Chapter 1, Snippet 7 - OpenGLBook.com

chapter.1.7.c

void IdleFunction(void)
{
  glutPostRedisplay();
}

void TimerFunction(int Value)
{
  if (0 != Value) {
    char* TempString = (char*)
      malloc(512 + strlen(WINDOW_TITLE_PREFIX));

    sprintf(
      TempString,
      "%s: %d Frames Per Second @ %d x %d",
      WINDOW_TITLE_PREFIX,
      FrameCount * 4,
      CurrentWidth,
      CurrentHeight
    );

    glutSetWindowTitle(TempString);
    free(TempString);
  }
  
  FrameCount = 0;
  glutTimerFunc(250, TimerFunction, 1);
}