Creating a foveated streaming client on visionOS

At a glance

Project structure

Source bundle/
└── FoveatedStreaming-Sample/
    ├── FoveatedStreaming-Sample/
    │   ├── FoveatedStreamingSampleApp.swift
    │   ├── Models/
    │   │   ├── AppModel.swift
    │   │   ├── MessageChannelModel.swift
    │   │   └── StreamActions.swift
    │   ├── Views/
    │   │   ├── StreamConnectionView.swift
    │   │   ├── ContentView.swift
    │   │   ├── MessageChannelView.swift
    │   │   ├── ReopenMainWindowView.swift
    │   │   ├── StreamControlsView.swift
    │   │   └── TransformStreamWidgetView.swift
    │   └── ViewModifiers/
    │       └── SetImmersivePresentationBehaviorsViewModifier.swift
    └── FoveatedStreamingSimulator/
        └── FoveatedStreamingSimulator.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 5 project/configuration file(s) and 21 source declaration(s).

Overall architecture

flowchart LR
    N1["FoveatedStreamingSampleApp"]
    N2["ContentView"]
    N3["AppModel"]
    N4["FoveatedStreaming / FoveatedStreamingSimulator APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

FoveatedStreaming-Sample/FoveatedStreaming-Sample/FoveatedStreamingSampleApp.swift:12 — architecture anchor

#if targetEnvironment(simulator)
@main
struct FoveatedStreamingSampleApp: App {
    // ...
            Text("FoveatedStreamingSampleApp is unsupported on the simulator. Please use a device to run this sample.")
    // ...
}
#endif

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into Foveated Streaming.

Ownership and state

classDiagram
    FoveatedStreamingSampleApp *-- FoveatedStreamingSession : session
    FoveatedStreamingSampleApp *-- AppModel : appModel
    FoveatedStreamingSampleApp o-- MessageChannelModel : messageChannelModel
    MessageChannelModel o-- FoveatedStreamingSession : session

Ownership evidence

FoveatedStreaming-Sample/FoveatedStreaming-Sample/FoveatedStreamingSampleApp.swift:26 — stored dependency or nearest verified ownership anchor

#if targetEnvironment(simulator)
// ...
#else
@main
struct FoveatedStreamingSampleApp: App {
    private let session = FoveatedStreamingSession()
    // ...
}
#endif

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

FoveatedStreaming-Sample/FoveatedStreaming-Sample/FoveatedStreamingSampleApp.swift:43 — representative execution boundary

#if targetEnvironment(simulator)
// ...
#else
@main
struct FoveatedStreamingSampleApp: App {
    // ...
}
#endif

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

FoveatedStreaming-Sample/FoveatedStreaming-Sample/FoveatedStreamingSampleApp.swift:13 — representative type boundary

#if targetEnvironment(simulator)
@main
struct FoveatedStreamingSampleApp: App {
    // ...
}
#endif

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

FoveatedStreaming-Sample/FoveatedStreaming-Sample/FoveatedStreamingSampleApp.swift:26 — representative boundary

#if targetEnvironment(simulator)
// ...
#else
@main
struct FoveatedStreamingSampleApp: App {
    // ...
}
#endif

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: App: FoveatedStreamingSampleApp; Model: AppModel, MessageChannelModel; View: ContentView, DeveloperSettingsView, ReopenMainWindowView, StreamConnectionView, StreamControlsView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: monitorAvailableChannels, setUpMessageChannel, startReceivingMessages, local, remote, sendMessage.
• Files: FoveatedStreaming-Sample/FoveatedStreaming-Sample/FoveatedStreamingSampleApp.swift, FoveatedStreaming-Sample/FoveatedStreaming-Sample/Models/AppModel.swift, FoveatedStreaming-Sample/FoveatedStreaming-Sample/Models/MessageChannelModel.swift, FoveatedStreaming-Sample/FoveatedStreaming-Sample/Views/StreamConnectionView.swift, FoveatedStreaming-Sample/FoveatedStreaming-Sample/Views/ContentView.swift, FoveatedStreaming-Sample/FoveatedStreaming-Sample/Views/ReopenMainWindowView.swift.

Architecture takeaways

• FoveatedStreamingSampleApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, FoveatedStreaming, FoveatedStreamingSimulator, RealityKit through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation