GCC Code Coverage Report
Directory: src/ Exec Total Coverage
File: src/sdl2gfx/SDL2_framerate.cpp Lines: 9 35 25.7 %
Date: 2019-10-15 Branches: 2 20 10.0 %

Line Branch Exec Source
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/*
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SDL2_framerate.c: framerate manager
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Copyright (C) 2012-2014  Andreas Schiffler
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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
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distribution.
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Andreas Schiffler -- aschiffler at ferzkopp dot net
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Changed for ManaPlus (C) 2013-2017  ManaPlus developers
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*/
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#include "sdl2gfx/SDL2_framerate.h"
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#include "debug.h"
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/*!
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\brief Internal wrapper to SDL_GetTicks that ensures a non-zero return value.
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\return The tick count.
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*/
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static Uint32 _getTicks()
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{
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    Uint32 ticks = SDL_GetTicks();
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    /*
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    * Since baseticks!=0 is used to track initialization
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    * we need to ensure that the tick count is always >0
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    * since SDL_GetTicks may not have incremented yet and
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    * return 0 depending on the timing of the calls.
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    */
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    if (ticks == 0)
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    {
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        return 1;
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    }
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    else
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    {
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        return ticks;
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    }
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}
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/*!
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\brief Initialize the framerate manager.
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Initialize the framerate manager, set default framerate of 30Hz and
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reset delay interpolation.
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\param manager Pointer to the framerate manager.
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*/
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void SDL_initFramerate(FPSmanager * manager)
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{
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    /*
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    * Store some sane values
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    */
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    manager->framecount = 0;
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    manager->rate = FPS_DEFAULT;
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    manager->rateticks = (1000.0F / static_cast<float>(FPS_DEFAULT));
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    manager->baseticks = _getTicks();
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    manager->lastticks = manager->baseticks;
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}
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/*!
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\brief Set the framerate in Hz
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Sets a new framerate for the manager and reset delay interpolation.
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Rate values must be between FPS_LOWER_LIMIT and FPS_UPPER_LIMIT inclusive to be accepted.
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\param manager Pointer to the framerate manager.
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\param rate The new framerate in Hz (frames per second).
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\return 0 for sucess and -1 for error.
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*/
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int SDL_setFramerate(FPSmanager * manager, Uint32 rate)
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{
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    if ((rate >= FPS_LOWER_LIMIT) && (rate <= FPS_UPPER_LIMIT))
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    {
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        manager->framecount = 0;
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        manager->rate = rate;
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        manager->rateticks = (1000.0F / static_cast<float>(rate));
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        return (0);
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    }
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    else
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    {
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        return (-1);
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    }
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}
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/*!
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\brief Return the current target framerate in Hz
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Get the currently set framerate of the manager.
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\param manager Pointer to the framerate manager.
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\return Current framerate in Hz or -1 for error.
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*/
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int SDL_getFramerate(FPSmanager * manager)
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{
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    if (manager == nullptr)
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    {
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        return (-1);
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    }
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    else
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    {
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        return (static_cast<int>(manager->rate));
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    }
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}
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/*!
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\brief Return the current framecount.
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Get the current framecount from the framerate manager.
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A frame is counted each time SDL_framerateDelay is called.
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\param manager Pointer to the framerate manager.
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\return Current frame count or -1 for error.
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*/
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int SDL_getFramecount(FPSmanager * manager)
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{
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    if (manager == nullptr)
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    {
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        return (-1);
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    }
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    else
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    {
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        return (static_cast<int>(manager->framecount));
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    }
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}
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/*!
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\brief Delay execution to maintain a constant framerate and calculate fps.
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Generate a delay to accomodate currently set framerate. Call once in the
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graphics/rendering loop. If the computer cannot keep up with the rate (i.e.
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drawing too slow), the delay is zero and the delay interpolation is reset.
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\param manager Pointer to the framerate manager.
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\return The time that passed since the last call to the function in ms. May return 0.
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*/
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Uint32 SDL_framerateDelay(FPSmanager * manager)
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{
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    Uint32 current_ticks;
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    Uint32 target_ticks;
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    Uint32 the_delay;
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    Uint32 time_passed = 0;
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    /*
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    * No manager, no delay
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    */
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    if (manager == nullptr)
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    {
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        return 0;
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    }
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    /*
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    * Initialize uninitialized manager
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    */
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    if (manager->baseticks == 0)
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    {
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        SDL_initFramerate(manager);
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    }
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    /*
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    * Next frame
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    */
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    manager->framecount++;
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    /*
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    * Get/calc ticks
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    */
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    current_ticks = _getTicks();
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    time_passed = current_ticks - manager->lastticks;
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    manager->lastticks = current_ticks;
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    target_ticks = manager->baseticks + static_cast<Uint32>(static_cast<float>(
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        manager->framecount) * manager->rateticks);
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    if (current_ticks <= target_ticks)
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    {
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        the_delay = target_ticks - current_ticks;
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        SDL_Delay(the_delay);
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    }
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    else
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    {
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        manager->framecount = 0;
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        manager->baseticks = _getTicks();
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    }
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    return time_passed;
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}