how do i get the active game controller

To get the active game controller in visionOS, you can follow these steps:

1. Set up an observer for GCCControllerDidConnect to be notified when a game controller connects to the system. This will alert you to any game controllers that are connected.

2. Listen for GCCControllerDidDisconnect events to handle cases where the game controller disconnects, allowing you to fall back on other forms of input if necessary.

3. Poll the state of specific buttons on the controller or set up change handlers to be notified when the input state updates.

4. Add the game controller interaction modifier to the Reality View that contains your game objects. This ensures that game controller input directed to your Reality View will be handled by your game.

Here is a code snippet to illustrate these steps:

// Set up an observer for game controller connection
NotificationCenter.default.addObserver(
    self,
    selector: #selector(controllerDidConnect),
    name: .GCCControllerDidConnect,
    object: nil
)

// Set up an observer for game controller disconnection
NotificationCenter.default.addObserver(
    self,
    selector: #selector(controllerDidDisconnect),
    name: .GCCControllerDidDisconnect,
    object: nil
)

@objc func controllerDidConnect(notification: Notification) {
    if let controller = notification.object as? GCController {
        // Set up input change handlers or poll the device for input
    }
}

@objc func controllerDidDisconnect(notification: Notification) {
    // Handle disconnection, fall back to other input methods
}

For more detailed information, you can refer to the session Explore game input in visionOS starting at the "Physical controllers" chapter.