From 735bc2d815969f5791ea4073309f0a353730daf0 Mon Sep 17 00:00:00 2001
From: Camilla Berglund <elmindreda@elmindreda.org>
Date: Wed, 7 Aug 2013 18:07:33 +0200
Subject: [PATCH] Added NvOptimusEnablement.

---
 CMakeLists.txt   | 4 ++++
 README.md        | 6 ++++++
 src/config.h.in  | 2 ++
 src/win32_init.c | 9 +++++++++
 4 files changed, 21 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 13d51d25..4e7983cb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,6 +18,7 @@ option(GLFW_DOCUMENT_INTERNALS "Include internals in documentation" OFF)
 
 if (WIN32)
     option(GLFW_USE_DWM_SWAP_INTERVAL "Set swap interval even when DWM compositing is enabled" OFF)
+    option(GLFW_USE_OPTIMUS_HPG "Force use of high-performance GPU on Optimus systems" OFF)
 endif()
 
 if (APPLE)
@@ -159,6 +160,9 @@ if (_GLFW_WIN32)
     if (GLFW_USE_DWM_SWAP_INTERVAL)
         set(_GLFW_USE_DWM_SWAP_INTERVAL 1)
     endif()
+    if (GLFW_USE_OPTIMUS_HPG)
+        set(_GLFW_USE_OPTIMUS_HPG 1)
+    endif()
 endif()
 
 #--------------------------------------------------------------------
diff --git a/README.md b/README.md
index 8cfad847..711b9cda 100644
--- a/README.md
+++ b/README.md
@@ -173,6 +173,10 @@ static library version of the Visual C++ runtime library.
 when DWM compositing is enabled.  This can lead to severe jitter and is not
 usually recommended.
 
+`GLFW_USE_OPTIMUS_HPG` determines whether to export the `NvOptimusEnablement`
+symbol, which forces the use of the high-performance GPU on nVidia Optimus
+systems.
+
 
 #### EGL specific options
 
@@ -204,6 +208,8 @@ See the [GLFW documentation](http://www.glfw.org/docs/latest/).
  - Bugfix: The default for `GLFW_ALPHA_BITS` was set to zero
  - [Win32] Added `_GLFW_USE_DWM_SWAP_INTERVAL` for forcing the swap interval
            to be set even when DWM compositing is enabled
+ - [Win32] Added support for forcing the use of the high-performance GPU
+           on nVidia Optimus systems
  - [Win32] Bugfix: The clipboard string was not freed on terminate
  - [Win32] Bugfix: Entry points for OpenGL 1.0 and 1.1 functions were not
                    returned by `glfwGetProcAddress`
diff --git a/src/config.h.in b/src/config.h.in
index 82af6fb9..59259661 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -55,6 +55,8 @@
 #cmakedefine _GLFW_NO_DLOAD_WINMM
 // Define this to 1 if glfwSwapInterval should ignore DWM compositing status
 #cmakedefine _GLFW_USE_DWM_SWAP_INTERVAL
+// Define this to 1 to force use of high-performance GPU on Optimus systems
+#cmakedefine _GLFW_USE_OPTIMUS_HPG
 
 // Define this to 1 if glXGetProcAddress is available
 #cmakedefine _GLFW_HAS_GLXGETPROCADDRESS
diff --git a/src/win32_init.c b/src/win32_init.c
index dc71130d..8e0c19b0 100644
--- a/src/win32_init.c
+++ b/src/win32_init.c
@@ -36,6 +36,15 @@
 #endif // __BORLANDC__
 
 
+#if defined(_GLFW_USE_OPTIMUS_HPG)
+
+// Applications exporting this symbol with this value will be automatically
+// directed to the high-performance GPU on nVidia Optimus systems
+//
+GLFWAPI DWORD NvOptimusEnablement = 0x00000001;
+
+#endif // _GLFW_USE_OPTIMUS_HPG
+
 #if defined(_GLFW_BUILD_DLL)
 
 // GLFW DLL entry point