The release announcement says that Gtk3 has switched to Cairo to draw the toolkit behind the scenes:
Cairo drawing throughout. GDK no longer wraps the antiquated
X11 drawing API; we've made a clean break and exclusively rely
on cairo for all our drawing needs now.
As for Clutter, the OpenGL based canvas, Gnome-Shell (aka the Gnome 3 desktop UI) uses cluttter throughout. The new window manager is called Mutter which is a fork of Metacity to use Clutter for hardware acceleration and all the panels and other desktop UI are also rendered this way.
Comments
The release announcement says that Gtk3 has switched to Cairo to draw the toolkit behind the scenes:
Cairo drawing throughout. GDK no longer wraps the antiquated X11 drawing API; we've made a clean break and exclusively rely on cairo for all our drawing needs now.
As for Clutter, the OpenGL based canvas, Gnome-Shell (aka the Gnome 3 desktop UI) uses cluttter throughout. The new window manager is called Mutter which is a fork of Metacity to use Clutter for hardware acceleration and all the panels and other desktop UI are also rendered this way.