Godot-iOSキーボードの高さの変化を通知するネイティブプラグインを作る

import SwiftGodot

#initSwiftExtension(
    cdecl: "keyboard_observer",
    types: [
        GodotKeyboardObserver.self,
    ]
)

@Godot
public final class GodotKeyboardObserver: Object {

    @Signal
    var changedKeyboardHeight: SignalWithArguments<Float, Double>

    #if os(iOS)
    // このプロパティは Godot から見えないが、Swift 側で保持する
    private var nativeObserver: KeyboardObserver?
    #endif

    @Callable
    func start() {
        #if os(iOS)
        nativeObserver = KeyboardObserver(target: self)
        #endif
    }

    @Callable
    func stop() {
        #if os(iOS)
        nativeObserver?.remove()
        nativeObserver = nil
        #endif
    }

    @Callable
    func notifyKeyboardHeight(_ height: Float, duration: Double) {
        changedKeyboardHeight.emit(max(height, 0), duration)
    }
}

#if canImport(UIKit)

import UIKit

final class KeyboardObserver {

    weak var godotTarget: GodotKeyboardObserver?

    init(target: GodotKeyboardObserver) {
        godotTarget = target
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(keyboardWillChangeFrame(_:)),
            name: UIResponder.keyboardWillChangeFrameNotification,
            object: nil
        )
    }

    @MainActor
    @objc func keyboardWillChangeFrame(_ notification: Notification) {
        guard let userInfo = notification.userInfo,
              let keyboardFrame = userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect,
            let duration: TimeInterval = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? Double else { return }

        let screenHeight = UIScreen.main.bounds.height
        let keyboardHeight = Float(screenHeight - keyboardFrame.origin.y)
        godotTarget?.notifyKeyboardHeight(keyboardHeight, duration: duration)
    }

    func remove() {
        NotificationCenter.default.removeObserver(self)
    }
}

#endif

var _observer: GodotKeyboardObserver


func _ready() -> void:
    if _observer == null && ClassDB.class_exists("GodotKeyboardObserver"):
        _observer = ClassDB.instantiate("GodotKeyboardObserver")
        # Swift で作ったシグナルを使う
        _observer.changed_keyboard_height.connect(_on_changed_keyboard_height)
        # Swift で作った関数を使う
        _observer.start()
        print("GodotKeyboardObserver あるよ", _observer)
    else:
        print("GodotKeyboardObserver ないよ")


func _on_changed_keyboard_height(height: float, duration: float):
    print("キーボードの高さ変わったよ！", height, duration)

func _on_changed_keyboard_height(height: float, duration: float) -> void:
    # iOS端末の座標 -> スクリーン座標 -> viewport座標への変換が必要.
    var target_position := position
    var screen_size := DisplayServer.screen_get_size()
    var screen_scale := DisplayServer.screen_get_scale()
    var viewport_size := get_viewport().get_visible_rect().size
    var scale_y := screen_size.y / viewport_size.y

    # スクリーン座標に変換
    var keyboard_height_in_screen := height * screen_scale
    # スクリーン座標を Viewport座標に変換
    var keyboard_height := keyboard_height_in_screen / scale_y
    # キーボードの上端の座標を取得
    var keyboard_top_y := viewport_size.y - keyboard_height