gcc has optimizations for include guards that only work if they are outermost in the the header. https://bugzilla.gnome.org/show_bug.cgi?id=689810
Add a search entry widget with the recommended behaviour implemented. As used in gnome-control-center, Totem, gnome-documents and many others. https://bugzilla.gnome.org/show_bug.cgi?id=652809