SwiftUI gains ProMotion

promotion.swift

import UIKit
import SwiftUI
import QuartzCore

var lastMediaTime: CFTimeInterval? = nil

struct YOffsetEffect: GeometryEffect {
    var y: CGFloat
    var animatableData: CGFloat {
        get { y }
        set { y = newValue }
    }
    func effectValue(size: CGSize) -> ProjectionTransform {
        let current = CACurrentMediaTime()
        if let last = lastMediaTime {
            let ms = (current - last) * 1000
            print(String(format: "%.1fms has elapsed since last update", ms))
        } else {
            print("First frame at mediaTime: \(current)")
        }
        lastMediaTime = current
        return ProjectionTransform(CGAffineTransform(translationX: 0, y: y))
    }
}

struct DualSquaresView: View {
    @State private var toggled = false
    var body: some View {
        HStack(spacing: 40) {
            Rectangle()
                .fill(Color.blue)
                .frame(width: 200, height: 200)
                .offset(y: toggled ? 300 : -300)
                .animation(.easeInOut(duration: 0.35), value: toggled)
                .onTapGesture { toggled.toggle() }
            Rectangle()
                .fill(Color.orange)
                .frame(width: 200, height: 200)
                .modifier(YOffsetEffect(y: toggled ? 300 : -300))
                .animation(.easeInOut(duration: 0.35), value: toggled)
                .onTapGesture { toggled.toggle() }
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(Color(.systemBackground))
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let hostingController = UIHostingController(rootView: DualSquaresView())
        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
        addChild(hostingController)
        view.addSubview(hostingController.view)
        NSLayoutConstraint.activate([
            hostingController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            hostingController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            hostingController.view.topAnchor.constraint(equalTo: view.topAnchor),
            hostingController.view.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
        hostingController.didMove(toParent: self)
    }
}