Glade

Glade is a RAD tool to enable quick & easy development of user interfaces
for the GTK+ 3 toolkit and the GNOME desktop environment.

The user interfaces designed in Glade are saved as XML and these can be
loaded by applications dynamically as needed by using GtkBuilder or used
directly to define a new GtkWidget derived object class using
GTK+ new template feature.

By using GtkBuilder, Glade XML files can be used in numerous programming
languages including C, C++, C#, Vala, Java, Perl, Python, and others.