source/gles2n64/src/FrameSkipper.cpp

   1 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
   2  *   Copyright (C) 2011 yongzh (freeman.yong@gmail.com)                    *
   3  *                                                                         *
   4  *   This program is free software; you can redistribute it and/or modify  *
   5  *   it under the terms of the GNU General Public License as published by  *
   6  *   the Free Software Foundation; either version 2 of the License, or     *
   7  *   (at your option) any later version.                                   *
   8  *                                                                         *
   9  *   This program is distributed in the hope that it will be useful,       *
  10  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  11  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  12  *   GNU General Public License for more details.                          *
  13  *                                                                         *
  14  *   You should have received a copy of the GNU General Public License     *
  15  *   along with this program; if not, write to the                         *
  16  *   Free Software Foundation, Inc.,                                       *
  17  *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.          *
  18  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
  19
  20 #include "FrameSkipper.h"
  21 #include "ticks.h"
  22
  23 FrameSkipper::FrameSkipper()
  24         : skipType(AUTO), maxSkips(2), targetFPS(60)
  25 {
  26 }
  27
  28 void FrameSkipper::start()
  29 {
  30         initialTicks = 0;
  31         virtualCount = 0;
  32         skipCounter = 0;
  33 }
  34
  35 void FrameSkipper::update()
  36 {
  37         // for the first frame
  38         if (initialTicks == 0) {
  39                 initialTicks = ticksGetTicks();
  40                 return;
  41         }
  42
  43         unsigned int elapsed = ticksGetTicks() - initialTicks;
  44         unsigned int realCount = elapsed * targetFPS / 1000;
  45
  46         virtualCount++;
  47         if (realCount >= virtualCount) {
  48                 if (realCount > virtualCount &&
  49                                 skipType == AUTO && skipCounter < maxSkips) {
  50                         skipCounter++;
  51                 } else {
  52                         virtualCount = realCount;
  53                         if (skipType == AUTO)
  54                                 skipCounter = 0;
  55                 }
  56         }
  57         if (skipType == MANUAL) {
  58                 if (++skipCounter > maxSkips)
  59                         skipCounter = 0;
  60         }
  61 }