Available C++ Libraries FAQ

Libraries available to download (D-L)

Fast Light Toolkit - GNU LGPL GUI toolkit for X11 and Windows

FLTK (pronounced "fulltick") is a LGPL C++ graphical user interface toolkit for X (UNIX®), OpenGL, and WIN32 (Microsoft® Windows® NT 4.0, 95, or 98). It is currently maintained by a small group of developers across the world with a central repository in the US.

FLTK was originally created to build in-house applications at Digital Domain for image processing and 3D graphics. The original author, Bill Spitzak, received permission from Digital Domain to release it to the public domain in the hopes that it could be used to make better, faster, and nicer-looking UNIX programs. Digital Domain has since withdrawn support for FLTK, but Bill is still able to work o!n it from time to time. FLTK was designed to be small and modular enough to be statically linked. FLTK also works fine as a shared library and has started being included on Linux distributions.

Here are some of the core features unique to FLTK:

  • sizeof(Fl_Widget) == 40 to 48
  • The "core" (the "hello" program compiled & linked with a static FLTK library using gcc on a 486 and then stripped) is 110k.
  • The FLUID program (which includes every widget) is 372k.
  • Does not use macros, templates, multiple inheritance, or exceptions.
  • Written directly atop Xlib (or the WIN32 API) for maximum speed, and carefully optimized for code size and performance.
  • Precise low-level compatibility between the X and Windows version (only about 10% of the code is different).
  • Interactive user interface builder program. Output is human-readable and editable C++ source code.
  • Support for overlay hardware (emulation if none and under Windows)
  • Very small & fast portable 2-D drawing library to hide Xlib and WIN32
  • OpenGL/Mesa drawing area widget
  • Support for OpenGL overlay hardware on both X and Windows. Emulation if none.
  • Text input fields with Emacs key bindings, cut & paste, and foreign letter compose!
  • Compatability header file for the GLUT library
  • Compatability header file for the XForms library

Operating Systems

  • Linux
  • PC 32-bit Windows
  • Sparc
  • SGI Irix
  • Solaris
  • HP UX
  • OS/2
  • Unix
  • X Windows
  • SYSV
  • Dec Alpha
  • SCO Open Desktop
  • Unisys Unixware
  • Dec OSF/1


  • Visual C++
  • GCC
  • Sun CC
  • IBM xlC
  • MetroWerks CodeWarrior
  • Borland C++
  • HP C++
  • Any standard C++ compiler

Added : 2000-04-26 Amended: 2000-04-26 Licensing : GNU copyleft

    Fast Light Toolkit - GNU LGPL GUI toolkit for X11 and Windows
  • FLTK Home Page
  • Submitted by:mike@easysw.com
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Copyright (c) 2019 Nikki Locke, Trumphurst Ltd.
Permission is granted to distribute over the Internet without charge. The author's permission is required (and usually given) to distribute in any other way, including on CD.