Appendix D. OpenGL and Window Systems
OpenGL is available on many different platforms and works with many different window systems. It is designed to complement window systems, not duplicate their functionality. Therefore, OpenGL performs geometric and image rendering in two and three dimensions, but it does not manage windows or handle input events.
However, the basic definitions of most window systems don’t support a library as sophisticated as OpenGL, with its complex and diverse pixel formats, including depth, stencil, and accumulation buffers, as well as double-buffering. For most window systems, some routines are added to extend the window system to support OpenGL.
This appendix introduces the extensions defined for several window ...