From 1f81f5940939b7add2431cddd7e4e51ecf78a3ca Mon Sep 17 00:00:00 2001
From: Zi Ree <zi.ree@phoenixviewer.com>
Date: Thu, 28 Jul 2022 17:53:47 +0200
Subject: [PATCH] Add support for shared OpenGL contexts when using SDL2 for
 multithreaded OpenGL image processing

---
 indra/llwindow/llwindowsdl2.cpp      | 46 ++++++++++++++++++++++++----
 indra/llwindow/llwindowsdl2.h        | 11 ++++---
 indra/newview/featuretable_linux.txt |  7 ++---
 3 files changed, 49 insertions(+), 15 deletions(-)

diff --git a/indra/llwindow/llwindowsdl2.cpp b/indra/llwindow/llwindowsdl2.cpp
index bf93216ff8..152f02d287 100644
--- a/indra/llwindow/llwindowsdl2.cpp
+++ b/indra/llwindow/llwindowsdl2.cpp
@@ -716,6 +716,8 @@ BOOL LLWindowSDL::createContext(int x, int y, int width, int height, int bits, B
 		SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, mFSAASamples);
 	}
 	
+	// <FS:Zi> Make shared context work on Linux for multithreaded OpenGL
+	SDL_GL_SetAttribute(SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
 	mWindow = SDL_CreateWindow( mWindowTitle.c_str(), SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, mSDLFlags );
 
 	if( mWindow )
@@ -2563,25 +2565,57 @@ std::vector<std::string> LLWindowSDL::getDynamicFallbackFontList()
 	return rtns;
 }
 
+// <FS:Zi> Make shared context work on Linux for multithreaded OpenGL
+class sharedContext
+{
+	public:
+		SDL_GLContext mContext;
+};
 
 void* LLWindowSDL::createSharedContext()
 {
-  return SDL_GL_CreateContext(mWindow);
+	sharedContext* sc = new sharedContext();
+	sc->mContext = SDL_GL_CreateContext(mWindow);
+	if (sc->mContext)
+	{
+		SDL_GL_SetSwapInterval(0);
+		SDL_GL_MakeCurrent(mWindow, mContext);
+
+		LLCoordScreen size;
+		if (getSize(&size))
+		{
+			setSize(size);
+		}
+
+		LL_WARNS() << "Creating shared OpenGL context successful!" << LL_ENDL;
+
+		return (void*)sc;
+	}
+
+	LL_WARNS() << "Creating shared OpenGL context failed!" << LL_ENDL;
+
+	return nullptr;
 }
 
-void LLWindowSDL::makeContextCurrent(void* contextPtr)
+void LLWindowSDL::makeContextCurrent(void* context)
 {
-    LL_PROFILER_GPU_CONTEXT;
-    SDL_GL_MakeCurrent( mWindow, contextPtr );
+	LL_PROFILER_GPU_CONTEXT;
+	SDL_GL_MakeCurrent(mWindow, ((sharedContext*)context)->mContext);
 }
 
-void LLWindowSDL::destroySharedContext(void* contextPtr)
+void LLWindowSDL::destroySharedContext(void* context)
 {
-  SDL_GL_DeleteContext( contextPtr );
+	sharedContext* sc = (sharedContext*)context;
+
+	SDL_GL_DeleteContext(sc->mContext);
+
+	delete sc;
 }
 
 void LLWindowSDL::toggleVSync(bool enable_vsync)
 {
+	SDL_GL_SetSwapInterval(enable_vsync);
 }
+// </FS:Zi>
 
 #endif // LL_SDL
diff --git a/indra/llwindow/llwindowsdl2.h b/indra/llwindow/llwindowsdl2.h
index 42c6a0d325..20adba802e 100644
--- a/indra/llwindow/llwindowsdl2.h
+++ b/indra/llwindow/llwindowsdl2.h
@@ -66,6 +66,12 @@ public:
 	/*virtual*/ BOOL setSizeImpl(LLCoordScreen size);
 	/*virtual*/ BOOL setSizeImpl(LLCoordWindow size);
 	/*virtual*/ BOOL switchContext(BOOL fullscreen, const LLCoordScreen &size, BOOL disable_vsync, const LLCoordScreen * const posp = NULL);
+	// <FS:Zi> Make shared context work on Linux for multithreaded OpenGL
+	void* createSharedContext() override;
+	void makeContextCurrent(void* context) override;
+	void destroySharedContext(void* context) override;
+	/*virtual*/ void toggleVSync(bool enable_vsync);
+	// </FS:Zi>
 	/*virtual*/ BOOL setCursorPosition(LLCoordWindow position);
 	/*virtual*/ BOOL getCursorPosition(LLCoordWindow *position);
 	/*virtual*/ void showCursor();
@@ -148,11 +154,6 @@ public:
 	static Display* get_SDL_Display(void);
 #endif // LL_X11	
 
-	void* createSharedContext() override;
-	void makeContextCurrent(void* context) override;
-	void destroySharedContext(void* context) override;
-	void toggleVSync(bool enable_vsync) override;
-	
 protected:
 	LLWindowSDL(LLWindowCallbacks* callbacks,
 		const std::string& title, int x, int y, int width, int height, U32 flags,
diff --git a/indra/newview/featuretable_linux.txt b/indra/newview/featuretable_linux.txt
index 1ee21efc12..fb16e7005d 100644
--- a/indra/newview/featuretable_linux.txt
+++ b/indra/newview/featuretable_linux.txt
@@ -33,7 +33,6 @@ RenderAvatarLODFactor		1	1.0
 RenderAvatarPhysicsLODFactor 1	1.0
 RenderAvatarMaxNonImpostors 1   16
 RenderAvatarMaxComplexity          1	350000
-RenderAvatarVP				1	1
 RenderAutoMuteSurfaceAreaLimit     1	1000.0
 RenderCubeMap				1	1
 RenderDelayVBUpdate			1	0
@@ -70,7 +69,7 @@ RenderShadowDetail			1	2
 RenderUseStreamVBO			1	1
 RenderFSAASamples			1	16
 RenderMaxTextureIndex		1	16
-RenderGLCoreProfile         1   1
+RenderGLContextCoreProfile  1   1
 RenderGLMultiThreaded       1   1
 
 
@@ -316,12 +315,12 @@ RenderAnisotropic			1	0
 RenderCubeMap				0	0
 RenderFSAASamples			1	0
 RenderGLMultiThreaded       1   0
-RenderGLCoreProfile         1   0
+RenderGLContextCoreProfile  1   0
 
 // AMD cards generally perform better when not using VBOs for streaming data
 // AMD cards also prefer an OpenGL Compatibility Profile Context
 list AMD
 RenderUseStreamVBO			1	0
-RenderGLCoreProfile         1   0
+RenderGLContextCoreProfile  1   0