The replacement for GtkSignals in libgobject are GSignals. As with most things in this new library, GSignals are a lot more versatile than GtkSignals.
Signals are a general purpose notification framework.
A type may have one or more signals, each of which may have an argument list and return value. Handlers can then be connected to instances of the type. When the signal is emitted on an instance, each of the connected handlers will be called. Inside libgobject , signals are used for property change notification. The closure argument says what function to call as a handler for the signal.