A simple SDL3 demo using the new GPU API

Game.swift

import CSDL3

public class Game {
  let window: OpaquePointer!
  let gpuDevice: OpaquePointer!

  public init() {

    guard SDL_Init(SDL_INIT_EVENTS | SDL_INIT_VIDEO) else {
      fatalError("Failed to initialize SDL: \(String(cString: SDL_GetError()))")
    }

    self.window = SDL_CreateWindow("Game", 800, 600, 0)

    guard let window else {
      fatalError("Failed to create window: \(String(cString: SDL_GetError()))")
    }

    let supportFlags = SDL_GPU_SHADERFORMAT_MSL

    self.gpuDevice = SDL_CreateGPUDevice(supportFlags, true, nil)
    guard let gpuDevice else {
      fatalError("Failed to create GPU device: \(String(cString: SDL_GetError()))")
    }

    SDL_ClaimWindowForGPUDevice(gpuDevice, window)
  }

  public func run() {
    var running = true
    while running {
      var event = SDL_Event()

      while SDL_PollEvent(&event) {
        switch event.type {
        case SDL_EVENT_QUIT.rawValue:
          running = false
        default:
          break
        }
      }

      let commandBuffer = SDL_AcquireGPUCommandBuffer(gpuDevice)
      var swapchainTexture: OpaquePointer?

      guard
        SDL_WaitAndAcquireGPUSwapchainTexture(commandBuffer, window, &swapchainTexture, nil, nil)
      else {
        fatalError("Failed to acquire swapchain texture: \(String(cString: SDL_GetError()))")
      }

      if let swapchainTexture {
        let currentTime = Double(SDL_GetPerformanceCounter() / SDL_GetPerformanceFrequency())
        var colorTargetInfo = SDL_GPUColorTargetInfo()
        let color = SDL_FColor(
          r: Float(0.5 + 0.5 * SDL_sin(currentTime)),
          g: Float(0.5 + 0.5 * SDL_sin(currentTime + 2.09439510239)),
          b: Float(0.5 + 0.5 * SDL_sin(currentTime + 4.18879020479)),
          a: 1.0
        )

        colorTargetInfo.texture = swapchainTexture
        colorTargetInfo.clear_color = color
        colorTargetInfo.load_op = SDL_GPU_LOADOP_CLEAR
        colorTargetInfo.store_op = SDL_GPU_STOREOP_STORE

        let renderPass = SDL_BeginGPURenderPass(commandBuffer, &colorTargetInfo, 1, nil)
        SDL_EndGPURenderPass(renderPass)
        SDL_SubmitGPUCommandBuffer(commandBuffer)
      } else {
        SDL_CancelGPUCommandBuffer(commandBuffer)
      }
    }
  }

  deinit {
    SDL_ReleaseWindowFromGPUDevice(gpuDevice, window)
    SDL_DestroyGPUDevice(gpuDevice)
    SDL_DestroyWindow(window)
    SDL_Quit()
  }
}