A notification call back indicating that main screen index has changed. This is only relevant for multiscreen setups. Implementing classes should update themselves accordingly if needed. Register for updates through GazeManager.AddTrackerStateListener().

A notification call back indicating that state of connected Tracker device has changed. Use this to detect if a tracker has been connected or disconnected. Implementing classes should update themselves accordingly if needed. Register for updates through GazeManager.AddTrackerStateListener().