SDL_gfx: I:/Sources/sdlgfx/SDL_framerate.c Source File

SDL_gfx 2.0.25

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I:/Sources/sdlgfx/SDL_framerate.c
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    00001 /*
    00002
    00003 SDL_framerate.c: framerate manager
    00004
    00005 Copyright (C) 2001-2012  Andreas Schiffler
    00006
    00007 This software is provided 'as-is', without any express or implied
    00008 warranty. In no event will the authors be held liable for any damages
    00009 arising from the use of this software.
    00010
    00011 Permission is granted to anyone to use this software for any purpose,
    00012 including commercial applications, and to alter it and redistribute it
    00013 freely, subject to the following restrictions:
    00014
    00015 1. The origin of this software must not be misrepresented; you must not
    00016 claim that you wrote the original software. If you use this software
    00017 in a product, an acknowledgment in the product documentation would be
    00018 appreciated but is not required.
    00019
    00020 2. Altered source versions must be plainly marked as such, and must not be
    00021 misrepresented as being the original software.
    00022
    00023 3. This notice may not be removed or altered from any source
    00024 distribution.
    00025
    00026 Andreas Schiffler -- aschiffler at ferzkopp dot net
    00027
    00028 */
    00029
    00030 #include "SDL_framerate.h"
    00031
    00037 Uint32 _getTicks()
    00038 {
    00039         Uint32 ticks = SDL_GetTicks();
    00040
    00041         /*
    00042         * Since baseticks!=0 is used to track initialization
    00043         * we need to ensure that the tick count is always >0
    00044         * since SDL_GetTicks may not have incremented yet and
    00045         * return 0 depending on the timing of the calls.
    00046         */
    00047         if (ticks == 0) {
    00048                 return 1;
    00049         } else {
    00050                 return ticks;
    00051         }
    00052 }
    00053
    00062 void SDL_initFramerate(FPSmanager * manager)
    00063 {
    00064         /*
    00065         * Store some sane values
    00066         */
    00067         manager->framecount = 0;
    00068         manager->rate = FPS_DEFAULT;
    00069         manager->rateticks = (1000.0f / (float) FPS_DEFAULT);
    00070         manager->baseticks = _getTicks();
    00071         manager->lastticks = manager->baseticks;
    00072
    00073 }
    00074
    00086 int SDL_setFramerate(FPSmanager * manager, Uint32 rate)
    00087 {
    00088         if ((rate >= FPS_LOWER_LIMIT) && (rate <= FPS_UPPER_LIMIT)) {
    00089                 manager->framecount = 0;
    00090                 manager->rate = rate;
    00091                 manager->rateticks = (1000.0f / (float) rate);
    00092                 return (0);
    00093         } else {
    00094                 return (-1);
    00095         }
    00096 }
    00097
    00107 int SDL_getFramerate(FPSmanager * manager)
    00108 {
    00109         if (manager == NULL) {
    00110                 return (-1);
    00111         } else {
    00112                 return ((int)manager->rate);
    00113         }
    00114 }
    00115
    00126 int SDL_getFramecount(FPSmanager * manager)
    00127 {
    00128         if (manager == NULL) {
    00129                 return (-1);
    00130         } else {
    00131                 return ((int)manager->framecount);
    00132         }
    00133 }
    00134
    00146 Uint32 SDL_framerateDelay(FPSmanager * manager)
    00147 {
    00148         Uint32 current_ticks;
    00149         Uint32 target_ticks;
    00150         Uint32 the_delay;
    00151         Uint32 time_passed = 0;
    00152
    00153         /*
    00154         * No manager, no delay
    00155         */
    00156         if (manager == NULL) {
    00157                 return 0;
    00158         }
    00159
    00160         /*
    00161         * Initialize uninitialized manager
    00162         */
    00163         if (manager->baseticks == 0) {
    00164                 SDL_initFramerate(manager);
    00165         }
    00166
    00167         /*
    00168         * Next frame
    00169         */
    00170         manager->framecount++;
    00171
    00172         /*
    00173         * Get/calc ticks
    00174         */
    00175         current_ticks = _getTicks();
    00176         time_passed = current_ticks - manager->lastticks;
    00177         manager->lastticks = current_ticks;
    00178         target_ticks = manager->baseticks + (Uint32) ((float) manager->framecount * manager->rateticks);
    00179
    00180         if (current_ticks <= target_ticks) {
    00181                 the_delay = target_ticks - current_ticks;
    00182                 SDL_Delay(the_delay);
    00183         } else {
    00184                 manager->framecount = 0;
    00185                 manager->baseticks = _getTicks();
    00186         }
    00187
    00188         return time_passed;
    00189 }