SDL logo |
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| Original author(s) | Sam Lantinga |
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| Developer(s) | Sam Lantinga |
| Stable release | 1.2.14 / October 19, 2009 |
| Preview release | 1.3 / Nightly |
| Written in | C |
| Operating system | Cross-platform |
| Type | API |
| License | zlib License |
| Website | www.libsdl.org |
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.
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.
Software developers use it to write computer games or other multimedia applications that can run on many operating systems including Android, AmigaOS, AmigaOS 4, FreeBSD, BeOS/Haiku, iOS, Linux, Mac OS 9, Mac OS X, MorphOS, OpenVMS, PlayStation Portable, Syllable, Symbian, webOS, and Windows. It manages video, events, digital audio, CD-ROM, sound, threads, shared object loading, networking and timers.[1]
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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 more functions. These comprise the "standard library", and are provided on the official website and included in the official documentation:
Other, non-standard libraries also exist. For example: SDL_Collide on Sourceforge created by Amir Taaki.
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 (such as Euphoria or Pliant). This, and it being open-source and licensed under the LGPL, makes SDL a common choice 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.
SDL 1.3 is a major update to the SDL 1.2 codebase. 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, multiple input device support (many mice, many keyboards, etc.), hardware-accelerated 2D graphics, and better Unicode support. You can look at the roadmap to get a sense of what needs to be done for the move to SDL 1.3/2.0.[2] SDL 1.3, when finished, will eventually become SDL 2.0.[3] SDL 1.3 also introduces a new licensing option, whereby one can obtain a commercial license to allow closed-source static linking.[4] This opens up possibilities for distribution on platforms that do not allow dynamic linking. .
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.[5]
On X Window System platforms, including Linux and OpenVMS, SDL uses Xlib to communicate with the X11 system for graphics and events.
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:
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