SDL : Introduction

SDL = Simple DirectMedia Layer is a free cross-platform multi-media development API. Its used for

• games
• game SDKs
• emulators
• demos
• multimedia applications

What can it do?

Video

• Set a video mode at any depth (8-bpp or greater) with optional conversion, if the video mode is not supported by the hardware.
• Write directly to a linear graphics framebuffer.
• Create surfaces with colorkey or alpha blending attributes.
• Surface blits are automatically converted to the target format using optimized blitters and are hardware accelerated, when possible. MMX optimized blits are available for the x86.
• Hardware accelerated blit and fill operations are used if supported by the hardware.

Events

• Events provided for:
  • Application visibility changes
  • Keyboard input
  • Mouse input
  • User-requested quit
• Each event can be enabled or disabled with SDL_EventState().
• Events are passed through a user-specified filter function before being posted to the internal event queue.
• Thread-safe event queue.

Audio

• Set audio playback of 8-bit and 16-bit audio, mono or stereo, with optional conversion if the format is not supported by the hardware.
• Audio runs independently in a separate thread, filled via a user callback mechanism.
• Designed for custom software audio mixers, but the example archive contains a complete audio/music output library.

CD-ROM audio

• Complete CD audio control API

Threads

• Simple thread creation API
• Simple binary semaphores for synchronization

Timers

• Get the number of milliseconds elapsed
• Wait a specified number of milliseconds
• Set a single periodic timer with 10ms resolution

Endian independence

• Detect the endianness of the current system
• Routines for fast swapping of data values
• Read and write data of a specified endianness

What platforms does it run on?

Linux

• Uses X11 for video display, taking advantage of XFree86 DGA extensions and new MTRR acceleration for fullscreen display.
• Uses the OSS API for sound.
• Threads are implemented using either the clone() system call and SysV IPC, or glibc-2.1 pthreads.

Win32

• Two versions, one safe for all systems based on Win32 APIs, and one with higher performance, based on DirectX APIs.
• Safe version uses GDI for video display. High performance version uses DirectDraw for video display, taking advantage of hardware acceleration if available.
• Safe version uses waveOut APIs for sound. High performace version uses DirectSound for audio playback.

BeOS

• BWindow is used for video display.
• BSoundPlayer API is used for sound.

Unofficial ports, ports in progress

• Solaris, IRIX, FreeBSD
• MacOS

Using the Simple DirectMedia Layer API

Initializing the library

SDL is composed of eight subsystems – Audio, CDROM, Event Handling, File I/O, Joystick Handling, Threading, Timers and Video. Use SDL_Init() to dynamically load and initialize the library. This function takes a set of flags corresponding to the portions you want to activate:

SDL_INIT_AUDIO

SDL_INIT_VIDEO

SDL_INIT_CDROM

SDL_INIT_TIMER

Use SDL_Quit() to clean up the library when you are done with it.

Example:-

#include “SDL/SDL.h”  //Include SDL functions and datatypes

int main( int argc, char* args[] ) {

SDL_Init( SDL_INIT_EVERYTHING );  //Start SDL

SDL_Quit(); //Quit SDL

return 0;

}