Editing OpenGL Utility Toolkit

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{{Infobox software
| name                   = OpenGL Utility Toolkit
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| screenshot             = Fenetre glut.png
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| author                 = 
| developer              = [[Mark Kilgard]]
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| programming language   = 
| operating system       = [[Cross-platform]]
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| genre                  = [[Application programming interface|API]]
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The '''OpenGL Utility Toolkit''' ('''GLUT''') is a [[library (computing)|library]] of utilities for [[OpenGL]] programs, which primarily perform system-level [[input/output|I/O]] with the host [[operating system]]. Functions performed include window definition, window control, and monitoring of [[Computer keyboard|keyboard]] and [[Computer mouse|mouse]] input. Routines for drawing a number of geometric primitives (both in solid and wireframe mode) are also provided, including [[cube (geometry)|cubes]], [[sphere]]s and the [[Utah teapot]]. GLUT also has some limited support for creating pop-up menus.

GLUT was written by [[Mark Kilgard|Mark J. Kilgard]], author of ''OpenGL Programming for the X Window System'' and ''The Cg Tutorial: The Definitive Guide to Programmable Real-Time Graphics'', while he was working for [[Silicon Graphics]] Inc.

The two aims of GLUT are to allow the creation of rather portable code between operating systems (GLUT is [[cross-platform]]) and to make learning OpenGL easier. Getting started with OpenGL programming while using GLUT often takes only a few lines of code and does not require knowledge of operating system–specific windowing [[application programming interface|APIs]].

All GLUT functions start with the <code>glut</code> prefix (for example, <code>glutPostRedisplay</code> marks the current window as needing to be redrawn).

== Implementations ==
The original GLUT library by Mark Kilgard supports the [[X Window System]] ([[GLX]]) and was ported to [[Microsoft Windows]] ([[WGL (software)|WGL]]) by [[Nate Robins]]. Additionally, [[macOS]] ships with a GLUT framework that supports its own NSGL/[[Core OpenGL|CGL]].

Kilgard's GLUT library is no longer maintained, and its license did not permit the redistribution of modified versions of the library. This spurred the need for [[free software]] or [[Open-source software|open source]] reimplementations of the API from scratch. The first such library was [[FreeGLUT]], which aims to be a reasonably close reproduction, though introducing a small number of new functions to deal with GLUT's limitations. OpenGLUT, a [[fork (software)|fork]] of FreeGLUT, adds a number of new features to the original API, but work on it ceased in May 2005.

Mark Kilgard has a GitHub repository for GLUT.<ref>{{Cite web|url = https://github.com/markkilgard/glut|title = Glut|website = [[GitHub]]|date = 21 November 2021|access-date = 13 October 2014|archive-date = 11 June 2018|archive-url = https://web.archive.org/web/20180611001101/https://github.com/markkilgard/glut|url-status = live}}</ref>  The glut.h header file contains the following license:<ref>{{Cite web|url = https://github.com/markkilgard/glut/blob/master/include/GL/glut.h|title = Glut|website = [[GitHub]]|date = 21 November 2021|access-date = 13 October 2014|archive-date = 3 August 2022|archive-url = https://web.archive.org/web/20220803003718/https://github.com/markkilgard/glut/blob/master/include/GL/glut.h|url-status = live}}</ref>

 /* Copyright (c) Mark J. Kilgard, 1994, 1995, 1996, 1998, 2000, 2006, 2010. */
 
 /* This program is freely distributable without licensing fees  and is
   provided without guarantee or warrantee expressed or  implied. This
   program is -not- in the public domain. */

== Limitations ==
Some of GLUT's original design decisions made it hard for programmers to perform desired tasks. This led many to create non-canon patches and extensions to GLUT.[http://www.mathies.com/glfaq/GLToolkitFAQ.html#II] Some [[free software]] or [[Open-source software|open source]] reimplementations also include fixes.

Some of the more notable limitations of the original GLUT library include:
* The library requires programmers to call <code>glutMainLoop()</code>, a function which never returns. This makes it hard for programmers to integrate GLUT into a program or library which wishes to have control of its own event loop. A common patch to fix this is to introduce a new function, called <code>glutCheckLoop()</code> (macOS) or <code>glutMainLoopEvent()</code> (FreeGLUT/OpenGLUT), which runs only a single iteration of the GLUT event loop. Another common workaround is to run GLUT's event loop in a separate [[thread (computing)|thread]], although this may vary by operating system, and also may introduce [[synchronization (computer science)|synchronization]] issues or other problems: for example, the macOS GLUT implementation requires that <code>glutMainLoop()</code> be run in the main thread.
* The fact that <code>glutMainLoop()</code> never returns also means that a GLUT program cannot exit the event loop. [[FreeGLUT]] fixes this by introducing a new function, <code>glutLeaveMainLoop()</code>.
* The library terminates the process when the window is closed; for some applications this may not be desired. Thus, many implementations include an extra callback, such as <code>glutWMCloseFunc()</code>.

Since it is no longer maintained (essentially replaced by the [[Open-source software|open source]] [[FreeGLUT]]) the above design issues are still not resolved in the original GLUT.

== See also ==
* [[EGL (API)|EGL]] is an interface between [[OpenGL ES]] or [[OpenVG]] and a [[windowing system]].
* [[FreeGLUT]] is intended to be a full replacement for GLUT, and has only a few differences.
* [[GLFW]]
* [[Simple DirectMedia Layer]] (SDL)
* [[OpenGL User Interface Library]] (GLUI)
* [[OpenGL Utility Library]] (GLU)

== References ==
{{Reflist}}

== External links ==
* [https://www.opengl.org/resources/libraries/glut/ GLUT - The OpenGL Utility Toolkit] {{Webarchive|url=https://web.archive.org/web/20180118221325/https://www.opengl.org/resources/libraries/glut/ |date=2018-01-18 }}
* [https://www.opengl.org/documentation/specs/glut/spec3/spec3.html The OpenGL Utility Toolkit (GLUT) Programming Interface API Version 3] (official documentation)
* [https://www.opengl.org/resources/libraries/glut/glut_downloads.php The OpenGL Utility Toolkit (GLUT) downloads] (source and pre-compiled libraries)

[[Category:OpenGL]]