One feature I have been dreaming of since ages is the following: being able to derive from a GtkWidget AND use GtkBuilder to initialize the derived widget from a UI description.

ATM one has two choices:

1) Derive from GtkWidget, get all the goodies for free, including easy integration into containers and the like.
   Disadvantage: one has to code each and every aspect by hand.

2) Load a widget from a UI description which allows for easy setup of trivial and sometimes more complex constructs.
   Disadvantage: the current object can only hold the widget as member, not BE it. Integration thus always involves reaching into the internals of the object to work with the widget.

Thus my request: allow for using GtkBuilder to initialize the widget directly into the current object.