This manual describes the Fast Light Tool Kit ("FLTK") version 2.0, a C++ Graphical User Interface (GUI) toolkit for UNIX and Microsoft Windows. Each of the chapters in this manual is designed as a tutorial for using FLTK, while the appendices provide a convenient reference for all FLTK widgets, functions, and operating system interfaces.
The Fast Light Tool Kit ("FLTK", pronounced "fulltick") is a LGPL'd C++ graphical user interface toolkit for X (UNIX®), OpenGL®, and Microsoft® Windows® NT 4.0, 95, or 98. 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 in the US.FLTK is ©1998-2003 by Bill Spitzak and others. Use and distribution of FLTK is governed by the FLTK Library License (which is the GNU Library General Public License with an exception added that allows you to distribute statically-linked programs using the library without providing source code to the program or the library).
UNIX is a registered trademark of the X Open Group, Inc. Microsoft and Windows are registered trademarks of Microsoft Corporation. OpenGL is a registered trademark of Silicon Graphics, Inc.
Here are some of the core features unique to FLTK:
FLTK comes with complete free source code. FLTK is ©1998-2003 by Bill Spitzak and others. Use and distribution of FLTK is governed by the FLTK Library License (which is the GNU Library General Public License with an exception added that allows you to distribute statically-linked programs using the library without providing source code to the program or the library). You can use it in commercial software!
Many of the ideas in FLTK were developed on a NeXT (but not using NextStep) in 1987 in a C toolkit Bill called "viewkit". Here he came up with passing events downward in the tree and having the handle routine return a value indicating they used the event, which got rid of the need for "interests" that so complicated Motif and NeWS.
After going to film school for a few years, Bill worked at Sun Microsystems on the (doomed) NeWS project. Here he found an even better and cleaner windowing system, and he reimplemented "viewkit" atop that. NeWS did have an unnecessarily complex method of delivering events which hurt it. But the designers did admit that perhaps the user could write just as good of a button as they could, and officially exposed the lower level interface.
With the death of NeWS Bill realized that he would have to live with X. The biggest problem with X is the "window manager", which means that the toolkit can no longer control the window borders or drag the window around. Indeed far more code is spent trying to talk to window managers than would be needed to draw the borders themselves. (fortunately the problems with X are also replicated on Windows, and thus solving them helped with the porting to Windows).
At Digital Domain Bill discovered another toolkit, "Forms". Forms was similar to his work, but provided many more widgets, since it was used in many real applications, rather then as theoretical work. Several large pieces of software were written using a version of Forms with the menus and file browser replaced with code from viewkit.
The need to switch to OpenGL, a desire to use C++, and the closed-source nature of XForms, all led to a rquirement to rewrite Forms. This produced the first version of FLTK. The conversion to C++ required so many changes it made it impossible to recompile any Forms objects. Since it was incompatible anyway, Bill decided to incorporate his older ideas as much as possible.
Bill received permission to release it for free on the Internet, with the GNU general public license. Response from Internet users indicated that the Linux market dwarfed the SGI and high-speed GL market, so he rewrote it to use X for all drawing, greatly speeding it up on these machines. That is the version you have now.
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