Step 3

apps/LoopThroughWithOpenGLCompositing/gl/RenderEngine.h

@@ -13,10 +13,19 @@
 
 #include <windows.h>
 
+#include <atomic>
 #include <cstdint>
 #include <chrono>
+#include <condition_variable>
 #include <functional>
+#include <future>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <sstream>
 #include <string>
+#include <thread>
+#include <utility>
 #include <vector>
 
 class RenderEngine
@@ -60,6 +69,9 @@ public:
 		PreviewPaintCallback previewPaint);
 	~RenderEngine();
 
+	bool StartRenderThread();
+	void StopRenderThread();
+
 	bool CompileDecodeShader(int errorMessageSize, char* errorMessage);
 	bool CompileOutputPackShader(int errorMessageSize, char* errorMessage);
 	bool InitializeResources(
@@ -98,6 +110,74 @@ public:
 	bool CaptureOutputFrameRgbaTopDown(unsigned width, unsigned height, std::vector<unsigned char>& topDownPixels);
 
 private:
+	static constexpr std::chrono::milliseconds kRenderThreadRequestTimeout{ 250 };
+
+	struct RenderThreadTaskState
+	{
+		std::atomic<bool> started = false;
+		std::atomic<bool> cancelled = false;
+	};
+
+	template<typename Func>
+	auto InvokeOnRenderThread(Func&& func) -> decltype(func())
+	{
+		using Result = decltype(func());
+		if (!mRenderThreadRunning || GetCurrentThreadId() == mRenderThreadId)
+			return func();
+
+		auto task = std::make_shared<std::packaged_task<Result()>>(std::forward<Func>(func));
+		std::future<Result> result = task->get_future();
+		{
+			std::lock_guard<std::mutex> lock(mRenderThreadMutex);
+			mRenderThreadTasks.push([task]() { (*task)(); });
+		}
+		mRenderThreadCondition.notify_one();
+		return result.get();
+	}
+
+	template<typename Func>
+	bool TryInvokeOnRenderThread(const char* operationName, Func&& func)
+	{
+		if (!mRenderThreadRunning || GetCurrentThreadId() == mRenderThreadId)
+			return func();
+
+		auto state = std::make_shared<RenderThreadTaskState>();
+		auto task = std::make_shared<std::packaged_task<bool()>>(
+			[state, func = std::forward<Func>(func)]() mutable {
+				state->started = true;
+				if (state->cancelled)
+					return false;
+
+				return func();
+			});
+		std::future<bool> result = task->get_future();
+		{
+			std::lock_guard<std::mutex> lock(mRenderThreadMutex);
+			if (mRenderThreadStopping)
+			{
+				ReportRenderThreadRequestFailure(operationName, "render thread is stopping");
+				return false;
+			}
+			mRenderThreadTasks.push([task]() { (*task)(); });
+		}
+		mRenderThreadCondition.notify_one();
+
+		if (result.wait_for(kRenderThreadRequestTimeout) == std::future_status::ready)
+			return result.get();
+
+		if (!state->started)
+		{
+			state->cancelled = true;
+			ReportRenderThreadRequestFailure(operationName, "timed out before execution");
+			return false;
+		}
+
+		ReportRenderThreadRequestFailure(operationName, "exceeded timeout while executing; waiting for safe completion");
+		return result.get();
+	}
+
+	void RenderThreadMain(std::promise<bool> ready);
+	void ReportRenderThreadRequestFailure(const char* operationName, const char* reason);
 	bool CommitPreparedLayerPrograms(const PreparedShaderBuild& preparedBuild, unsigned inputFrameWidth, unsigned inputFrameHeight, int errorMessageSize, char* errorMessage);
 	void RenderLayerStack(
 		bool hasInputSource,
@@ -129,4 +209,12 @@ private:
 	RenderCommandQueue mRenderCommandQueue;
 	RenderFrameStateResolver mFrameStateResolver;
 	RuntimeLiveState mRuntimeLiveState;
+	std::thread mRenderThread;
+	std::atomic<DWORD> mRenderThreadId = 0;
+	std::mutex mRenderThreadMutex;
+	std::condition_variable mRenderThreadCondition;
+	std::queue<std::function<void()>> mRenderThreadTasks;
+	std::atomic<bool> mRenderThreadRunning = false;
+	bool mRenderThreadStopping = false;
+	bool mResourcesDestroyed = false;
 };