a high-level multi-platform, thread-safe C/C++ windowing and graphics library built upon a fast, low-level graphics kernel. (new feature is FGX - dynamic GUI via XML file aka XUI file format)
a free user interface builder for GTK+ and GNOME interfaces designed are saved as XML, and by using the libglade library these can be loaded by applications dynamically as needed. (Glade can also generate C code)