... what you get is a complete, adaptive design method.
GTK+ is the form language of Gnome, of course, and Qt is the form language of KDE.
We have similar patterns, and different forms.
If your pattern or form languages are not rich enough, you get a bad construction. The problem with Clutter right now is that it doesn't have a rich widget system, so building interfaces with it, “by hand”, is very painful and you need to reinvent the wheel all the time.