size_request is now get_preferred_(width,height)
expose_event is now draw, second param is different
GtkObject is gone

GtkObject has been removed in GTK+ 3. Its remaining functionality, the ::destroy signal, has been moved to GtkWidget. If you have non-widget classes that are directly derived from GtkObject, you have to make them derive from GInitiallyUnowned (or, if you don't need the floating functionality, GObject). If you have widgets that override the destroy class handler, you have to adjust your class_init function, since destroy is now a member of GtkWidgetClass.

See https://developer.gnome.org/gtk3/3.10/ch24s02.html#id-1.6.3.4.15
Some more porting; Now DT fully builds with gtk+3!
And now even runs and displays lighttable, however crashing when switching to other view