Creating a 3D painting space

At a glance

Project structure

Source bundle/
├── Painting/
│   ├── App/
│   │   └── EntryPoint.swift
│   ├── Components/
│   │   └── ClosureComponent.swift
│   ├── Views/
│   │   ├── MainView.swift
│   │   └── PaintingView.swift
│   ├── Canvas/
│   │   ├── PaintingCanvas.swift
│   │   └── Stroke.swift
│   ├── Trackers/
│   │   └── PaintingHandTracking.swift
│   └── Extensions/
│       ├── Entity.swift
│       └── Float.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── Painting.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

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 4 project/configuration file(s) and 8 source declaration(s).

Overall architecture

flowchart LR
    N1["EntryPoint"]
    N2["MainView"]
    N3["ClosureSystem"]
    N4["RealityKit / SwiftUI APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

Painting/App/EntryPoint.swift:10 — architecture anchor

@main
struct EntryPoint: App {
    // ...
        WindowGroup {
            MainView()
        }
    // ...
}

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 visionOS.

Ownership and state

classDiagram
    ClosureComponent o-- Callback : closure
    ClosureSystem *-- EntityQuery : query
    PaintingView *-- PaintingHandTracking : paintingHandTracking
    PaintingView *-- PaintingCanvas : canvas

Ownership evidence

Painting/Components/ClosureComponent.swift:14 — stored dependency or nearest verified ownership anchor

struct ClosureComponent: Component {
    // ...
    let closure: (TimeInterval) -> Void
    // ...
}

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

Painting/Trackers/PaintingHandTracking.swift:13 — representative execution boundary

@MainActor class PaintingHandTracking: ObservableObject {
    // ...
    let arSession = ARKitSession()
    // ...
}

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

Painting/Components/ClosureComponent.swift:12 — representative type boundary

struct ClosureComponent: Component {
    // ...
    let closure: (TimeInterval) -> Void
    // ...
}

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

Access control

Reference code

Painting/Canvas/PaintingCanvas.swift:36 — representative boundary

    private func addBox(size: SIMD3<Float>, position: SIMD3<Float>) -> Entity {
        // ...
        let box = Entity()
        // ...
    }

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: Component: ClosureComponent; System: ClosureSystem; View: MainView, PaintingView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: update, addBox, addPoint, finishStroke, updateMesh, generateMeshData, calculateRadiusAndDirection, calculateAxes.
• Files: Painting/App/EntryPoint.swift, Painting/Components/ClosureComponent.swift, Painting/Views/MainView.swift, Painting/Views/PaintingView.swift, Painting/Canvas/PaintingCanvas.swift, Painting/Canvas/Stroke.swift.

Architecture takeaways

• EntryPoint is the main source-visible entry or composition anchor for this sample.
• Framework work reaches RealityKit, SwiftUI, ARKit, simd 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