Achieving smooth frame rates with a Metal display link

At a glance

Project structure

Source bundle/
├── iOS/
│   └── main.m
├── macOS/
│   └── main.m
├── tvOS/
│   └── main.m
└── Shared/
    ├── AppDelegate.h
    ├── AppDelegate.m
    ├── GameView.h
    ├── ShaderTypes.h
    ├── AssetLoader.h
    ├── AssetLoader.mm
    ├── GameView.m
    ├── GameViewController.h
    └── GameViewController.mm

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C/Objective-C header, Metal, Objective-C, Objective-C++.
• The verified tree contains 9 project/configuration file(s) and 16 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["iOS"]
    V2["macOS"]
    V3["tvOS"]
    Boundary["Metal APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary
    Bundle --> V3
    V3 --> Boundary

Reference code

iOS/main.m:11 — architecture anchor

int main(int argc, char * argv[]) {
    NSString * appDelegateClassName;
    @autoreleasepool {
        // Setup code that might create autoreleased objects goes here.
        appDelegateClassName = NSStringFromClass([AppDelegate class]);
    }
    return UIApplicationMain(argc, argv, nil, appDelegateClassName);
}

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
    AppDelegate o-- NSWindow : window
    GameView o-- CAMetalLayer : metalLayer
    GameView o-- BOOL : paused
    GameView o-- id : delegate

Ownership evidence

Shared/AppDelegate.h:20 — stored dependency or nearest verified ownership anchor

#if TARGET_IOS || TARGET_TVOS
// ...
#else
@property(strong, nonatomic) IBOutlet NSWindow *window;
#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.

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

Shared/GameView.h:22 — representative type boundary

@protocol GameViewDelegate <NSObject>
// ...
@end

The source explicitly defines local protocol relationships: GameViewController → GameViewDelegate.

Access control

Reference code

Shared/AppDelegate.h:20 — representative boundary

#if TARGET_IOS || TARGET_TVOS
// ...
#else
@property(strong, nonatomic) IBOutlet NSWindow *window;
#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

Main application flow

sequenceDiagram
    participant GameView
    participant NSNotificationCenter
    participant notificationCenter
    GameView->>GameView: stopRenderLoop()
    GameView->>GameView: makeMetalLink()
    GameView->>NSNotificationCenter: defaultCenter()
    GameView->>notificationCenter: addObserver()

Reference code

Shared/GameView.m:142 — setupCAMetalLink()

- (void)setupCAMetalLink
{
    [self stopRenderLoop];
    [self makeMetalLink:self.metalLayer];

#if TARGET_MACOS
    // Register to receive a notification when the window closes so that you
    // can stop the display link.
    NSNotificationCenter* notificationCenter = [NSNotificationCenter defaultCenter];
    [notificationCenter addObserver:self
                           selector:@selector(windowWillClose:)
                               name:NSWindowWillCloseNotification
                             object:self.window];
#endif
}

Naming conventions

• Types: Controller: GameViewController; Delegate: AppDelegate, GameViewDelegate, WindowSceneDelegate; Loader: AssetLoader; Renderer: Renderer; View: GameView.
• Protocols: GameViewDelegate.
• Methods: application, applicationShouldTerminateAfterLastWindowClosed, drawableResize, renderTo, initCommon, resizeDrawable, stopRenderLoop, renderUpdate.
• Files: Shared/AppDelegate.h, Shared/AppDelegate.m, Shared/GameView.h, Shared/AssetLoader.h, Shared/AssetLoader.mm, Shared/GameView.m.

Architecture takeaways

• main is the main source-visible entry or composition anchor for this sample.
• Framework work reaches QuartzCore, simd, UIKit, Metal 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.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation