DisplayLink.swift

import os

class DisplayLink {
    static let shared = DisplayLink()
    var displayLink: CADisplayLink!
    var lastTimestamp: CFTimeInterval?
    
    private let pointsOfInterestLog = OSLog(subsystem: "displaylink", category: .pointsOfInterest)

    init() {
        self.displayLink = CADisplayLink(target: self, selector: #selector(update))
        self.displayLink.add(to: .main, forMode: .common)
    }
    
    @objc func update() {
        let duration = displayLink.timestamp - (lastTimestamp ?? displayLink.timestamp)
        lastTimestamp = displayLink.timestamp
        
        if duration > 0.017 {
            os_signpost(.event, log: self.pointsOfInterestLog, name: "Frame Drop", "%f", duration * 1000)
        }
    }
}