Change Mac Catalyst SwiftUI app UISplitViewController background style to sidebar as in native Mac SwiftUI app

gistfile1.txt

// Apple Forum Question https://developer.apple.com/forums/thread/129211?answerId=620460022#620460022 

//
//	SceneDelegate.swift
//
//	Created by Egor Merkushev on 11.07.2020.
//	Copyright © 2020 Egor Merkushev. All rights reserved.
//
import UIKit
import SwiftUI
import CoreData
extension UIView {
		func findViews<T: UIView>(subclassOf: T.Type) -> [T] {
				return recursiveSubviews.compactMap { $0 as? T }
		}
		var recursiveSubviews: [UIView] {
				return subviews + subviews.flatMap { $0.recursiveSubviews }
		}
}
class SceneDelegate: UIResponder, UIWindowSceneDelegate {
		var window: UIWindow?
		public static func vc<T: UIViewController>(vcKind: T.Type? = nil, window: UIWindow?) -> T? {
				 if let vc = window?.rootViewController as? T {
						 return vc
				 } else if let vc = window?.rootViewController?.presentedViewController as? T {
						 return vc
				 } else if let vc = window?.rootViewController?.children {
						 return vc.lazy.compactMap { $0 as? T }.first
				 }
				 return nil
		 }
		func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
				// Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
				// If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
				// This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
				
				// Get the managed object context from the shared persistent container.
				let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
				// Create the SwiftUI view and set the context as the value for the managedObjectContext environment keyPath.
				// Add `@Environment(\.managedObjectContext)` in the views that will need the context.
				let contentView = ContentView().environment(\.managedObjectContext, context)
				
				// Use a UIHostingController as window root view controller.
				if let windowScene = scene as? UIWindowScene {
			// hide title bar for macOS
				#if targetEnvironment(macCatalyst)
					if let titlebar = windowScene.titlebar {
						titlebar.titleVisibility = .hidden
						titlebar.toolbar = nil
				}
			        #endif
						let window = UIWindow(windowScene: windowScene)
						window.rootViewController = UIHostingController(rootView: contentView)
						self.window = window
						window.makeKeyAndVisible()
						
						#if targetEnvironment(macCatalyst)
						let dispatchTime: DispatchTime = DispatchTime.now() + Double(Int64(0.1 * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC)
						DispatchQueue.main.asyncAfter(deadline: dispatchTime, execute: {
								let vc = type(of: self).vc(vcKind: UISplitViewController.self, window: window)
								if let split = vc {
										split.primaryBackgroundStyle = .sidebar // this line changes style and adds visual effect with blur
										
										if let sidebarController = split.viewControllers.first {
												sidebarController.view.recursiveSubviews.forEach { (view) in
														if view.backgroundColor != nil {
																view.backgroundColor = .clear // aggressively makes all opaque views transparent, you can change it to fix only hosting view of SwiftUI in this sidebar controller
														}
												}
										}
								}
						})
						#endif
				}
		}
...