public void Tick()
{
double current_frame_time = Platform.GetPerformanceCounter();
double delta_time = current_frame_time - _prevFrameTime;
_prevFrameTime = current_frame_time;
// Handle unexpected timer anomalies (overflow, extra slow frames, etc)
if (delta_time > _desiredFrametime * 8)
{
delta_time = _desiredFrametime;
}
if (delta_time < 0)
{
delta_time = 0;
}
// VSync Time Snapping
for (int i = 0; i < _snapFreqs.Length; ++i)
{
var snap_freq = _snapFreqs[i];
if (Math.Abs(delta_time - snap_freq) < _vsyncMaxError)
{
delta_time = snap_freq;
break;
}
}
// Delta Time Averaging
for (int i = 0; i < TimeHistoryCount - 1; ++i)
{
_timeAverager[i] = _timeAverager[i + 1];
}
_timeAverager[TimeHistoryCount - 1] = delta_time;
delta_time = 0;
for (int i = 0; i < TimeHistoryCount; ++i)
{
delta_time += _timeAverager[i];
}
delta_time /= TimeHistoryCount;
// Add To Accumulator
_frameAccum += delta_time;
// Spiral of Death Protection
if (_frameAccum > _desiredFrametime * 8)
{
_resync = true;
}
// Timer Resync Requested
if (_resync)
{
_frameAccum = 0;
delta_time = _desiredFrametime;
_resync = false;
}
// Process Events and Input
Engine.ProcessEvents();
Engine.ProcessInput();
// Unlocked Frame Rate, Interpolation Enabled
if (UnlockFrameRate)
{
double consumed_delta_time = delta_time;
while (_frameAccum >= _desiredFrametime)
{
FixedUpdate((float)_fixedDeltatime);
// Cap Variable Update's dt to not be larger than fixed update,
// and interleave it (so game state can always get animation frame it needs)
if (consumed_delta_time > _desiredFrametime)
{
Update((float)_fixedDeltatime);
consumed_delta_time -= _desiredFrametime;
}
_frameAccum -= _desiredFrametime;
}
Update((float)(consumed_delta_time / Platform.GetPerformanceFrequency()));
if (Engine.Canvas.NeedsResetDisplay)
{
Engine.Canvas.HandleDisplayChange();
OnDisplayResize();
}
Draw(Engine.Canvas, (float)(_frameAccum / _desiredFrametime));
GraphicsContext.Frame();
}
// Locked Frame Rate, No Interpolation
else
{
while (_frameAccum >= _desiredFrametime * UpdateMult)
{
for (int i = 0; i < UpdateMult; ++i)
{
FixedUpdate((float)_fixedDeltatime);
Update((float)_fixedDeltatime);
_frameAccum -= _desiredFrametime;
}
}
if (Engine.Canvas.NeedsResetDisplay)
{
Engine.Canvas.HandleDisplayChange();
OnDisplayResize();
}
Draw(Engine.Canvas, 1.0f);
GraphicsContext.Frame();
}
}
