From 750c1949597179a1bb60daaad4fa71d80ecc7e47 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@zdoom.fake>
Date: Mon, 26 Sep 2016 01:38:25 +0200
Subject: [PATCH] - changed order of SwapBuffers and glFinish call. The new
 order with glFinish coming last is recommended by OpenGL and it fixes a
 stalling problem with portals and camera textures visible at the same time. -
 check and use WGL_EXT_swap_control_tear extension. The above change makes the
 system always wait for a full vsync with a wglSwapInterval of 1, so it now
 uses the official extension that enables adaptive vsync. Hopefully this also
 works on the cards where the old setup did not.

---
 src/gl/scene/gl_portal.cpp       |  6 +++---
 src/gl/system/gl_framebuffer.cpp |  2 +-
 src/win32/win32gliface.cpp       | 34 +++++++++++++++++++++++++++-----
 src/win32/win32gliface.h         |  1 +
 4 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/src/gl/scene/gl_portal.cpp b/src/gl/scene/gl_portal.cpp
index f34b5e23f..4a7fa9d7a 100644
--- a/src/gl/scene/gl_portal.cpp
+++ b/src/gl/scene/gl_portal.cpp
@@ -176,12 +176,12 @@ void GLPortal::DrawPortalStencil()
 bool GLPortal::Start(bool usestencil, bool doquery)
 {
 	rendered_portals++;
-	PortalAll.Clock();
+//	PortalAll.Clock();
 	if (usestencil)
 	{
 		if (!gl_portals) 
 		{
-			PortalAll.Unclock();
+//			PortalAll.Unclock();
 			return false;
 		}
 	
@@ -297,7 +297,7 @@ bool GLPortal::Start(bool usestencil, bool doquery)
 	GLRenderer->mCurrentPortal = this;
 
 	if (PrevPortal != NULL) PrevPortal->PushState();
-	PortalAll.Unclock();
+//	PortalAll.Unclock();
 	return true;
 }
 
diff --git a/src/gl/system/gl_framebuffer.cpp b/src/gl/system/gl_framebuffer.cpp
index 94eba0817..08aca521f 100644
--- a/src/gl/system/gl_framebuffer.cpp
+++ b/src/gl/system/gl_framebuffer.cpp
@@ -209,13 +209,13 @@ void OpenGLFrameBuffer::Swap()
 {
 	Finish.Reset();
 	Finish.Clock();
-	glFinish();
 	if (needsetgamma) 
 	{
 		//DoSetGamma();
 		needsetgamma = false;
 	}
 	SwapBuffers();
+	glFinish();
 	Finish.Unclock();
 	swapped = true;
 	FHardwareTexture::UnbindAll();
diff --git a/src/win32/win32gliface.cpp b/src/win32/win32gliface.cpp
index 7ca001e1e..5d68d8427 100644
--- a/src/win32/win32gliface.cpp
+++ b/src/win32/win32gliface.cpp
@@ -37,7 +37,9 @@ extern int NewWidth, NewHeight, NewBits, DisplayBits;
 // these get used before GLEW is initialized so we have to use separate pointers with different names
 PFNWGLCHOOSEPIXELFORMATARBPROC myWglChoosePixelFormatARB; // = (PFNWGLCHOOSEPIXELFORMATARBPROC)wglGetProcAddress("wglChoosePixelFormatARB");
 PFNWGLCREATECONTEXTATTRIBSARBPROC myWglCreateContextAttribsARB;
-PFNWGLSWAPINTERVALEXTPROC vsyncfunc;
+PFNWGLSWAPINTERVALEXTPROC myWglSwapIntervalExtProc;
+
+
 
 
 CUSTOM_CVAR(Bool, gl_debug, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG | CVAR_NOINITCALL)
@@ -933,10 +935,32 @@ Win32GLFrameBuffer::Win32GLFrameBuffer(void *hMonitor, int width, int height, in
 		vid_renderer = 0;
 		return;
 	}
-
-	vsyncfunc = (PFNWGLSWAPINTERVALEXTPROC)wglGetProcAddress("wglSwapIntervalEXT");
-
 	HDC hDC = GetDC(Window);
+	const char *wglext = nullptr;
+
+	myWglSwapIntervalExtProc = (PFNWGLSWAPINTERVALEXTPROC)wglGetProcAddress("wglSwapIntervalEXT");
+	auto myWglGetExtensionsStringARB = (PFNWGLGETEXTENSIONSSTRINGARBPROC)wglGetProcAddress("wglGetExtensionsStringARB");
+	if (myWglGetExtensionsStringARB)
+	{
+		wglext = myWglGetExtensionsStringARB(hDC);
+	}
+	else
+	{
+		auto myWglGetExtensionsStringEXT = (PFNWGLGETEXTENSIONSSTRINGEXTPROC)wglGetProcAddress("wglGetExtensionsStringEXT");
+		if (myWglGetExtensionsStringEXT)
+		{
+			wglext = myWglGetExtensionsStringEXT();
+		}
+	}
+	SwapInterval = 1; 
+	if (wglext != nullptr)
+	{
+		if (strstr(wglext, "WGL_EXT_swap_control_tear"))
+		{
+			SwapInterval = -1;
+		}
+	}
+
 	m_supportsGamma = !!GetDeviceGammaRamp(hDC, (void *)m_origGamma);
 	ReleaseDC(Window, hDC);
 }
@@ -1091,7 +1115,7 @@ void Win32GLFrameBuffer::ReleaseResources ()
 
 void Win32GLFrameBuffer::SetVSync (bool vsync)
 {
-	if (vsyncfunc != NULL) vsyncfunc(vsync ? 1 : 0);
+	if (myWglSwapIntervalExtProc != NULL) myWglSwapIntervalExtProc(vsync ? SwapInterval : 0);
 }
 
 void Win32GLFrameBuffer::SwapBuffers()
diff --git a/src/win32/win32gliface.h b/src/win32/win32gliface.h
index 6320e2903..e767073c4 100644
--- a/src/win32/win32gliface.h
+++ b/src/win32/win32gliface.h
@@ -148,6 +148,7 @@ protected:
 	int m_Lock;
 	char m_displayDeviceNameBuffer[CCHDEVICENAME];
 	char *m_displayDeviceName;
+	int SwapInterval;
 
 	friend class Win32GLVideo;