From 634a52e29654751c294b85d1ec54f893796d79d9 Mon Sep 17 00:00:00 2001
From: Mikhail Gorobets <misha.friman@mail.ru>
Date: Wed, 10 Jan 2024 06:37:11 +0600
Subject: [PATCH] OpenGL: Add option to control desired adapter type in OpenGL
 (close #450)

---
 .../GraphicsEngine/interface/GraphicsTypes.h  |  6 ++++
 .../src/EngineFactoryOpenGL.cpp               | 33 +++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/Graphics/GraphicsEngine/interface/GraphicsTypes.h b/Graphics/GraphicsEngine/interface/GraphicsTypes.h
index 605ec6199b..1a386ddbae 100644
--- a/Graphics/GraphicsEngine/interface/GraphicsTypes.h
+++ b/Graphics/GraphicsEngine/interface/GraphicsTypes.h
@@ -3485,6 +3485,12 @@ struct EngineGLCreateInfo DILIGENT_DERIVE(EngineCreateInfo)
     /// Use IRenderDevice::GetDeviceInfo().NDC to get current NDC.
     Bool         ZeroToOneNDZ DEFAULT_INITIALIZER(false);
 
+    /// The GPU preference allows you to request either the integrated or dedicated GPU
+    /// on systems having both onboard and dedicated GPUs. Currently this works only on Windows and Linux
+    /// - On Windows this is done by setting the `NvOptimusEnablement` and  `AmdPowerXpressRequestHighPerformance` 
+    /// - On Linux this affects the `DRI_PRIME` environment variable that's used by Mesa drivers that support PRIME.
+    ADAPTER_TYPE PreferredAdapterType DEFAULT_INITIALIZER(ADAPTER_TYPE_UNKNOWN);
+
 #if PLATFORM_EMSCRIPTEN
     /// WebGL context attributes.
     WebGLContextAttribs WebGLAttribs;
diff --git a/Graphics/GraphicsEngineOpenGL/src/EngineFactoryOpenGL.cpp b/Graphics/GraphicsEngineOpenGL/src/EngineFactoryOpenGL.cpp
index 06d1e5575b..7bb8c482f7 100644
--- a/Graphics/GraphicsEngineOpenGL/src/EngineFactoryOpenGL.cpp
+++ b/Graphics/GraphicsEngineOpenGL/src/EngineFactoryOpenGL.cpp
@@ -58,6 +58,24 @@
 #    include "RenderDeviceGLESImpl.hpp"
 #endif
 
+#if PLATFORM_WIN32 || PLATFORM_UNIVERSAL_WINDOWS
+#    define DILIGENT_INTERFACE_EXPORT
+#elif PLATFORM_LINUX
+#    define DILIGENT_INTERFACE_EXPORT __attribute__((visibility("default")))
+#else
+#    define DILIGENT_INTERFACE_EXPORT
+#endif
+
+/// Let the NVIDIA and AMD know we want to use their graphics card on a dual graphics card system.
+extern "C"
+{
+    /// https://community.amd.com/thread/169965
+    DILIGENT_INTERFACE_EXPORT uint64_t AmdPowerXpressRequestHighPerformance = 0x0;
+
+    /// http://developer.download.nvidia.com/devzone/devcenter/gamegraphics/files/OptimusRenderingPolicies.pdf
+    DILIGENT_INTERFACE_EXPORT uint64_t NvOptimusEnablement = 0x0;
+}
+
 namespace Diligent
 {
 
@@ -137,6 +155,20 @@ static void SetDefaultGraphicsAdapterInfo(GraphicsAdapterInfo& AdapterInfo)
     AdapterInfo.Queues[0].TextureCopyGranularity[2] = 1;
 }
 
+static void SetPreferredAdapter(const EngineGLCreateInfo& EngineCI)
+{
+    bool IsEnableDedicatedGPU = EngineCI.PreferredAdapterType == ADAPTER_TYPE_DISCRETE;
+#if PLATFORM_WIN32 || PLATFORM_UNIVERSAL_WINDOWS
+    AmdPowerXpressRequestHighPerformance = IsEnableDedicatedGPU;
+    NvOptimusEnablement                  = IsEnableDedicatedGPU;
+#elif PLAtTFORM_LINUX
+    setenv("DRI_PRIME", IsEnableDedicatedGPU ? "1" : "0", 1);
+#else
+    if (EngineCI.PreferredAdapterType != ADAPTER_TYPE_UNKNOWN)
+        LOG_WARNING_MESSAGE("Setting prefered adapter type isn't supported on this platform")
+#endif
+}
+
 void EngineFactoryOpenGLImpl::EnumerateAdapters(Version              MinVersion,
                                                 Uint32&              NumAdapters,
                                                 GraphicsAdapterInfo* Adapters) const
@@ -303,6 +335,7 @@ void EngineFactoryOpenGLImpl::AttachToActiveGLContext(const EngineGLCreateInfo&
         SetRawAllocator(EngineCI.pRawMemAllocator);
         auto& RawMemAllocator = GetRawAllocator();
 
+        SetPreferredAdapter(EngineCI);
         RenderDeviceGLImpl* pRenderDeviceOpenGL{
             NEW_RC_OBJ(RawMemAllocator, "TRenderDeviceGLImpl instance", TRenderDeviceGLImpl)(
                 RawMemAllocator, this, EngineCI //