Simple DirectMedia Layer

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Simple DirectMedia Layer
Logo
Developed by	Sam Lantinga
Latest release	1.2.13 / December 31, 2007
Written in	C
OS	Cross-platform
Genre	API
License	GNU Lesser General Public License
Website	http://www.libsdl.org/

Simple DirectMedia Layer (SDL) is a cross-platform, multimedia, free and open source software library written in C that creates an abstraction over various platforms' graphics, sound, and input APIs, allowing a developer to write a computer game or other multimedia application once and run it on many operating systems including Linux, Syllable, Windows, Mac OS X, AmigaOS and its clone MorphOS. It manages video, events, digital audio, CD-ROM, sound, threads, shared object loading, networking and timers^[1].

1 History
2 Architecture
3 Syntax and subsystems
4 Gallery
5 Extensions
6 See also
7 References
8 External links

[edit] History

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 appeared to work with SDL, such as SMPEG and OpenAL.

The SDL library has bindings with almost every programming language there is, from the popular (C++, Perl, Python (through pygame), Pascal etc.) to the less known (such as Euphoria or Pliant). This, and the fact that it is open-source and licensed under the LGPL, make SDL a common choice for many multimedia applications.

SDL itself is very simple; it merely 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 additional functionality. 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

[edit] Architecture

Abstraction layers of several SDL platforms.

SDL has the word "layer" in its title because it is actually a wrapper around operating-system-specific functionality. The chief purpose of SDL is to provide a common framework for accessing this functionality.

Because of the way SDL is designed, a lot of the source code is split into separate modules for each operating system, in order to make calls to the underlying system. When SDL is compiled, the correct modules are selected for the target system.

On Microsoft Windows, SDL actually wraps around DirectX, which in turn wraps around the video driver. 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[1].

On X11 platforms, including Linux, SDL uses Xlib to communicate with the X11 system for graphics and events.

On Mac OS X, SDL uses Quartz.

[edit] 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 functionality for video, multi-threading, and event handling.
The Audio subsystem - this provides audio functionality.
The Time subsystem
The Joystick subsystem
The CD-ROM subsystem