src/timer/dummy/SDL_systimer.c
author Sam Lantinga
Sat, 01 Mar 2014 09:50:52 -0800
changeset 8268 3f8410f20405
parent 8149 681eb46b8ac4
child 9619 b94b6d0bff0f
permissions -rw-r--r--
Fixed bug 2423 - timeBeginPeriod & timeEndPeriod mismatch

Coriiander

In src\timer\windows\SDL_systimer.c there is an error with regards to timeBeginPeriod and timeEndPeriod. These functions typically get called when no high resolution timer is available, and GetTickCount is not used.

According to MSDN (link: http://msdn.microsoft.com/en-us/library/windows/desktop/dd757624(v=vs.85).aspx), for every call to timeBeginPeriod a subsequent call to timeEndPeriod is required. While SDL is currently doing this, it fails to call timeEndPeriod when cleaning up/shutting down SDL. Please note that these functions affect things on a system level. Failing to call timeEndPeriod, disables applications for using WINMM-timers after usage&shutdown of SDL, as effectively they the mechanism is now broken.

Solution:
Ensure this code gets called when shutting down the timer subsystem:

#ifndef USE_GETTICKCOUNT
if (!hires_timer_available)
{
timeSetPeriod(0);
}
#endif
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/*
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  Simple DirectMedia Layer
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  Copyright (C) 1997-2014 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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#include "../../SDL_internal.h"
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#if defined(SDL_TIMER_DUMMY) || defined(SDL_TIMERS_DISABLED)
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#include "SDL_timer.h"
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static SDL_bool ticks_started = SDL_FALSE;
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void
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SDL_TicksInit(void)
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{
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    if (ticks_started) {
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        return;
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    }
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    ticks_started = SDL_TRUE;
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}
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void
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SDL_TicksQuit(void)
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{
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    ticks_started = SDL_FALSE;
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}
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Uint32
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SDL_GetTicks(void)
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{
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    if (!ticks_started) {
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        SDL_TicksInit();
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    }
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    SDL_Unsupported();
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    return 0;
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}
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Uint64
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SDL_GetPerformanceCounter(void)
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{
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    return SDL_GetTicks();
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}
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Uint64
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SDL_GetPerformanceFrequency(void)
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{
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    return 1000;
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}
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void
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SDL_Delay(Uint32 ms)
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{
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    SDL_Unsupported();
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}
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#endif /* SDL_TIMER_DUMMY || SDL_TIMERS_DISABLED */
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/* vi: set ts=4 sw=4 expandtab: */