Using TextKit 2 to interact with text

At a glance

Project structure

Source bundle/
├── iOS/
│   ├── AppDelegate.swift
│   ├── TextDocumentView.swift
│   ├── CommentPopoverViewController.swift
│   ├── SceneDelegate.swift
│   └── TextDocumentViewController.swift
├── macOS/
│   ├── AppDelegate.swift
│   ├── TextDocumentView.swift
│   ├── CommentPopoverViewController.swift
│   ├── Document.swift
│   ├── TextDocumentViewController.swift
│   └── WindowController.swift
└── Shared/
    └── BubbleLayoutFragment.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 9 project/configuration file(s) and 17 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["iOS"]
    V2["macOS"]
    Boundary["UIKit APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary

Reference code

iOS/AppDelegate.swift:10 — architecture anchor

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        return true
    }

    // MARK: UISceneSession Lifecycle

    func application(_ application: UIApplication,
                     configurationForConnecting connectingSceneSession: UISceneSession,
                     options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // Called by iOS when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }

    func application(_ application: UIApplication,
                     didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
        // Called by iOS when the user discards a scene session.
        // If any sessions were discarded while the application was not running,
        // this will be called shortly after application:didFinishLaunchingWithOptions.
        // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
    }

}

Interpretation

The branches represent separate entry-bearing project variants in the downloaded bundle, not runtime calls between those variants. Each branch is intentionally collapsed at the documented framework boundary; the detailed target-local flow remains in the cited files. Ownership is claimed only where the next section cites a stored property or assignment.

Ownership and state

classDiagram
    TextDocumentView o-- CALayer : contentLayer
    TextDocumentView o-- CALayer : selectionLayer
    TextDocumentView o-- NSMapTable : fragmentLayerMap
    TextDocumentView *-- CGFloat : padding

Ownership evidence

iOS/TextDocumentView.swift:141 — stored dependency or nearest verified ownership anchor

class TextDocumentView: UIScrollView,
                        NSTextViewportLayoutControllerDelegate,
                        NSTextLayoutManagerDelegate,
                        UIGestureRecognizerDelegate {
    // ...
}

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.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@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.

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

iOS/AppDelegate.swift:11 — representative type boundary

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
        return true
    // ...
}

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

Access control

Reference code

Shared/BubbleLayoutFragment.swift:23 — representative boundary

    private var tightTextBounds: CGRect {
        var fragmentTextBounds = CGRect.null
        // ...
    }

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: Controller: CommentPopoverViewController, TextDocumentViewController, WindowController; Delegate: AppDelegate, SceneDelegate; Document: Document; View: TextDocumentView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: application, applicationDidFinishLaunching, applicationWillTerminate, defaultAction, viewportBounds, viewportAnchor, textViewportLayoutControllerWillLayout, animate.
• Files: iOS/AppDelegate.swift, macOS/AppDelegate.swift, iOS/TextDocumentView.swift, macOS/TextDocumentView.swift, iOS/CommentPopoverViewController.swift, iOS/SceneDelegate.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches Cocoa, UIKit, CoreGraphics 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