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Fix draw cap math

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Floating point nonsense made the common case of draw cap = fps cap sometimes skip frames. This commit essentially duplicates the tick scheduling logic over to draw scheduling, with the exception that the draw schedule's "how much time to sleep" output goes nowhere; instead, we explicitly check whether we should be drawing a frame every tick.
This commit is contained in:
Tamás Bálint Misius 2024-12-20 22:53:16 +01:00
parent c645269c86
commit 3b70324b78
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GPG Key ID: 5B472A12F6ECA9F2
1 changed files with 65 additions and 25 deletions
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90
src/PowderToySDL.cpp
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@ -27,9 +27,46 @@ bool mouseDown = false;
bool calculatedInitialMouse = false;
bool hasMouseMoved = false;
double correctedFrameTimeAvg = 0;
uint64_t drawingTimer = 0;
uint64_t frameStart = 0;
uint64_t oldFrameStart = 0;
class FrameSchedule
{
uint64_t startNs = 0;
uint64_t oldStartNs = 0;
public:
void SetNow(uint64_t nowNs)
{
oldStartNs = startNs;
startNs = nowNs;
}
uint64_t GetNow() const
{
return startNs;
}
uint64_t GetFrameTime() const
{
return startNs - oldStartNs;
}
uint64_t Arm(float fps)
{
auto oldNowNs = startNs;
auto timeBlockDurationNs = uint64_t(UINT64_C(1'000'000'000) / fps);
auto oldStartTimeBlock = oldStartNs / timeBlockDurationNs;
auto startTimeBlock = oldStartTimeBlock + 1U;
startNs = std::max(startNs, startTimeBlock * timeBlockDurationNs);
return startNs - oldNowNs;
}
bool HasElapsed(uint64_t nowNs) const
{
return nowNs >= startNs;
}
};
static FrameSchedule tickSchedule;
static FrameSchedule drawSchedule;
void StartTextInput()
{
@ -396,17 +433,16 @@ static void EventProcess(const SDL_Event &event)
void EngineProcess()
{
auto &engine = ui::Engine::Ref();
auto correctedFrameTime = frameStart - oldFrameStart;
drawingTimer += correctedFrameTime;
auto correctedFrameTime = tickSchedule.GetFrameTime();
correctedFrameTimeAvg = correctedFrameTimeAvg + (correctedFrameTime - correctedFrameTimeAvg) * 0.05;
if (correctedFrameTime && frameStart - lastFpsUpdate > UINT64_C(200'000'000))
if (correctedFrameTime && tickSchedule.GetNow() - lastFpsUpdate > UINT64_C(200'000'000))
{
engine.SetFps(1e9f / correctedFrameTimeAvg);
lastFpsUpdate = frameStart;
lastFpsUpdate = tickSchedule.GetNow();
}
if (frameStart - lastTick > UINT64_C(100'000'000))
if (tickSchedule.GetNow() - lastTick > UINT64_C(100'000'000))
{
lastTick = frameStart;
lastTick = tickSchedule.GetNow();
TickClient();
}
if (showLargeScreenDialog)
@ -423,24 +459,28 @@ void EngineProcess()
engine.Tick();
auto fpsLimit = ui::Engine::Ref().GetFpsLimit();
int drawcap = ui::Engine::Ref().GetDrawingFrequencyLimit();
if (!drawcap || drawingTimer > 1e9f / drawcap)
{
engine.Draw();
drawingTimer = 0;
SDLSetScreen();
blit(engine.g->Data());
int drawcap = ui::Engine::Ref().GetDrawingFrequencyLimit();
auto nowNs = uint64_t(SDL_GetTicks()) * UINT64_C(1'000'000);
if (!drawcap || drawSchedule.HasElapsed(nowNs))
{
engine.Draw();
drawSchedule.SetNow(nowNs);
if (drawcap)
{
drawSchedule.Arm(float(drawcap));
}
SDLSetScreen();
blit(engine.g->Data());
}
}
auto now = uint64_t(SDL_GetTicks()) * UINT64_C(1'000'000);
oldFrameStart = frameStart;
frameStart = now;
if (auto *fpsLimitExplicit = std::get_if<FpsLimitExplicit>(&fpsLimit))
{
auto timeBlockDuration = uint64_t(UINT64_C(1'000'000'000) / fpsLimitExplicit->value);
auto oldFrameStartTimeBlock = oldFrameStart / timeBlockDuration;
auto frameStartTimeBlock = oldFrameStartTimeBlock + 1U;
frameStart = std::max(frameStart, frameStartTimeBlock * timeBlockDuration);
SDL_Delay((frameStart - now) / UINT64_C(1'000'000));
auto fpsLimit = ui::Engine::Ref().GetFpsLimit();
auto nowNs = uint64_t(SDL_GetTicks()) * UINT64_C(1'000'000);
tickSchedule.SetNow(nowNs);
if (auto *fpsLimitExplicit = std::get_if<FpsLimitExplicit>(&fpsLimit))
{
SDL_Delay(tickSchedule.Arm(fpsLimitExplicit->value) / UINT64_C(1'000'000));
}
}
}