listless

ListlessiOS/Helpers/KeyboardWarmup.swift (1476B)

1import UIKit
2
3/// Pre-pays the ~400ms `RemoteTextInput` / autocorrect subsystem spin-up that
4/// otherwise happens on the first real text field focus after a cold launch.
5/// Creates an offscreen `UITextField`, makes it first responder, then resigns
6/// immediately — enough to trigger the keyboard process to initialize without
7/// visibly animating anything.
8@MainActor
9enum KeyboardWarmup {
10    private static var didWarm = false
11
12    static func prime() {
13        guard !didWarm else { return }
14        guard let window = keyWindow() else { return }
15        didWarm = true
16
17        PerfSampler.shared.measure("Keyboard.warmup") {
18            let field = UITextField(frame: CGRect(x: -100, y: -100, width: 1, height: 1))
19            field.autocorrectionType = .default
20            field.autocapitalizationType = .sentences
21            window.addSubview(field)
22            field.becomeFirstResponder()
23            field.resignFirstResponder()
24            field.removeFromSuperview()
25        }
26    }
27
28    private static func keyWindow() -> UIWindow? {
29        for case let scene as UIWindowScene in UIApplication.shared.connectedScenes {
30            if let key = scene.windows.first(where: \.isKeyWindow) {
31                return key
32            }
33        }
34        for case let scene as UIWindowScene in UIApplication.shared.connectedScenes {
35            if let first = scene.windows.first {
36                return first
37            }
38        }
39        return nil
40    }
41}