Get the current window scene from SwiftUI

[aheze]

If you want support multiple screens, and use frame tags or Popovers.popover(tagged:), you need to specify the window scene. The problem is, getting a view's window scene in SwiftUI is weird.

My current workaround (involves 0.5 second hardcoded delay):

Popovers/Sources/PopoverFrameTag.swift

Lines 67 to 114 in 5fcaa9d

	/// Get the parent window from a view. Help needed! From https://stackoverflow.com/a/63276688/14351818
	struct WindowSceneReader: UIViewRepresentable {
	/// A closure that's called when the window is found.
	var found: ((UIWindowScene?) -> Void)
	func makeUIView(context: Context) -> UIView {
	let view = UIView()
	/**
	The 0.5 second delay is needed to wait until the window is first initialized.
	However, it's hardcoded. Does anyone know how to work around this?
	*/
	DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { [weak view] in
	if let windowScene = view?.window?.windowScene {
	found(windowScene)
	}
	}
	return view
	}
	func updateUIView(_ uiView: UIView, context: Context) { }
	}
	/**
	Read the window scene from a view and inject it as an environment object. iOS 14+ due to `@StateObject`.
	*/
	@available(iOS 14, *)
	public struct WindowSceneInjectorModifier: ViewModifier {
	/// This is only iOS 14+. Looking for help in making this available for iOS 13.
	@StateObject var windowSceneModel = WindowSceneModel()
	public func body(content: Content) -> some View {
	content
	/// Inject the window into the subview.
	.environmentObject(windowSceneModel)
	/// Read the window.
	.background(
	WindowSceneReader { scene in
	windowSceneModel.windowScene = scene
	}
	)
	}
	}

You can then use this in your app's root view via injectWindowScene.

Popovers/Sources/PopoverFrameTag.swift

Lines 130 to 138 in 8e22ac7

	/**
	Get a view's window and make it accessible to all subviews. iOS 14+ due to `@StateObject` - looking for help in making it available for iOS 13.
	Only necessary if your app supports multiple windows.
	*/
	@available(iOS 14, *)
	func injectWindowScene() -> some View {
	return self.modifier(WindowSceneInjectorModifier())
	}

WindowGroup {
    ContentView()
        .injectWindowScene() /// Make the window scene available to all subviews. Not ideal, but it works (usually).
}

struct ContentView: View {
    @EnvironmentObject var windowSceneModel: WindowSceneModel

    /// ... 

    Text("Hello").frameTag("Your Frame Tag Name", in: windowSceneModel.windowScene)
}

The hardcoded delay especially is annoying. Typing out @EnvironmentObject var windowSceneModel: WindowSceneModel every time you want to access the window scene is ok, but it's still kind of long.

Does anyone know how to get a view's window in SwiftUI? Preferably, something like this:

struct ContentView: View {
    var body: some View {
        Text("Hello")
            .frameTag("Your Frame Tag Name")
    }
}
public extension View {
    func frameTag(_ tag: String) -> some View {
        let windowScene = theWindowSceneThatHostsThisView /// Something like this? So no more need to specify the window scene manually.
        return self.modifier(FrameTagModifier(tag: tag, windowScene: windowScene))
    }
}

[sans-connaissance]

Would something like this work?

struct WindowSceneReader: UIViewRepresentable {
    
    /// A closure that's called when the window is found.
    var found: ((UIWindowScene?) -> Void)
    
    func makeUIView(context: Context) -> UIView {
        let view = UIView()

        /**
         The 0.5 second delay is needed to wait until the window is first initialized.
         However, it's hardcoded. Does anyone know how to work around this?
         */
/// Use windowSceneDelegate to pass an initialized windowScene to found(...)
/// From https://stackoverflow.com/questions/62652555/how-to-get-uiwindow-value-in-ios-14-main-file
        var window: UIWindow? {
            guard let scene = UIApplication.shared.connectedScenes.first,
                  let windowSceneDelegate = scene.delegate as? UIWindowSceneDelegate,
                  let window = windowSceneDelegate.window else {
                return nil
            }
            return window
        }
        
        DispatchQueue.main.async {
            found(window?.windowScene)
        }
        
        return view
    }
    
    func updateUIView(_ uiView: UIView, context: Context) { }
}

[aheze]

@sans-connaissance thanks, that would indeed get the main window. But I need the current window that hosts the view. Around 99% of the time this is the same as the main window... but if your app supports multiple windows (iPadOS), it will be different. Should have been more clear, sorry.

/// Multiple copies of this view can be created if your app supports multiple windows.
struct ContentView: View {
    var body: some View {
        Text("Hello!") /// <- what window scene is this embedded in?
    }
}

But anyway, I think ShezHsky's #5 PR fixes this issue. I'm still checking over it to see if it will work out, but will update this thread when I'm done.

https://github.com/aheze/Popovers/pull/5/files#diff-a1c21266189878135a0f3c0581755fcd2da315bfa06f0e3c1d8de478d85d48f3

[sans-connaissance]

Thanks for taking a look! This issue and your comment helped me to better understand the window and view relationship in SwiftUI projects.

[aheze]

Fixed in #5.

[rijieli]

WindowSceneReader is very useful on visionOS when you have multiple windows and want to lock the window resize ratio.