Agar is a cross-platform GUI system. It provides a base framework and
a toolkit of widgets from which portable, high-performance graphical
applications can be built.

The toolkit is extensible through class registration. A style engine
allows precise control over the appearance of elements. Agar applications
work under X Windows, MS Windows, MacOS, SDL (1.2 and 2.0) and others.
It can attach to an existing graphical context and work as self contained
window manager. Agar is fully thread-safe when built with threads support.