Initializing SDL

SDL is composed of eight subsystems - Audio, CDROM, Event Handling, File I/O, Joystick Handling, Threading, Timers and Video. Before you can use any of these subsystems they must be initialized by calling SDL_Init (or SDL_InitSubSystem. SDL_Init must be called before any other SDL function. It automatically initializes the Event Handling, File I/O and Threading subsystems and it takes a parameter specifying which other subsystems to initialize. So, to initialize the default subsystems and the Video subsystems you would call:

    SDL_Init ( SDL_INIT_VIDEO );
To initialize the default subsystems, the Video subsystem and the Timers subsystem you would call:

SDL_Init is complemented by SDL_Quit (and SDL_QuitSubSystem). SDL_Quit shuts down all subsystems, including the default ones. It should always be called before a SDL application exits.

With SDL_Init and SDL_Quit firmly embedded in your programmers toolkit you can write your first and most basic SDL application. However, we must be prepare to handle errors. Many SDL functions return a value and indicates whether the function has succeeded or failed, SDL_Init, for instance, returns -1 if it could not initialize a subsystem. SDL provides a useful facility that allows you to determine exactly what the problem was, every time an error occurs within SDL an error message is stored which can be retrieved using SDL_GetError. Use this often, you can never know too much about an error.

Example 1-1. Initializing SDL

#include "SDL.h"   /* All SDL App's need this */
#include <stdio.h>

int main() {
    printf("Initializing SDL.\n");
    /* Initialize defaults, Video and Audio */
    if((SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO)==-1)) { 
        printf("Could not initialize SDL: %s.\n", SDL_GetError());

    printf("SDL initialized.\n");

    printf("Quiting SDL.\n");
    /* Shutdown all subsystems */