GSPreFilterCallbackName and GSFilterCallbackName

Are these implemented? I have tried to find the callback signature in my delegate but it seems they don’t affect anything. I wish to know exactly when a filter, its name and params, and on which layer it is run.

Are you trying this in python or ObjectiveC?

Objective-C with GSCallbackHandler…

[GSCallbackHandler addCallback:self forOperation:GSPreFilterCallbackName];
[GSCallbackHandler addCallback:self forOperation:GSFilterCallbackName];