_gtkWidgetCB defines a generic callback to any Widgets object. Almost 100% of GTK+ signals can be defined by this way.
** Warning ** : this function works fine but the developer should be rigourous when it is used. He/She should read the GTK+ documentation for each asked signal.If you are NOT an advanced GTK developer, you are strongly recommended to use the specific functions in sub classes, even if they are much less.