GTK+ is a multi-platform toolkit for creating graphical user
interfaces. Offering a complete set of widgets, GTK+ is suitable for
projects ranging from small one-off tools to complete application
suites.

GTK+ has been designed from the ground up to support a range of
languages, not only C/C++. Using GTK+ from languages such as Perl and
Python (especially in combination with the Glade GUI builder) provides
an effective method of rapid application development.