You're reading the documentation for an older, but still supported version
(GL013300).
For information on the latest version, please have a look at GL013301.
For information on the latest version, please have a look at GL013301.
2.4 Callback Function
This section describes the callback function types supported by the DRFL. Callback definitions specify the function signatures used for event-driven communication, allowing user applications to receive asynchronous robot updates such as logging, monitoring data, and safety events.