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73 | ><H1 |
74 | CLASS="SECT1" |
75 | ><A |
76 | NAME="GUIDEBASICSINIT" |
77 | ></A |
78 | >Initializing SDL</H1 |
79 | ><P |
80 | >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 |
81 | HREF="sdlinit.html" |
82 | ><TT |
83 | CLASS="FUNCTION" |
84 | >SDL_Init</TT |
85 | ></A |
86 | > (or <A |
87 | HREF="sdlinitsubsystem.html" |
88 | ><TT |
89 | CLASS="FUNCTION" |
90 | >SDL_InitSubSystem</TT |
91 | ></A |
92 | >). <TT |
93 | CLASS="FUNCTION" |
94 | >SDL_Init</TT |
95 | > 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: |
96 | <PRE |
97 | CLASS="PROGRAMLISTING" |
98 | > SDL_Init ( SDL_INIT_VIDEO );</PRE |
99 | > |
100 | To initialize the default subsystems, the Video subsystem and the Timers subsystem you would call: |
101 | <PRE |
102 | CLASS="PROGRAMLISTING" |
103 | > SDL_Init ( SDL_INIT_VIDEO | SDL_INIT_TIMER );</PRE |
104 | ></P |
105 | ><P |
106 | ><TT |
107 | CLASS="FUNCTION" |
108 | >SDL_Init</TT |
109 | > is complemented by <A |
110 | HREF="sdlquit.html" |
111 | ><TT |
112 | CLASS="FUNCTION" |
113 | >SDL_Quit</TT |
114 | ></A |
115 | > (and <A |
116 | HREF="sdlquitsubsystem.html" |
117 | ><TT |
118 | CLASS="FUNCTION" |
119 | >SDL_QuitSubSystem</TT |
120 | ></A |
121 | >). <TT |
122 | CLASS="FUNCTION" |
123 | >SDL_Quit</TT |
124 | > shuts down all subsystems, including the default ones. It should always be called before a SDL application exits.</P |
125 | ><P |
126 | >With <TT |
127 | CLASS="FUNCTION" |
128 | >SDL_Init</TT |
129 | > and <TT |
130 | CLASS="FUNCTION" |
131 | >SDL_Quit</TT |
132 | > 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 |
133 | CLASS="FUNCTION" |
134 | >SDL_Init</TT |
135 | >, 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 |
136 | CLASS="FUNCTION" |
137 | >SDL_GetError</TT |
138 | >. Use this often, you can never know too much about an error.</P |
139 | ><DIV |
140 | CLASS="EXAMPLE" |
141 | ><A |
142 | NAME="AEN60" |
143 | ></A |
144 | ><P |
145 | ><B |
146 | >Example 1-1. Initializing SDL</B |
147 | ></P |
148 | ><PRE |
149 | CLASS="PROGRAMLISTING" |
150 | >#include "SDL.h" /* All SDL App's need this */ |
151 | #include <stdio.h> |
152 | |
153 | int main(int argc, char *argv[]) { |
154 | |
155 | printf("Initializing SDL.\n"); |
156 | |
157 | /* Initialize defaults, Video and Audio */ |
158 | if((SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO)==-1)) { |
159 | printf("Could not initialize SDL: %s.\n", SDL_GetError()); |
160 | exit(-1); |
161 | } |
162 | |
163 | printf("SDL initialized.\n"); |
164 | |
165 | printf("Quiting SDL.\n"); |
166 | |
167 | /* Shutdown all subsystems */ |
168 | SDL_Quit(); |
169 | |
170 | printf("Quiting....\n"); |
171 | |
172 | exit(0); |
173 | } </PRE |
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