Reland "Define and expose EGL_ANGLE_power_preference extension."

This is a reland of ac58e63295

The original CL was reverted in a rush because I thought there was an
uninitialized variable bug, but upon later re-review this turned out to
not be the case.

Original change's description:
> Define and expose EGL_ANGLE_power_preference extension.
>
> Allows application to select the integrated or discrete GPU on
> dual-GPU macOS systems.
>
> Tested by modifying the example program at:
> https://github.com/grorg/ANGLEIOSurfaceTest
>
> and verifying that both integrated and discrete GPUs can be selected.
> (The changes to that program will be upstreamed once some build issues
> are resolved.)
>
> Bug: 2813
> Change-Id: Ibeb17778512896456d220e9bc4cf8f222aa57057
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1570081
> Commit-Queue: Kenneth Russell <kbr@chromium.org>
> Reviewed-by: Geoff Lang <geofflang@chromium.org>

Bug: 2813
Tbr: geofflang@chromium.org
Tbr: cwallez@chromium.org
Change-Id: Iea000dd718f4f4b4f57237adb1dc44381b10106b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1575419
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>

extensions/EGL_ANGLE_power_preference.txt

@@ -0,0 +1,85 @@
+Name
+
+    ANGLE_power_preference
+
+Name Strings
+
+    EGL_ANGLE_power_preference
+
+Contributors
+
+    Kenneth Russell
+
+Contacts
+
+    Kenneth Russell, Google Inc. (kbr 'at' google.com)
+
+Status
+
+    Draft
+
+Version
+
+    Version 1, April 16, 2019
+
+Number
+
+    EGL Extension #??
+
+Dependencies
+
+    This extension is written against the wording of the EGL 1.4
+    Specification.
+
+Overview
+
+    This extension allows selection of the high- or low-power GPU on
+    dual-GPU systems, specifically on macOS.
+
+New Types
+
+    None
+
+New Procedures and Functions
+
+    None
+
+New Tokens
+
+    Accepted as an attribute name in the <*attrib_list> argument to
+    eglCreateContext:
+
+        EGL_POWER_PREFERENCE_ANGLE  0x3482
+
+    Accepted as an attribute value in the <*attrib_list> argument to
+    eglCreateContext:
+
+        EGL_LOW_POWER_ANGLE         0x0001
+        EGL_HIGH_POWER_ANGLE        0x0002
+
+Additions to the EGL 1.4 Specification
+
+    Add the following to section 3.7.1 "Creating Rendering Contexts":
+
+    EGL_POWER_PREFERENCE_ANGLE indicates whether the context should be
+    created on the integrated (low-power) or discrete (high-power) GPU
+    on dual-GPU systems. EGL_POWER_PREFERENCE_ANGLE is only a legal
+    context creation attribute when the EGL_ANGLE_power_preference
+    extension is advertised. The valid values for this attribute are
+    EGL_LOW_POWER_ANGLE and EGL_HIGH_POWER_ANGLE. If this extension is
+    advertised and this context creation attribute is not specified,
+    the default value is EGL_LOW_POWER_ANGLE.
+
+    The containing application must set the
+    NSSupportsAutomaticGraphicsSwitching attribute to true in its
+    Info.plist in order for this extension to operate as advertised.
+
+Issues
+
+    None yet.
+
+Revision History
+
+    Rev.    Date         Author     Changes
+    ----  -------------  ---------  ----------------------------------------
+      1   Apr 16, 2019   kbr        Initial version

include/EGL/eglext_angle.h

@@ -202,6 +202,13 @@ EGLAPI EGLBoolean EGLAPIENTRY eglGetSyncValuesCHROMIUM(EGLDisplay dpy,
 #endif
 #endif /* EGL_CHROMIUM_get_sync_values */
 
+#ifndef EGL_ANGLE_power_preference
+#define EGL_ANGLE_power_preference 1
+#define EGL_POWER_PREFERENCE_ANGLE 0x3482
+#define EGL_LOW_POWER_ANGLE 0x0001
+#define EGL_HIGH_POWER_ANGLE 0x0002
+#endif /* EGL_ANGLE_power_preference */
+
 // clang-format on
 
 #endif  // INCLUDE_EGL_EGLEXT_ANGLE_

src/gpu_info_util/SystemInfo.h

@@ -67,6 +67,8 @@ struct SystemInfo
 
     bool isOptimus       = false;
     bool isAMDSwitchable = false;
+    // Only true on dual-GPU Mac laptops.
+    bool isMacSwitchable = false;
 
     // Only available on Android
     std::string machineManufacturer;

src/gpu_info_util/SystemInfo_mac.mm

@@ -164,6 +164,19 @@ bool GetSystemInfo(SystemInfo *info)
 
     FindPrimaryGPU(info);
 
+    // Figure out whether this is a dual-GPU system.
+    //
+    // TODO(kbr): this code was ported over from Chromium, and its correctness
+    // could be improved - need to use Mac-specific APIs to determine whether
+    // offline renderers are allowed, and whether these two GPUs are really the
+    // integrated/discrete GPUs in a laptop.
+    if (info->gpus.size() == 2 &&
+        ((IsIntel(info->gpus[0].vendorId) && !IsIntel(info->gpus[1].vendorId)) ||
+         (!IsIntel(info->gpus[0].vendorId) && IsIntel(info->gpus[1].vendorId))))
+    {
+        info->isMacSwitchable = true;
+    }
+
     return true;
 }
 

src/libANGLE/AttributeMap.cpp

@@ -37,7 +37,7 @@ EGLAttrib AttributeMap::get(EGLAttrib key) const
 EGLAttrib AttributeMap::get(EGLAttrib key, EGLAttrib defaultValue) const
 {
     auto iter = mAttributes.find(key);
-    return (mAttributes.find(key) != mAttributes.end()) ? iter->second : defaultValue;
+    return (iter != mAttributes.end()) ? iter->second : defaultValue;
 }
 
 EGLint AttributeMap::getAsInt(EGLAttrib key) const

src/libANGLE/Caps.cpp

@@ -1391,7 +1391,8 @@ DisplayExtensions::DisplayExtensions()
       blobCache(false),
       imageNativeBuffer(false),
       getFrameTimestamps(false),
-      recordable(false)
+      recordable(false),
+      powerPreference(false)
 {}
 
 std::vector<std::string> DisplayExtensions::getStrings() const
@@ -1444,7 +1445,8 @@ std::vector<std::string> DisplayExtensions::getStrings() const
     InsertExtensionString("EGL_ANDROID_blob_cache",                              blobCache,                          &extensionStrings);
     InsertExtensionString("EGL_ANDROID_image_native_buffer",                     imageNativeBuffer,                  &extensionStrings);
     InsertExtensionString("EGL_ANDROID_get_frame_timestamps",                    getFrameTimestamps,                 &extensionStrings);
-    InsertExtensionString("EGL_ANDROID_recordable",                              recordable,                 &extensionStrings);
+    InsertExtensionString("EGL_ANDROID_recordable",                              recordable,                         &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_power_preference",                          powerPreference,                    &extensionStrings);
     // TODO(jmadill): Enable this when complete.
     //InsertExtensionString("KHR_create_context_no_error",                       createContextNoError,               &extensionStrings);
     // clang-format on

src/libANGLE/Caps.h

@@ -870,6 +870,9 @@ struct DisplayExtensions
 
     // EGL_ANDROID_recordable
     bool recordable;
+
+    // EGL_ANGLE_power_preference
+    bool powerPreference;
 };
 
 struct DeviceExtensions

src/libANGLE/renderer/gl/cgl/ContextCGL.cpp

@@ -0,0 +1,41 @@
+//
+// Copyright 2019 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// ContextCGL:
+//   Mac-specific subclass of ContextGL.
+//
+
+#include "libANGLE/renderer/gl/cgl/ContextCGL.h"
+
+#include "libANGLE/Context.h"
+#include "libANGLE/Display.h"
+#include "libANGLE/renderer/gl/cgl/DisplayCGL.h"
+
+namespace rx
+{
+
+ContextCGL::ContextCGL(const gl::State &state,
+                       gl::ErrorSet *errorSet,
+                       const std::shared_ptr<RendererGL> &renderer,
+                       bool usesDiscreteGPU)
+    : ContextGL(state, errorSet, renderer), mUsesDiscreteGpu(usesDiscreteGPU)
+{}
+
+void ContextCGL::onDestroy(const gl::Context *context)
+{
+    if (mUsesDiscreteGpu)
+    {
+        egl::Display *display = context->getDisplay();
+        // TODO(kbr): if the context is created and destroyed without ever
+        // making it current, it is possible to leak retentions of the
+        // discrete GPU.
+        if (display)
+        {
+            GetImplAs<DisplayCGL>(display)->unreferenceDiscreteGPU();
+        }
+    }
+}
+
+}  // namespace rx

src/libANGLE/renderer/gl/cgl/ContextCGL.h

@@ -0,0 +1,35 @@
+//
+// Copyright 2019 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// ContextCGL:
+//   Mac-specific subclass of ContextGL.
+//
+
+#ifndef LIBANGLE_RENDERER_GL_CGL_CONTEXTCGL_H_
+#define LIBANGLE_RENDERER_GL_CGL_CONTEXTCGL_H_
+
+#include "libANGLE/renderer/gl/ContextGL.h"
+#include "libANGLE/renderer/gl/RendererGL.h"
+
+namespace rx
+{
+
+class ContextCGL : public ContextGL
+{
+  public:
+    ContextCGL(const gl::State &state,
+               gl::ErrorSet *errorSet,
+               const std::shared_ptr<RendererGL> &renderer,
+               bool usesDiscreteGPU);
+
+    void onDestroy(const gl::Context *context) override;
+
+  private:
+    bool mUsesDiscreteGpu;
+};
+
+}  // namespace rx
+
+#endif  // LIBANGLE_RENDERER_GL_CGL_CONTEXTCGL_H_

src/libANGLE/renderer/gl/cgl/DisplayCGL.h

@@ -74,6 +74,11 @@ class DisplayCGL : public DisplayGL
 
     WorkerContext *createWorkerContext(std::string *infoLog);
 
+    // Support for dual-GPU MacBook Pros. If the context was created
+    // preferring the high-power GPU, unreference that GPU during
+    // context destruction.
+    void unreferenceDiscreteGPU();
+
   private:
     egl::Error makeCurrentSurfaceless(gl::Context *context) override;
 
@@ -85,6 +90,9 @@ class DisplayCGL : public DisplayGL
     egl::Display *mEGLDisplay;
     CGLContextObj mContext;
     CGLPixelFormatObj mPixelFormat;
+    bool mSupportsGPUSwitching;
+    CGLPixelFormatObj mDiscreteGPUPixelFormat;
+    int mDiscreteGPURefs;
 };
 
 }  // namespace rx

src/libANGLE/renderer/gl/cgl/DisplayCGL.mm

@@ -13,8 +13,9 @@
 #include <dlfcn.h>
 
 #include "common/debug.h"
+#include "gpu_info_util/SystemInfo.h"
 #include "libANGLE/Display.h"
-#include "libANGLE/renderer/gl/ContextGL.h"
+#include "libANGLE/renderer/gl/cgl/ContextCGL.h"
 #include "libANGLE/renderer/gl/cgl/IOSurfaceSurfaceCGL.h"
 #include "libANGLE/renderer/gl/cgl/PbufferSurfaceCGL.h"
 #include "libANGLE/renderer/gl/cgl/RendererCGL.h"
@@ -49,7 +50,13 @@ class FunctionsGLCGL : public FunctionsGL
 };
 
 DisplayCGL::DisplayCGL(const egl::DisplayState &state)
-    : DisplayGL(state), mEGLDisplay(nullptr), mContext(nullptr), mPixelFormat(nullptr)
+    : DisplayGL(state),
+      mEGLDisplay(nullptr),
+      mContext(nullptr),
+      mPixelFormat(nullptr),
+      mSupportsGPUSwitching(false),
+      mDiscreteGPUPixelFormat(nullptr),
+      mDiscreteGPURefs(0)
 {}
 
 DisplayCGL::~DisplayCGL() {}
@@ -58,13 +65,25 @@ egl::Error DisplayCGL::initialize(egl::Display *display)
 {
     mEGLDisplay = display;
 
+    angle::SystemInfo info;
+    if (!angle::GetSystemInfo(&info))
+    {
+        return egl::EglNotInitialized() << "Unable to query ANGLE's SystemInfo.";
+    }
+    mSupportsGPUSwitching = info.isMacSwitchable;
+
     {
         // TODO(cwallez) investigate which pixel format we want
-        CGLPixelFormatAttribute attribs[] = {
-            kCGLPFAOpenGLProfile, static_cast<CGLPixelFormatAttribute>(kCGLOGLPVersion_3_2_Core),
-            static_cast<CGLPixelFormatAttribute>(0)};
+        std::vector<CGLPixelFormatAttribute> attribs;
+        attribs.push_back(kCGLPFAOpenGLProfile);
+        attribs.push_back(static_cast<CGLPixelFormatAttribute>(kCGLOGLPVersion_3_2_Core));
+        if (mSupportsGPUSwitching)
+        {
+            attribs.push_back(kCGLPFAAllowOfflineRenderers);
+        }
+        attribs.push_back(static_cast<CGLPixelFormatAttribute>(0));
         GLint nVirtualScreens = 0;
-        CGLChoosePixelFormat(attribs, &mPixelFormat, &nVirtualScreens);
+        CGLChoosePixelFormat(attribs.data(), &mPixelFormat, &nVirtualScreens);
 
         if (mPixelFormat == nullptr)
         {
@@ -161,7 +180,29 @@ ContextImpl *DisplayCGL::createContext(const gl::State &state,
                                        const gl::Context *shareContext,
                                        const egl::AttributeMap &attribs)
 {
-    return new ContextGL(state, errorSet, mRenderer);
+    bool usesDiscreteGPU = false;
+
+    if (attribs.get(EGL_POWER_PREFERENCE_ANGLE, EGL_LOW_POWER_ANGLE) == EGL_HIGH_POWER_ANGLE)
+    {
+        // Should have been rejected by validation if not supported.
+        ASSERT(mSupportsGPUSwitching);
+        // Create discrete pixel format if necessary.
+        if (!mDiscreteGPUPixelFormat)
+        {
+            CGLPixelFormatAttribute discreteAttribs[] = {static_cast<CGLPixelFormatAttribute>(0)};
+            GLint numPixelFormats                     = 0;
+            if (CGLChoosePixelFormat(discreteAttribs, &mDiscreteGPUPixelFormat, &numPixelFormats) !=
+                kCGLNoError)
+            {
+                ERR() << "Error choosing discrete pixel format.";
+                return nullptr;
+            }
+        }
+        ++mDiscreteGPURefs;
+        usesDiscreteGPU = true;
+    }
+
+    return new ContextCGL(state, errorSet, mRenderer, usesDiscreteGPU);
 }
 
 DeviceImpl *DisplayCGL::createDevice()
@@ -288,6 +329,11 @@ void DisplayCGL::generateExtensions(egl::DisplayExtensions *outExtensions) const
     // Contexts are virtualized so textures can be shared globally
     outExtensions->displayTextureShareGroup = true;
 
+    if (mSupportsGPUSwitching)
+    {
+        outExtensions->powerPreference = true;
+    }
+
     DisplayGL::generateExtensions(outExtensions);
 }
 
@@ -370,4 +416,14 @@ WorkerContext *DisplayCGL::createWorkerContext(std::string *infoLog)
 
     return new WorkerContextCGL(context);
 }
+
+void DisplayCGL::unreferenceDiscreteGPU()
+{
+    ASSERT(mDiscreteGPURefs > 0);
+    if (--mDiscreteGPURefs == 0)
+    {
+        CGLDestroyPixelFormat(mDiscreteGPUPixelFormat);
+        mDiscreteGPUPixelFormat = nullptr;
+    }
+}
 }

src/libANGLE/validationEGL.cpp

@@ -1127,6 +1127,20 @@ Error ValidateCreateContext(Display *display,
                 }
                 break;
 
+            case EGL_POWER_PREFERENCE_ANGLE:
+                if (!display->getExtensions().powerPreference)
+                {
+                    return EglBadAttribute() << "Attribute EGL_POWER_PREFERENCE_ANGLE "
+                                                "requires EGL_ANGLE_power_preference.";
+                }
+                if (value != EGL_LOW_POWER_ANGLE && value != EGL_HIGH_POWER_ANGLE)
+                {
+                    return EglBadAttribute()
+                           << "EGL_POWER_PREFERENCE_ANGLE must be "
+                              "either EGL_LOW_POWER_ANGLE or EGL_HIGH_POWER_ANGLE.";
+                }
+                break;
+
             default:
                 return EglBadAttribute() << "Unknown attribute.";
         }

src/libGLESv2.gni

@@ -747,6 +747,8 @@ libangle_gl_egl_android_sources = [
 ]
 
 libangle_gl_cgl_sources = [
+  "src/libANGLE/renderer/gl/cgl/ContextCGL.cpp",
+  "src/libANGLE/renderer/gl/cgl/ContextCGL.h",
   "src/libANGLE/renderer/gl/cgl/DisplayCGL.mm",
   "src/libANGLE/renderer/gl/cgl/DisplayCGL.h",
   "src/libANGLE/renderer/gl/cgl/IOSurfaceSurfaceCGL.mm",