显示MTKView的当前帧速率

import MetalKit

class ViewController: UIViewController {
    private var metalView: MTKView!
    private var displayLink: CADisplayLink!
    private var frameCount: Int = 0
    private var startTime: CFTimeInterval = 0

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建MTKView并设置相关属性
        metalView = MTKView(frame: view.bounds)
        metalView.device = MTLCreateSystemDefaultDevice()
        metalView.colorPixelFormat = .bgra8Unorm
        view.addSubview(metalView)
        
        // 创建CADisplayLink并与MTKView关联
        displayLink = CADisplayLink(target: self, selector: #selector(render))
        displayLink.add(to: .current, forMode: .default)
        
        // 初始化帧计数和开始时间
        frameCount = 0
        startTime = CACurrentMediaTime()
    }
    
    @objc private func render() {
        // 更新MTKView的内容
        
        // 计算帧速率
        frameCount += 1
        let currentTime = CACurrentMediaTime()
        let elapsedTime = currentTime - startTime
        if elapsedTime > 1.0 {
            let frameRate = Double(frameCount) / elapsedTime
            print("当前帧速率：\(frameRate) fps")
            frameCount = 0
            startTime = currentTime
        }
    }
}