Metal API SwiftUI view

MetalView.swift

//
//  Created by Szymon Błaszczyński on 26/08/2021.
//

import Foundation
import MetalKit
import SwiftUI

struct MetalView: NSViewRepresentable {
    func makeCoordinator() -> Coordinator {
        Coordinator(self, mtkView: mtkView)
    }
    
    
    typealias NSViewType = MTKView
    var mtkView: MTKView
    
    func makeNSView(context: NSViewRepresentableContext<MetalView>) -> MTKView {
        mtkView.delegate = context.coordinator
        mtkView.preferredFramesPerSecond = 60
        mtkView.enableSetNeedsDisplay = true
        mtkView.isPaused = false
        mtkView.colorPixelFormat = MTLPixelFormat.bgra8Unorm
        return mtkView
    }
    
    func updateNSView(_ nsView: MTKView, context: NSViewRepresentableContext<MetalView>) {
        
    }
    
    class Coordinator: NSObject, MTKViewDelegate {
        var parent: MetalView
        var ciContext: CIContext!
        var metalDevice: MTLDevice!

        var metalCommandQueue: MTLCommandQueue!
        var mtlTexture: MTLTexture!

        var startTime: Date!

        init(_ parent: MetalView, mtkView: MTKView) {
           self.parent = parent
           if let metalDevice = MTLCreateSystemDefaultDevice() {
               mtkView.device = metalDevice
               self.metalDevice = metalDevice
           }
           self.ciContext = CIContext(mtlDevice: metalDevice)
           self.metalCommandQueue = metalDevice.makeCommandQueue()!
           
           super.init()
           mtkView.framebufferOnly = false
           mtkView.clearColor = MTLClearColor(red: 0, green: 0, blue: 0, alpha: 0)
           mtkView.drawableSize = mtkView.frame.size
           mtkView.enableSetNeedsDisplay = true
        }

        func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {
           
        }
        
        func draw(in view: MTKView) {
            guard let drawable = view.currentDrawable else {
                return
            }
            let texture: MTLTexture = drawable.texture
            let passDescriptor = view.currentRenderPassDescriptor
            passDescriptor?.colorAttachments[0].texture = texture
            passDescriptor?.colorAttachments[0].loadAction = .clear
            passDescriptor?.colorAttachments[0].storeAction = .store
            passDescriptor?.colorAttachments[0].clearColor = MTLClearColorMake(1, 0, 0, 1)
            let commandQueue = metalDevice.makeCommandQueue()!
            let commandBuffer = commandQueue.makeCommandBuffer()!
            let commandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: passDescriptor!)
            commandEncoder?.endEncoding()
            commandBuffer.present(drawable)
            commandBuffer.commit()
        }
    }
}

Usage: MetalView(mtkView: MTKView() in your SwiftUI body