Window created from that group in order to scope the right child store. Curious if there's something I'm missing, or should I just drop down to AppKit.