FLTK

FLTK was originally designed to be compatible with the Forms Library written for Silicon Graphics (SGI) machines (a derivative of this library called XForms is still used quite often). In that library, all functions and structures start with fl_. This naming was extended to all new methods and widgets in the C++ library, and this prefix FL was taken as the name of the library. After FL was released as open source, it was discovered that searching "FL" on the Internet was a problem, because it is also the abbreviation for Florida. After much debating and searching for a new name for the toolkit, which was already in use by several people, Bill Spitzak came up with Fast Light Tool Kit (FLTK).[5]

FLTK is an object-oriented widget toolkit written in the programming language C++. While GTK is mainly for the X Window System, FLTK works on other platforms, including Microsoft Windows (interfaced with the Windows API), and OS X (interfaced with Quartz). HTML5 and Wayland back-ends are in development. FLTK2 has gained experimental support for optionally using the cairo graphics library.

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Button.H>

int main(int argc, char *argv[]) {
   Fl_Window* w = new Fl_Window(330, 190);
   new Fl_Button(110, 130, 100, 35, "Okay");
   w->end();
   w->show(argc, argv);
   return Fl::run();
}

Many programs and projects use FLTK, including:

• Nanolinux, 14 MB Linux distribution[12][13][14][15][16][17]
• XFDOS, a FreeDOS-based distribution with a GUI, porting Nano-X and FLTK[18][19][20][21]
• Agenda VR3, a Linux-based personal digital assistant with software based on FLTK.
  • third-party Agenda VR3 software
• Amnesia: The Dark Descent, by Frictional Games uses FLTK as its launcher application
• MwendanoWD, Logic puzzle for personal computer by YPH.[22]
• Audio:
  • Fldigi, amateur radio software, allows data transmission and text chat via digital modes such as PSK31
  • Giada, looper, micro-sequencer, sample player software, open-source[23]
  • Prodatum, synthesizer preset editor, uses a lifelike interface design[24]
  • ZynAddSubFX, an open-source software synthesizer
• DiSTI GL Studio, human-machine interface development tool[25]
• Engineering:
  • ForcePAD, an intuitive tool to visualise the behavior of structures subject to loading and boundary conditions[26]
  • Gmsh, an open-source finite element mesh generator
  • RoboCIM, software to simulate and control operation of a servo robot system and external devices[27]
• Equinox Desktop Environment (EDE)
• FlBurn optical disc burning software for Linux[28]
• Graphics:
  • Avimator, a Biovision Hierarchy (BVH) editor
  • CinePaint, deep-paint software, migrating from GTK to FLTK, open-source
  • ITK-SNAP, software application for medical image segmentation, open-source
  • Nuke, a digital compositing program. Until version 5, now replaced by Qt
  • Open Movie Editor[29]
  • OpenVSP, NASA parametric aircraft sketching, recently open-sourced[30]
  • PosteRazor, open-source poster printing software for Windows, OS X, Linux[31]
• SmallBASIC, Windows port
• Web browsers:
  • Dillo, Dillo-2 was based on FLTK-2, abandoning this FLTK branch, with no official release, was a major cause of Dillo-3 being started, using FLTK1.3
  • Fifth, replicates functioning of early Opera[32]
  • NetRider[33]
• X window managers:
  • FLWM
  • miwm

This version history is an example of the sometimes tumultuous nature of open-source development.[34]

• GTK
• gtkmm (C++ binding of GTK)
• FOX toolkit
• IUP (software) - a multi-platform toolkit to build native graphical user interfaces
• Juce
• Qt (software)
• Visual Component Framework (VCF)
• Widget toolkit
• wxWidgets - cross platform open source C++ widgets toolkit developed by community
• Ultimate++
• List of widget toolkits

• Official website
• Beginner FLTK Tutorial
• FLTK 1.3.0 Tutorial
• Erco's FLTK Cheat Page