Foveated Streaming for visionOS

import SwiftUI
import FoveatedStreaming

// MARK: - App entry point

@main
struct FoveatedStreamingApp: App {
    @State private var session = FoveatedStreamingSession()

    var body: some Scene {
        // Native SwiftUI control window
        WindowGroup("Controls", id: "controls") {
            ControlView(session: session)
        }

        // Immersive space that hosts the streamed content
        ImmersiveSpace(id: "stream") {
            StreamingImmersiveView(session: session)
        }
        .immersionStyle(selection: .constant(.progressive), in: .progressive)
    }
}

// MARK: - Control window

struct ControlView: View {
    let session: FoveatedStreamingSession
    @Environment(\.openImmersiveSpace) private var openImmersiveSpace
    @Environment(\.dismissImmersiveSpace) private var dismissImmersiveSpace
    @State private var isStreaming = false
    @State private var connectionError: String?

    var body: some View {
        VStack(spacing: 20) {
            Text("Foveated Streaming")
                .font(.title)

            if let error = connectionError {
                Text(error)
                    .foregroundStyle(.red)
                    .font(.caption)
            }

            Button(isStreaming ? "Disconnect" : "Connect to Endpoint") {
                Task {
                    if isStreaming {
                        session.disconnect()
                        await dismissImmersiveSpace()
                        isStreaming = false
                    } else {
                        await startStreaming()
                    }
                }
            }
            .buttonStyle(.borderedProminent)
        }
        .padding(40)
    }

    private func startStreaming() async {
        do {
            // connect() surfaces the system endpoint picker and QR-code
            // pairing UI automatically; it returns once streaming begins.
            try await session.connect()
            await openImmersiveSpace(id: "stream")
            isStreaming = true
        } catch {
            connectionError = error.localizedDescription
        }
    }
}

// MARK: - Immersive space content

struct StreamingImmersiveView: View {
    let session: FoveatedStreamingSession

    var body: some View {
        // Passing the session to the ImmersiveSpace view hierarchy
        // causes visionOS to composite the foveated stream into the space.
        FoveatedStreamingView(session: session)
            .onAppear {
                // Example: send an opaque message to the OpenXR host
                // once the immersive space is visible.
                let payload = Data("{ \"event\": \"immersiveSpaceReady\" }".utf8)
                session.sendMessage(payload, channel: "app-events")
            }
    }
}