Well, that’s exactly what I would expect, but unless I am totally blind or stupid (or both) we seem to talk about different variants of SimConnect_RequestDataOnSimObject!
The one I am referring to:
does not have such a callback parameter! And again, all the provides examples seem to suggest that you need to poll for messages, with SimConnect_CallDispatch.
UPDATE: And just to be clear: the SimConnect.h header file from the FS 2020 SDK (the previous iteration - haven’t downloaded the SDK from the “December update”, in case that’s different anyway) does not have such a “callback parameter” either: so it seems to be consistent with the “Prepar3D” API docu (even though I understand the current FS 2020 SimConnect.dll supports way less functionality than the Prepar3D API).
All those examples have a “while(true)”-kind of loop which keeps polling for messages in 1 second (sleep(1)) intervals.
So unless you can point us to a concrete example or API documentation I just don’t see how to avoid this polling code pattern (except this funky “DLL start” voodoo magic, which I have not tried yet and which may only work with the Prepar3D specific implementation anyway…).