include/SDL_timer.h
author Sam Lantinga <slouken@libsdl.org>
Fri, 10 Feb 2006 03:19:02 +0000
changeset 1356 67114343400d
parent 1312 c9b51268668f
child 1358 c71e05b4dc2e
permissions -rw-r--r--
*** empty log message ***
     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 
    30 #include "begin_code.h"
    31 /* Set up for C function definitions, even when using C++ */
    32 #ifdef __cplusplus
    33 extern "C" {
    34 #endif
    35 
    36 /* This is the OS scheduler timeslice, in milliseconds */
    37 #define SDL_TIMESLICE		10
    38 
    39 /* This is the maximum resolution of the SDL timer on all platforms */
    40 #define TIMER_RESOLUTION	10	/* Experimentally determined */
    41 
    42 /* Get the number of milliseconds since the SDL library initialization.
    43  * Note that this value wraps if the program runs for more than ~49 days.
    44  */ 
    45 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
    46 
    47 /* Wait a specified number of milliseconds before returning */
    48 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
    49 
    50 /* Function prototype for the timer callback function */
    51 typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);
    52 
    53 /* Set a callback to run after the specified number of milliseconds has
    54  * elapsed. The callback function is passed the current timer interval
    55  * and returns the next timer interval.  If the returned value is the 
    56  * same as the one passed in, the periodic alarm continues, otherwise a
    57  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
    58  * is cancelled.
    59  *
    60  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
    61  *
    62  * The timer callback function may run in a different thread than your
    63  * main code, and so shouldn't call any functions from within itself.
    64  *
    65  * The maximum resolution of this timer is 10 ms, which means that if
    66  * you request a 16 ms timer, your callback will run approximately 20 ms
    67  * later on an unloaded system.  If you wanted to set a flag signaling
    68  * a frame update at 30 frames per second (every 33 ms), you might set a 
    69  * timer for 30 ms:
    70  *   SDL_SetTimer((33/10)*10, flag_update);
    71  *
    72  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
    73  *
    74  * Under UNIX, you should not use raise or use SIGALRM and this function
    75  * in the same program, as it is implemented using setitimer().  You also
    76  * should not use this function in multi-threaded applications as signals
    77  * to multi-threaded apps have undefined behavior in some implementations.
    78  *
    79  * This function returns 0 if successful, or -1 if there was an error.
    80  */
    81 extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);
    82 
    83 /* New timer API, supports multiple timers
    84  * Written by Stephane Peter <megastep@lokigames.com>
    85  */
    86 
    87 /* Function prototype for the new timer callback function.
    88  * The callback function is passed the current timer interval and returns
    89  * the next timer interval.  If the returned value is the same as the one
    90  * passed in, the periodic alarm continues, otherwise a new alarm is
    91  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
    92  */
    93 typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);
    94 
    95 /* Definition of the timer ID type */
    96 typedef struct _SDL_TimerID *SDL_TimerID;
    97 
    98 /* Add a new timer to the pool of timers already running.
    99    Returns a timer ID, or NULL when an error occurs.
   100  */
   101 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);
   102 
   103 /* Remove one of the multiple timers knowing its ID.
   104  * Returns a boolean value indicating success.
   105  */
   106 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
   107 
   108 /* Ends C function definitions when using C++ */
   109 #ifdef __cplusplus
   110 }
   111 #endif
   112 #include "close_code.h"
   113 
   114 #endif /* _SDL_timer_h */