GLUT

GLUT, the OpenGL Utility Toolkit, is a cross-platform library that provides a simple API for creating windows with OpenGL contexts, handling input, and managing the event loop. It was originally developed by Mark J. Kilgard at Silicon Graphics in the 1990s to facilitate the creation of small OpenGL demonstrations and tutorials.

GLUT wraps the commonly needed functionality: creating a window and its OpenGL context (glutInit, glutInitDisplayMode, glutCreateWindow), entering the main event loop (glutMainLoop), and registering callback functions for display, reshape, keyboard and mouse input, motion, passive motion, entry, visibility, and timer events. It also offers a simple menu system (glutCreateMenu, glutAddMenuEntry) and basic bitmap fonts for rendering text.

GLUT is designed to be portable across major platforms, using GLX on Unix-like systems, WGL on Windows, and a Cocoa/Carbon bridge on macOS. It follows a callback-driven model in which the application configures callbacks and then relinquishes control to the library’s event loop.

Because GLUT provides a compact, straightforward API, it was popular for teaching and early OpenGL programming. Over time, it has been superseded in many contexts by FreeGLUT, an open-source reimplementation that adds features and bug fixes while remaining API-compatible with GLUT. Modern OpenGL development often uses other toolkits such as GLFW or SDL that provide more comprehensive windowing, input, and context management, along with better support for advanced features and multi-platform needs.

See also: OpenGL, FreeGLUT, GLFW, SDL, GLX, WGL, Cocoa.