The customer requested a multi-platform and flexible GUI solution.
GTK+ is a multi-platform free software GUI Toolkit, primarily designed for the X Window System. GTK+ is licensed under the GNU LGPL, which allows us to develop free software or even commercial non-free software without great costs.
GTK+ is a set of libraries supporting programmers at creating graphical user interfaces. It has a C-based object-oriented architecture that allows for maximum flexibility. It consists of the following component libraries:
GLib - Provides many useful data types, macros, type conversions, string utilities and a lexical scanner.
GDK - A wrapper for low-level windowing functions.
GTK - An advanced widget set.
The Ada-Binding has some smaller drawbacks which we try to get around.