WGL: Support unvirtualized contexts and unsafe multithreading.

extensions/EGL_ANGLE_platform_angle_context_virtualization.txt

+Name
+
+    ANGLE_platform_angle_context_virtualization
+
+Name Strings
+
+    EGL_ANGLE_platform_angle_context_virtualization
+
+Contributors
+
+    Geoff Lang, Google
+
+Contacts
+
+    Geoff Lang, Google (geofflang 'at' chromium 'dot' org)
+
+Status
+
+    Draft
+
+Version
+
+    Version 1, 2018-06-11
+
+Number
+
+    EGL Extension XXX
+
+Extension Type
+
+    EGL client extension
+
+Dependencies
+
+    Requires ANGLE_platform_angle.
+
+Overview
+
+    This extension allows the client to request a Display that internally
+    virtualizes contexts. Requesting virtualized contexts may impact
+    performance or ability to render from multiple threads simultaneously.
+
+New Types
+
+    None
+
+New Procedures and Functions
+
+    None
+
+New Tokens
+
+    Accepted as an attribute name in the <attrib_list> argument of
+    eglGetPlatformDisplayEXT:
+
+        EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE    0x3481
+
+Additions to the EGL Specification
+
+    None.
+
+New Behavior
+
+    To request a display that internally utilizes context virtualization,
+    use the attribute EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE.
+    EGL_TRUE enables context virtualization and EGL false disables it.
+    If it is set to EGL_DONT_CARE, the default setting depends on the
+    implementation. Any value other than these will result in an error.
+    The default value for EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE
+    is EGL_DONT_CARE. Display creation may fail if hardware limitations
+    prohibit the requested setting.
+
+Issues
+
+    None
+
+Revision History
+
+    Version 1, 2018-06-11 (Geoff Lang)
+      - Initial draft

include/EGL/eglext_angle.h

@@ -82,6 +82,11 @@
 #define EGL_PLATFORM_ANGLE_TYPE_VULKAN_ANGLE 0x3450
 #endif /* EGL_ANGLE_platform_angle_vulkan */
 
+#ifndef EGL_ANGLE_platform_angle_context_virtualization
+#define EGL_ANGLE_platform_angle_context_virtualization 1
+#define EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE 0x3481
+#endif /* EGL_ANGLE_platform_angle_context_virtualization */
+
 #ifndef EGL_ANGLE_x11_visual
 #define EGL_ANGLE_x11_visual
 #define EGL_X11_VISUAL_ID_ANGLE 0x33A3

src/libANGLE/Caps.cpp

@@ -1389,13 +1389,14 @@ ClientExtensions::ClientExtensions()
       platformANGLED3D(false),
       platformANGLEOpenGL(false),
       platformANGLEVulkan(false),
+      platformANGLEContextVirtualization(false),
       deviceCreation(false),
       deviceCreationD3D11(false),
       x11Visual(false),
       experimentalPresentPath(false),
       clientGetAllProcAddresses(false),
-      explicitContext(false),
-      debug(false)
+      debug(false),
+      explicitContext(false)
 {
 }
 
@@ -1406,22 +1407,23 @@ std::vector<std::string> ClientExtensions::getStrings() const
     std::vector<std::string> extensionStrings;
 
     // clang-format off
-    //                   | Extension name                         | Supported flag           | Output vector   |
-    InsertExtensionString("EGL_EXT_client_extensions",             clientExtensions,          &extensionStrings);
-    InsertExtensionString("EGL_EXT_platform_base",                 platformBase,              &extensionStrings);
-    InsertExtensionString("EGL_EXT_platform_device",               platformDevice,            &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_platform_angle",              platformANGLE,             &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_platform_angle_d3d",          platformANGLED3D,          &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_platform_angle_opengl",       platformANGLEOpenGL,       &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_platform_angle_null",         platformANGLENULL,         &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_platform_angle_vulkan",       platformANGLEVulkan,       &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_device_creation",             deviceCreation,            &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_device_creation_d3d11",       deviceCreationD3D11,       &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_x11_visual",                  x11Visual,                 &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_experimental_present_path",   experimentalPresentPath,   &extensionStrings);
-    InsertExtensionString("EGL_KHR_client_get_all_proc_addresses", clientGetAllProcAddresses, &extensionStrings);
-    InsertExtensionString("EGL_ANGLE_explicit_context",            explicitContext,           &extensionStrings);
-    InsertExtensionString("EGL_KHR_debug",                         debug,                     &extensionStrings);
+    //                   | Extension name                                   | Supported flag                   | Output vector   |
+    InsertExtensionString("EGL_EXT_client_extensions",                       clientExtensions,                   &extensionStrings);
+    InsertExtensionString("EGL_EXT_platform_base",                           platformBase,                       &extensionStrings);
+    InsertExtensionString("EGL_EXT_platform_device",                         platformDevice,                     &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_platform_angle",                        platformANGLE,                      &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_platform_angle_d3d",                    platformANGLED3D,                   &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_platform_angle_opengl",                 platformANGLEOpenGL,                &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_platform_angle_null",                   platformANGLENULL,                  &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_platform_angle_vulkan",                 platformANGLEVulkan,                &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_platform_angle_context_virtualization", platformANGLEContextVirtualization, &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_device_creation",                       deviceCreation,                     &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_device_creation_d3d11",                 deviceCreationD3D11,                &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_x11_visual",                            x11Visual,                          &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_experimental_present_path",             experimentalPresentPath,            &extensionStrings);
+    InsertExtensionString("EGL_KHR_client_get_all_proc_addresses",           clientGetAllProcAddresses,          &extensionStrings);
+    InsertExtensionString("EGL_KHR_debug",                                   debug,                              &extensionStrings);
+    InsertExtensionString("EGL_ANGLE_explicit_context",                      explicitContext,                    &extensionStrings);
     // clang-format on
 
     return extensionStrings;

src/libANGLE/Caps.h

@@ -813,6 +813,9 @@ struct ClientExtensions
     // EGL_ANGLE_platform_angle_vulkan
     bool platformANGLEVulkan;
 
+    // EGL_ANGLE_platform_angle_context_virtualization
+    bool platformANGLEContextVirtualization;
+
     // EGL_ANGLE_device_creation
     bool deviceCreation;
 
@@ -828,11 +831,11 @@ struct ClientExtensions
     // EGL_KHR_client_get_all_proc_addresses
     bool clientGetAllProcAddresses;
 
-    // EGL_ANGLE_explicit_context
-    bool explicitContext;
-
     // EGL_KHR_debug
     bool debug;
+
+    // EGL_ANGLE_explicit_context
+    bool explicitContext;
 };
 
 }  // namespace egl

src/libANGLE/Display.cpp

@@ -1027,6 +1027,9 @@ static ClientExtensions GenerateClientExtensions()
 
 #if defined(ANGLE_ENABLE_OPENGL)
     extensions.platformANGLEOpenGL = true;
+
+    // Selecting context virtualization is currently only supported in the OpenGL backend.
+    extensions.platformANGLEContextVirtualization = true;
 #endif
 
 #if defined(ANGLE_ENABLE_NULL)

src/libANGLE/renderer/gl/wgl/DisplayWGL.cpp

@@ -24,6 +24,7 @@
 #include "libANGLE/renderer/gl/wgl/RendererWGL.h"
 #include "libANGLE/renderer/gl/wgl/WindowSurfaceWGL.h"
 #include "libANGLE/renderer/gl/wgl/wgl_utils.h"
+#include "libANGLE/renderer/renderer_utils.h"
 
 #include "platform/Platform.h"
 
@@ -34,6 +35,9 @@
 namespace rx
 {
 
+// Use context virtualization by default because Chrome uses it.
+static constexpr bool kDefaultWGLVirtualizedContexts = true;
+
 class FunctionsGLWindows : public FunctionsGL
 {
   public:
@@ -65,6 +69,7 @@ class FunctionsGLWindows : public FunctionsGL
 DisplayWGL::DisplayWGL(const egl::DisplayState &state)
     : DisplayGL(state),
       mRenderer(nullptr),
+      mVirtualizedContexts(kDefaultWGLVirtualizedContexts),
       mCurrentData(),
       mOpenGLModule(nullptr),
       mFunctionsWGL(nullptr),
@@ -103,6 +108,9 @@ egl::Error DisplayWGL::initializeImpl(egl::Display *display)
 {
     mDisplayAttributes = display->getAttributeMap();
 
+    mVirtualizedContexts =
+        ShouldUseVirtualizedContexts(mDisplayAttributes, kDefaultWGLVirtualizedContexts);
+
     mOpenGLModule = LoadLibraryA("opengl32.dll");
     if (!mOpenGLModule)
     {
@@ -250,7 +258,7 @@ egl::Error DisplayWGL::initializeImpl(egl::Display *display)
                << "Failed to set the pixel format on the intermediate OpenGL window.";
     }
 
-    ANGLE_TRY(createRenderer(&mRenderer));
+    ANGLE_TRY(createRenderer(nullptr, true, &mRenderer));
     const FunctionsGL *functionsGL = mRenderer->getFunctions();
 
     mHasRobustness = functionsGL->getGraphicsResetStatus != nullptr;
@@ -439,7 +447,23 @@ SurfaceImpl *DisplayWGL::createPixmapSurface(const egl::SurfaceState &state,
 
 ContextImpl *DisplayWGL::createContext(const gl::ContextState &state)
 {
-    return new ContextWGL(state, mRenderer);
+    std::shared_ptr<RendererWGL> renderer;
+    if (mVirtualizedContexts)
+    {
+        renderer = mRenderer;
+    }
+    else
+    {
+        // Create a new renderer that shares with the Display-level one.
+        egl::Error error = createRenderer(mRenderer->getContext(), false, &renderer);
+        if (error.isError())
+        {
+            ERR() << "Failed to create a shared renderer: " << error.getMessage();
+            return nullptr;
+        }
+    }
+
+    return new ContextWGL(state, renderer);
 }
 
 DeviceImpl *DisplayWGL::createDevice()
@@ -527,8 +551,11 @@ egl::ConfigSet DisplayWGL::generateConfigs()
 
 bool DisplayWGL::testDeviceLost()
 {
-    if (mHasRobustness)
+    // Can only call Renderer::getResetStatus if we know that it's context is current.  This is only
+    // guarenteed when we're using virtualized contexts.
+    if (mVirtualizedContexts && mHasRobustness)
     {
+        ASSERT(mCurrentData.at(std::this_thread::get_id()).glrc == mRenderer->getContext());
         return mRenderer->getResetStatus() != GL_NO_ERROR;
     }
 
@@ -665,20 +692,45 @@ egl::Error DisplayWGL::makeCurrent(egl::Surface *drawSurface,
 {
     CurrentNativeContext &currentContext = mCurrentData[std::this_thread::get_id()];
 
-    HDC newDC = currentContext.dc;
+    HDC newDC = nullptr;
     if (drawSurface)
     {
         SurfaceWGL *drawSurfaceWGL = GetImplAs<SurfaceWGL>(drawSurface);
         newDC                      = drawSurfaceWGL->getDC();
     }
 
-    HGLRC newContext = currentContext.glrc;
+    HGLRC newContext = nullptr;
     if (context)
     {
         ContextWGL *contextWGL = GetImplAs<ContextWGL>(context);
         newContext             = contextWGL->getContext();
     }
 
+    // The context should never change when context virtualization is being used, even when a null
+    // context is being bound.
+    if (mVirtualizedContexts)
+    {
+        ASSERT(newContext == nullptr || currentContext.glrc == nullptr ||
+               newContext == currentContext.glrc);
+        newContext = mRenderer->getContext();
+
+        // When contexts are virtualized, only single-threaded rendering is supported. This allows
+        // us to leave the previous surface bound if a null surface is being bound and emulate the
+        // surfaceless functionality because we know that this surface can not be made current on
+        // another thread.
+        if (newDC == nullptr)
+        {
+            newDC = currentContext.dc;
+        }
+    }
+
+    // WGL sometimes fails to make current a null DC even though it should support surfaceless make
+    // current calls, bind root device context for the intermediate window in this case.
+    if (newDC == nullptr && newContext != nullptr)
+    {
+        newDC = mDeviceContext;
+    }
+
     if (newDC != currentContext.dc || newContext != currentContext.glrc)
     {
         if (!mFunctionsWGL->makeCurrent(newDC, newContext))
@@ -749,9 +801,19 @@ gl::Version DisplayWGL::getMaxSupportedESVersion() const
 void DisplayWGL::destroyNativeContext(HGLRC context)
 {
     mFunctionsWGL->deleteContext(context);
+
+    // If this context is current, remove it from the tracking of current contexts to make sure we
+    // don't try to make it current again.
+    CurrentNativeContext &currentContext = mCurrentData[std::this_thread::get_id()];
+    if (currentContext.glrc == context)
+    {
+        currentContext.dc   = nullptr;
+        currentContext.glrc = nullptr;
+    }
 }
 
-HGLRC DisplayWGL::initializeContextAttribs(const egl::AttributeMap &eglAttributes) const
+HGLRC DisplayWGL::initializeContextAttribs(HGLRC shareContext,
+                                           const egl::AttributeMap &eglAttributes) const
 {
     EGLint requestedDisplayType = static_cast<EGLint>(
         eglAttributes.get(EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE));
@@ -770,7 +832,7 @@ HGLRC DisplayWGL::initializeContextAttribs(const egl::AttributeMap &eglAttribute
         {
             profileMask |= WGL_CONTEXT_CORE_PROFILE_BIT_ARB;
         }
-        return createContextAttribs(requestedVersion, profileMask);
+        return createContextAttribs(shareContext, requestedVersion, profileMask);
     }
 
     // Try all the GL version in order as a workaround for Mesa context creation where the driver
@@ -787,7 +849,7 @@ HGLRC DisplayWGL::initializeContextAttribs(const egl::AttributeMap &eglAttribute
             profileFlag |= WGL_CONTEXT_ES_PROFILE_BIT_EXT;
         }
 
-        HGLRC context = createContextAttribs(info.version, profileFlag);
+        HGLRC context = createContextAttribs(shareContext, info.version, profileFlag);
         if (context != nullptr)
         {
             return context;
@@ -797,7 +859,9 @@ HGLRC DisplayWGL::initializeContextAttribs(const egl::AttributeMap &eglAttribute
     return nullptr;
 }
 
-HGLRC DisplayWGL::createContextAttribs(const gl::Version &version, int profileMask) const
+HGLRC DisplayWGL::createContextAttribs(HGLRC shareContext,
+                                       const gl::Version &version,
+                                       int profileMask) const
 {
     std::vector<int> attribs;
 
@@ -824,15 +888,17 @@ HGLRC DisplayWGL::createContextAttribs(const gl::Version &version, int profileMa
     attribs.push_back(0);
     attribs.push_back(0);
 
-    return mFunctionsWGL->createContextAttribsARB(mDeviceContext, nullptr, &attribs[0]);
+    return mFunctionsWGL->createContextAttribsARB(mDeviceContext, shareContext, &attribs[0]);
 }
 
-egl::Error DisplayWGL::createRenderer(std::shared_ptr<RendererWGL> *outRenderer)
+egl::Error DisplayWGL::createRenderer(HGLRC shareContext,
+                                      bool makeNewContextCurrent,
+                                      std::shared_ptr<RendererWGL> *outRenderer)
 {
     HGLRC context = nullptr;
     if (mFunctionsWGL->createContextAttribsARB)
     {
-        context = initializeContextAttribs(mDisplayAttributes);
+        context = initializeContextAttribs(shareContext, mDisplayAttributes);
     }
 
     // If wglCreateContextAttribsARB is unavailable or failed, try the standard wglCreateContext
@@ -840,6 +906,14 @@ egl::Error DisplayWGL::createRenderer(std::shared_ptr<RendererWGL> *outRenderer)
     {
         // Don't have control over GL versions
         context = mFunctionsWGL->createContext(mDeviceContext);
+        if (context && shareContext)
+        {
+            if (!mFunctionsWGL->shareLists(shareContext, context))
+            {
+                return egl::EglNotInitialized()
+                       << "Failed to share lists to newly created context.";
+            }
+        }
     }
 
     if (!context)
@@ -852,9 +926,6 @@ egl::Error DisplayWGL::createRenderer(std::shared_ptr<RendererWGL> *outRenderer)
     {
         return egl::EglNotInitialized() << "Failed to make the intermediate WGL context current.";
     }
-    CurrentNativeContext &currentContext = mCurrentData[std::this_thread::get_id()];
-    currentContext.dc                    = mDeviceContext;
-    currentContext.glrc                  = context;
 
     std::unique_ptr<FunctionsGL> functionsGL(
         new FunctionsGLWindows(mOpenGLModule, mFunctionsWGL->getProcAddress));
@@ -862,6 +933,21 @@ egl::Error DisplayWGL::createRenderer(std::shared_ptr<RendererWGL> *outRenderer)
 
     outRenderer->reset(new RendererWGL(std::move(functionsGL), mDisplayAttributes, this, context));
 
+    CurrentNativeContext &currentContext = mCurrentData[std::this_thread::get_id()];
+    if (makeNewContextCurrent)
+    {
+        currentContext.dc   = mDeviceContext;
+        currentContext.glrc = context;
+    }
+    else
+    {
+        // Reset the current context back to the previous state
+        if (!mFunctionsWGL->makeCurrent(currentContext.dc, currentContext.glrc))
+        {
+            return egl::EglNotInitialized() << "Failed reset the current context.";
+        }
+    }
+
     return egl::NoError();
 }
 }

src/libANGLE/renderer/gl/wgl/DisplayWGL.h

@@ -87,12 +87,18 @@ class DisplayWGL : public DisplayGL
 
     egl::Error makeCurrentSurfaceless(gl::Context *context) override;
 
-    HGLRC initializeContextAttribs(const egl::AttributeMap &eglAttributes) const;
-    HGLRC createContextAttribs(const gl::Version &version, int profileMask) const;
+    HGLRC initializeContextAttribs(HGLRC shareContext,
+                                   const egl::AttributeMap &eglAttributes) const;
+    HGLRC createContextAttribs(HGLRC shareContext,
+                               const gl::Version &version,
+                               int profileMask) const;
 
-    egl::Error createRenderer(std::shared_ptr<RendererWGL> *outRenderer);
+    egl::Error createRenderer(HGLRC shareContext,
+                              bool makeNewContextCurrent,
+                              std::shared_ptr<RendererWGL> *outRenderer);
 
     std::shared_ptr<RendererWGL> mRenderer;
+    bool mVirtualizedContexts;
 
     struct CurrentNativeContext
     {

src/libANGLE/renderer/renderer_utils.cpp

@@ -442,6 +442,20 @@ bool ShouldUseDebugLayers(const egl::AttributeMap &attribs)
 #endif  // defined(ANGLE_ENABLE_ASSERTS)
 }
 
+bool ShouldUseVirtualizedContexts(const egl::AttributeMap &attribs, bool defaultValue)
+{
+    EGLAttrib virtualizedContextRequest =
+        attribs.get(EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE, EGL_DONT_CARE);
+    if (defaultValue)
+    {
+        return (virtualizedContextRequest != EGL_FALSE);
+    }
+    else
+    {
+        return (virtualizedContextRequest == EGL_TRUE);
+    }
+}
+
 void CopyImageCHROMIUM(const uint8_t *sourceData,
                        size_t sourceRowPitch,
                        size_t sourcePixelBytes,

src/libANGLE/renderer/renderer_utils.h

@@ -209,6 +209,7 @@ struct LoadImageFunctionInfo
 using LoadFunctionMap = LoadImageFunctionInfo (*)(GLenum);
 
 bool ShouldUseDebugLayers(const egl::AttributeMap &attribs);
+bool ShouldUseVirtualizedContexts(const egl::AttributeMap &attribs, bool defaultValue);
 
 void CopyImageCHROMIUM(const uint8_t *sourceData,
                        size_t sourceRowPitch,

src/libANGLE/validationEGL.cpp

@@ -409,6 +409,27 @@ Error ValidateGetPlatformDisplayCommon(EGLenum platform,
                     }
                     break;
 
+                case EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE:
+                    if (!clientExtensions.platformANGLEContextVirtualization)
+                    {
+                        return EglBadAttribute() << "EGL_ANGLE_platform_angle_context_"
+                                                    "virtualization extension not active";
+                    }
+
+                    switch (value)
+                    {
+                        case EGL_DONT_CARE:
+                        case EGL_FALSE:
+                        case EGL_TRUE:
+                            break;
+
+                        default:
+                            return EglBadAttribute() << "Invalid value for "
+                                                        "EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_"
+                                                        "ANGLE attrib";
+                    }
+                    break;
+
                 default:
                     break;
             }

src/tests/gl_tests/MultithreadingTest.cpp

@@ -26,9 +26,10 @@ class MultithreadingTest : public ANGLETest
         setConfigGreenBits(8);
         setConfigBlueBits(8);
         setConfigAlphaBits(8);
+        setContextVirtualization(false);
     }
 
-    bool platformSupportsMultithreading() const { return false; }
+    bool platformSupportsMultithreading() const { return IsOpenGL() && IsWindows(); }
 };
 
 // Test that it's possible to make one context current on different threads
@@ -92,7 +93,7 @@ TEST_P(MultithreadingTest, MakeCurrentMultiContext)
     std::array<std::thread, kThreadCount> threads;
     for (size_t thread = 0; thread < kThreadCount; thread++)
     {
-        threads[thread] = std::thread([&]() {
+        threads[thread] = std::thread([&, thread]() {
             EGLSurface pbuffer= EGL_NO_SURFACE;
             EGLConfig ctx= EGL_NO_CONTEXT;
 
@@ -102,7 +103,6 @@ TEST_P(MultithreadingTest, MakeCurrentMultiContext)
                 // Initialize the pbuffer and context
                 EGLint pbufferAttributes[] = {
                     EGL_WIDTH,          kPBufferSize,     EGL_HEIGHT,         kPBufferSize,
-                    EGL_TEXTURE_FORMAT, EGL_TEXTURE_RGBA, EGL_TEXTURE_TARGET, EGL_TEXTURE_2D,
                     EGL_NONE,           EGL_NONE,
                 };
                 pbuffer = eglCreatePbufferSurface(dpy, config, pbufferAttributes);

src/tests/test_utils/ANGLETest.cpp

@@ -897,6 +897,11 @@ void ANGLETestBase::setContextProgramCacheEnabled(bool enabled)
     mEGLWindow->setContextProgramCacheEnabled(enabled);
 }
 
+void ANGLETestBase::setContextVirtualization(bool enabled)
+{
+    mEGLWindow->setContextVirtualization(enabled);
+}
+
 void ANGLETestBase::setDeferContextInit(bool enabled)
 {
     mDeferContextInit = enabled;

src/tests/test_utils/ANGLETest.h

@@ -341,6 +341,7 @@ class ANGLETestBase
     void setClientArraysEnabled(bool enabled);
     void setRobustResourceInit(bool enabled);
     void setContextProgramCacheEnabled(bool enabled);
+    void setContextVirtualization(bool enabled);
 
     // Some EGL extension tests would like to defer the Context init until the test body.
     void setDeferContextInit(bool enabled);

util/EGLWindow.cpp

@@ -127,6 +127,7 @@ EGLWindow::EGLWindow(EGLint glesMajorVersion,
       mSamples(-1),
       mDebugLayersEnabled(),
       mContextProgramCacheEnabled(),
+      mContextVirtualization(),
       mPlatformMethods(nullptr)
 {
 }
@@ -205,6 +206,12 @@ bool EGLWindow::initializeDisplayAndSurface(OSWindow *osWindow)
         displayAttributes.push_back(mDebugLayersEnabled.value() ? EGL_TRUE : EGL_FALSE);
     }
 
+    if (mContextVirtualization.valid())
+    {
+        displayAttributes.push_back(EGL_PLATFORM_ANGLE_CONTEXT_VIRTUALIZATION_ANGLE);
+        displayAttributes.push_back(mContextVirtualization.value() ? EGL_TRUE : EGL_FALSE);
+    }
+
     if (mPlatformMethods)
     {
         static_assert(sizeof(EGLAttrib) == sizeof(mPlatformMethods), "Unexpected pointer size");

util/EGLWindow.h

@@ -89,6 +89,7 @@ class ANGLE_EXPORT EGLWindow : angle::NonCopyable
         mPlatformMethods = platformMethods;
     }
     void setContextProgramCacheEnabled(bool enabled) { mContextProgramCacheEnabled = enabled; }
+    void setContextVirtualization(bool enabled) { mContextVirtualization = enabled; }
 
     static EGLBoolean FindEGLConfig(EGLDisplay dpy, const EGLint *attrib_list, EGLConfig *config);
 
@@ -162,6 +163,7 @@ class ANGLE_EXPORT EGLWindow : angle::NonCopyable
     EGLint mSamples;
     Optional<bool> mDebugLayersEnabled;
     Optional<bool> mContextProgramCacheEnabled;
+    Optional<bool> mContextVirtualization;
     angle::PlatformMethods *mPlatformMethods;
 };