Simple DirectMedia Layer
||This article needs additional citations for verification. (February 2011)|
|Original author(s)||Sam Lantinga|
|Developer(s)||SDL Community ?|
|Stable release||1.2.15 / ~ 20 January 2012|
|Preview release||2.0 / Nightly|
|License||1.2 GNU LGPL / 2.0 zlib License|
Simple DirectMedia Layer (SDL) is a cross-platform, free and open source multimedia library written in C that presents a simple interface to various platforms' graphics, sound, and input devices. It is widely used due to its simplicity. Over 700 games, 180 applications, and 120 demos have been posted on its website.
SDL has the word "layer" in its title because it is actually a wrapper around operating-system-specific functions. The main purpose of SDL is to provide a common framework for accessing these functions. For further functionality beyond this goal, many libraries have been created to work on top of SDL.
Software developers use it to write computer games and other multimedia applications that can run on many operating systems: Android, iOS, Linux, Mac OS X, Windows and other (unofficially supported) platforms. It manages video, events, digital audio, CD-ROM, threads, shared object loading, networking and timers.
SDL acts as a thin, cross-platform wrapper, providing support for 2D pixel operations, sound, file access, event handling, timing, threading, and more. It is often used to complement OpenGL by setting up the graphical output and providing mouse and keyboard input, which are beyond the scope of OpenGL.
The library is divided into several subsystems, namely the video (handles both surface functions and OpenGL), audio, CD-ROM, joystick, and timer subsystems. Besides this basic, low-level support, there also are a few separate official libraries that provide some more functions. These comprise the "standard library", and are provided on the official website and included in the official documentation:
- SDL_image — support for multiple image formats
- SDL_mixer — complex audio functions, mainly for sound mixing
- SDL_net — networking support
- SDL_ttf — TrueType font rendering support
- SDL_rtf — simple Rich Text Format rendering
The SDL library has language bindings for many programming languages, from the popular (C, C++, Pascal, Perl, Python (via Pygame), etc.) to the less known languages such as Ch (via ChSDL), Euphoria and Pliant. This makes SDL a commonly used open source library for many multimedia applications.
Sam Lantinga created the library, first releasing it in early 1998, while working for Loki Software. He got the idea while porting a Windows application to Macintosh. He then used SDL to port Doom to BeOS (see Doom source ports). Several other free libraries were developed to work alongside SDL, such as SMPEG and OpenAL. He also founded Galaxy Gameworks in 2008 to help commercially support SDL, although the company plans are currently on hold due to time constraints.
SDL 2.0 is a major update to the SDL 1.2 codebase with a different, not backwards-compatible API. It replaces several parts of the 1.2 API with more general support for multiple input and output options.
SDL 2.0 is zlib-licensed, and therefore freely available for static linking in commercial closed-source projects, unlike SDL 1.2. The same day Sam Lantinga announced that he will be joining Valve Software, he also announced that "it's time to unleash SDL 2.0 on the masses".
Because of the way SDL is designed, much of the source code is split into separate modules for each operating system, to make calls to the underlying system. When SDL is compiled, the correct modules are selected for the target system.
On Microsoft Windows, SDL uses a GDI backend by default. A DirectX backend is also available. Older versions of SDL used DirectX 5, but SDL 1.2 (the current stable release) requires DirectX 7 by default. Sam Lantinga has stated that he plans to use DirectX 8 in future SDL releases.
Syntax and subsystems 
The syntax of SDL is function-based: all operations done in SDL are done by passing parameters to functions. Special structures are also used to store the specific information SDL needs to handle. There are a few different subsystems SDL categorizes its functions under:
- The video, events and threads subsystem: this provides functions for video, multi-threading, and event handling
- The audio subsystem: this provides functions for audio
- The time subsystem
- The joystick subsystem
- The CD-ROM subsystem
See also 
- List of games using SDL
- Allegro library
- Cross-Platform Support Middleware
- Microsoft XNA
- General Graphics Interface
Further reading 
- Alberto García Serrano: Programación de videojuegos en SDL, Ediversitas, ISBN 84-95836-08-4 (Spanish)
- Ernest Pazera: Focus On SDL, Muska & Lipman/Premier-Trade, ISBN 1-59200-030-4
- Ron Penton: Data Structures for Game Programmers, Muska & Lipman/Premier-Trade, ISBN 1-931841-94-2 (game programming examples with SDL)
- John R. Hall: Programming Linux Games, No Starch, ISBN 1-886411-49-2 (First SDL book, by Loki Games, archived online version: PDF, LaTex sources)
- "SDL libraries". Libsdl.org. Retrieved 15 January 2012.
- "a list of the platforms SDL supports". Libsdl.org. Retrieved 26 Nov 2012.
- "SDL official website". Libsdl.org. Retrieved 19 March 2010.
- "Exploring the Galaxy". 6 April 2011. Retrieved 30 Jan 2012.
- "SDL 1.3 Roadmap". 14 June 2011. Retrieved 25 July 2011.
- "Licensing the Simple DirectMedia Layer library". Retrieved 30 Jan 2012.
- "SDL 2.0 Is Coming Very Soon With New Features". Retrieved 17 Aug 2012.
- "SDL mailing list". Libsdl.org. Retrieved 23 March 2010.