gtkmm (formerly known as gtk-- or gtk minus minus) is the official C++ interface for the popular GUI library GTK+. gtkmm is free software distributed under the GNU Lesser General Public License (LGPL).gtkmm allows the creation of user interfaces either in code or with the Glade Interface Designer, using the Gtk::Builder class. Other features include typesafe callbacks, a comprehensive set of graphical control elements, and the extensibility of widgets via inheritance.