Free C++ GUI Toolkit for the X Window System, OpenGL, and WIN32
The Fast Light Tool Kit ("FLTK", pronounced "fulltick") is a C++
graphical user interface toolkit for the X Window System (UNIX(r)),
OpenGL(r), and Microsoft(r) Windows(r) NT 4.0, 95, or 98. The
installation of this package requires you to install a 3D library. If
you do not have hardware 3D, you can use the software OpenGL library in
the mesasoft package (series x3d). The library can be recompiled
without 3D support.