Everything about Simple Directmedia Layer totally explained
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,
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.
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's 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
Architecture
SDL has the word "layer" in its title because it's 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
(External Link
).
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.
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
Gallery
Image:OpenTTD-screenshot.png|OpenTTD
Image:Battle_for_Wesnoth_0.9.6_tutorial.png|The Battle for Wesnoth
Image:Strogg_harvester_patrol.jpg|Quake 4
Image:NWN showdown.jpg|Neverwinter Nights
Image:Freeciv-2.1.0-beta3-sdl slack11.0.png|Freeciv
Extensions
SMPEG - SDL MPEG Player Library
Guichan, ParaGUI and SdlWidgets
- Widget sets
GGI - a free cross-platform graphics interfaceFurther Information
Get more info on 'Simple Directmedia Layer'.
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