fltk: fltk (Fast Light Tool Kit 1.3.x series) fltk: fltk: The Fast Light Tool Kit ("FLTK", pronounced "fulltick") is a fltk: a cross-platform C++ GUI toolkit for UNIX(r)/Linux(r) (X11), fltk: Microsoft(r) Windows(r), and MacOS(r) X. FLTK provides fltk: modern GUI functionality without the bloat and supports 3D fltk: graphics via OpenGL(r) and its built-in GLUT emulation. It fltk: was originally developed by Mr. Bill Spitzak and is fltk: currently maintained by a small group of developers across fltk: the world with a central repository in the US. fltk: