Fetches a symbol previously added to builder with Builder.addCallbackSymbols
This function is intended for possible use in language bindings or for any case that one might be cusomizing signal connections using Builder.connectSignalsFull
The name of the callback
The callback symbol in builder for callback_name, or NULL
3.10
Fetches a symbol previously added to builder with Builder.addCallbackSymbols
This function is intended for possible use in language bindings or for any case that one might be cusomizing signal connections using Builder.connectSignalsFull