Simple DirectMedia Layer

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Simple DirectMedia Layer
Sdl-logo.png
SDL logo
Original author(s) Sam Lantinga
Developer(s) SDL Community
Stable release 2.0.3[1] / 16 March 2014; 33 days ago (2014-03-16)[2]
Previous v1.2.15: 20 January 2012; 2 years ago (2012-01-20)
Written in C
Operating system Cross-platform
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+
Type API
License zlib License
Before 2.0.0:
GNU LGPL[3]
Website www.libsdl.org
Rendering calculations are outsourced over OpenGL to the GPU to be done in real-time. DRI-components like GEM/TTM regulate access and do book-keeping. It all seems superfluous when only a full-screen 3D game is running, but hardware access is a fundamental kernel task. The Simple DirectMedia Layer provides APIs for sound and input.

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 to the requirements of the zlib License since version 2.0 and GNU Lesser General Public License prior versions.[3]

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.[4] It manages video, events, digital audio, CD-ROM, threads, shared object loading, networking and timers.[5]

Software architecture[edit]

SDL has the word "layer" in its title because it is actually a wrapper around operating-system-specific functions.[6] 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.[7]

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_ttfTrueType font rendering support
  • SDL_rtf — simple Rich Text Format rendering

Other, non-standard libraries also exist. For example: SDL_Collide on Sourceforge created by Amir Taaki.

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[edit]

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

Supported back-ends[edit]

Abstraction layers of several SDL platforms

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:[8]

SDL 1.2 has support for RISC OS (dropped in 2.0).

History[edit]

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.[13] 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.[14] 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.[15] Lantinga announced the stable release of SDL 2.0.0 on 13 August 2013.[16]

SDL 2.0 is a major update to the SDL 1.2 codebase with a different, not backwards-compatible[17] API. It replaces several parts of the 1.2 API with more general support for multiple input and output options.

Some feature additions include multiple window support, hardware-accelerated 2D graphics, and better Unicode support.[18]

SDL 2.0 is zlib-licensed, and therefore freely available for static linking in commercial closed-source projects, unlike SDL 1.2.[19]

Support for Mir and Wayland will be available from SDL 2.0.2 (disabled by default).[20]

Reception and adoption[edit]

Workshop on SDL, University of Cádiz

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[21] and the SDL website itself listed around 700 games in 2012.[22] Important commercial examples are Angry Birds[23] or Unreal Tournament, from the open source domain OpenTTD,[24] The Battle for Wesnoth[25] or Freeciv.[26]

The cross-platform game releases of the popular Humble Indie Bundles for Linux, Mac and Android are often SDL based.

SDL is also often used for later ports on new platforms with existing legacy code, for instance the PC game Homeworld was ported to the Pandora handheld[27] and Jagged Alliance 2 for Android[28] via SDL.

Also, several non video game software uses SDL, examples are the emulators DOSBox and VisualBoyAdvance.

There were several books written for the development with SDL (see further readings).

SDL is used in university courses teaching multimedia and computer science, for instance, in a workshop about game programming using libSDL at the University of Cadiz in 2010.

Video game examples using SDL[edit]

Video games adopting Simple DirectMedia Layer
Oolite, a 3D space game 
Screenshots

See also[edit]

Further reading[edit]

References[edit]

  1. ^ Simple DirectMedia Layer - SDL version 2.0.3 (stable). Libsdl.org (2001-01-05). Retrieved on 2014-03-28.
  2. ^ Index of /release. Libsdl.org (2013-08-17). Retrieved on 2014-03-28.
  3. ^ a b "SDL license". Retrieved 2014-03-03. 
  4. ^ "a list of the platforms SDL supports". Libsdl.org. Retrieved 15 Jul 2013. 
  5. ^ "SDL official website". Libsdl.org. Retrieved 19 March 2010. 
  6. ^ "Introduction to SDL". Retrieved 2014-03-03. 
  7. ^ "SDL libraries". Libsdl.org. Retrieved 2012-01-15. 
  8. ^ "SDL officially and unofficially supported platforms". 
  9. ^ "SDL mailing list". Libsdl.org. Retrieved 23 March 2010. 
  10. ^ SDL: README-platforms.txt@3e2f230a6d62. Hg.libsdl.org. Retrieved on 2013-12-08.
  11. ^ "SDL and Wayland". 
  12. ^ Larabel, Michael (September 30, 2013). "Raspberry Pi Support Added To SDL2 Library". 
  13. ^ "Exploring the Galaxy". 6 April 2011. Retrieved 30 Jan 2012. 
  14. ^ SDL 1.3 to be zLib Licensed, SDL Mailing List, 2011-04-07
  15. ^ "SDL 2.0 Is Coming Very Soon With New Features". Retrieved 17 Aug 2012. 
  16. ^ Announcing SDL 2.0.0, SDL Mailing List, 2013-08-13
  17. ^ MigrationGuide - SDL Wiki'. Wiki.libsdl.org (2013-11-21). Retrieved on 2013-12-08.
  18. ^ "SDL 1.3 Roadmap". 14 June 2011. Retrieved 25 July 2011. 
  19. ^ "Licensing the Simple DirectMedia Layer library". Retrieved 30 Jan 2012. 
  20. ^ Sneddon, Joey-Elijah (5 February 2014). "Some of Linux’s Most Popular Games Will Run Natively On Mir". Retrieved 19 March 2014. 
  21. ^ "Middleware: SDL Group Description". MobyGames. 2013-09-27. Retrieved 2012-05-18. "Games that use the very portable Simple DirectMedia Layer." 
  22. ^ "Games". libsdl.org. 2012-05-18. Retrieved 2012-05-18. 
  23. ^ "SDL Testimonials". Galaxygameworks.com. Archived from the original on 2011-07-16. Retrieved 2012-02-01. 
  24. ^ "Development". OpenTTD. Retrieved 2010-03-19. 
  25. ^ "CompilingWesnoth". Wesnoth. 2010-02-27. Retrieved 2010-03-19. 
  26. ^ "SDLClient - Freeciv.org". Freeciv.wikia.com. Retrieved 2010-03-19. 
  27. ^ 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." 
  28. ^ JA2 Stracciatella Feedback » Jagged Alliance 2 Android Stracciatella Port RC2 Release - please test on the Bear's Pit Forum, 3 October 2011

External links[edit]