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| >Chapter 1. The Basics</TD |
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| >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 <stdio.h> |
| |
| 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); |
| } </PRE |
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