Simple DirectMedia Layer
|This article needs additional citations for verification. (February 2011)|
|Original author(s)||Sam Lantinga|
|Stable release||2.0.1 / 24 October 2013
Previous v1.2.15: 20 January 2012
|Platform||Windows, Mac OS X 10.5+, Linux 2.6+, iOS 3.1.3+, Android 2.3.3+, FreeBSD 8.4+, Haiku
Previous v1.2.15: Windows, Mac OS X 10.4+, Linux 2.6+, FreeBSD 8.4+
Simple DirectMedia Layer (SDL) is a cross-platform development library designed to provide low level access to audio, input devices, and graphics hardware via OpenGL and Direct3D (i.e. not DirectX). SDL is written in C and is free and open-source software subject the the requirements of the zlib License since version 2.0 and GNU Lesser General Public License prior versions.
Over 700 games, 180 applications, and 120 demos have been posted on its website.
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 platforms. It manages video, events, digital audio, CD-ROM, threads, shared object loading, networking and timers.
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, a couple of libraries have been created to work on top of SDL.
SDL acts as a cross-platform wrapper, providing support for 2D pixel operations, sound, file access, event handling, timing and threading. It is often used to complement OpenGL by setting up the graphical output and providing mouse and keyboard input, which are not supported by 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 2.0 library has language bindings for many programming languages, C, C++, Pascal, Python (via PySDL2.0) , Vala and Genie. This makes SDL a commonly used open source library for many multimedia applications.
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
Because of the way SDL is designed, much of its 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. Following back-ends are available:
- GDI back-end for Microsoft Windows.
- DirectX back-end; but SDL 1.2 requires DirectX 7 by default. Sam Lantinga has stated that he plans to use DirectX 8 in future SDL releases.
- Quartz back-end for Mac OS X
- Xlib back-end for X11-based windowing system on various operating systems.
- EGL back-end when used in conjunction with Wayland-based windowing system., Raspberry Pi and other systems.
- sceGu back-end, a Sony OpenGL-like backend native to the PSP.
SDL 1.2 has support for RISC OS (dropped in 2.0).
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. Soon after putting Galaxy Gameworks on hold, Lantinga announced that SDL 1.3 (which would then later become SDL 2.0) would be licensed under the zlib License. Lantinga announced SDL 2.0 on 14 July 2012, at the same time announcing that he was joining Valve Software, the first version of which was announced the same day he joined the company. Lantinga announced the stable release of SDL 2.0.0 on 13 August 2013.
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.
Reception and adoption
Over the years SDL was used for many commercial and non-commercial video game projects, for instance MobyGames listed 120 games using SDL in 2013 and the SDL website itself listed around 700 games in 2012. Important commercial examples are Angry Birds or Unreal Tournament, from the open source domain OpenTTD, The Battle for Wesnoth or Freeciv.
Often is SDL also used for later ports on new platforms with existing legacy code, for instance the PC game Homeworld was ported to the Pandora handheld and Jagged Alliance 2 for Android via SDL.
There were several books written for the development with SDL (see further readings).
Video game examples using SDL
|Video games adopting Simple DirectMedia Layer|
- Allegro library
- Cross-platform support middleware
- General Graphics Interface
- 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 Game Development by Shaun Mitchell
- Simple DirectMedia Layer - SDL version 2.0.1 (stable). Libsdl.org (2001-01-05). Retrieved on 2013-12-08.
- Index of /release. Libsdl.org (2013-08-17). Retrieved on 2013-12-08.
- "SDL license". Retrieved 2014-03-03.
- "a list of the platforms SDL supports". Libsdl.org. Retrieved 15 Jul 2013.
- "SDL official website". Libsdl.org. Retrieved 19 March 2010.
- "Introduction to SDL". Retrieved 2014-03-03.
- "SDL libraries". Libsdl.org. Retrieved 2012-01-15.
- "SDL officially and unofficially supported platforms".
- "SDL mailing list". Libsdl.org. Retrieved 23 March 2010.
- SDL: README-platforms.txt@3e2f230a6d62. Hg.libsdl.org. Retrieved on 2013-12-08.
- "SDL and Wayland".
- Larabel, Michael (September 30, 2013). "Raspberry Pi Support Added To SDL2 Library".
- "Exploring the Galaxy". 6 April 2011. Retrieved 30 Jan 2012.
- SDL 1.3 to be zLib Licensed, SDL Mailing List, 2011-04-07
- "SDL 2.0 Is Coming Very Soon With New Features". Retrieved 17 Aug 2012.
- Announcing SDL 2.0.0, SDL Mailing List, 2013-08-13
- MigrationGuide - SDL Wiki'. Wiki.libsdl.org (2013-11-21). Retrieved on 2013-12-08.
- "SDL 1.3 Roadmap". 14 June 2011. Retrieved 25 July 2011.
- "Licensing the Simple DirectMedia Layer library". Retrieved 30 Jan 2012.
- Sneddon, Joey-Elijah (5 February 2014). "Some of Linux’s Most Popular Games Will Run Natively On Mir". Retrieved 19 March 2014.
- "Middleware: SDL Group Description". MobyGames. 2013-09-27. Retrieved 2012-05-18. "Games that use the very portable Simple DirectMedia Layer."
- "Games". libsdl.org. 2012-05-18. Retrieved 2012-05-18.
- "SDL Testimonials". Galaxygameworks.com. Archived from the original on 2011-07-16. Retrieved 2012-02-01.
- "Development". OpenTTD. Retrieved 2010-03-19.
- "CompilingWesnoth". Wesnoth. 2010-02-27. Retrieved 2010-03-19.
- "SDLClient - Freeciv.org". Freeciv.wikia.com. Retrieved 2010-03-19.
- may88 (2011-06-23). "Game of the Week #3 – Homeworld SDL". pandorapress.net. Retrieved 2012-05-08. "[...] released port of HomeworldSDL. Forum member Edglex enables your Pandora to experience the excellent work done by the guys at HomeworldSDL."
- JA2 Stracciatella Feedback » Jagged Alliance 2 Android Stracciatella Port RC2 Release - please test on the Bear's Pit Forum, 3 October 2011