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223 lines
7.1 KiB
C
223 lines
7.1 KiB
C
/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef SDL_timer_h_
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#define SDL_timer_h_
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/**
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* \file SDL_timer.h
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*
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* Header for the SDL time management routines.
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*/
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#include "SDL_stdinc.h"
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#include "SDL_error.h"
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#include "begin_code.h"
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/* Set up for C function definitions, even when using C++ */
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* Get the number of milliseconds since SDL library initialization.
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*
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* This value wraps if the program runs for more than ~49 days.
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*
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* This function is not recommended as of SDL 2.0.18; use SDL_GetTicks64()
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* instead, where the value doesn't wrap every ~49 days. There are places in
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* SDL where we provide a 32-bit timestamp that can not change without
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* breaking binary compatibility, though, so this function isn't officially
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* deprecated.
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*
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* \returns an unsigned 32-bit value representing the number of milliseconds
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* since the SDL library initialized.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_TICKS_PASSED
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*/
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extern DECLSPEC Uint32 SDLCALL SDL_GetTicks(void);
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/**
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* Get the number of milliseconds since SDL library initialization.
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*
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* Note that you should not use the SDL_TICKS_PASSED macro with values
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* returned by this function, as that macro does clever math to compensate for
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* the 32-bit overflow every ~49 days that SDL_GetTicks() suffers from. 64-bit
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* values from this function can be safely compared directly.
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*
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* For example, if you want to wait 100 ms, you could do this:
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*
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* ```c
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* const Uint64 timeout = SDL_GetTicks64() + 100;
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* while (SDL_GetTicks64() < timeout) {
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* // ... do work until timeout has elapsed
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* }
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* ```
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*
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* \returns an unsigned 64-bit value representing the number of milliseconds
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* since the SDL library initialized.
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*
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* \since This function is available since SDL 2.0.18.
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*/
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extern DECLSPEC Uint64 SDLCALL SDL_GetTicks64(void);
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/**
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* Compare 32-bit SDL ticks values, and return true if `A` has passed `B`.
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*
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* This should be used with results from SDL_GetTicks(), as this macro
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* attempts to deal with the 32-bit counter wrapping back to zero every ~49
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* days, but should _not_ be used with SDL_GetTicks64(), which does not have
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* that problem.
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*
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* For example, with SDL_GetTicks(), if you want to wait 100 ms, you could
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* do this:
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*
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* ```c
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* const Uint32 timeout = SDL_GetTicks() + 100;
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* while (!SDL_TICKS_PASSED(SDL_GetTicks(), timeout)) {
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* // ... do work until timeout has elapsed
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* }
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* ```
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*
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* Note that this does not handle tick differences greater
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* than 2^31 so take care when using the above kind of code
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* with large timeout delays (tens of days).
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*/
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#define SDL_TICKS_PASSED(A, B) ((Sint32)((B) - (A)) <= 0)
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/**
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* Get the current value of the high resolution counter.
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*
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* This function is typically used for profiling.
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*
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* The counter values are only meaningful relative to each other. Differences
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* between values can be converted to times by using
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* SDL_GetPerformanceFrequency().
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*
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* \returns the current counter value.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_GetPerformanceFrequency
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*/
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extern DECLSPEC Uint64 SDLCALL SDL_GetPerformanceCounter(void);
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/**
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* Get the count per second of the high resolution counter.
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*
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* \returns a platform-specific count per second.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_GetPerformanceCounter
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*/
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extern DECLSPEC Uint64 SDLCALL SDL_GetPerformanceFrequency(void);
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/**
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* Wait a specified number of milliseconds before returning.
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*
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* This function waits a specified number of milliseconds before returning. It
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* waits at least the specified time, but possibly longer due to OS
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* scheduling.
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*
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* \param ms the number of milliseconds to delay
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*
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* \since This function is available since SDL 2.0.0.
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*/
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extern DECLSPEC void SDLCALL SDL_Delay(Uint32 ms);
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/**
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* Function prototype for the timer callback function.
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*
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* The callback function is passed the current timer interval and returns
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* the next timer interval. If the returned value is the same as the one
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* passed in, the periodic alarm continues, otherwise a new alarm is
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* scheduled. If the callback returns 0, the periodic alarm is cancelled.
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*/
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typedef Uint32 (SDLCALL * SDL_TimerCallback) (Uint32 interval, void *param);
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/**
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* Definition of the timer ID type.
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*/
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typedef int SDL_TimerID;
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/**
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* Call a callback function at a future time.
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*
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* If you use this function, you must pass `SDL_INIT_TIMER` to SDL_Init().
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*
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* The callback function is passed the current timer interval and the user
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* supplied parameter from the SDL_AddTimer() call and should return the next
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* timer interval. If the value returned from the callback is 0, the timer is
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* canceled.
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*
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* The callback is run on a separate thread.
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*
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* Timers take into account the amount of time it took to execute the
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* callback. For example, if the callback took 250 ms to execute and returned
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* 1000 (ms), the timer would only wait another 750 ms before its next
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* iteration.
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*
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* Timing may be inexact due to OS scheduling. Be sure to note the current
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* time with SDL_GetTicks() or SDL_GetPerformanceCounter() in case your
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* callback needs to adjust for variances.
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*
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* \param interval the timer delay, in milliseconds, passed to `callback`
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* \param callback the SDL_TimerCallback function to call when the specified
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* `interval` elapses
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* \param param a pointer that is passed to `callback`
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* \returns a timer ID or 0 if an error occurs; call SDL_GetError() for more
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* information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_RemoveTimer
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*/
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extern DECLSPEC SDL_TimerID SDLCALL SDL_AddTimer(Uint32 interval,
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SDL_TimerCallback callback,
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void *param);
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/**
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* Remove a timer created with SDL_AddTimer().
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*
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* \param id the ID of the timer to remove
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* \returns SDL_TRUE if the timer is removed or SDL_FALSE if the timer wasn't
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* found.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_AddTimer
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*/
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extern DECLSPEC SDL_bool SDLCALL SDL_RemoveTimer(SDL_TimerID id);
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/* Ends C function definitions when using C++ */
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#ifdef __cplusplus
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}
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#endif
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#include "close_code.h"
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#endif /* SDL_timer_h_ */
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/* vi: set ts=4 sw=4 expandtab: */
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