From 2a438d6e03958369240eb67bc22987a47c437230 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Mon, 12 Mar 2018 20:07:31 +0100
Subject: [PATCH] Fix VSync on Windows. Should fix #10711

---
 Windows/GPU/WindowsGLContext.cpp      | 15 +++++++++------
 ext/native/thin3d/GLRenderManager.cpp |  6 ++++++
 ext/native/thin3d/GLRenderManager.h   | 16 ++++++++++++++++
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/Windows/GPU/WindowsGLContext.cpp b/Windows/GPU/WindowsGLContext.cpp
index 7bed8d1e69..8feae44307 100644
--- a/Windows/GPU/WindowsGLContext.cpp
+++ b/Windows/GPU/WindowsGLContext.cpp
@@ -332,8 +332,6 @@ bool WindowsGLContext::InitFromRenderThread(std::string *error_message) {
 
 	hRC = m_hrc;
 
-	SwapInterval(0);
-
 	if (g_Config.bGfxDebugOutput) {
 		if (wglewIsSupported("GL_KHR_debug") == 1) {
 			glGetError();
@@ -375,16 +373,21 @@ bool WindowsGLContext::InitFromRenderThread(std::string *error_message) {
 	renderManager_ = (GLRenderManager *)draw_->GetNativeObject(Draw::NativeObject::RENDER_MANAGER);
 	SetGPUBackend(GPUBackend::OPENGL);
 	bool success = draw_->CreatePresets();  // if we get this far, there will always be a GLSL compiler capable of compiling these.
-	renderManager_->SetSwapFunction([&]() {::SwapBuffers(hDC); });
 	assert(success);
+	renderManager_->SetSwapFunction([&]() {::SwapBuffers(hDC); });
+	if (wglSwapIntervalEXT) {
+		// glew loads wglSwapIntervalEXT if available
+		renderManager_->SetSwapIntervalFunction([&](int interval) {
+			wglSwapIntervalEXT(interval);
+		});
+	}
 	CHECK_GL_ERROR_IF_DEBUG();
 	return true;												// Success
 }
 
 void WindowsGLContext::SwapInterval(int interval) {
-	// glew loads wglSwapIntervalEXT if available
-	if (wglSwapIntervalEXT)
-		wglSwapIntervalEXT(interval);
+	// Delegate to the render manager to make sure it's done on the right thread.
+	renderManager_->SwapInterval(interval);
 }
 
 void WindowsGLContext::Shutdown() {
diff --git a/ext/native/thin3d/GLRenderManager.cpp b/ext/native/thin3d/GLRenderManager.cpp
index e126fd34e8..31e571c295 100644
--- a/ext/native/thin3d/GLRenderManager.cpp
+++ b/ext/native/thin3d/GLRenderManager.cpp
@@ -436,6 +436,12 @@ void GLRenderManager::EndSubmitFrame(int frame) {
 	Submit(frame, true);
 
 	if (!frameData.skipSwap) {
+		if (swapIntervalChanged_) {
+			swapIntervalChanged_ = false;
+			if (swapIntervalFunction_) {
+				swapIntervalFunction_(swapInterval_);
+			}
+		}
 		if (swapFunction_) {
 			swapFunction_();
 		}
diff --git a/ext/native/thin3d/GLRenderManager.h b/ext/native/thin3d/GLRenderManager.h
index 11b93dafd9..5cb4e54e61 100644
--- a/ext/native/thin3d/GLRenderManager.h
+++ b/ext/native/thin3d/GLRenderManager.h
@@ -682,6 +682,7 @@ public:
 	void RegisterPushBuffer(int frame, GLPushBuffer *buffer) {
 		frameData_[frame].activePushBuffers.insert(buffer);
 	}
+
 	void UnregisterPushBuffer(int frame, GLPushBuffer *buffer) {
 		auto iter = frameData_[frame].activePushBuffers.find(buffer);
 		_assert_(iter != frameData_[frame].activePushBuffers.end());
@@ -692,6 +693,17 @@ public:
 		swapFunction_ = swapFunction;
 	}
 
+	void SetSwapIntervalFunction(std::function<void(int)> swapIntervalFunction) {
+		swapIntervalFunction_ = swapIntervalFunction;
+	}
+
+	void SwapInterval(int interval) {
+		if (interval != swapInterval_) {
+			swapInterval_ = interval;
+			swapIntervalChanged_ = true;
+		}
+	}
+
 	void StopThread();
 
 	bool SawOutOfMemory() {
@@ -765,8 +777,12 @@ private:
 	int curFrame_ = 0;
 
 	std::function<void()> swapFunction_;
+	std::function<void(int)> swapIntervalFunction_;
 	GLBufferStrategy bufferStrategy_ = GLBufferStrategy::SUBDATA;
 
+	int swapInterval_ = 0;
+	bool swapIntervalChanged_ = true;
+
 	int targetWidth_ = 0;
 	int targetHeight_ = 0;
 };