include/SDL_timer.h
author Sam Lantinga <slouken@libsdl.org>
Mon, 29 May 2006 04:04:35 +0000
branchSDL-1.3
changeset 1668 4da1ee79c9af
parent 1662 782fd950bd46
permissions -rw-r--r--
more tweaking indent options
     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 /**
    27  * \file SDL_timer.h
    28  *
    29  * Header for the SDL time management routines
    30  */
    31 
    32 #include "SDL_stdinc.h"
    33 #include "SDL_error.h"
    34 
    35 #include "begin_code.h"
    36 /* Set up for C function definitions, even when using C++ */
    37 #ifdef __cplusplus
    38 /* *INDENT-OFF* */
    39 extern "C" {
    40 /* *INDENT-ON* */
    41 #endif
    42 
    43 /* This is the OS scheduler timeslice, in milliseconds */
    44 #define SDL_TIMESLICE		10
    45 
    46 /* This is the maximum resolution of the SDL timer on all platforms */
    47 #define TIMER_RESOLUTION	10      /* Experimentally determined */
    48 
    49 /* Get the number of milliseconds since the SDL library initialization.
    50  * Note that this value wraps if the program runs for more than ~49 days.
    51  */
    52 extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
    53 
    54 /* Wait a specified number of milliseconds before returning */
    55 extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
    56 
    57 /* Function prototype for the timer callback function */
    58 typedef Uint32(SDLCALL * SDL_TimerCallback) (Uint32 interval);
    59 
    60 /* Set a callback to run after the specified number of milliseconds has
    61  * elapsed. The callback function is passed the current timer interval
    62  * and returns the next timer interval.  If the returned value is the 
    63  * same as the one passed in, the periodic alarm continues, otherwise a
    64  * new alarm is scheduled.  If the callback returns 0, the periodic alarm
    65  * is cancelled.
    66  *
    67  * To cancel a currently running timer, call SDL_SetTimer(0, NULL);
    68  *
    69  * The timer callback function may run in a different thread than your
    70  * main code, and so shouldn't call any functions from within itself.
    71  *
    72  * The maximum resolution of this timer is 10 ms, which means that if
    73  * you request a 16 ms timer, your callback will run approximately 20 ms
    74  * later on an unloaded system.  If you wanted to set a flag signaling
    75  * a frame update at 30 frames per second (every 33 ms), you might set a 
    76  * timer for 30 ms:
    77  *   SDL_SetTimer((33/10)*10, flag_update);
    78  *
    79  * If you use this function, you need to pass SDL_INIT_TIMER to SDL_Init().
    80  *
    81  * Under UNIX, you should not use raise or use SIGALRM and this function
    82  * in the same program, as it is implemented using setitimer().  You also
    83  * should not use this function in multi-threaded applications as signals
    84  * to multi-threaded apps have undefined behavior in some implementations.
    85  *
    86  * This function returns 0 if successful, or -1 if there was an error.
    87  */
    88 extern DECLSPEC int SDLCALL SDL_SetTimer(Uint32 interval,
    89                                          SDL_TimerCallback callback);
    90 
    91 /* New timer API, supports multiple timers
    92  * Written by Stephane Peter <megastep@lokigames.com>
    93  */
    94 
    95 /* Function prototype for the new timer callback function.
    96  * The callback function is passed the current timer interval and returns
    97  * the next timer interval.  If the returned value is the same as the one
    98  * passed in, the periodic alarm continues, otherwise a new alarm is
    99  * scheduled.  If the callback returns 0, the periodic alarm is cancelled.
   100  */
   101 typedef Uint32(SDLCALL * SDL_NewTimerCallback) (Uint32 interval, void *param);
   102 
   103 /* Definition of the timer ID type */
   104 typedef struct _SDL_TimerID *SDL_TimerID;
   105 
   106 /* Add a new timer to the pool of timers already running.
   107    Returns a timer ID, or NULL when an error occurs.
   108  */
   109 extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval,
   110                                                  SDL_NewTimerCallback
   111                                                  callback, void *param);
   112 
   113 /* Remove one of the multiple timers knowing its ID.
   114  * Returns a boolean value indicating success.
   115  */
   116 extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID t);
   117 
   118 /* Ends C function definitions when using C++ */
   119 #ifdef __cplusplus
   120 /* *INDENT-OFF* */
   121 }
   122 /* *INDENT-ON* */
   123 #endif
   124 #include "close_code.h"
   125 
   126 #endif /* _SDL_timer_h */
   127 
   128 /* vi: set ts=4 sw=4 expandtab: */