GtkWidget is an abstract base class providing
its descendants with properties, methods and signals pertinent to
displayable user interface elements. The only objects that do not
inherit GtkWidget characteristics are
GtkTooltips, GtkAdjustment
and GtkItemFactory - all of which are relatively
abstract concepts. Everything else that is a member of the object
hierarchy is a descendant of the GtkWidget
class, takes up screen space, and may be referred to as a
widget.
Note that GtkWidget cannot be constructed
directly.