A wrapper around SwiftUI defaultWindowPlacement that is a no-op on visionOS 1

DefaultWindowPlacement_visionOS2.swift

//
//  DefaultWindowPlacement_visionOS2.swift
//
//  Created by Drew Olbrich on 6/11/24.
//  Copyright © 2024 Lunar Skydiving LLC. All rights reserved.
//
//  MIT License
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import SwiftUI

enum WindowPlacementPosition {
    case utilityPanel
    case leading(_ id: String)
    case trailing(_ id: String)
    case above(_ id: String)
    case below(_ id: String)
}

extension SwiftUI.Scene {
    
    /// A wrapper around `defaultWindowPlacement` that applies it only on visionOS 2 and
    /// later, and is a no-op on visionOS 1.
    ///
    /// This is necessary because there doesn't appear to be an easy way to
    /// conditionally apply SwiftUI view modifiers or scene modifiers for specific OS
    /// versions.
    func defaultWindowPlacement_visionOS2(_ windowPlacementPosition: WindowPlacementPosition) -> some SwiftUI.Scene {
        if #available(visionOS 2.0, *) {
            return self.defaultWindowPlacement { content, context in
                func firstWindowProxy(withID id: String) -> WindowProxy? {
                    if let windowProxy = context.windows.first(where: { $0.id == id }) {
                        return windowProxy
                    } else {
                        assertionFailure("windowProxy is undefined")
                        return nil
                    }
                }
                
                switch windowPlacementPosition {
                case .utilityPanel:
                    return WindowPlacement(.utilityPanel)
                case .leading(let id):
                    if let windowProxy = firstWindowProxy(withID: id) {
                        return WindowPlacement(.leading(windowProxy))
                    } else {
                        return WindowPlacement(.none)
                    }
                case .trailing(let id):
                    if let windowProxy = firstWindowProxy(withID: id) {
                        return WindowPlacement(.trailing(windowProxy))
                    } else {
                        return WindowPlacement(.none)
                    }
                case .above(let id):
                    if let windowProxy = firstWindowProxy(withID: id) {
                        return WindowPlacement(.above(windowProxy))
                    } else {
                        return WindowPlacement(.none)
                    }
                case .below(let id):
                    if let windowProxy = firstWindowProxy(withID: id) {
                        return WindowPlacement(.below(windowProxy))
                    } else {
                        return WindowPlacement(.none)
                    }
                }
            }
        } else {
            return self
        }
    }
    
}