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70 | WIDTH="100%"></DIV |
71 | ><H1 |
72 | ><A |
73 | NAME="SDLADDTIMER" |
74 | ></A |
75 | >SDL_AddTimer</H1 |
76 | ><DIV |
77 | CLASS="REFNAMEDIV" |
78 | ><A |
79 | NAME="AEN8482" |
80 | ></A |
81 | ><H2 |
82 | >Name</H2 |
83 | >SDL_AddTimer -- Add a timer which will call a callback after the specified number of milliseconds has |
84 | elapsed.</DIV |
85 | ><DIV |
86 | CLASS="REFSYNOPSISDIV" |
87 | ><A |
88 | NAME="AEN8485" |
89 | ></A |
90 | ><H2 |
91 | >Synopsis</H2 |
92 | ><DIV |
93 | CLASS="FUNCSYNOPSIS" |
94 | ><A |
95 | NAME="AEN8486" |
96 | ></A |
97 | ><P |
98 | ></P |
99 | ><PRE |
100 | CLASS="FUNCSYNOPSISINFO" |
101 | >#include "SDL.h"</PRE |
102 | ><P |
103 | ><CODE |
104 | ><CODE |
105 | CLASS="FUNCDEF" |
106 | >SDL_TimerID <B |
107 | CLASS="FSFUNC" |
108 | >SDL_AddTimer</B |
109 | ></CODE |
110 | >(Uint32 interval, SDL_NewTimerCallback callback, void *param);</CODE |
111 | ></P |
112 | ><P |
113 | ></P |
114 | ></DIV |
115 | ></DIV |
116 | ><DIV |
117 | CLASS="REFSECT1" |
118 | ><A |
119 | NAME="SDLNEWTIMERCALLBACK" |
120 | ></A |
121 | ><H2 |
122 | >Callback</H2 |
123 | ><PRE |
124 | CLASS="PROGRAMLISTING" |
125 | >/* type definition for the "new" timer callback function */ |
126 | typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);</PRE |
127 | ></DIV |
128 | ><DIV |
129 | CLASS="REFSECT1" |
130 | ><A |
131 | NAME="AEN8495" |
132 | ></A |
133 | ><H2 |
134 | >Description</H2 |
135 | ><P |
136 | >Adds a callback function to be run after the specified number of |
137 | milliseconds has elapsed. The callback function is passed the current |
138 | timer interval and the user supplied parameter from the |
139 | <TT |
140 | CLASS="FUNCTION" |
141 | >SDL_AddTimer</TT |
142 | > call and returns the next timer |
143 | interval. If the returned value from the callback is the same as the one |
144 | passed in, the periodic alarm continues, otherwise a new alarm is |
145 | scheduled.</P |
146 | ><P |
147 | >To cancel a currently running timer call |
148 | <A |
149 | HREF="sdlremovetimer.html" |
150 | >SDL_RemoveTimer</A |
151 | > with the |
152 | timer ID returned from |
153 | <TT |
154 | CLASS="FUNCTION" |
155 | >SDL_AddTimer</TT |
156 | >.</P |
157 | ><P |
158 | >The timer callback function may run in a different thread than your |
159 | main program, and so shouldn't call any functions from within itself. |
160 | You may always call <A |
161 | HREF="sdlpushevent.html" |
162 | >SDL_PushEvent</A |
163 | >, however.</P |
164 | ><P |
165 | >The granularity of the timer is platform-dependent, but you should count |
166 | on it being at least 10 ms as this is the most common number. |
167 | This means that if |
168 | you request a 16 ms timer, your callback will run approximately 20 ms |
169 | later on an unloaded system. If you wanted to set a flag signaling |
170 | a frame update at 30 frames per second (every 33 ms), you might set a |
171 | timer for 30 ms (see example below). |
172 | |
173 | If you use this function, you need to pass <TT |
174 | CLASS="LITERAL" |
175 | >SDL_INIT_TIMER</TT |
176 | > |
177 | to <A |
178 | HREF="sdlinit.html" |
179 | >SDL_Init</A |
180 | >.</P |
181 | ></DIV |
182 | ><DIV |
183 | CLASS="REFSECT1" |
184 | ><A |
185 | NAME="AEN8507" |
186 | ></A |
187 | ><H2 |
188 | >Return Value</H2 |
189 | ><P |
190 | >Returns an ID value for the added timer or |
191 | <SPAN |
192 | CLASS="RETURNVALUE" |
193 | >NULL</SPAN |
194 | > if there was an error.</P |
195 | ></DIV |
196 | ><DIV |
197 | CLASS="REFSECT1" |
198 | ><A |
199 | NAME="AEN8511" |
200 | ></A |
201 | ><H2 |
202 | >Examples</H2 |
203 | ><P |
204 | ><PRE |
205 | CLASS="PROGRAMLISTING" |
206 | >my_timer_id = SDL_AddTimer((33/10)*10, my_callbackfunc, my_callback_param);</PRE |
207 | ></P |
208 | ></DIV |
209 | ><DIV |
210 | CLASS="REFSECT1" |
211 | ><A |
212 | NAME="AEN8515" |
213 | ></A |
214 | ><H2 |
215 | >See Also</H2 |
216 | ><P |
217 | ><A |
218 | HREF="sdlremovetimer.html" |
219 | ><TT |
220 | CLASS="FUNCTION" |
221 | >SDL_RemoveTimer</TT |
222 | ></A |
223 | >, |
224 | <A |
225 | HREF="sdlpushevent.html" |
226 | ><TT |
227 | CLASS="FUNCTION" |
228 | >SDL_PushEvent</TT |
229 | ></A |
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