How can this not work??

I'm having essentially the same issue while trying to compile Metal files: // swift-tools-version: 6.0 import PackageDescription let package = Package( name: "BaseMetal", platforms: [.macOS(.v14)], targets: [ .executableTarget(name: "BaseMetal"), .target( name: "BaseMetalShaders", path: "Sources/Shaders", resources: [ .process("Canvas.metal"), .process("Shader.metal") ] ) ] ) My tree looks like this: . ├── Package.swift └── Sources ├── BaseMetal │ ├── Main.swift │ ├── Metalic.swift │ └── Renderer.swift └── Shaders ├── Canvas.metal └── Shader.metal This is the exact error message: ❯ swift run error: 'basemetal': public headers ("include") directory path for 'BaseMetalShaders' is invalid or not contained in the target

Fundamentally, in either case, you're just letting the system get on with other work until something is ready to be processed, then picking up where it left off. There shouldn't be much difference in performance between calling an asynchronous function and passing a callback. That said, you can do more advanced stuff with Swift Concurrency, like async let, which can improve performance, by running things in parallel that would otherwise be forced to take it in turns. That could make a big difference in some cases.

There's an open source project named Xcodes. They have a desktop app that makes it trivial to install and manage various Xcode versions (from old stuff to the latest betas (like Xcode 16 beta 3)), as well as the platform SDKs that go with them. It plays nice with stable versions (installed via the App Store etc). It's very easy to use. They also have a (pure Swift) command line version, which looks pretty cool.

I love IBM Plex. It's a really nice font, but I only have a 13.3 inch display (and my eyes aint great), so I can only render code side-by-side when the font is relatively narrow.

No problem, @talhadayanik. It should be available (from Dropbox) at this address: https://www.dropbox.com/scl/fi/32ejwcrazu7lnwkuf8nwh/Custom-Dark.xccolortheme?rlkey=cksos7rd85w29gmn68e3y7xad&dl=0 This site doesn't let me link to Dropbox directly, and I'm new to Dropbox too, so let me know if there's an issue. Best.

One more thing: Looking through the docs, I noticed that the NSViewRepresentableContext<Self> type has an alias: typealias Context = NSViewRepresentableContext<Self> So, you can simplify the signatures for makeNSView and updateNSView. For example, this... func updateNSView(_ nsView: MTKView, context: NSViewRepresentableContext<MetalView>) { } ...can be written like this: func updateNSView(_ nsView: MTKView, context: Context) { }

Supporting MetalKt in SwiftUI might make things easier, but even currently, rendering a MTKView with SwiftUI is no more or less involved than it is with AppKit. The code ends up structured a little differently, but it's the same code, and more or less the same methods. I've implemented the same simple pixel shader roughly four different ways now - twice with AppKit, twice with SwiftUI. IMO, the best approach uses SwiftUI, and was derived from the example given above (posted a few years ago, by an anonymous Apple dev). The code turns out very similar either way, but AppKit also uses a storyboard (which makes it feel clunky and magical), and SwiftUI is the future etc, so I went with SwiftUI. I'll include a minimal example here (for my own future reference, as much as anyone else's). The app's called Console. This is is the entrypoint, named ConsoleApp.swift: import SwiftUI @main struct ConsoleApp: App { var body: some Scene { WindowGroup { MetalView() } } } #Preview { MetalView() } The bulk of the Swift code is in a file named MetalView.swift. It initializes everything, including a buffer for passing vertices to the shader. These vertices are used by the vertex function to render a rectangle (formed from two triangles, in a triangle-strip), so the frag shader runs once for each pixel in the framebuffer. import SwiftUI import MetalKit struct MetalView: NSViewRepresentable { static private let pixelFormat = MTLPixelFormat.bgra8Unorm_srgb static private let clearColor = MTLClearColor(red: 0, green: 0, blue: 0, alpha: 0) class Coordinator: NSObject, MTKViewDelegate { var device: MTLDevice private var commandQueue: MTLCommandQueue private var pipelineState: MTLRenderPipelineState private var vertexBuffer: MTLBuffer override init() { device = MTLCreateSystemDefaultDevice()! let library = device.makeDefaultLibrary()! let descriptor = MTLRenderPipelineDescriptor() let vertices: [simd_float2] = [[-1, +1], [+1, +1], [-1, -1], [+1, -1]] let verticesLength = 4 * MemoryLayout<simd_float2>.stride descriptor.label = "Pixel Shader" descriptor.vertexFunction = library.makeFunction(name: "init") descriptor.fragmentFunction = library.makeFunction(name: "draw") descriptor.colorAttachments[0].pixelFormat = MetalView.pixelFormat commandQueue = device.makeCommandQueue()! pipelineState = try! device.makeRenderPipelineState(descriptor: descriptor) vertexBuffer = device.makeBuffer(bytes: vertices, length: verticesLength, options: [])! super.init() } func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) { } func draw(in view: MTKView) { let buffer = commandQueue.makeCommandBuffer()! let descriptor = view.currentRenderPassDescriptor! let encoder = buffer.makeRenderCommandEncoder(descriptor: descriptor)! encoder.setRenderPipelineState(pipelineState) encoder.setVertexBuffer(self.vertexBuffer, offset: 0, index: 0) encoder.drawPrimitives(type: .triangleStrip, vertexStart: 0, vertexCount: 4) encoder.endEncoding() buffer.present(view.currentDrawable!) buffer.commit() } } // finish by defining the three methods that are required by `NSViewRepresentable` conformance... func makeCoordinator() -> Coordinator { Coordinator() } func makeNSView(context: NSViewRepresentableContext<MetalView>) -> MTKView { let view = MTKView() view.delegate = context.coordinator view.device = context.coordinator.device view.colorPixelFormat = MetalView.pixelFormat view.clearColor = MetalView.clearColor view.drawableSize = view.frame.size view.preferredFramesPerSecond = 60 view.enableSetNeedsDisplay = false view.needsDisplay = true view.isPaused = false return view } func updateNSView(_ nsView: MTKView, context: NSViewRepresentableContext<MetalView>) { } } The shader boilerplate is simple. The vert function returns the vertices we pass into it, and the frag function just outputs purple, filling the viewport. #include <metal_stdlib> using namespace metal; vertex float4 init(const device float2 * vertices[[buffer(0)]], const uint vid[[vertex_id]]) { return float4(vertices[vid], 0, 1); } fragment float4 draw() { return float4(0.5, 0, 0.5, 1); } In practice, you'll want to create more buffers (like the vertex buffer), and use them to pass data to the GPU (by pointer). You can easily populate the buffers with primitives (including SIMD types). Beyond that, you can create a bridging header, which allows you to define structs in a (separate) C header file, and instantiate them in Metal code and Swift. You can then put any data you want in the buffers. Note: You should also look into using a semaphore to prevent race cases between the CPU and GPU threads. Note: There are tutorials (mostly on Apple Developer and Medium) that cover all of these things in enough depth to figure the rest out from the official API docs.