Example of game engine tick loop

gistfile1.txt

static constexpr uint64_t g_fixed_frame_rate = 60;
static constexpr double   g_fixed_delta_time = 1.0 / g_fixed_frame_rate;

// Time counters
uint64_t m_start_tick = 0;
uint64_t m_prev_tick  = 0;
uint64_t m_delta_tick = 0;

// Last processed frame number
uint64_t m_fixed_last_frame = 0;

void engine_tick(void)
{
  const uint64_t perf_freq = SDL_GetPerformanceFrequency();
  const uint64_t perf_tick = SDL_GetPerformanceCounter();
  const uint64_t delta_tick = perf_tick - m_prev_tick;
  const float    delta_time = delta_tick / (float)perf_freq;

  constexpr float e = 1e-15F;
  if (delta_time > e)
  {
    update(delta_time);
  }

  const uint64_t fixed_tick_duration = (uint64_t)(g_fixed_delta_time * perf_freq);
  const uint64_t target_frame = (perf_tick - m_start_tick) / fixed_tick_duration;
  while (m_fixed_last_frame < target_frame)
  {
    ++m_fixed_last_frame;
    fixed_update();
  }

  m_prev_tick = perf_tick;
}