Agar

Agar provides a base GUI framework and a standard set of widgets from which graphical applications can be built which run natively under X11, Windows, MacOS X, SDL and others. It takes advantage of texture and GPU acceleration wherever available. Agar can also attach to an existing framebuffer, SDL or OpenGL context and operate as a self-contained window-manager.

It includes a standard library of general-purpose widgets, and is also designed to be extended externally. New widgets can be implemented as part of an application or library. Complex user interface elements can be realized often in few lines of code. Agar is also extensible at the low-level. The low-level API is documented such that modular drivers can be written which enable Agar applications to work seamlessly under many platforms graphics systems without any change at the application level.