The default destructor automatically unregisters this callback, if not already unregistered. Plugins should always unregister a tablet callback when they are done using the tablet. This is a safety measure to be sure the TabletCallback is unregistered before it is destroyed, preventing a dangling pointer to the destroyed object.
This method is called whenever a tablet event is detected. All attributes of the event are available via the TabletManager's access methods. When plugins receive this callback, they can query the TabletManager as desired to retrieve more information about the tablet event.