C++ AttributeMap::get方法代码示例

egl::Error DisplayD3D::createWindowSurface(const egl::Config *configuration, EGLNativeWindowType window,
                                           const egl::AttributeMap &attribs, SurfaceImpl **outSurface)
{
    ASSERT(mRenderer != nullptr);

    EGLint width = attribs.get(EGL_WIDTH, 0);
    EGLint height = attribs.get(EGL_HEIGHT, 0);
    EGLint fixedSize = attribs.get(EGL_FIXED_SIZE_ANGLE, EGL_FALSE);

    if (!fixedSize)
    {
        width = -1;
        height = -1;
    }

    SurfaceD3D *surface = SurfaceD3D::createFromWindow(mRenderer, mDisplay, configuration, window, fixedSize,
                                                       width, height);
    egl::Error error = surface->initialize();
    if (error.isError())
    {
        SafeDelete(surface);
        return error;
    }

    *outSurface = surface;
    return egl::Error(EGL_SUCCESS);
}

EGLImageD3D::EGLImageD3D(RendererD3D *renderer,
                         EGLenum target,
                         egl::ImageSibling *buffer,
                         const egl::AttributeMap &attribs)
    : mRenderer(renderer), mBuffer(buffer), mAttachmentBuffer(nullptr), mRenderTarget(nullptr)
{
    ASSERT(renderer != nullptr);
    ASSERT(buffer != nullptr);

    if (egl::IsTextureTarget(target))
    {
        mAttachmentBuffer = GetImplAs<TextureD3D>(GetAs<gl::Texture>(buffer));
        mAttachmentTarget = gl::FramebufferAttachment::Target(
            GL_NONE, GetImageIndex(egl_gl::EGLImageTargetToGLTextureTarget(target),
                                   attribs.get(EGL_GL_TEXTURE_LEVEL_KHR, 0),
                                   attribs.get(EGL_GL_TEXTURE_ZOFFSET_KHR, 0)));
    }
    else if (egl::IsRenderbufferTarget(target))
    {
        mAttachmentBuffer = GetImplAs<RenderbufferD3D>(GetAs<gl::Renderbuffer>(buffer));
        mAttachmentTarget =
            gl::FramebufferAttachment::Target(GL_NONE, gl::ImageIndex::MakeInvalid());
    }
    else
    {
        UNREACHABLE();
    }
}

egl::Error DisplayGL::createContext(const egl::Config *config, const gl::Context *shareContext, const egl::AttributeMap &attribs, gl::Context **outContext)
{
    ASSERT(mRenderer != nullptr);

    EGLint clientVersion = attribs.get(EGL_CONTEXT_CLIENT_VERSION, 1);
    bool notifyResets = (attribs.get(EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY_EXT, EGL_NO_RESET_NOTIFICATION_EXT) == EGL_LOSE_CONTEXT_ON_RESET_EXT);
    bool robustAccess = (attribs.get(EGL_CONTEXT_OPENGL_ROBUST_ACCESS_EXT, EGL_FALSE) == EGL_TRUE);

    *outContext = new gl::Context(config, clientVersion, shareContext, mRenderer, notifyResets, robustAccess);
    return egl::Error(EGL_SUCCESS);
}

RendererGL::RendererGL(const FunctionsGL *functions, const egl::AttributeMap &attribMap)
    : Renderer(),
      mMaxSupportedESVersion(0, 0),
      mFunctions(functions),
      mStateManager(nullptr),
      mBlitter(nullptr),
      mSkipDrawCalls(false)
{
    ASSERT(mFunctions);
    mStateManager = new StateManagerGL(mFunctions, getRendererCaps());
    nativegl_gl::GenerateWorkarounds(mFunctions, &mWorkarounds);
    mBlitter = new BlitGL(functions, mWorkarounds, mStateManager);

#ifndef NDEBUG
    if (mFunctions->debugMessageControl && mFunctions->debugMessageCallback)
    {
        mFunctions->enable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_HIGH, 0, nullptr, GL_TRUE);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_MEDIUM, 0, nullptr, GL_TRUE);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_LOW, 0, nullptr, GL_FALSE);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_NOTIFICATION, 0, nullptr, GL_FALSE);
        mFunctions->debugMessageCallback(&LogGLDebugMessage, nullptr);
    }
#endif

    EGLint deviceType = attribMap.get(EGL_PLATFORM_ANGLE_DEVICE_TYPE_ANGLE, EGL_NONE);
    if (deviceType == EGL_PLATFORM_ANGLE_DEVICE_TYPE_NULL_ANGLE)
    {
        mSkipDrawCalls = true;
    }
}

RendererGL::RendererGL(const FunctionsGL *functions, const egl::AttributeMap &attribMap)
    : mMaxSupportedESVersion(0, 0),
      mFunctions(functions),
      mStateManager(nullptr),
      mBlitter(nullptr),
      mMultiviewClearer(nullptr),
      mUseDebugOutput(false),
      mSkipDrawCalls(false),
      mCapsInitialized(false),
      mMultiviewImplementationType(MultiviewImplementationTypeGL::UNSPECIFIED)
{
    ASSERT(mFunctions);
    nativegl_gl::GenerateWorkarounds(mFunctions, &mWorkarounds);
    mStateManager = new StateManagerGL(mFunctions, getNativeCaps(), getNativeExtensions());
    mBlitter      = new BlitGL(functions, mWorkarounds, mStateManager);
    mMultiviewClearer = new ClearMultiviewGL(functions, mStateManager);

    bool hasDebugOutput = mFunctions->isAtLeastGL(gl::Version(4, 3)) ||
                          mFunctions->hasGLExtension("GL_KHR_debug") ||
                          mFunctions->isAtLeastGLES(gl::Version(3, 2)) ||
                          mFunctions->hasGLESExtension("GL_KHR_debug");

    mUseDebugOutput = hasDebugOutput && ShouldUseDebugLayers(attribMap);

    if (mUseDebugOutput)
    {
        mFunctions->enable(GL_DEBUG_OUTPUT);
        mFunctions->enable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_HIGH, 0,
                                        nullptr, GL_TRUE);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_MEDIUM, 0,
                                        nullptr, GL_TRUE);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_LOW, 0,
                                        nullptr, GL_FALSE);
        mFunctions->debugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DEBUG_SEVERITY_NOTIFICATION,
                                        0, nullptr, GL_FALSE);
        mFunctions->debugMessageCallback(&LogGLDebugMessage, nullptr);
    }

    EGLint deviceType =
        static_cast<EGLint>(attribMap.get(EGL_PLATFORM_ANGLE_DEVICE_TYPE_ANGLE, EGL_NONE));
    if (deviceType == EGL_PLATFORM_ANGLE_DEVICE_TYPE_NULL_ANGLE)
    {
        mSkipDrawCalls = true;
    }

    if (mWorkarounds.initializeCurrentVertexAttributes)
    {
        GLint maxVertexAttribs = 0;
        mFunctions->getIntegerv(GL_MAX_VERTEX_ATTRIBS, &maxVertexAttribs);

        for (GLint i = 0; i < maxVertexAttribs; ++i)
        {
            mFunctions->vertexAttrib4f(i, 0.0f, 0.0f, 0.0f, 1.0f);
        }
    }
}

bool ShouldUseDebugLayers(const egl::AttributeMap &attribs)
{
    EGLAttrib debugSetting =
        attribs.get(EGL_PLATFORM_ANGLE_DEBUG_LAYERS_ENABLED_ANGLE, EGL_DONT_CARE);

// Prefer to enable debug layers if compiling in Debug, and disabled in Release.
#if defined(ANGLE_ENABLE_ASSERTS)
    return (debugSetting != EGL_FALSE);
#else
    return (debugSetting == EGL_TRUE);
#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);
    }
}

ImageEGL::ImageEGL(const egl::ImageState &state,
                   const gl::Context *context,
                   EGLenum target,
                   const egl::AttributeMap &attribs,
                   const FunctionsEGL *egl)
    : ImageGL(state),
      mEGL(egl),
      mContext(EGL_NO_CONTEXT),
      mTarget(target),
      mPreserveImage(false),
      mImage(EGL_NO_IMAGE)
{
    if (context)
    {
        mContext = GetImplAs<ContextEGL>(context)->getContext();
    }
    mPreserveImage = attribs.get(EGL_IMAGE_PRESERVED, EGL_FALSE) == EGL_TRUE;
}

egl::Error DisplayGLX::initializeContext(glx::FBConfig config,
                                         const egl::AttributeMap &eglAttributes,
                                         glx::Context *context)
{
    int profileMask = 0;

    EGLint requestedDisplayType =
        eglAttributes.get(EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE);
    if (requestedDisplayType == EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE)
    {
        if (!mHasEXTCreateContextES2Profile)
        {
            return egl::Error(EGL_NOT_INITIALIZED,
                              "Cannot create an OpenGL ES platform on GLX without the "
                              "GLX_EXT_create_context_es_profile extension.");
        }

        ASSERT(mHasARBCreateContextProfile);
        profileMask |= GLX_CONTEXT_ES2_PROFILE_BIT_EXT;
    }

    // Create a context of the requested version, if any.
    gl::Version requestedVersion(
        eglAttributes.get(EGL_PLATFORM_ANGLE_MAX_VERSION_MAJOR_ANGLE, EGL_DONT_CARE),
        eglAttributes.get(EGL_PLATFORM_ANGLE_MAX_VERSION_MINOR_ANGLE, EGL_DONT_CARE));
    if (static_cast<EGLint>(requestedVersion.major) != EGL_DONT_CARE &&
        static_cast<EGLint>(requestedVersion.minor) != EGL_DONT_CARE)
    {
        if (!(profileMask & GLX_CONTEXT_ES2_PROFILE_BIT_EXT) &&
            requestedVersion >= gl::Version(3, 2))
        {
            profileMask |= GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
        }
        return createContextAttribs(config, requestedVersion, profileMask, context);
    }

    // It is commonly assumed that glXCreateContextAttrib will create a context
    // of the highest version possible but it is not specified in the spec and
    // is not true on the Mesa drivers. Instead we try to create a context per
    // GL version until we succeed, starting from newer version. When the default
    // platform is selected, if no desktop context can be created, we fallback to
    // an ES context.
    // clang-format off
    const gl::Version desktopVersionsFrom3_2[] = {
        gl::Version(4, 5),
        gl::Version(4, 4),
        gl::Version(4, 3),
        gl::Version(4, 2),
        gl::Version(4, 1),
        gl::Version(4, 0),
        gl::Version(3, 3),
        gl::Version(3, 2),
    };
    const gl::Version desktopVersionsPre3_2[] = {
        gl::Version(3, 1),
        gl::Version(3, 0),
        gl::Version(2, 0),
        gl::Version(1, 5),
        gl::Version(1, 4),
        gl::Version(1, 3),
        gl::Version(1, 2),
        gl::Version(1, 1),
        gl::Version(1, 0),
    };
    const gl::Version esVersionsFrom2_0[] = {
        gl::Version(3, 2),
        gl::Version(3, 1),
        gl::Version(3, 0),
        gl::Version(2, 0),
    };
    // clang-format on

    // NOTE: below we return as soon as we're able to create a context so the
    // "error" variable is EGL_SUCCESS when returned contrary to the common idiom
    // of returning "error" when there is an actual error.
    if (requestedDisplayType != EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE)
    {
        for (auto &version : desktopVersionsFrom3_2)
        {
            egl::Error error =
                createContextAttribs(config, version, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, context);
            if (!error.isError())
            {
                return error;
            }
        }
        for (auto &version : desktopVersionsPre3_2)
        {
            egl::Error error = createContextAttribs(config, version, 0, context);
            if (!error.isError())
            {
                return error;
            }
        }
    }

    if (requestedDisplayType != EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE)
    {
        for (auto &version : esVersionsFrom2_0)
        {
//.........这里部分代码省略.........

glx::Context DisplayGLX::initializeContext(glx::FBConfig config,
                                           const egl::AttributeMap &eglAttributes)
{
    // Create a context of the requested version, if any.
    EGLint requestedMajorVersion =
        eglAttributes.get(EGL_PLATFORM_ANGLE_MAX_VERSION_MAJOR_ANGLE, EGL_DONT_CARE);
    EGLint requestedMinorVersion =
        eglAttributes.get(EGL_PLATFORM_ANGLE_MAX_VERSION_MINOR_ANGLE, EGL_DONT_CARE);
    if (requestedMajorVersion != EGL_DONT_CARE && requestedMinorVersion != EGL_DONT_CARE)
    {
        std::vector<int> contextAttributes;
        contextAttributes.push_back(GLX_CONTEXT_MAJOR_VERSION_ARB);
        contextAttributes.push_back(requestedMajorVersion);

        contextAttributes.push_back(GLX_CONTEXT_MINOR_VERSION_ARB);
        contextAttributes.push_back(requestedMinorVersion);

        contextAttributes.push_back(None);
        return createContextAttribs(config, contextAttributes);
    }

    // It is commonly assumed that glXCreateContextAttrib will create a context
    // of the highest version possible but it is not specified in the spec and
    // is not true on the Mesa drivers. Instead we try to create a context per
    // desktop GL version until we succeed, starting from newer version.
    // clang-format off
    const gl::Version desktopVersions[] = {
        gl::Version(4, 5),
        gl::Version(4, 4),
        gl::Version(4, 3),
        gl::Version(4, 2),
        gl::Version(4, 1),
        gl::Version(4, 0),
        gl::Version(3, 3),
        gl::Version(3, 2),
        gl::Version(3, 1),
        gl::Version(3, 0),
        gl::Version(2, 0),
        gl::Version(1, 5),
        gl::Version(1, 4),
        gl::Version(1, 3),
        gl::Version(1, 2),
        gl::Version(1, 1),
        gl::Version(1, 0),
    };
    // clang-format on

    bool useProfile = mGLX.hasExtension("GLX_ARB_create_context_profile");
    for (size_t i = 0; i < ArraySize(desktopVersions); ++i)
    {
        const auto &version = desktopVersions[i];

        std::vector<int> contextAttributes;
        contextAttributes.push_back(GLX_CONTEXT_MAJOR_VERSION_ARB);
        contextAttributes.push_back(version.major);

        contextAttributes.push_back(GLX_CONTEXT_MINOR_VERSION_ARB);
        contextAttributes.push_back(version.minor);

        if (useProfile && version >= gl::Version(3, 2))
        {
            contextAttributes.push_back(GLX_CONTEXT_PROFILE_MASK_ARB);
            contextAttributes.push_back(GLX_CONTEXT_CORE_PROFILE_BIT_ARB);
        }

        contextAttributes.push_back(None);
        auto context = createContextAttribs(config, contextAttributes);

        if (context)
        {
            return context;
        }
    }

    return nullptr;
}

egl::Error DisplayGLX::initializeContext(glx::FBConfig config,
                                         const egl::AttributeMap &eglAttributes,
                                         glx::Context *context)
{
    int profileMask = 0;

    EGLint requestedDisplayType = static_cast<EGLint>(
        eglAttributes.get(EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE));
    if (requestedDisplayType == EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE)
    {
        if (!mHasEXTCreateContextES2Profile)
        {
            return egl::Error(EGL_NOT_INITIALIZED,
                              "Cannot create an OpenGL ES platform on GLX without the "
                              "GLX_EXT_create_context_es_profile extension.");
        }

        ASSERT(mHasARBCreateContextProfile);
        profileMask |= GLX_CONTEXT_ES2_PROFILE_BIT_EXT;
    }

    // Create a context of the requested version, if any.
    gl::Version requestedVersion(static_cast<EGLint>(eglAttributes.get(
                                     EGL_PLATFORM_ANGLE_MAX_VERSION_MAJOR_ANGLE, EGL_DONT_CARE)),
                                 static_cast<EGLint>(eglAttributes.get(
                                     EGL_PLATFORM_ANGLE_MAX_VERSION_MINOR_ANGLE, EGL_DONT_CARE)));
    if (static_cast<EGLint>(requestedVersion.major) != EGL_DONT_CARE &&
        static_cast<EGLint>(requestedVersion.minor) != EGL_DONT_CARE)
    {
        if (!(profileMask & GLX_CONTEXT_ES2_PROFILE_BIT_EXT) &&
            requestedVersion >= gl::Version(3, 2))
        {
            profileMask |= GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
        }
        return createContextAttribs(config, requestedVersion, profileMask, context);
    }

    // It is commonly assumed that glXCreateContextAttrib will create a context
    // of the highest version possible but it is not specified in the spec and
    // is not true on the Mesa drivers. On Mesa, Instead we try to create a
    // context per GL version until we succeed, starting from newer version.
    // On both Mesa and other drivers we try to create a desktop context and fall
    // back to ES context.
    // The code could be simpler if the Mesa code path was used for all drivers,
    // however the cost of failing a context creation can be high (3 milliseconds
    // for the NVIDIA driver). The good thing is that failed context creation only
    // takes 0.1 milliseconds on Mesa.

    struct ContextCreationInfo
    {
        EGLint displayType;
        int profileFlag;
        Optional<gl::Version> version;
    };

    // clang-format off
    // For regular drivers we try to create a core, compatibility, then ES context.
    // Without requiring any specific version (the Optional version is undefined).
    const ContextCreationInfo contextsToTry[] = {
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, {} },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, {} },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE, GLX_CONTEXT_ES2_PROFILE_BIT_EXT, {} },
    };

    // On Mesa we try to create a core context, except for versions below 3.2
    // where it is not applicable. (and fallback to ES as well)
    const ContextCreationInfo mesaContextsToTry[] = {
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(4, 5) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(4, 4) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(4, 3) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(4, 2) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(4, 1) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(4, 0) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(3, 3) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, GLX_CONTEXT_CORE_PROFILE_BIT_ARB, { gl::Version(3, 2) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(3, 1) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(3, 0) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(2, 0) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(1, 5) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(1, 4) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(1, 3) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(1, 2) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(1, 1) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE, 0, { gl::Version(1, 0) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE, GLX_CONTEXT_ES2_PROFILE_BIT_EXT, { gl::Version(3, 2) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE, GLX_CONTEXT_ES2_PROFILE_BIT_EXT, { gl::Version(3, 1) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE, GLX_CONTEXT_ES2_PROFILE_BIT_EXT, { gl::Version(3, 0) } },
        { EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE, GLX_CONTEXT_ES2_PROFILE_BIT_EXT, { gl::Version(2, 0) } },
    };
    // clang-format on

    const ContextCreationInfo *toTry = contextsToTry;
    size_t toTryLength = ArraySize(contextsToTry);
    if (mIsMesa)
    {
        toTry       = mesaContextsToTry;
        toTryLength = ArraySize(mesaContextsToTry);
    }

    // NOTE: below we return as soon as we're able to create a context so the
//.........这里部分代码省略.........

egl::Error DisplayGLX::initializeContext(glx::FBConfig config,
                                         const egl::AttributeMap &eglAttributes,
                                         glx::Context *context)
{
    int profileMask = 0;

    EGLint requestedDisplayType = static_cast<EGLint>(
        eglAttributes.get(EGL_PLATFORM_ANGLE_TYPE_ANGLE, EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE));
    if (requestedDisplayType == EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE)
    {
        if (!mHasEXTCreateContextES2Profile)
        {
            return egl::EglNotInitialized() << "Cannot create an OpenGL ES platform on GLX without "
                                               "the GLX_EXT_create_context_es_profile extension.";
        }

        ASSERT(mHasARBCreateContextProfile);
        profileMask |= GLX_CONTEXT_ES2_PROFILE_BIT_EXT;
    }

    // Create a context of the requested version, if any.
    gl::Version requestedVersion(static_cast<EGLint>(eglAttributes.get(
                                     EGL_PLATFORM_ANGLE_MAX_VERSION_MAJOR_ANGLE, EGL_DONT_CARE)),
                                 static_cast<EGLint>(eglAttributes.get(
                                     EGL_PLATFORM_ANGLE_MAX_VERSION_MINOR_ANGLE, EGL_DONT_CARE)));
    if (static_cast<EGLint>(requestedVersion.major) != EGL_DONT_CARE &&
        static_cast<EGLint>(requestedVersion.minor) != EGL_DONT_CARE)
    {
        if (!(profileMask & GLX_CONTEXT_ES2_PROFILE_BIT_EXT) &&
            requestedVersion >= gl::Version(3, 2))
        {
            profileMask |= GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
        }
        return createContextAttribs(config, requestedVersion, profileMask, context);
    }

    // The only way to get a core profile context of the highest version using
    // glXCreateContextAttrib is to try creationg contexts in decreasing version
    // numbers. It might look that asking for a core context of version (0, 0)
    // works on some driver but it create a _compatibility_ context of the highest
    // version instead. The cost of failing a context creation is small (< 0.1 ms)
    // on Mesa but is unfortunately a bit expensive on the Nvidia driver (~3ms).
    // Also try to get any Desktop GL context, but if that fails fallback to
    // asking for OpenGL ES contexts.

    // NOTE: below we return as soon as we're able to create a context so the
    // "error" variable is EGL_SUCCESS when returned contrary to the common idiom
    // of returning "error" when there is an actual error.
    for (const auto &info : GenerateContextCreationToTry(requestedDisplayType, mIsMesa))
    {
        int profileFlag = 0;
        if (info.type == ContextCreationTry::Type::DESKTOP_CORE)
        {
            profileFlag |= GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
        }
        else if (info.type == ContextCreationTry::Type::ES)
        {
            profileFlag |= GLX_CONTEXT_ES2_PROFILE_BIT_EXT;
        }

        egl::Error error = createContextAttribs(config, info.version, profileFlag, context);
        if (!error.isError())
        {
            return error;
        }
    }

    return egl::EglNotInitialized() << "Could not create a backing OpenGL context.";
}