internal void UnregisterHandleBehaviour(HandleBehaviour behaviour)
        {
            m_HandleBehaviours.Remove(behaviour);

            var interactiveHandle = behaviour as InteractiveHandle;

            if (interactiveHandle != null)
            {
                m_InteractiveHandles.Remove(interactiveHandle);
            }
        }
        internal void RegisterHandleBehaviour(HandleBehaviour behaviour)
        {
            m_HandleBehaviours.Add(behaviour);

            var interactiveHandle = behaviour as InteractiveHandle;

            if (interactiveHandle != null)
            {
                m_InteractiveHandles.Add(interactiveHandle);
            }
        }