Check a bus message to see if it is a #GstNavigation event, and return the #GstNavigationMessageType identifying the type of the message if so.
A #GstMessage to inspect.
The type of the #GstMessage, or #GST_NAVIGATION_MESSAGE_INVALID if the message is not a #GstNavigation notification.
Check a bus message to see if it is a #GstNavigation event, and return the #GstNavigationMessageType identifying the type of the message if so.