fltk/README.md

README - Fast Light Tool Kit (FLTK) Version 1.4.0

WHAT IS FLTK?

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

For more information see README.txt:
https://github.com/fltk/fltk/blob/master/README.txt