Control Interactive Dismissal of Navigation Zoom Transition SwiftUI

NavigationAllowedDismissalGesturesModifier.swift

// AllowedNavigationDismissalGestures.swift
// PaperPuppy
// Created by Ao XU on 5/19/25.

import SwiftUI
import UIKit
import Foundation

// MARK: - AllowedNavigationDismissalGestures

public struct AllowedNavigationDismissalGestures: OptionSet, Sendable {
    public let rawValue: Int
    public init(rawValue: Int) { self.rawValue = rawValue }
    
    public static let none: AllowedNavigationDismissalGestures = []
    /// Default behaviour: 左缘滑 + 缩放相关手势
    public static let all: AllowedNavigationDismissalGestures = [.swipeToGoBack, .zoomTransitionGesturesOnly]
    /// 左缘滑 + 缩放边缘滑动
    public static let edgePanGesturesOnly: AllowedNavigationDismissalGestures = [.swipeToGoBack, .zoomEdgePanToDismiss]
    /// 所有缩放过渡手势（缩放边缘、下拉、捏合）
    public static let zoomTransitionGesturesOnly: AllowedNavigationDismissalGestures = [.zoomEdgePanToDismiss, .zoomSwipeDownToDismiss, .zoomPinchToDismiss]
    
    public static let swipeToGoBack = AllowedNavigationDismissalGestures(rawValue: 1 << 0)
    public static let zoomEdgePanToDismiss = AllowedNavigationDismissalGestures(rawValue: 1 << 1)
    public static let zoomSwipeDownToDismiss = AllowedNavigationDismissalGestures(rawValue: 1 << 2)
    public static let zoomPinchToDismiss = AllowedNavigationDismissalGestures(rawValue: 1 << 3)
}

public extension View {
    /// 原有静态版
    func navigationAllowDismissalGestures(_ gestures: AllowedNavigationDismissalGestures = .all) -> some View {
        modifier(NavigationAllowedDismissalGesturesModifier(allowedDismissalGestures: gestures))
    }
    
    /// 新增：通过 Bool 动态开关。当 isEnabled == false 时，相当于 .none
    func navigationAllowDismissalGestures(_ gestures: AllowedNavigationDismissalGestures = .all,
                                          isEnabled: Bool) -> some View {
        let allowed = isEnabled ? gestures : .none
        return modifier(NavigationAllowedDismissalGesturesModifier(allowedDismissalGestures: allowed))
    }
}

// MARK: - NavigationAllowedDismissalGesturesModifier

private struct NavigationAllowedDismissalGesturesModifier: ViewModifier {
    var allowedDismissalGestures: AllowedNavigationDismissalGestures
    
    func body(content: Content) -> some View {
        content
            .background(
                NavigationDismissalGestureUpdater(allowedDismissalGestures: allowedDismissalGestures)
                    .frame(width: 0, height: 0)
            )
    }
}

// MARK: - NavigationDismissalGestureUpdater

private struct NavigationDismissalGestureUpdater: UIViewControllerRepresentable {
    @State private var viewMountRetryCount = 0
    var allowedDismissalGestures: AllowedNavigationDismissalGestures
    
    func makeUIViewController(context: Context) -> UIViewController { .init() }
    func updateUIViewController(_ vc: UIViewController, context: Context) {
        Task { @MainActor in
            guard
                let parent = vc.parent,
                let nav = parent.navigationController
            else {
                if viewMountRetryCount < Constants.maxRetryCountForNavigationHeirarchy {
                    viewMountRetryCount += 1
                    try await Task.sleep(for: .milliseconds(100))
                    return updateUIViewController(vc, context: context)
                }
                return
            }
            guard nav.topViewController == parent else { return }
            
            // 系统左缘滑动
            nav.interactivePopGestureRecognizer?.isEnabled = allowedDismissalGestures.contains(.swipeToGoBack)
            
            // 私有的缩放手势
            let recognizers = parent.view.gestureRecognizers ?? []
            for gr in recognizers {
                switch String(describing: type(of: gr)) {
                case Constants.zoomEdgePanToDismissClassType:
                    gr.isEnabled = allowedDismissalGestures.contains(.zoomEdgePanToDismiss)
                case Constants.zoomSwipeDownToDismissClassType:
                    gr.isEnabled = allowedDismissalGestures.contains(.zoomSwipeDownToDismiss)
                case Constants.zoomPinchToDismissClassType:
                    gr.isEnabled = allowedDismissalGestures.contains(.zoomPinchToDismiss)
                default:
                    continue
                }
            }
        }
    }
    
    static func dismantleUIViewController(_ vc: UIViewController, coordinator: ()) {
        vc.parent?.navigationController?.interactivePopGestureRecognizer?.isEnabled = true
        (vc.parent?.view.gestureRecognizers ?? []).forEach { gr in
            if Constants.navigationZoomGestureTypeClasses.contains(String(describing: type(of: gr))) {
                gr.isEnabled = true
            }
        }
    }
    
    private enum Constants {
        static let maxRetryCountForNavigationHeirarchy = 2
        static let zoomEdgePanToDismissClassType    = "_UIParallaxTransitionPanGestureRecognizer"
        static let zoomSwipeDownToDismissClassType  = "_UISwipeDownGestureRecognizer"
        static let zoomPinchToDismissClassType      = "_UITransformGestureRecognizer"
        static let navigationZoomGestureTypeClasses: Set<String> = [
            zoomEdgePanToDismissClassType,
            zoomSwipeDownToDismissClassType,
            zoomPinchToDismissClassType,
        ]
    }
}

.navigationAllowDismissalGestures(.edgePanGesturesOnly, isEnabled: allowSwipeBack)