How to differentiate between user-generated NSEvents and programmatically posted events in AppKit?

Hi all,

In my AppKit app, I sometimes simulate events programmatically, for example:

func simulateKeyPress(characters: String, keyCode: UInt16) {
    guard let keyDown = NSEvent.keyEvent(
        with: .keyDown,
        location: .zero,
        modifierFlags: [],
        timestamp: 0,
        windowNumber: NSApp.mainWindow?.windowNumber ?? 0,
        context: nil,
        characters: characters,
        charactersIgnoringModifiers: characters,
        isARepeat: false,
        keyCode: keyCode
    ) else { return }

    NSApp.postEvent(keyDown, atStart: false)
}

At the same time, I install a local event monitor:

NSEvent.addLocalMonitorForEvents(matching: .any) { event in
    // Ideally, detect whether this event came from a real user
    // (mouse, keyboard, trackpad, etc.)
    // or was programmatically generated via NSEvent + postEvent.
    return event
}

The problem: Events I generate with NSEvent.* factory methods and post using NSApp.postEvent look the same as real system events when received in the monitor.

My question: Is there a supported way to tell whether an incoming NSEvent is system/user-generated vs programmatically posted?