SwiftUI NSCursor support on MacOS.swift

import SwiftUI


struct Cursor: Equatable {
    let ns: NSCursor?
    let id: String
}


struct CursorPreference: PreferenceKey {

    typealias Value = [Cursor]
    static var defaultValue: Value = []

    static func reduce(value: inout Value, nextValue: () -> Value) {
        let newCursors = nextValue()
        guard let newCursor = newCursors.first else { return }
        value.removeAll {
            $0.id == newCursor.id
        }
        if newCursor.ns != nil {
            value.append(newCursor)
        }
    }
}


extension View {
    func cursor(type ns: NSCursor?, id: String) -> some View {
        preference(key: CursorPreference.self, value: [Cursor(ns: ns, id: id)])
    }
}


struct CursorReader: ViewModifier {

    @State private var cursors: [Cursor] = [] {
        didSet {
            handle(current: oldValue.last, new: cursors.last)
        }
    }

    func body(content: Content) -> some View {
        content
            .onPreferenceChange(CursorPreference.self) {
                cursors = $0
            }
    }

    private func handle(current: Cursor?, new: Cursor?) {
        if let current = current?.ns {
            current.pop()
        }
        if let new = new?.ns {
            NSApp.windows.forEach { $0.disableCursorRects() }
            new.push()
        }
        if new?.ns == nil {
            NSApp.windows.forEach { $0.enableCursorRects() }
        }
    }
}


extension View {
    func enableCursors() -> some View {
        modifier(CursorReader())
    }
}


//struct CursorModifier: ViewModifier {
//
//    struct IdCursor: Equatable {
//        let cursor: NSCursor
//        let id: Int
//    }
//
//    var cursor: IdCursor?
//
//    func body(content: Content) -> some View {
//        content
//            .onChange(of: cursor) { [current = cursor] new in
//                if let current = current {
//                    current.cursor.pop()
//                }
//                if let new = new {
//                    NSApp.windows.forEach { $0.disableCursorRects() }
//                    new.cursor.push()
//                }
//                if new == nil, current?.cursor == NSCursor.current {
//                    NSApp.windows.forEach { $0.enableCursorRects() }
//                }
//            }
//    }
//}


//extension View {
//    func cursor(_ cursor: NSCursor?, id: Int) -> some View {
//        modifier(CursorModifier(cursor: cursor.flatMap { .init(cursor: $0, id: id) }))
//    }
//}