luma/Luma/CursorOverrideRegion.swift

import SwiftUI

#if canImport(AppKit)
    import AppKit

    struct CursorOverrideRegion: NSViewRepresentable {
        func makeNSView(context: Context) -> NSView {
            CursorOverrideNSView()
        }

        func updateNSView(_ nsView: NSView, context: Context) {}
    }

    private final class CursorOverrideNSView: NSView {
        private nonisolated(unsafe) var monitor: Any?

        override func viewDidMoveToWindow() {
            super.viewDidMoveToWindow()
            if window != nil {
                installMonitor()
            } else {
                uninstallMonitor()
            }
        }

        deinit {
            if let monitor {
                NSEvent.removeMonitor(monitor)
            }
        }

        private func installMonitor() {
            guard monitor == nil else { return }
            monitor = NSEvent.addLocalMonitorForEvents(matching: .mouseMoved) { [weak self] event in
                guard let self,
                    let window = self.window,
                    event.window === window,
                    self.convert(self.bounds, to: nil).contains(event.locationInWindow)
                else {
                    return event
                }
                NSCursor.arrow.set()
                return nil
            }
        }

        private func uninstallMonitor() {
            if let monitor {
                NSEvent.removeMonitor(monitor)
            }
            monitor = nil
        }

        override func hitTest(_ point: NSPoint) -> NSView? {
            nil
        }
    }
#else
    struct CursorOverrideRegion: View {
        var body: some View { Color.clear }
    }
#endif