include/SDL_timer.h
author Sam Lantinga <slouken@libsdl.org>
Sun, 06 Oct 2002 20:31:34 +0000
changeset 515 230b156829ed
parent 337 9154ec9ca3d2
child 769 b8d311d90021
permissions -rw-r--r--
*** empty log message ***
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Library General Public
     7     License as published by the Free Software Foundation; either
     8     version 2 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     Library General Public License for more details.
    14 
    15     You should have received a copy of the GNU Library General Public
    16     License along with this library; if not, write to the Free
    17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    18 
    19     Sam Lantinga
    20     slouken@libsdl.org
    21 */
    22 
    23 #ifdef SAVE_RCSID
    24 static char rcsid =
    25  "@(#) $Id$";
    26 #endif
    27 
    28 #ifndef _SDL_timer_h
    29 #define _SDL_timer_h
    30 
    31 /* Header for the SDL time management routines */
    32 
    33 #include "SDL_main.h"
    34 #include "SDL_types.h"
    35 
    36 #include "begin_code.h"
    37 /* Set up for C function definitions, even when using C++ */
    38 #ifdef __cplusplus
    39 extern "C" {
    40 #endif
    41 
    42 /* This is the OS scheduler timeslice, in milliseconds */
    43 #define SDL_TIMESLICE		10
    44 
    45 /* This is the maximum resolution of the SDL timer on all platforms */
    46 #define TIMER_RESOLUTION	10	/* Experimentally determined */
    47 
    48 /* Get the number of milliseconds since the SDL library initialization.
    49  * Note that this value wraps if the program runs for more than ~49 days.
    50  */ 
    51 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
    52 
    53 /* Wait a specified number of milliseconds before returning */
    54 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
    55 
    56 /* Function prototype for the timer callback function */
    57 typedef Uint32 (SDLCALL *SDL_TimerCallback)(Uint32 interval);
    58 
    59 /* Set a callback to run after the specified number of milliseconds has
    60  * elapsed. The callback function is passed the current timer interval
    61  * and returns the next timer interval.  If the returned value is the 
    62  * same as the one passed in, the periodic alarm continues, otherwise a
    63  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
    64  * is cancelled.
    65  *
    66  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
    67  *
    68  * The timer callback function may run in a different thread than your
    69  * main code, and so shouldn't call any functions from within itself.
    70  *
    71  * The maximum resolution of this timer is 10 ms, which means that if
    72  * you request a 16 ms timer, your callback will run approximately 20 ms
    73  * later on an unloaded system.  If you wanted to set a flag signaling
    74  * a frame update at 30 frames per second (every 33 ms), you might set a 
    75  * timer for 30 ms:
    76  *   SDL_SetTimer((33/10)*10, flag_update);
    77  *
    78  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
    79  *
    80  * Under UNIX, you should not use raise or use SIGALRM and this function
    81  * in the same program, as it is implemented using setitimer().  You also
    82  * should not use this function in multi-threaded applications as signals
    83  * to multi-threaded apps have undefined behavior in some implementations.
    84  */
    85 extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval, SDL_TimerCallback callback);
    86 
    87 /* New timer API, supports multiple timers
    88  * Written by Stephane Peter <megastep@lokigames.com>
    89  */
    90 
    91 /* Function prototype for the new timer callback function.
    92  * The callback function is passed the current timer interval and returns
    93  * the next timer interval.  If the returned value is the same as the one
    94  * passed in, the periodic alarm continues, otherwise a new alarm is
    95  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
    96  */
    97 typedef Uint32 (SDLCALL *SDL_NewTimerCallback)(Uint32 interval, void *param);
    98 
    99 /* Definition of the timer ID type */
   100 typedef struct _SDL_TimerID *SDL_TimerID;
   101 
   102 /* Add a new timer to the pool of timers already running.
   103    Returns a timer ID, or NULL when an error occurs.
   104  */
   105 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval, SDL_NewTimerCallback callback, void *param);
   106 
   107 /* Remove one of the multiple timers knowing its ID.
   108  * Returns a boolean value indicating success.
   109  */
   110 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
   111 
   112 /* Ends C function definitions when using C++ */
   113 #ifdef __cplusplus
   114 }
   115 #endif
   116 #include "close_code.h"
   117 
   118 #endif /* _SDL_timer_h */