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Diffstat (limited to 'src/sdl2gfx/SDL_framerate.c')
| -rw-r--r-- | src/sdl2gfx/SDL_framerate.c | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/src/sdl2gfx/SDL_framerate.c b/src/sdl2gfx/SDL_framerate.c new file mode 100644 index 000000000..6735f6355 --- /dev/null +++ b/src/sdl2gfx/SDL_framerate.c @@ -0,0 +1,189 @@ +/* + +SDL_framerate.c: framerate manager + +Copyright (C) 2001-2012 Andreas Schiffler + +This software is provided 'as-is', without any express or implied +warranty. In no event will the authors be held liable for any damages +arising from the use of this software. + +Permission is granted to anyone to use this software for any purpose, +including commercial applications, and to alter it and redistribute it +freely, subject to the following restrictions: + +1. The origin of this software must not be misrepresented; you must not +claim that you wrote the original software. If you use this software +in a product, an acknowledgment in the product documentation would be +appreciated but is not required. + +2. Altered source versions must be plainly marked as such, and must not be +misrepresented as being the original software. + +3. This notice may not be removed or altered from any source +distribution. + +Andreas Schiffler -- aschiffler at ferzkopp dot net + +*/ + +#include "SDL_framerate.h" + +/*! +\brief Internal wrapper to SDL_GetTicks that ensures a non-zero return value. + +\return The tick count. +*/ +Uint32 _getTicks() +{ + Uint32 ticks = SDL_GetTicks(); + + /* + * Since baseticks!=0 is used to track initialization + * we need to ensure that the tick count is always >0 + * since SDL_GetTicks may not have incremented yet and + * return 0 depending on the timing of the calls. + */ + if (ticks == 0) { + return 1; + } else { + return ticks; + } +} + +/*! +\brief Initialize the framerate manager. + +Initialize the framerate manager, set default framerate of 30Hz and +reset delay interpolation. + +\param manager Pointer to the framerate manager. +*/ +void SDL_initFramerate(FPSmanager * manager) +{ + /* + * Store some sane values + */ + manager->framecount = 0; + manager->rate = FPS_DEFAULT; + manager->rateticks = (1000.0f / (float) FPS_DEFAULT); + manager->baseticks = _getTicks(); + manager->lastticks = manager->baseticks; + +} + +/*! +\brief Set the framerate in Hz + +Sets a new framerate for the manager and reset delay interpolation. +Rate values must be between FPS_LOWER_LIMIT and FPS_UPPER_LIMIT inclusive to be accepted. + +\param manager Pointer to the framerate manager. +\param rate The new framerate in Hz (frames per second). + +\return 0 for sucess and -1 for error. +*/ +int SDL_setFramerate(FPSmanager * manager, Uint32 rate) +{ + if ((rate >= FPS_LOWER_LIMIT) && (rate <= FPS_UPPER_LIMIT)) { + manager->framecount = 0; + manager->rate = rate; + manager->rateticks = (1000.0f / (float) rate); + return (0); + } else { + return (-1); + } +} + +/*! +\brief Return the current target framerate in Hz + +Get the currently set framerate of the manager. + +\param manager Pointer to the framerate manager. + +\return Current framerate in Hz or -1 for error. +*/ +int SDL_getFramerate(FPSmanager * manager) +{ + if (manager == NULL) { + return (-1); + } else { + return ((int)manager->rate); + } +} + +/*! +\brief Return the current framecount. + +Get the current framecount from the framerate manager. +A frame is counted each time SDL_framerateDelay is called. + +\param manager Pointer to the framerate manager. + +\return Current frame count or -1 for error. +*/ +int SDL_getFramecount(FPSmanager * manager) +{ + if (manager == NULL) { + return (-1); + } else { + return ((int)manager->framecount); + } +} + +/*! +\brief Delay execution to maintain a constant framerate and calculate fps. + +Generate a delay to accomodate currently set framerate. Call once in the +graphics/rendering loop. If the computer cannot keep up with the rate (i.e. +drawing too slow), the delay is zero and the delay interpolation is reset. + +\param manager Pointer to the framerate manager. + +\return The time that passed since the last call to the function in ms. May return 0. +*/ +Uint32 SDL_framerateDelay(FPSmanager * manager) +{ + Uint32 current_ticks; + Uint32 target_ticks; + Uint32 the_delay; + Uint32 time_passed = 0; + + /* + * No manager, no delay + */ + if (manager == NULL) { + return 0; + } + + /* + * Initialize uninitialized manager + */ + if (manager->baseticks == 0) { + SDL_initFramerate(manager); + } + + /* + * Next frame + */ + manager->framecount++; + + /* + * Get/calc ticks + */ + current_ticks = _getTicks(); + time_passed = current_ticks - manager->lastticks; + manager->lastticks = current_ticks; + target_ticks = manager->baseticks + (Uint32) ((float) manager->framecount * manager->rateticks); + + if (current_ticks <= target_ticks) { + the_delay = target_ticks - current_ticks; + SDL_Delay(the_delay); + } else { + manager->framecount = 0; + manager->baseticks = _getTicks(); + } + + return time_passed; +} |