Stage 1 rewrite

apps/LoopThroughWithOpenGLCompositing/videoio/RenderCadenceController.h

@@ -0,0 +1,68 @@
+#pragma once
+
+#include <chrono>
+#include <cstdint>
+
+enum class RenderCadenceAction
+{
+	Wait,
+	Render
+};
+
+struct RenderCadencePolicy
+{
+	bool skipLateTicks = true;
+	uint64_t maxSkippedTicksPerDecision = 4;
+	double skipThresholdFrames = 2.0;
+};
+
+struct RenderCadenceDecision
+{
+	RenderCadenceAction action = RenderCadenceAction::Wait;
+	uint64_t frameIndex = 0;
+	uint64_t skippedTicks = 0;
+	std::chrono::steady_clock::time_point renderTargetTime;
+	std::chrono::steady_clock::time_point nextRenderTime;
+	std::chrono::steady_clock::duration waitDuration = std::chrono::steady_clock::duration::zero();
+	std::chrono::steady_clock::duration lateness = std::chrono::steady_clock::duration::zero();
+	const char* reason = "waiting-for-next-render-tick";
+};
+
+struct RenderCadenceMetrics
+{
+	uint64_t nextFrameIndex = 0;
+	uint64_t renderedFrameCount = 0;
+	uint64_t skippedTickCount = 0;
+	uint64_t lateFrameCount = 0;
+	std::chrono::steady_clock::duration lastLateness = std::chrono::steady_clock::duration::zero();
+	std::chrono::steady_clock::duration maxLateness = std::chrono::steady_clock::duration::zero();
+};
+
+class RenderCadenceController
+{
+public:
+	using Clock = std::chrono::steady_clock;
+	using TimePoint = Clock::time_point;
+	using Duration = Clock::duration;
+
+	void Configure(Duration targetFrameDuration, TimePoint firstRenderTime, const RenderCadencePolicy& policy = RenderCadencePolicy());
+	void Reset(TimePoint firstRenderTime);
+	RenderCadenceDecision Tick(TimePoint now);
+
+	Duration TargetFrameDuration() const { return mTargetFrameDuration; }
+	TimePoint NextRenderTime() const { return mNextRenderTime; }
+	uint64_t NextFrameIndex() const { return mNextFrameIndex; }
+	const RenderCadenceMetrics& Metrics() const { return mMetrics; }
+
+private:
+	uint64_t SkippedTicksForLateness(Duration lateness) const;
+	static bool IsPositive(Duration duration);
+
+	Duration mTargetFrameDuration = std::chrono::milliseconds(16);
+	TimePoint mNextRenderTime;
+	uint64_t mNextFrameIndex = 0;
+	RenderCadencePolicy mPolicy;
+	RenderCadenceMetrics mMetrics;
+};
+
+const char* RenderCadenceActionName(RenderCadenceAction action);