Throughout the book, the exact header file which declares
each function is given alongside the function prototype.
This is to facilitate your exploration of the source
code. However, you probably don't want to manually
include the hundreds of headers found in GTK+ and Gnome.
You can include all GTK+ headers en
masse by including the
gtk/gtk.h header file.
gtk/gtk.h also includes
gdk/gdk.h for you. You can include all Gnome headers
by including gnome.h; gnome.h includes gtk/gtk.h for you. Most Gnome application
files simply include gnome.h.