include/SDL_timer.h
author Sam Lantinga <slouken@libsdl.org>
Wed, 17 May 2006 08:18:28 +0000
branchSDL-1.3
changeset 1659 14717b52abc0
parent 1358 c71e05b4dc2e
child 1662 782fd950bd46
child 1895 c121d94672cb
child 4159 a1b03ba2fcd0
permissions -rw-r--r--
Merge trunk-1.3-3
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2006 Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Lesser General Public
     7     License as published by the Free Software Foundation; either
     8     version 2.1 of the License, or (at your option) any later version.
     9 
    10     This library is distributed in the hope that it will be useful,
    11     but WITHOUT ANY WARRANTY; without even the implied warranty of
    12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13     Lesser General Public License for more details.
    14 
    15     You should have received a copy of the GNU Lesser General Public
    16     License along with this library; if not, write to the Free Software
    17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
    18 
    19     Sam Lantinga
    20     slouken@libsdl.org
    21 */
    22 
    23 #ifndef _SDL_timer_h
    24 #define _SDL_timer_h
    25 
    26 /* Header for the SDL time management routines */
    27 
    28 #include "SDL_stdinc.h"
    29 #include "SDL_error.h"
    30 
    31 #include "begin_code.h"
    32 /* Set up for C function definitions, even when using C++ */
    33 #ifdef __cplusplus
    34 extern "C" {
    35 #endif
    36 
    37 /* This is the OS scheduler timeslice, in milliseconds */
    38 #define SDL_TIMESLICE		10
    39 
    40 /* This is the maximum resolution of the SDL timer on all platforms */
    41 #define TIMER_RESOLUTION	10	/* Experimentally determined */
    42 
    43 /* Get the number of milliseconds since the SDL library initialization.
    44  * Note that this value wraps if the program runs for more than ~49 days.
    45  */ 
    46 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
    47 
    48 /* Wait a specified number of milliseconds before returning */
    49 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
    50 
    51 /* Function prototype for the timer callback function */
    52 typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);
    53 
    54 /* Set a callback to run after the specified number of milliseconds has
    55  * elapsed. The callback function is passed the current timer interval
    56  * and returns the next timer interval.  If the returned value is the 
    57  * same as the one passed in, the periodic alarm continues, otherwise a
    58  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
    59  * is cancelled.
    60  *
    61  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
    62  *
    63  * The timer callback function may run in a different thread than your
    64  * main code, and so shouldn't call any functions from within itself.
    65  *
    66  * The maximum resolution of this timer is 10 ms, which means that if
    67  * you request a 16 ms timer, your callback will run approximately 20 ms
    68  * later on an unloaded system.  If you wanted to set a flag signaling
    69  * a frame update at 30 frames per second (every 33 ms), you might set a 
    70  * timer for 30 ms:
    71  *   SDL_SetTimer((33/10)*10, flag_update);
    72  *
    73  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
    74  *
    75  * Under UNIX, you should not use raise or use SIGALRM and this function
    76  * in the same program, as it is implemented using setitimer().  You also
    77  * should not use this function in multi-threaded applications as signals
    78  * to multi-threaded apps have undefined behavior in some implementations.
    79  *
    80  * This function returns 0 if successful, or -1 if there was an error.
    81  */
    82 extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);
    83 
    84 /* New timer API, supports multiple timers
    85  * Written by Stephane Peter <megastep@lokigames.com>
    86  */
    87 
    88 /* Function prototype for the new timer callback function.
    89  * The callback function is passed the current timer interval and returns
    90  * the next timer interval.  If the returned value is the same as the one
    91  * passed in, the periodic alarm continues, otherwise a new alarm is
    92  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
    93  */
    94 typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);
    95 
    96 /* Definition of the timer ID type */
    97 typedef struct _SDL_TimerID *SDL_TimerID;
    98 
    99 /* Add a new timer to the pool of timers already running.
   100    Returns a timer ID, or NULL when an error occurs.
   101  */
   102 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);
   103 
   104 /* Remove one of the multiple timers knowing its ID.
   105  * Returns a boolean value indicating success.
   106  */
   107 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
   108 
   109 /* Ends C function definitions when using C++ */
   110 #ifdef __cplusplus
   111 }
   112 #endif
   113 #include "close_code.h"
   114 
   115 #endif /* _SDL_timer_h */