Exemplo n.º 1
0
JS::Value
WebGLContext::GetParameter(JSContext* cx, GLenum pname, ErrorResult& rv)
{
    if (IsContextLost())
        return JS::NullValue();

    MakeContextCurrent();

    if (MinCapabilityMode()) {
        switch(pname) {
            ////////////////////////////
            // Single-value params

            // int
            case LOCAL_GL_MAX_VERTEX_ATTRIBS:
                return JS::Int32Value(MINVALUE_GL_MAX_VERTEX_ATTRIBS);

            case LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS:
                return JS::Int32Value(MINVALUE_GL_MAX_FRAGMENT_UNIFORM_VECTORS);

            case LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS:
                return JS::Int32Value(MINVALUE_GL_MAX_VERTEX_UNIFORM_VECTORS);

            case LOCAL_GL_MAX_VARYING_VECTORS:
                return JS::Int32Value(MINVALUE_GL_MAX_VARYING_VECTORS);

            case LOCAL_GL_MAX_TEXTURE_SIZE:
                return JS::Int32Value(MINVALUE_GL_MAX_TEXTURE_SIZE);

            case LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE:
                return JS::Int32Value(MINVALUE_GL_MAX_CUBE_MAP_TEXTURE_SIZE);

            case LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS:
                return JS::Int32Value(MINVALUE_GL_MAX_TEXTURE_IMAGE_UNITS);

            case LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS:
                return JS::Int32Value(MINVALUE_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS);

            case LOCAL_GL_MAX_RENDERBUFFER_SIZE:
                return JS::Int32Value(MINVALUE_GL_MAX_RENDERBUFFER_SIZE);

            default:
                // Return the real value; we're not overriding this one
                break;
        }
    }

    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_draw_buffers)) {
        if (pname == LOCAL_GL_MAX_COLOR_ATTACHMENTS) {
            return JS::Int32Value(mGLMaxColorAttachments);

        } else if (pname == LOCAL_GL_MAX_DRAW_BUFFERS) {
            return JS::Int32Value(mGLMaxDrawBuffers);

        } else if (pname >= LOCAL_GL_DRAW_BUFFER0 &&
                   pname < GLenum(LOCAL_GL_DRAW_BUFFER0 + mGLMaxDrawBuffers))
        {
            GLint iv = 0;
            gl->fGetIntegerv(pname, &iv);

            if (mBoundDrawFramebuffer)
                return JS::Int32Value(iv);

            const GLint index = (pname - LOCAL_GL_DRAW_BUFFER0);
            if (iv == LOCAL_GL_COLOR_ATTACHMENT0 + index)
                return JS::Int32Value(LOCAL_GL_BACK);

            return JS::Int32Value(LOCAL_GL_NONE);
        }
    }

    if (IsExtensionEnabled(WebGLExtensionID::OES_vertex_array_object)) {
        if (pname == LOCAL_GL_VERTEX_ARRAY_BINDING) {
            WebGLVertexArray* vao =
                (mBoundVertexArray != mDefaultVertexArray) ? mBoundVertexArray.get() : nullptr;
            return WebGLObjectAsJSValue(cx, vao, rv);
        }
    }

    if (IsExtensionEnabled(WebGLExtensionID::EXT_disjoint_timer_query)) {
        if (pname == LOCAL_GL_TIMESTAMP_EXT) {
            GLuint64 iv = 0;
            gl->fGetInteger64v(pname, (GLint64*) &iv);
            // TODO: JS doesn't support 64-bit integers. Be lossy and
            // cast to double (53 bits)
            return JS::NumberValue(static_cast<double>(iv));
        } else if (pname == LOCAL_GL_GPU_DISJOINT_EXT) {
            // When disjoint isn't supported, leave as false.
            realGLboolean disjoint = LOCAL_GL_FALSE;
            if (gl->IsExtensionSupported(gl::GLContext::EXT_disjoint_timer_query)) {
                gl->fGetBooleanv(pname, &disjoint);
            }
            return JS::BooleanValue(bool(disjoint));
        }
    }

    // Privileged string params exposed by WEBGL_debug_renderer_info.
    // The privilege check is done in WebGLContext::IsExtensionSupported.
    // So here we just have to check that the extension is enabled.
    if (IsExtensionEnabled(WebGLExtensionID::WEBGL_debug_renderer_info)) {
        switch (pname) {
        case UNMASKED_VENDOR_WEBGL:
        case UNMASKED_RENDERER_WEBGL:
            {
                const char* overridePref = nullptr;
                GLenum driverEnum = LOCAL_GL_NONE;

                switch (pname) {
                case UNMASKED_RENDERER_WEBGL:
                    overridePref = "webgl.renderer-string-override";
                    driverEnum = LOCAL_GL_RENDERER;
                    break;
                case UNMASKED_VENDOR_WEBGL:
                    overridePref = "webgl.vendor-string-override";
                    driverEnum = LOCAL_GL_VENDOR;
                    break;
                default:
                    MOZ_CRASH("bad `pname`");
                }

                bool hasRetVal = false;

                nsAutoString ret;
                if (overridePref) {
                    nsresult res = Preferences::GetString(overridePref, &ret);
                    if (NS_SUCCEEDED(res) && ret.Length() > 0)
                        hasRetVal = true;
                }

                if (!hasRetVal) {
                    const char* chars = reinterpret_cast<const char*>(gl->fGetString(driverEnum));
                    ret = NS_ConvertASCIItoUTF16(chars);
                    hasRetVal = true;
                }

                return StringValue(cx, ret, rv);
            }
        }
    }

    if (IsExtensionEnabled(WebGLExtensionID::OES_standard_derivatives)) {
        if (pname == LOCAL_GL_FRAGMENT_SHADER_DERIVATIVE_HINT) {
            GLint i = 0;
            gl->fGetIntegerv(pname, &i);
            return JS::Int32Value(i);
        }
    }

    if (IsExtensionEnabled(WebGLExtensionID::EXT_texture_filter_anisotropic)) {
        if (pname == LOCAL_GL_MAX_TEXTURE_MAX_ANISOTROPY_EXT) {
            GLfloat f = 0.f;
            gl->fGetFloatv(pname, &f);
            return JS::NumberValue(f);
        }
    }

    switch (pname) {
        //
        // String params
        //
        case LOCAL_GL_VENDOR:
        case LOCAL_GL_RENDERER:
            return StringValue(cx, "Mozilla", rv);
        case LOCAL_GL_VERSION:
            return StringValue(cx, "WebGL 1.0", rv);
        case LOCAL_GL_SHADING_LANGUAGE_VERSION:
            return StringValue(cx, "WebGL GLSL ES 1.0", rv);

        ////////////////////////////////
        // Single-value params

        // unsigned int
        case LOCAL_GL_CULL_FACE_MODE:
        case LOCAL_GL_FRONT_FACE:
        case LOCAL_GL_ACTIVE_TEXTURE:
        case LOCAL_GL_STENCIL_FUNC:
        case LOCAL_GL_STENCIL_FAIL:
        case LOCAL_GL_STENCIL_PASS_DEPTH_FAIL:
        case LOCAL_GL_STENCIL_PASS_DEPTH_PASS:
        case LOCAL_GL_STENCIL_BACK_FUNC:
        case LOCAL_GL_STENCIL_BACK_FAIL:
        case LOCAL_GL_STENCIL_BACK_PASS_DEPTH_FAIL:
        case LOCAL_GL_STENCIL_BACK_PASS_DEPTH_PASS:
        case LOCAL_GL_DEPTH_FUNC:
        case LOCAL_GL_BLEND_SRC_RGB:
        case LOCAL_GL_BLEND_SRC_ALPHA:
        case LOCAL_GL_BLEND_DST_RGB:
        case LOCAL_GL_BLEND_DST_ALPHA:
        case LOCAL_GL_BLEND_EQUATION_RGB:
        case LOCAL_GL_BLEND_EQUATION_ALPHA:
        case LOCAL_GL_GENERATE_MIPMAP_HINT: {
            GLint i = 0;
            gl->fGetIntegerv(pname, &i);
            return JS::NumberValue(uint32_t(i));
        }
        case LOCAL_GL_IMPLEMENTATION_COLOR_READ_TYPE: {
            if (mBoundReadFramebuffer) {
                FBStatus status = mBoundReadFramebuffer->CheckFramebufferStatus();
                if (status != LOCAL_GL_FRAMEBUFFER_COMPLETE) {
                    ErrorInvalidOperation("getParameter: Read framebuffer must be"
                                          " complete before querying"
                                          " IMPLEMENTATION_COLOR_READ_TYPE.");
                    return JS::NullValue();
                }
            }

            GLint i = 0;
            if (gl->IsSupported(gl::GLFeature::ES2_compatibility)) {
                gl->fGetIntegerv(pname, &i);
            } else {
                i = LOCAL_GL_UNSIGNED_BYTE;
            }
            return JS::NumberValue(uint32_t(i));
        }
        case LOCAL_GL_IMPLEMENTATION_COLOR_READ_FORMAT: {
            if (mBoundReadFramebuffer) {
                FBStatus status = mBoundReadFramebuffer->CheckFramebufferStatus();
                if (status != LOCAL_GL_FRAMEBUFFER_COMPLETE) {
                    ErrorInvalidOperation("getParameter: Read framebuffer must be"
                                          " complete before querying"
                                          " IMPLEMENTATION_COLOR_READ_FORMAT.");
                    return JS::NullValue();
                }
            }

            GLint i = 0;
            if (gl->IsSupported(gl::GLFeature::ES2_compatibility)) {
                gl->fGetIntegerv(pname, &i);
            } else {
                i = LOCAL_GL_RGBA;
            }
            return JS::NumberValue(uint32_t(i));
        }
        // int
        case LOCAL_GL_STENCIL_REF:
        case LOCAL_GL_STENCIL_BACK_REF: {
            GLint stencilBits = 0;
            if (!GetStencilBits(&stencilBits))
                return JS::NullValue();

            // Assuming stencils have 8 bits
            const GLint stencilMask = (1 << stencilBits) - 1;

            GLint refValue = 0;
            gl->fGetIntegerv(pname, &refValue);

            return JS::Int32Value(refValue & stencilMask);
        }
        case LOCAL_GL_STENCIL_BITS: {
            GLint stencilBits = 0;
            GetStencilBits(&stencilBits);
            return JS::Int32Value(stencilBits);
        }
        case LOCAL_GL_STENCIL_CLEAR_VALUE:
        case LOCAL_GL_UNPACK_ALIGNMENT:
        case LOCAL_GL_PACK_ALIGNMENT:
        case LOCAL_GL_SUBPIXEL_BITS:
        case LOCAL_GL_SAMPLE_BUFFERS:
        case LOCAL_GL_SAMPLES:
        case LOCAL_GL_MAX_VERTEX_ATTRIBS:
        case LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS:
        case LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS:
        case LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS:
        case LOCAL_GL_RED_BITS:
        case LOCAL_GL_GREEN_BITS:
        case LOCAL_GL_BLUE_BITS:
        case LOCAL_GL_DEPTH_BITS: {
            GLint i = 0;
            gl->fGetIntegerv(pname, &i);
            return JS::Int32Value(i);
        }
        case LOCAL_GL_ALPHA_BITS: {
            GLint i = 0;
            if (!mNeedsFakeNoAlpha) {
                gl->fGetIntegerv(pname, &i);
            }
            return JS::Int32Value(i);
        }
        case LOCAL_GL_MAX_TEXTURE_SIZE:
            return JS::Int32Value(mGLMaxTextureSize);

        case LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE:
            return JS::Int32Value(mGLMaxCubeMapTextureSize);

        case LOCAL_GL_MAX_RENDERBUFFER_SIZE:
            return JS::Int32Value(mGLMaxRenderbufferSize);

        case LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS:
            return JS::Int32Value(mGLMaxVertexUniformVectors);

        case LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS:
            return JS::Int32Value(mGLMaxFragmentUniformVectors);

        case LOCAL_GL_MAX_VARYING_VECTORS:
            return JS::Int32Value(mGLMaxVaryingVectors);

        case LOCAL_GL_NUM_COMPRESSED_TEXTURE_FORMATS:
            return JS::Int32Value(0);
        case LOCAL_GL_COMPRESSED_TEXTURE_FORMATS: {
            uint32_t length = mCompressedTextureFormats.Length();
            JSObject* obj = dom::Uint32Array::Create(cx, this, length,
                                                     mCompressedTextureFormats.Elements());
            if (!obj) {
                rv = NS_ERROR_OUT_OF_MEMORY;
            }
            return JS::ObjectOrNullValue(obj);
        }

        // unsigned int. here we may have to return very large values like 2^32-1 that can't be represented as
        // javascript integer values. We just return them as doubles and javascript doesn't care.
        case LOCAL_GL_STENCIL_BACK_VALUE_MASK:
            return JS::DoubleValue(mStencilValueMaskBack); // pass as FP value to allow large values such as 2^32-1.

        case LOCAL_GL_STENCIL_BACK_WRITEMASK:
            return JS::DoubleValue(mStencilWriteMaskBack);

        case LOCAL_GL_STENCIL_VALUE_MASK:
            return JS::DoubleValue(mStencilValueMaskFront);

        case LOCAL_GL_STENCIL_WRITEMASK:
            return JS::DoubleValue(mStencilWriteMaskFront);

        // float
        case LOCAL_GL_DEPTH_CLEAR_VALUE:
        case LOCAL_GL_LINE_WIDTH:
        case LOCAL_GL_POLYGON_OFFSET_FACTOR:
        case LOCAL_GL_POLYGON_OFFSET_UNITS:
        case LOCAL_GL_SAMPLE_COVERAGE_VALUE: {
            GLfloat f = 0.f;
            gl->fGetFloatv(pname, &f);
            return JS::DoubleValue(f);
        }

        // bool
        case LOCAL_GL_BLEND:
        case LOCAL_GL_DEPTH_TEST:
        case LOCAL_GL_STENCIL_TEST:
        case LOCAL_GL_CULL_FACE:
        case LOCAL_GL_DITHER:
        case LOCAL_GL_POLYGON_OFFSET_FILL:
        case LOCAL_GL_SCISSOR_TEST:
        case LOCAL_GL_SAMPLE_COVERAGE_INVERT:
        case LOCAL_GL_DEPTH_WRITEMASK: {
            realGLboolean b = 0;
            gl->fGetBooleanv(pname, &b);
            return JS::BooleanValue(bool(b));
        }

        // bool, WebGL-specific
        case UNPACK_FLIP_Y_WEBGL:
            return JS::BooleanValue(mPixelStoreFlipY);
        case UNPACK_PREMULTIPLY_ALPHA_WEBGL:
            return JS::BooleanValue(mPixelStorePremultiplyAlpha);

        // uint, WebGL-specific
        case UNPACK_COLORSPACE_CONVERSION_WEBGL:
            return JS::NumberValue(uint32_t(mPixelStoreColorspaceConversion));

        ////////////////////////////////
        // Complex values

        // 2 floats
        case LOCAL_GL_DEPTH_RANGE:
        case LOCAL_GL_ALIASED_POINT_SIZE_RANGE:
        case LOCAL_GL_ALIASED_LINE_WIDTH_RANGE: {
            GLfloat fv[2] = { 0 };
            gl->fGetFloatv(pname, fv);
            JSObject* obj = dom::Float32Array::Create(cx, this, 2, fv);
            if (!obj) {
                rv = NS_ERROR_OUT_OF_MEMORY;
            }
            return JS::ObjectOrNullValue(obj);
        }

        // 4 floats
        case LOCAL_GL_COLOR_CLEAR_VALUE:
        case LOCAL_GL_BLEND_COLOR: {
            GLfloat fv[4] = { 0 };
            gl->fGetFloatv(pname, fv);
            JSObject* obj = dom::Float32Array::Create(cx, this, 4, fv);
            if (!obj) {
                rv = NS_ERROR_OUT_OF_MEMORY;
            }
            return JS::ObjectOrNullValue(obj);
        }

        // 2 ints
        case LOCAL_GL_MAX_VIEWPORT_DIMS: {
            GLint iv[2] = { 0 };
            gl->fGetIntegerv(pname, iv);
            JSObject* obj = dom::Int32Array::Create(cx, this, 2, iv);
            if (!obj) {
                rv = NS_ERROR_OUT_OF_MEMORY;
            }
            return JS::ObjectOrNullValue(obj);
        }

        // 4 ints
        case LOCAL_GL_SCISSOR_BOX:
        case LOCAL_GL_VIEWPORT: {
            GLint iv[4] = { 0 };
            gl->fGetIntegerv(pname, iv);
            JSObject* obj = dom::Int32Array::Create(cx, this, 4, iv);
            if (!obj) {
                rv = NS_ERROR_OUT_OF_MEMORY;
            }
            return JS::ObjectOrNullValue(obj);
        }

        // 4 bools
        case LOCAL_GL_COLOR_WRITEMASK: {
            realGLboolean gl_bv[4] = { 0 };
            gl->fGetBooleanv(pname, gl_bv);
            bool vals[4] = { bool(gl_bv[0]), bool(gl_bv[1]),
                             bool(gl_bv[2]), bool(gl_bv[3]) };
            JS::Rooted<JS::Value> arr(cx);
            if (!dom::ToJSValue(cx, vals, &arr)) {
                rv = NS_ERROR_OUT_OF_MEMORY;
            }
            return arr;
        }

        case LOCAL_GL_ARRAY_BUFFER_BINDING: {
            return WebGLObjectAsJSValue(cx, mBoundArrayBuffer.get(), rv);
        }

        case LOCAL_GL_ELEMENT_ARRAY_BUFFER_BINDING: {
            return WebGLObjectAsJSValue(cx, mBoundVertexArray->mElementArrayBuffer.get(), rv);
        }

        case LOCAL_GL_RENDERBUFFER_BINDING: {
            return WebGLObjectAsJSValue(cx, mBoundRenderbuffer.get(), rv);
        }

        // DRAW_FRAMEBUFFER_BINDING is the same as FRAMEBUFFER_BINDING.
        case LOCAL_GL_FRAMEBUFFER_BINDING: {
            return WebGLObjectAsJSValue(cx, mBoundDrawFramebuffer.get(), rv);
        }

        case LOCAL_GL_CURRENT_PROGRAM: {
            return WebGLObjectAsJSValue(cx, mCurrentProgram.get(), rv);
        }

        case LOCAL_GL_TEXTURE_BINDING_2D: {
            return WebGLObjectAsJSValue(cx, mBound2DTextures[mActiveTexture].get(), rv);
        }

        case LOCAL_GL_TEXTURE_BINDING_CUBE_MAP: {
            return WebGLObjectAsJSValue(cx, mBoundCubeMapTextures[mActiveTexture].get(), rv);
        }

        default:
            break;
    }

    ErrorInvalidEnumInfo("getParameter: parameter", pname);
    return JS::NullValue();
}
bool
WebGLContext::InitAndValidateGL()
{
    if (!gl)
        return false;

    // Unconditionally create a new format usage authority. This is
    // important when restoring contexts and extensions need to add
    // formats back into the authority.
    mFormatUsage = CreateFormatUsage(gl);
    if (!mFormatUsage)
        return false;

    GLenum error = gl->fGetError();
    if (error != LOCAL_GL_NO_ERROR) {
        GenerateWarning("GL error 0x%x occurred during OpenGL context"
                        " initialization, before WebGL initialization!", error);
        return false;
    }

    mMinCapability = gfxPrefs::WebGLMinCapabilityMode();
    mDisableExtensions = gfxPrefs::WebGLDisableExtensions();
    mLoseContextOnMemoryPressure = gfxPrefs::WebGLLoseContextOnMemoryPressure();
    mCanLoseContextInForeground = gfxPrefs::WebGLCanLoseContextInForeground();
    mRestoreWhenVisible = gfxPrefs::WebGLRestoreWhenVisible();

    if (MinCapabilityMode())
        mDisableFragHighP = true;

    // These are the default values, see 6.2 State tables in the
    // OpenGL ES 2.0.25 spec.
    mColorWriteMask[0] = 1;
    mColorWriteMask[1] = 1;
    mColorWriteMask[2] = 1;
    mColorWriteMask[3] = 1;
    mDepthWriteMask = 1;
    mColorClearValue[0] = 0.f;
    mColorClearValue[1] = 0.f;
    mColorClearValue[2] = 0.f;
    mColorClearValue[3] = 0.f;
    mDepthClearValue = 1.f;
    mStencilClearValue = 0;
    mStencilRefFront = 0;
    mStencilRefBack = 0;

    /*
    // Technically, we should be setting mStencil[...] values to
    // `allOnes`, but either ANGLE breaks or the SGX540s on Try break.
    GLuint stencilBits = 0;
    gl->GetUIntegerv(LOCAL_GL_STENCIL_BITS, &stencilBits);
    GLuint allOnes = ~(UINT32_MAX << stencilBits);
    mStencilValueMaskFront = allOnes;
    mStencilValueMaskBack  = allOnes;
    mStencilWriteMaskFront = allOnes;
    mStencilWriteMaskBack  = allOnes;
    */

    gl->GetUIntegerv(LOCAL_GL_STENCIL_VALUE_MASK,      &mStencilValueMaskFront);
    gl->GetUIntegerv(LOCAL_GL_STENCIL_BACK_VALUE_MASK, &mStencilValueMaskBack);
    gl->GetUIntegerv(LOCAL_GL_STENCIL_WRITEMASK,       &mStencilWriteMaskFront);
    gl->GetUIntegerv(LOCAL_GL_STENCIL_BACK_WRITEMASK,  &mStencilWriteMaskBack);

    AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_VALUE_MASK,      mStencilValueMaskFront);
    AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_BACK_VALUE_MASK, mStencilValueMaskBack);
    AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_WRITEMASK,       mStencilWriteMaskFront);
    AssertUintParamCorrect(gl, LOCAL_GL_STENCIL_BACK_WRITEMASK,  mStencilWriteMaskBack);

    mDitherEnabled = true;
    mRasterizerDiscardEnabled = false;
    mScissorTestEnabled = false;

    // Bindings, etc.
    mActiveTexture = 0;
    mDefaultFB_DrawBuffer0 = LOCAL_GL_BACK;

    mEmitContextLostErrorOnce = true;
    mWebGLError = LOCAL_GL_NO_ERROR;
    mUnderlyingGLError = LOCAL_GL_NO_ERROR;

    mBound2DTextures.Clear();
    mBoundCubeMapTextures.Clear();
    mBound3DTextures.Clear();
    mBound2DArrayTextures.Clear();
    mBoundSamplers.Clear();

    mBoundArrayBuffer = nullptr;
    mBoundTransformFeedbackBuffer = nullptr;
    mCurrentProgram = nullptr;

    mBoundDrawFramebuffer = nullptr;
    mBoundReadFramebuffer = nullptr;
    mBoundRenderbuffer = nullptr;

    MakeContextCurrent();

    // For OpenGL compat. profiles, we always keep vertex attrib 0 array enabled.
    if (gl->IsCompatibilityProfile())
        gl->fEnableVertexAttribArray(0);

    if (MinCapabilityMode())
        mGLMaxVertexAttribs = MINVALUE_GL_MAX_VERTEX_ATTRIBS;
    else
        gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_ATTRIBS, &mGLMaxVertexAttribs);

    if (mGLMaxVertexAttribs < 8) {
        GenerateWarning("GL_MAX_VERTEX_ATTRIBS: %d is < 8!",
                        mGLMaxVertexAttribs);
        return false;
    }

    // Note: GL_MAX_TEXTURE_UNITS is fixed at 4 for most desktop hardware,
    // even though the hardware supports much more.  The
    // GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS value is the accurate value.
    if (MinCapabilityMode())
        mGLMaxTextureUnits = MINVALUE_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS;
    else
        gl->fGetIntegerv(LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &mGLMaxTextureUnits);

    if (mGLMaxTextureUnits < 8) {
        GenerateWarning("GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS: %d is < 8!",
                        mGLMaxTextureUnits);
        return false;
    }

    mBound2DTextures.SetLength(mGLMaxTextureUnits);
    mBoundCubeMapTextures.SetLength(mGLMaxTextureUnits);
    mBound3DTextures.SetLength(mGLMaxTextureUnits);
    mBound2DArrayTextures.SetLength(mGLMaxTextureUnits);
    mBoundSamplers.SetLength(mGLMaxTextureUnits);

    ////////////////

    if (MinCapabilityMode()) {
        mImplMaxTextureSize = MINVALUE_GL_MAX_TEXTURE_SIZE;
        mImplMaxCubeMapTextureSize = MINVALUE_GL_MAX_CUBE_MAP_TEXTURE_SIZE;
        mImplMaxRenderbufferSize = MINVALUE_GL_MAX_RENDERBUFFER_SIZE;

        mImplMax3DTextureSize = MINVALUE_GL_MAX_3D_TEXTURE_SIZE;
        mImplMaxArrayTextureLayers = MINVALUE_GL_MAX_ARRAY_TEXTURE_LAYERS;

        mGLMaxTextureImageUnits = MINVALUE_GL_MAX_TEXTURE_IMAGE_UNITS;
        mGLMaxVertexTextureImageUnits = MINVALUE_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS;
    } else {
        gl->fGetIntegerv(LOCAL_GL_MAX_TEXTURE_SIZE, (GLint*)&mImplMaxTextureSize);
        gl->fGetIntegerv(LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE, (GLint*)&mImplMaxCubeMapTextureSize);
        gl->fGetIntegerv(LOCAL_GL_MAX_RENDERBUFFER_SIZE, (GLint*)&mImplMaxRenderbufferSize);

        if (!gl->GetPotentialInteger(LOCAL_GL_MAX_3D_TEXTURE_SIZE, (GLint*)&mImplMax3DTextureSize))
            mImplMax3DTextureSize = 0;
        if (!gl->GetPotentialInteger(LOCAL_GL_MAX_ARRAY_TEXTURE_LAYERS, (GLint*)&mImplMaxArrayTextureLayers))
            mImplMaxArrayTextureLayers = 0;

        gl->fGetIntegerv(LOCAL_GL_MAX_TEXTURE_IMAGE_UNITS, &mGLMaxTextureImageUnits);
        gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS, &mGLMaxVertexTextureImageUnits);
    }

    // If we don't support a target, its max size is 0. We should only floor-to-POT if the
    // value if it's non-zero. (NB log2(0) is -Inf, so zero isn't an integer power-of-two)
    const auto fnFloorPOTIfSupported = [](uint32_t& val) {
        if (val) {
            val = FloorPOT(val);
        }
    };

    fnFloorPOTIfSupported(mImplMaxTextureSize);
    fnFloorPOTIfSupported(mImplMaxCubeMapTextureSize);
    fnFloorPOTIfSupported(mImplMaxRenderbufferSize);

    fnFloorPOTIfSupported(mImplMax3DTextureSize);
    fnFloorPOTIfSupported(mImplMaxArrayTextureLayers);

    ////////////////

    mGLMaxColorAttachments = 1;
    mGLMaxDrawBuffers = 1;
    gl->GetPotentialInteger(LOCAL_GL_MAX_COLOR_ATTACHMENTS,
                            (GLint*)&mGLMaxColorAttachments);
    gl->GetPotentialInteger(LOCAL_GL_MAX_DRAW_BUFFERS, (GLint*)&mGLMaxDrawBuffers);

    if (MinCapabilityMode()) {
        mGLMaxColorAttachments = std::min(mGLMaxColorAttachments,
                                          kMinMaxColorAttachments);
        mGLMaxDrawBuffers = std::min(mGLMaxDrawBuffers, kMinMaxDrawBuffers);
    }

    if (IsWebGL2()) {
        mImplMaxColorAttachments = mGLMaxColorAttachments;
        mImplMaxDrawBuffers = std::min(mGLMaxDrawBuffers, mImplMaxColorAttachments);
    } else {
        mImplMaxColorAttachments = 1;
        mImplMaxDrawBuffers = 1;
    }

    ////////////////

    if (MinCapabilityMode()) {
        mGLMaxFragmentUniformVectors = MINVALUE_GL_MAX_FRAGMENT_UNIFORM_VECTORS;
        mGLMaxVertexUniformVectors = MINVALUE_GL_MAX_VERTEX_UNIFORM_VECTORS;
        mGLMaxVaryingVectors = MINVALUE_GL_MAX_VARYING_VECTORS;
    } else {
        if (gl->IsSupported(gl::GLFeature::ES2_compatibility)) {
            gl->fGetIntegerv(LOCAL_GL_MAX_FRAGMENT_UNIFORM_VECTORS, &mGLMaxFragmentUniformVectors);
            gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_UNIFORM_VECTORS, &mGLMaxVertexUniformVectors);
            gl->fGetIntegerv(LOCAL_GL_MAX_VARYING_VECTORS, &mGLMaxVaryingVectors);
        } else {
            gl->fGetIntegerv(LOCAL_GL_MAX_FRAGMENT_UNIFORM_COMPONENTS, &mGLMaxFragmentUniformVectors);
            mGLMaxFragmentUniformVectors /= 4;
            gl->fGetIntegerv(LOCAL_GL_MAX_VERTEX_UNIFORM_COMPONENTS, &mGLMaxVertexUniformVectors);
            mGLMaxVertexUniformVectors /= 4;

            /* We are now going to try to read GL_MAX_VERTEX_OUTPUT_COMPONENTS
             * and GL_MAX_FRAGMENT_INPUT_COMPONENTS, however these constants
             * only entered the OpenGL standard at OpenGL 3.2. So we will try
             * reading, and check OpenGL error for INVALID_ENUM.
             *
             * On the public_webgl list, "problematic GetParameter pnames"
             * thread, the following formula was given:
             *   maxVaryingVectors = min(GL_MAX_VERTEX_OUTPUT_COMPONENTS,
             *                           GL_MAX_FRAGMENT_INPUT_COMPONENTS) / 4
             */
            GLint maxVertexOutputComponents = 0;
            GLint maxFragmentInputComponents = 0;

            const bool ok = (gl->GetPotentialInteger(LOCAL_GL_MAX_VERTEX_OUTPUT_COMPONENTS,
                                                     &maxVertexOutputComponents) &&
                             gl->GetPotentialInteger(LOCAL_GL_MAX_FRAGMENT_INPUT_COMPONENTS,
                                                     &maxFragmentInputComponents));

            if (ok) {
                mGLMaxVaryingVectors = std::min(maxVertexOutputComponents,
                                                maxFragmentInputComponents) / 4;
            } else {
                mGLMaxVaryingVectors = 16;
                // 16 = 64/4, and 64 is the min value for
                // maxVertexOutputComponents in the OpenGL 3.2 spec.
            }
        }
    }

    if (gl->IsCompatibilityProfile()) {
        // gl_PointSize is always available in ES2 GLSL, but has to be
        // specifically enabled on desktop GLSL.
        gl->fEnable(LOCAL_GL_VERTEX_PROGRAM_POINT_SIZE);

        /* gl_PointCoord is always available in ES2 GLSL and in newer desktop
         * GLSL versions, but apparently not in OpenGL 2 and apparently not (due
         * to a driver bug) on certain NVIDIA setups. See:
         *   http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=261472
         *
         * Note that this used to cause crashes on old ATI drivers... Hopefully
         * not a significant anymore. See bug 602183.
         */
        gl->fEnable(LOCAL_GL_POINT_SPRITE);
    }

#ifdef XP_MACOSX
    if (gl->WorkAroundDriverBugs() &&
        gl->Vendor() == gl::GLVendor::ATI &&
        !nsCocoaFeatures::IsAtLeastVersion(10,9))
    {
        // The Mac ATI driver, in all known OSX version up to and including
        // 10.8, renders points sprites upside-down. (Apple bug 11778921)
        gl->fPointParameterf(LOCAL_GL_POINT_SPRITE_COORD_ORIGIN,
                             LOCAL_GL_LOWER_LEFT);
    }
#endif

    if (gl->IsSupported(gl::GLFeature::seamless_cube_map_opt_in)) {
        gl->fEnable(LOCAL_GL_TEXTURE_CUBE_MAP_SEAMLESS);
    }

    // Check the shader validator pref
    mBypassShaderValidation = gfxPrefs::WebGLBypassShaderValidator();

    // initialize shader translator
    if (!ShInitialize()) {
        GenerateWarning("GLSL translator initialization failed!");
        return false;
    }

    // Mesa can only be detected with the GL_VERSION string, of the form
    // "2.1 Mesa 7.11.0"
    const char* versionStr = (const char*)(gl->fGetString(LOCAL_GL_VERSION));
    mIsMesa = strstr(versionStr, "Mesa");

    // Notice that the point of calling fGetError here is not only to check for
    // errors, but also to reset the error flags so that a subsequent WebGL
    // getError call will give the correct result.
    error = gl->fGetError();
    if (error != LOCAL_GL_NO_ERROR) {
        GenerateWarning("GL error 0x%x occurred during WebGL context"
                        " initialization!", error);
        return false;
    }

    if (IsWebGL2() &&
        !InitWebGL2())
    {
        // Todo: Bug 898404: Only allow WebGL2 on GL>=3.0 on desktop GL.
        return false;
    }

    // Default value for all disabled vertex attributes is [0, 0, 0, 1]
    mVertexAttribType = MakeUnique<GLenum[]>(mGLMaxVertexAttribs);
    for (int32_t index = 0; index < mGLMaxVertexAttribs; ++index) {
        mVertexAttribType[index] = LOCAL_GL_FLOAT;
        VertexAttrib4f(index, 0, 0, 0, 1);
    }

    mDefaultVertexArray = WebGLVertexArray::Create(this);
    mDefaultVertexArray->mAttribs.SetLength(mGLMaxVertexAttribs);
    mBoundVertexArray = mDefaultVertexArray;

    // OpenGL core profiles remove the default VAO object from version
    // 4.0.0. We create a default VAO for all core profiles,
    // regardless of version.
    //
    // GL Spec 4.0.0:
    // (https://www.opengl.org/registry/doc/glspec40.core.20100311.pdf)
    // in Section E.2.2 "Removed Features", pg 397: "[...] The default
    // vertex array object (the name zero) is also deprecated. [...]"

    if (gl->IsCoreProfile()) {
        MakeContextCurrent();
        mDefaultVertexArray->GenVertexArray();
        mDefaultVertexArray->BindVertexArray();
    }

    mPixelStore_FlipY = false;
    mPixelStore_PremultiplyAlpha = false;
    mPixelStore_ColorspaceConversion = BROWSER_DEFAULT_WEBGL;

    // GLES 3.0.4, p259:
    mPixelStore_UnpackImageHeight = 0;
    mPixelStore_UnpackSkipImages = 0;
    mPixelStore_UnpackRowLength = 0;
    mPixelStore_UnpackSkipRows = 0;
    mPixelStore_UnpackSkipPixels = 0;
    mPixelStore_UnpackAlignment = 4;
    mPixelStore_PackRowLength = 0;
    mPixelStore_PackSkipRows = 0;
    mPixelStore_PackSkipPixels = 0;
    mPixelStore_PackAlignment = 4;

    return true;
}