Support dynamic switching between integrated and discrete GPUs on Mac OS X.

ui/gfx/gl/gl_context_mac.cc

Index: ui/gfx/gl/gl_context_mac.cc
===================================================================
--- ui/gfx/gl/gl_context_mac.cc	(revision 105357)
+++ ui/gfx/gl/gl_context_mac.cc	(working copy)
@@ -4,6 +4,8 @@
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "base/mac/mac_util.h"
+#include "base/memory/scoped_generic_obj.h"
 #include "base/memory/scoped_ptr.h"
 #include "third_party/mesa/MesaLib/include/GL/osmesa.h"
 #include "ui/gfx/gl/gl_bindings.h"
@@ -14,24 +16,37 @@
 #include "ui/gfx/gl/gl_surface_cgl.h"
 #include "ui/gfx/gl/gl_surface_osmesa.h"
 
+namespace {
+
+// ScopedGenericObj functor for CGLDestroyRendererInfo().
+class ScopedDestroyRendererInfo {
+ public:
+  void operator()(CGLRendererInfoObj x) const {
+    CGLDestroyRendererInfo(x);
+  }
+};
+
+}  // namespace
+
 namespace gfx {
 
 class GLShareGroup;
 
 scoped_refptr<GLContext> GLContext::CreateGLContext(
     GLShareGroup* share_group,
-    GLSurface* compatible_surface) {
+    GLSurface* compatible_surface,
+    GpuPreference gpu_preference) {
   switch (GetGLImplementation()) {
     case kGLImplementationDesktopGL: {
       scoped_refptr<GLContext> context(new GLContextCGL(share_group));
-      if (!context->Initialize(compatible_surface))
+      if (!context->Initialize(compatible_surface, gpu_preference))
         return NULL;
 
       return context;
     }
     case kGLImplementationOSMesaGL: {
       scoped_refptr<GLContext> context(new GLContextOSMesa(share_group));
-      if (!context->Initialize(compatible_surface))
+      if (!context->Initialize(compatible_surface, gpu_preference))
         return NULL;
 
       return context;
@@ -44,4 +59,85 @@
   }
 }
 
+bool GLContext::SupportsDualGpus() {
+  // We need to know the GL implementation in order to correctly
+  // answer whether dual GPUs are supported. This introduces an
+  // initialization cycle with GLSurface::InitializeOneOff() which we
+  // need to break.
+  static bool initialized = false;
+  static bool initializing = false;
+  static bool supports_dual_gpus = false;
+
+  if (initialized) {
+    return supports_dual_gpus;
+  } else {
+    if (!initializing) {
+      initializing = true;
+      if (!GLSurface::InitializeOneOff()) {
+        return false;
+      }
+    }
+    initialized = true;
+  }
+
+  if (!base::mac::IsOSLionOrLater()) {
+    return false;
+  }
+
+  if (GetGLImplementation() != kGLImplementationDesktopGL) {
+    return false;
+  }
+
+  // Enumerate all hardware-accelerated renderers. If we find one
+  // online and one offline, assume we're on a dual-GPU system.
+  GLuint display_mask = static_cast<GLuint>(-1);
+  CGLRendererInfoObj renderer_info = NULL;
+  GLint num_renderers = 0;
+
+  bool found_online = false;
+  bool found_offline = false;
+
+  if (CGLQueryRendererInfo(display_mask,
+                           &renderer_info,
+                           &num_renderers) != kCGLNoError) {
+    return false;
+  }
+
+  ScopedGenericObj<CGLRendererInfoObj, ScopedDestroyRendererInfo>
+      scoper(renderer_info);
+
+  for (GLint i = 0; i < num_renderers; ++i) {
+    GLint accelerated = 0;
+    if (CGLDescribeRenderer(renderer_info,
+                            i,
+                            kCGLRPAccelerated,
+                            &accelerated) != kCGLNoError) {
+      return false;
+    }
+
+    if (!accelerated)
+      continue;
+
+    GLint online = 0;
+    if (CGLDescribeRenderer(renderer_info,
+                            i,
+                            kCGLRPOnline,
+                            &online) != kCGLNoError) {
+      return false;
+    }
+
+    if (online) {
+      found_online = true;
+    } else {
+      found_offline = true;
+    }
+  }
+
+  if (found_online && found_offline) {
+    supports_dual_gpus = true;
+  }
+
+  return supports_dual_gpus;
+}
+
 }  // namespace gfx