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Fixed SDL 1.2 compatibility problem. The API specifies that SDL_OpenAudio() will fill out the 'desired' audio spec with the correct samples and size set by the driver. This value is important since it may be used by applications that size audio buffers, etc. However, we want to allow advanced applications to call SDL_OpenAudioDevice() which gets passed a const 'desired' parameter, and have the correct data filled into the 'obtained' parameter, possibly allowing or not allowing format changes. So... 'obtained' becomes the audio format the user callback is expected to use, and we add flags to allow the application to specify which format changes are allowed. Note: We really need to add a way to query the 'obtained' audio spec.
author Sam Lantinga <slouken@libsdl.org>
date Sat, 13 Dec 2008 06:36:47 +0000
parents 355632dca928
children
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<HTML
><HEAD
><TITLE
>Initializing SDL</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
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TITLE="The Basics"
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><TR
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>SDL Library Documentation</TH
></TR
><TR
><TD
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><A
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>Prev</A
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><TD
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>Chapter 1. The Basics</TD
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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="GUIDEBASICSINIT"
></A
>Initializing SDL</H1
><P
>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 <A
HREF="sdlinit.html"
><TT
CLASS="FUNCTION"
>SDL_Init</TT
></A
> (or <A
HREF="sdlinitsubsystem.html"
><TT
CLASS="FUNCTION"
>SDL_InitSubSystem</TT
></A
>). <TT
CLASS="FUNCTION"
>SDL_Init</TT
> 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:
<PRE
CLASS="PROGRAMLISTING"
>    SDL_Init ( SDL_INIT_VIDEO );</PRE
>
To initialize the default subsystems, the Video subsystem and the Timers subsystem you would call:
<PRE
CLASS="PROGRAMLISTING"
>    SDL_Init ( SDL_INIT_VIDEO | SDL_INIT_TIMER );</PRE
></P
><P
><TT
CLASS="FUNCTION"
>SDL_Init</TT
> is complemented by <A
HREF="sdlquit.html"
><TT
CLASS="FUNCTION"
>SDL_Quit</TT
></A
> (and <A
HREF="sdlquitsubsystem.html"
><TT
CLASS="FUNCTION"
>SDL_QuitSubSystem</TT
></A
>). <TT
CLASS="FUNCTION"
>SDL_Quit</TT
> shuts down all subsystems, including the default ones. It should always be called before a SDL application exits.</P
><P
>With <TT
CLASS="FUNCTION"
>SDL_Init</TT
> and <TT
CLASS="FUNCTION"
>SDL_Quit</TT
> 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, <TT
CLASS="FUNCTION"
>SDL_Init</TT
>, 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 <TT
CLASS="FUNCTION"
>SDL_GetError</TT
>. Use this often, you can never know too much about an error.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN60"
></A
><P
><B
>Example 1-1. Initializing SDL</B
></P
><PRE
CLASS="PROGRAMLISTING"
>#include "SDL.h"   /* All SDL App's need this */
#include &#60;stdio.h&#62;

int main(int argc, char *argv[]) {
    
    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());
        exit(-1);
    }

    printf("SDL initialized.\n");

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

    exit(0);
}&#13;</PRE
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>