BuilderCScope 
    A GtkBuilderScope implementation for the C language.
GtkBuilderCScope instances use symbols explicitly added to @builder with prior calls to method@Gtk.BuilderCScope.add_callback_symbol. If developers want to do that, they are encouraged to create their own scopes for that purpose.
In the case that symbols are not explicitly added; GTK will uses GModule’s introspective features (by opening the module null) to look at the application’s symbol table. From here it tries to match the signal function names given in the interface description with symbols in the application.
Note that unless method@Gtk.BuilderCScope.add_callback_symbol is called for all signal callbacks which are referenced by the loaded XML, this functionality will require that GModule be supported on the platform.
Skipped during bindings generation
- parameter - callback_symbol: GObject.Callback
- method - add_callback_symbols: Varargs parameter is not supported
- method - lookup_callback_symbol: Return type GObject.Callback is not supported