Replace all uses of gtk_container_add on popovers by gtk_scrolled_window_set_child.
Replace most uses of gtk_style_context_add/remove_class by the new APIs. The only remaining uses of the old API are in save/restore situations.
This demo has everything: - a GtkFixed inside another GtkFixed - a cube made out of GtkFrame widgets - an example of 3D transformations And what's there, in the window once I launch it? The GTK logo made of widgets.
