/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef WEBGLCONTEXT_H_
#define WEBGLCONTEXT_H_

#include <stdarg.h>

#include "GLContextTypes.h"
#include "GLDefs.h"
#include "mozilla/Attributes.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/dom/BindingDeclarations.h"
#include "mozilla/dom/HTMLCanvasElement.h"
#include "mozilla/dom/TypedArray.h"
#include "mozilla/EnumeratedArray.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/LinkedList.h"
#include "mozilla/UniquePtr.h"
#include "nsCycleCollectionNoteChild.h"
#include "nsICanvasRenderingContextInternal.h"
#include "nsLayoutUtils.h"
#include "nsTArray.h"
#include "nsWrapperCache.h"
#include "SurfaceTypes.h"
#include "ScopedGLHelpers.h"
#include "TexUnpackBlob.h"

#ifdef XP_MACOSX
#include "ForceDiscreteGPUHelperCGL.h"
#endif

// Local
#include "WebGLContextLossHandler.h"
#include "WebGLContextUnchecked.h"
#include "WebGLFormats.h"
#include "WebGLObjectModel.h"
#include "WebGLStrongTypes.h"
#include "WebGLTexture.h"

// Generated
#include "nsIDOMEventListener.h"
#include "nsIDOMWebGLRenderingContext.h"
#include "nsICanvasRenderingContextInternal.h"
#include "nsIObserver.h"
#include "mozilla/dom/HTMLCanvasElement.h"
#include "nsWrapperCache.h"
#include "nsLayoutUtils.h"
#include "mozilla/dom/WebGLRenderingContextBinding.h"
#include "mozilla/dom/WebGL2RenderingContextBinding.h"

class nsIDocShell;

/*
 * Minimum value constants defined in 6.2 State Tables of OpenGL ES - 2.0.25
 *   https://bugzilla.mozilla.org/show_bug.cgi?id=686732
 *
 * Exceptions: some of the following values are set to higher values than in the spec because
 * the values in the spec are ridiculously low. They are explicitly marked below
 */
#define MINVALUE_GL_MAX_TEXTURE_SIZE                  1024  // Different from the spec, which sets it to 64 on page 162
#define MINVALUE_GL_MAX_CUBE_MAP_TEXTURE_SIZE         512   // Different from the spec, which sets it to 16 on page 162
#define MINVALUE_GL_MAX_VERTEX_ATTRIBS                8     // Page 164
#define MINVALUE_GL_MAX_FRAGMENT_UNIFORM_VECTORS      16    // Page 164
#define MINVALUE_GL_MAX_VERTEX_UNIFORM_VECTORS        128   // Page 164
#define MINVALUE_GL_MAX_VARYING_VECTORS               8     // Page 164
#define MINVALUE_GL_MAX_TEXTURE_IMAGE_UNITS           8     // Page 164
#define MINVALUE_GL_MAX_VERTEX_TEXTURE_IMAGE_UNITS    0     // Page 164
#define MINVALUE_GL_MAX_RENDERBUFFER_SIZE             1024  // Different from the spec, which sets it to 1 on page 164
#define MINVALUE_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS  8     // Page 164

/*
 * Minimum value constants define in 6.2 State Tables of OpenGL ES - 3.0.4
 */
#define MINVALUE_GL_MAX_3D_TEXTURE_SIZE             256
#define MINVALUE_GL_MAX_ARRAY_TEXTURE_LAYERS        256

/*
 * WebGL-only GLenums
 */
#define LOCAL_GL_BROWSER_DEFAULT_WEBGL                       0x9244
#define LOCAL_GL_CONTEXT_LOST_WEBGL                          0x9242
#define LOCAL_GL_MAX_CLIENT_WAIT_TIMEOUT_WEBGL               0x9247
#define LOCAL_GL_UNPACK_COLORSPACE_CONVERSION_WEBGL          0x9243
#define LOCAL_GL_UNPACK_FLIP_Y_WEBGL                         0x9240
#define LOCAL_GL_UNPACK_PREMULTIPLY_ALPHA_WEBGL              0x9241

namespace mozilla {
class ScopedCopyTexImageSource;
class ScopedResolveTexturesForDraw;
class ScopedUnpackReset;
class WebGLActiveInfo;
class WebGLBuffer;
class WebGLExtensionBase;
class WebGLFramebuffer;
class WebGLProgram;
class WebGLQuery;
class WebGLRenderbuffer;
class WebGLSampler;
class WebGLShader;
class WebGLShaderPrecisionFormat;
class WebGLSync;
class WebGLTexture;
class WebGLTransformFeedback;
class WebGLUniformLocation;
class WebGLVertexArray;

namespace dom {
class Element;
class ImageData;
class OwningHTMLCanvasElementOrOffscreenCanvas;
struct WebGLContextAttributes;
template<typename> struct Nullable;
} // namespace dom

namespace gfx {
class SourceSurface;
class VRLayerChild;
} // namespace gfx

namespace webgl {
struct LinkedProgramInfo;
class ShaderValidator;
class TexUnpackBlob;
struct UniformInfo;
struct UniformBlockInfo;
} // namespace webgl

WebGLTexelFormat GetWebGLTexelFormat(TexInternalFormat format);

void AssertUintParamCorrect(gl::GLContext* gl, GLenum pname, GLuint shadow);

struct WebGLContextOptions
{
    // these are defaults
    WebGLContextOptions();

    bool operator==(const WebGLContextOptions& other) const {
        return
            alpha == other.alpha &&
            depth == other.depth &&
            stencil == other.stencil &&
            premultipliedAlpha == other.premultipliedAlpha &&
            antialias == other.antialias &&
            preserveDrawingBuffer == other.preserveDrawingBuffer;
    }

    bool operator!=(const WebGLContextOptions& other) const {
        return !operator==(other);
    }

    bool alpha;
    bool depth;
    bool stencil;
    bool premultipliedAlpha;
    bool antialias;
    bool preserveDrawingBuffer;
    bool failIfMajorPerformanceCaveat;
};

// From WebGLContextUtils
TexTarget TexImageTargetToTexTarget(TexImageTarget texImageTarget);

struct WebGLIntOrFloat {
    const enum {
        Int,
        Float,
        Uint
    } mType;

    union {
        GLint i;
        GLfloat f;
        GLuint u;
    } mValue;

    explicit WebGLIntOrFloat(GLint i) : mType(Int) { mValue.i = i; }
    explicit WebGLIntOrFloat(GLfloat f) : mType(Float) { mValue.f = f; }

    GLint AsInt() const { return (mType == Int) ? mValue.i : NS_lroundf(mValue.f); }
    GLfloat AsFloat() const { return (mType == Float) ? mValue.f : GLfloat(mValue.i); }
};

struct IndexedBufferBinding
{
    WebGLRefPtr<WebGLBuffer> mBufferBinding;
    uint64_t mRangeStart;
    uint64_t mRangeSize;

    IndexedBufferBinding();

    uint64_t ByteCount() const;
};

////

struct FloatOrInt final // For TexParameter[fi] and friends.
{
    const bool isFloat;
    const GLfloat f;
    const GLint i;

    explicit FloatOrInt(GLint x)
        : isFloat(false)
        , f(x)
        , i(x)
    { }

    explicit FloatOrInt(GLfloat x)
        : isFloat(true)
        , f(x)
        , i(roundf(x))
    { }

    FloatOrInt& operator =(const FloatOrInt& x) {
        memcpy(this, &x, sizeof(x));
        return *this;
    }
};

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

struct TexImageSource
{
    const dom::ArrayBufferView* mView;
    GLuint mViewElemOffset;
    GLuint mViewElemLengthOverride;

    const WebGLsizeiptr* mPboOffset;

    const dom::ImageBitmap* mImageBitmap;
    const dom::ImageData* mImageData;

    const dom::Element* mDomElem;
    ErrorResult* mOut_error;

protected:
    TexImageSource() {
        memset(this, 0, sizeof(*this));
    }
};

////

struct TexImageSourceAdapter final : public TexImageSource
{
    TexImageSourceAdapter(const dom::Nullable<dom::ArrayBufferView>* maybeView,
                          ErrorResult*)
    {
        if (!maybeView->IsNull()) {
            mView = &(maybeView->Value());
        }
    }

    TexImageSourceAdapter(const dom::ArrayBufferView* view, ErrorResult*) {
        mView = view;
    }

    TexImageSourceAdapter(const dom::ArrayBufferView* view, GLuint viewElemOffset,
                          GLuint viewElemLengthOverride = 0)
    {
        mView = view;
        mViewElemOffset = viewElemOffset;
        mViewElemLengthOverride = viewElemLengthOverride;
    }

    TexImageSourceAdapter(const WebGLsizeiptr* pboOffset, GLuint ignored1, GLuint ignored2 = 0) {
        mPboOffset = pboOffset;
    }

    TexImageSourceAdapter(const WebGLsizeiptr* pboOffset, ErrorResult* ignored) {
        mPboOffset = pboOffset;
    }

    TexImageSourceAdapter(const dom::ImageBitmap* imageBitmap, ErrorResult*) {
        mImageBitmap = imageBitmap;
    }

    TexImageSourceAdapter(const dom::ImageData* imageData, ErrorResult*) {
        mImageData = imageData;
    }

    TexImageSourceAdapter(const dom::Element* domElem, ErrorResult* const out_error) {
        mDomElem = domElem;
        mOut_error = out_error;
    }
};

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

class WebGLContext
    : public nsIDOMWebGLRenderingContext
    , public nsICanvasRenderingContextInternal
    , public nsSupportsWeakReference
    , public WebGLContextUnchecked
    , public WebGLRectangleObject
    , public nsWrapperCache
{
    friend class ScopedDrawHelper;
    friend class ScopedDrawWithTransformFeedback;
    friend class ScopedFBRebinder;
    friend class WebGL2Context;
    friend class WebGLContextUserData;
    friend class WebGLExtensionCompressedTextureATC;
    friend class WebGLExtensionCompressedTextureES3;
    friend class WebGLExtensionCompressedTextureETC1;
    friend class WebGLExtensionCompressedTexturePVRTC;
    friend class WebGLExtensionCompressedTextureS3TC;
    friend class WebGLExtensionDepthTexture;
    friend class WebGLExtensionDisjointTimerQuery;
    friend class WebGLExtensionDrawBuffers;
    friend class WebGLExtensionLoseContext;
    friend class WebGLExtensionVertexArray;
    friend class WebGLMemoryTracker;
    friend struct webgl::UniformBlockInfo;

    enum {
        UNPACK_FLIP_Y_WEBGL = 0x9240,
        UNPACK_PREMULTIPLY_ALPHA_WEBGL = 0x9241,
        CONTEXT_LOST_WEBGL = 0x9242,
        UNPACK_COLORSPACE_CONVERSION_WEBGL = 0x9243,
        BROWSER_DEFAULT_WEBGL = 0x9244,
        UNMASKED_VENDOR_WEBGL = 0x9245,
        UNMASKED_RENDERER_WEBGL = 0x9246
    };

    static const uint32_t kMinMaxColorAttachments;
    static const uint32_t kMinMaxDrawBuffers;

public:
    WebGLContext();

protected:
    virtual ~WebGLContext();

public:
    NS_DECL_CYCLE_COLLECTING_ISUPPORTS

    NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(WebGLContext,
                                                           nsIDOMWebGLRenderingContext)

    virtual JSObject* WrapObject(JSContext* cx, JS::Handle<JSObject*> givenProto) override = 0;

    NS_DECL_NSIDOMWEBGLRENDERINGCONTEXT

    virtual void OnVisibilityChange() override;
    virtual void OnMemoryPressure() override;

    // nsICanvasRenderingContextInternal
    virtual int32_t GetWidth() const override;
    virtual int32_t GetHeight() const override;

    NS_IMETHOD SetDimensions(int32_t width, int32_t height) override;
    NS_IMETHOD InitializeWithDrawTarget(nsIDocShell*,
                                        NotNull<gfx::DrawTarget*>) override
    {
        return NS_ERROR_NOT_IMPLEMENTED;
    }

    NS_IMETHOD Reset() override {
        /* (InitializeWithSurface) */
        return NS_ERROR_NOT_IMPLEMENTED;
    }

    virtual UniquePtr<uint8_t[]> GetImageBuffer(int32_t* out_format) override;
    NS_IMETHOD GetInputStream(const char* mimeType,
                              const char16_t* encoderOptions,
                              nsIInputStream** out_stream) override;

    already_AddRefed<mozilla::gfx::SourceSurface>
    GetSurfaceSnapshot(bool* out_premultAlpha) override;

    NS_IMETHOD SetIsOpaque(bool) override { return NS_OK; };
    bool GetIsOpaque() override { return false; }
    NS_IMETHOD SetContextOptions(JSContext* cx,
                                 JS::Handle<JS::Value> options,
                                 ErrorResult& aRvForDictionaryInit) override;

    NS_IMETHOD SetIsIPC(bool) override {
        return NS_ERROR_NOT_IMPLEMENTED;
    }

    /**
     * An abstract base class to be implemented by callers wanting to be notified
     * that a refresh has occurred. Callers must ensure an observer is removed
     * before it is destroyed.
     */
    virtual void DidRefresh() override;

    NS_IMETHOD Redraw(const gfxRect&) override {
        return NS_ERROR_NOT_IMPLEMENTED;
    }

    void SynthesizeGLError(GLenum err);
    void SynthesizeGLError(GLenum err, const char* fmt, ...);

    void ErrorInvalidEnum(const char* fmt = 0, ...);
    void ErrorInvalidOperation(const char* fmt = 0, ...);
    void ErrorInvalidValue(const char* fmt = 0, ...);
    void ErrorInvalidFramebufferOperation(const char* fmt = 0, ...);
    void ErrorInvalidEnumInfo(const char* info, GLenum enumValue);
    void ErrorInvalidEnumInfo(const char* info, const char* funcName,
                              GLenum enumValue);
    void ErrorOutOfMemory(const char* fmt = 0, ...);
    void ErrorImplementationBug(const char* fmt = 0, ...);

    void ErrorInvalidEnumArg(const char* funcName, const char* argName, GLenum val);

    const char* ErrorName(GLenum error);

    /**
     * Return displayable name for GLenum.
     * This version is like gl::GLenumToStr but with out the GL_ prefix to
     * keep consistency with how errors are reported from WebGL.
     * Returns hex formatted version of glenum if glenum is unknown.
     */
    static void EnumName(GLenum val, nsCString* out_name);

    void DummyReadFramebufferOperation(const char* funcName);

    WebGLTexture* ActiveBoundTextureForTarget(const TexTarget texTarget) const {
        switch (texTarget.get()) {
        case LOCAL_GL_TEXTURE_2D:
            return mBound2DTextures[mActiveTexture];
        case LOCAL_GL_TEXTURE_CUBE_MAP:
            return mBoundCubeMapTextures[mActiveTexture];
        case LOCAL_GL_TEXTURE_3D:
            return mBound3DTextures[mActiveTexture];
        case LOCAL_GL_TEXTURE_2D_ARRAY:
            return mBound2DArrayTextures[mActiveTexture];
        default:
            MOZ_CRASH("GFX: bad target");
        }
    }

    /* Use this function when you have the texture image target, for example:
     * GL_TEXTURE_2D, GL_TEXTURE_CUBE_MAP_[POSITIVE|NEGATIVE]_[X|Y|Z], and
     * not the actual texture binding target: GL_TEXTURE_2D or GL_TEXTURE_CUBE_MAP.
     */
    WebGLTexture*
    ActiveBoundTextureForTexImageTarget(const TexImageTarget texImgTarget) const
    {
        const TexTarget texTarget = TexImageTargetToTexTarget(texImgTarget);
        return ActiveBoundTextureForTarget(texTarget);
    }

    void InvalidateResolveCacheForTextureWithTexUnit(const GLuint);

    already_AddRefed<Layer>
    GetCanvasLayer(nsDisplayListBuilder* builder, Layer* oldLayer,
                   LayerManager* manager,
                   bool aMirror = false) override;

    // Note that 'clean' here refers to its invalidation state, not the
    // contents of the buffer.
    void MarkContextClean() override { mInvalidated = false; }

    void MarkContextCleanForFrameCapture() override { mCapturedFrameInvalidated = false; }

    bool IsContextCleanForFrameCapture() override { return !mCapturedFrameInvalidated; }

    gl::GLContext* GL() const { return gl; }

    bool IsPremultAlpha() const { return mOptions.premultipliedAlpha; }

    bool IsPreservingDrawingBuffer() const { return mOptions.preserveDrawingBuffer; }

    bool PresentScreenBuffer();

    // Prepare the context for capture before compositing
    void BeginComposition();
    // Clean up the context after captured for compositing
    void EndComposition();

    // a number that increments every time we have an event that causes
    // all context resources to be lost.
    uint32_t Generation() const { return mGeneration.value(); }

    // This is similar to GLContext::ClearSafely, but tries to minimize the
    // amount of work it does.
    // It only clears the buffers we specify, and can reset its state without
    // first having to query anything, as WebGL knows its state at all times.
    void ForceClearFramebufferWithDefaultValues(GLbitfield bufferBits, bool fakeNoAlpha);

    // Calls ForceClearFramebufferWithDefaultValues() for the Context's 'screen'.
    void ClearScreen();
    void ClearBackbufferIfNeeded();

    bool MinCapabilityMode() const { return mMinCapability; }

    void RunContextLossTimer();
    void UpdateContextLossStatus();
    void EnqueueUpdateContextLossStatus();

    bool TryToRestoreContext();

    void AssertCachedBindings();
    void AssertCachedGlobalState();

    dom::HTMLCanvasElement* GetCanvas() const { return mCanvasElement; }

    // WebIDL WebGLRenderingContext API
    void Commit();
    void GetCanvas(Nullable<dom::OwningHTMLCanvasElementOrOffscreenCanvas>& retval);
    GLsizei DrawingBufferWidth() const { return IsContextLost() ? 0 : mWidth; }
    GLsizei DrawingBufferHeight() const {
        return IsContextLost() ? 0 : mHeight;
    }

    layers::LayersBackend GetCompositorBackendType() const;

    void
    GetContextAttributes(dom::Nullable<dom::WebGLContextAttributes>& retval);

    bool IsContextLost() const { return mContextStatus != ContextNotLost; }
    void GetSupportedExtensions(dom::Nullable< nsTArray<nsString> >& retval,
                                dom::CallerType callerType);
    void GetExtension(JSContext* cx, const nsAString& name,
                      JS::MutableHandle<JSObject*> retval,
                      dom::CallerType callerType, ErrorResult& rv);
    void AttachShader(WebGLProgram& prog, WebGLShader& shader);
    void BindAttribLocation(WebGLProgram& prog, GLuint location,
                            const nsAString& name);
    void BindFramebuffer(GLenum target, WebGLFramebuffer* fb);
    void BindRenderbuffer(GLenum target, WebGLRenderbuffer* fb);
    void BindVertexArray(WebGLVertexArray* vao);
    void BlendColor(GLclampf r, GLclampf g, GLclampf b, GLclampf a);
    void BlendEquation(GLenum mode);
    void BlendEquationSeparate(GLenum modeRGB, GLenum modeAlpha);
    void BlendFunc(GLenum sfactor, GLenum dfactor);
    void BlendFuncSeparate(GLenum srcRGB, GLenum dstRGB,
                           GLenum srcAlpha, GLenum dstAlpha);
    GLenum CheckFramebufferStatus(GLenum target);
    void Clear(GLbitfield mask);
    void ClearColor(GLclampf r, GLclampf g, GLclampf b, GLclampf a);
    void ClearDepth(GLclampf v);
    void ClearStencil(GLint v);
    void ColorMask(WebGLboolean r, WebGLboolean g, WebGLboolean b, WebGLboolean a);
    void CompileShader(WebGLShader& shader);
    void CompileShaderANGLE(WebGLShader* shader);
    void CompileShaderBypass(WebGLShader* shader, const nsCString& shaderSource);
    already_AddRefed<WebGLFramebuffer> CreateFramebuffer();
    already_AddRefed<WebGLProgram> CreateProgram();
    already_AddRefed<WebGLRenderbuffer> CreateRenderbuffer();
    already_AddRefed<WebGLShader> CreateShader(GLenum type);
    already_AddRefed<WebGLVertexArray> CreateVertexArray();
    void CullFace(GLenum face);
    void DeleteFramebuffer(WebGLFramebuffer* fb);
    void DeleteProgram(WebGLProgram* prog);
    void DeleteRenderbuffer(WebGLRenderbuffer* rb);
    void DeleteShader(WebGLShader* shader);
    void DeleteVertexArray(WebGLVertexArray* vao);
    void DepthFunc(GLenum func);
    void DepthMask(WebGLboolean b);
    void DepthRange(GLclampf zNear, GLclampf zFar);
    void DetachShader(WebGLProgram& prog, const WebGLShader& shader);
    void DrawBuffers(const dom::Sequence<GLenum>& buffers);
    void Flush();
    void Finish();
    void FramebufferRenderbuffer(GLenum target, GLenum attachment,
                                 GLenum rbTarget, WebGLRenderbuffer* rb);
    void FramebufferTexture2D(GLenum target, GLenum attachment,
                              GLenum texImageTarget, WebGLTexture* tex,
                              GLint level);

    void FrontFace(GLenum mode);
    already_AddRefed<WebGLActiveInfo> GetActiveAttrib(const WebGLProgram& prog,
                                                      GLuint index);
    already_AddRefed<WebGLActiveInfo> GetActiveUniform(const WebGLProgram& prog,
                                                       GLuint index);

    void
    GetAttachedShaders(const WebGLProgram& prog,
                       dom::Nullable<nsTArray<RefPtr<WebGLShader>>>& retval);

    GLint GetAttribLocation(const WebGLProgram& prog, const nsAString& name);
    JS::Value GetBufferParameter(GLenum target, GLenum pname);

    void GetBufferParameter(JSContext*, GLenum target, GLenum pname,
                            JS::MutableHandle<JS::Value> retval)
    {
        retval.set(GetBufferParameter(target, pname));
    }

    GLenum GetError();
    virtual JS::Value GetFramebufferAttachmentParameter(JSContext* cx, GLenum target,
                                                        GLenum attachment, GLenum pname,
                                                        ErrorResult& rv);

    void GetFramebufferAttachmentParameter(JSContext* cx, GLenum target,
                                           GLenum attachment, GLenum pname,
                                           JS::MutableHandle<JS::Value> retval,
                                           ErrorResult& rv)
    {
        retval.set(GetFramebufferAttachmentParameter(cx, target, attachment,
                                                     pname, rv));
    }

    JS::Value GetProgramParameter(const WebGLProgram& prog, GLenum pname);

    void  GetProgramParameter(JSContext*, const WebGLProgram& prog, GLenum pname,
                              JS::MutableHandle<JS::Value> retval)
    {
        retval.set(GetProgramParameter(prog, pname));
    }

    void GetProgramInfoLog(const WebGLProgram& prog, nsACString& retval);
    void GetProgramInfoLog(const WebGLProgram& prog, nsAString& retval);
    JS::Value GetRenderbufferParameter(GLenum target, GLenum pname);

    void GetRenderbufferParameter(JSContext*, GLenum target, GLenum pname,
                                  JS::MutableHandle<JS::Value> retval)
    {
        retval.set(GetRenderbufferParameter(target, pname));
    }

    JS::Value GetShaderParameter(const WebGLShader& shader, GLenum pname);

    void GetShaderParameter(JSContext*, const WebGLShader& shader, GLenum pname,
                            JS::MutableHandle<JS::Value> retval)
    {
        retval.set(GetShaderParameter(shader, pname));
    }

    already_AddRefed<WebGLShaderPrecisionFormat>
    GetShaderPrecisionFormat(GLenum shadertype, GLenum precisiontype);

    void GetShaderInfoLog(const WebGLShader& shader, nsACString& retval);
    void GetShaderInfoLog(const WebGLShader& shader, nsAString& retval);
    void GetShaderSource(const WebGLShader& shader, nsAString& retval);

    JS::Value GetUniform(JSContext* cx, const WebGLProgram& prog,
                         const WebGLUniformLocation& loc);

    void GetUniform(JSContext* cx, const WebGLProgram& prog,
                    const WebGLUniformLocation& loc,
                    JS::MutableHandle<JS::Value> retval)
    {
        retval.set(GetUniform(cx, prog, loc));
    }

    already_AddRefed<WebGLUniformLocation>
    GetUniformLocation(const WebGLProgram& prog, const nsAString& name);

    void Hint(GLenum target, GLenum mode);
    bool IsFramebuffer(const WebGLFramebuffer* fb);
    bool IsProgram(const WebGLProgram* prog);
    bool IsRenderbuffer(const WebGLRenderbuffer* rb);
    bool IsShader(const WebGLShader* shader);
    bool IsVertexArray(const WebGLVertexArray* vao);
    void LineWidth(GLfloat width);
    void LinkProgram(WebGLProgram& prog);
    void PixelStorei(GLenum pname, GLint param);
    void PolygonOffset(GLfloat factor, GLfloat units);

    already_AddRefed<layers::SharedSurfaceTextureClient> GetVRFrame();
    bool StartVRPresentation();

    ////

    webgl::PackingInfo
    ValidImplementationColorReadPI(const webgl::FormatUsageInfo* usage) const;

protected:
    bool ReadPixels_SharedPrecheck(ErrorResult* const out_error);
    void ReadPixelsImpl(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
                        GLenum type, void* data, uint32_t dataLen);
    bool DoReadPixelsAndConvert(const webgl::FormatInfo* srcFormat, GLint x, GLint y,
                                GLsizei width, GLsizei height, GLenum format,
                                GLenum destType, void* dest, uint32_t dataLen,
                                uint32_t rowStride);
public:
    void ReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
                    GLenum type, const dom::Nullable<dom::ArrayBufferView>& maybeView,
                    ErrorResult& rv)
    {
        const char funcName[] = "readPixels";
        if (maybeView.IsNull()) {
            ErrorInvalidValue("%s: `pixels` must not be null.", funcName);
            return;
        }
        ReadPixels(x, y, width, height, format, type, maybeView.Value(), 0, rv);
    }

    void ReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
                    GLenum type, WebGLsizeiptr offset, ErrorResult& out_error);

    void ReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format,
                    GLenum type, const dom::ArrayBufferView& dstData, GLuint dstOffset,
                    ErrorResult& out_error);

    ////

    void RenderbufferStorage(GLenum target, GLenum internalFormat,
                             GLsizei width, GLsizei height);
protected:
    void RenderbufferStorage_base(const char* funcName, GLenum target,
                                  GLsizei samples, GLenum internalformat,
                                  GLsizei width, GLsizei height);
public:
    void SampleCoverage(GLclampf value, WebGLboolean invert);
    void Scissor(GLint x, GLint y, GLsizei width, GLsizei height);
    void ShaderSource(WebGLShader& shader, const nsAString& source);
    void StencilFunc(GLenum func, GLint ref, GLuint mask);
    void StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask);
    void StencilMask(GLuint mask);
    void StencilMaskSeparate(GLenum face, GLuint mask);
    void StencilOp(GLenum sfail, GLenum dpfail, GLenum dppass);
    void StencilOpSeparate(GLenum face, GLenum sfail, GLenum dpfail,
                           GLenum dppass);

    //////

    void Uniform1f(WebGLUniformLocation* loc, GLfloat x);
    void Uniform2f(WebGLUniformLocation* loc, GLfloat x, GLfloat y);
    void Uniform3f(WebGLUniformLocation* loc, GLfloat x, GLfloat y, GLfloat z);
    void Uniform4f(WebGLUniformLocation* loc, GLfloat x, GLfloat y, GLfloat z, GLfloat w);

    void Uniform1i(WebGLUniformLocation* loc, GLint x);
    void Uniform2i(WebGLUniformLocation* loc, GLint x, GLint y);
    void Uniform3i(WebGLUniformLocation* loc, GLint x, GLint y, GLint z);
    void Uniform4i(WebGLUniformLocation* loc, GLint x, GLint y, GLint z, GLint w);

    void Uniform1ui(WebGLUniformLocation* loc, GLuint v0);
    void Uniform2ui(WebGLUniformLocation* loc, GLuint v0, GLuint v1);
    void Uniform3ui(WebGLUniformLocation* loc, GLuint v0, GLuint v1, GLuint v2);
    void Uniform4ui(WebGLUniformLocation* loc, GLuint v0, GLuint v1, GLuint v2,
                    GLuint v3);

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

    typedef dom::Float32ArrayOrUnrestrictedFloatSequence Float32ListU;
    typedef dom::Int32ArrayOrLongSequence Int32ListU;
    typedef dom::Uint32ArrayOrUnsignedLongSequence Uint32ListU;

protected:
    template<typename elemT, typename viewT>
    struct Arr {
        const size_t elemCount;
        const elemT* const elemBytes;

    private:
        static size_t ComputeAndReturnLength(const viewT& view) {
            view.ComputeLengthAndData();
            return view.LengthAllowShared();
        }

    public:
        explicit Arr(const viewT& view)
            : elemCount(ComputeAndReturnLength(view))
            , elemBytes(view.DataAllowShared())
        { }

        explicit Arr(const dom::Sequence<elemT>& seq)
            : elemCount(seq.Length())
            , elemBytes(seq.Elements())
        { }

        Arr(size_t _elemCount, const elemT* _elemBytes)
            : elemCount(_elemCount)
            , elemBytes(_elemBytes)
        { }

        ////

        static Arr From(const Float32ListU& list) {
            if (list.IsFloat32Array())
                return Arr(list.GetAsFloat32Array());

            return Arr(list.GetAsUnrestrictedFloatSequence());
        }

        static Arr From(const Int32ListU& list) {
            if (list.IsInt32Array())
                return Arr(list.GetAsInt32Array());

            return Arr(list.GetAsLongSequence());
        }

        static Arr From(const Uint32ListU& list) {
            if (list.IsUint32Array())
                return Arr(list.GetAsUint32Array());

            return Arr(list.GetAsUnsignedLongSequence());
        }
    };

    typedef Arr<GLfloat, dom::Float32Array> Float32Arr;
    typedef Arr<GLint, dom::Int32Array> Int32Arr;
    typedef Arr<GLuint, dom::Uint32Array> Uint32Arr;

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

    void UniformNfv(const char* funcName, uint8_t N, WebGLUniformLocation* loc,
                    const Float32Arr& arr, GLuint elemOffset, GLuint elemCountOverride);
    void UniformNiv(const char* funcName, uint8_t N, WebGLUniformLocation* loc,
                    const Int32Arr& arr, GLuint elemOffset, GLuint elemCountOverride);
    void UniformNuiv(const char* funcName, uint8_t N, WebGLUniformLocation* loc,
                     const Uint32Arr& arr, GLuint elemOffset, GLuint elemCountOverride);

    void UniformMatrixAxBfv(const char* funcName, uint8_t A, uint8_t B,
                            WebGLUniformLocation* loc, bool transpose,
                            const Float32Arr& arr, GLuint elemOffset,
                            GLuint elemCountOverride);

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

public:
    #define FOO(N) \
        void Uniform ## N ## fv(WebGLUniformLocation* loc, const Float32ListU& list,  \
                                GLuint elemOffset = 0, GLuint elemCountOverride = 0)  \
        {                                                                             \
            UniformNfv("uniform" #N "fv", N, loc, Float32Arr::From(list), elemOffset, \
                       elemCountOverride);                                            \
        }

    FOO(1)
    FOO(2)
    FOO(3)
    FOO(4)

    #undef FOO

    //////

    #define FOO(N) \
        void Uniform ## N ## iv(WebGLUniformLocation* loc, const Int32ListU& list,   \
                                GLuint elemOffset = 0, GLuint elemCountOverride = 0) \
        {                                                                            \
            UniformNiv("uniform" #N "iv", N, loc, Int32Arr::From(list), elemOffset,  \
                       elemCountOverride);                                           \
        }

    FOO(1)
    FOO(2)
    FOO(3)
    FOO(4)

    #undef FOO

    //////

    #define FOO(N) \
        void Uniform ## N ## uiv(WebGLUniformLocation* loc, const Uint32ListU& list,   \
                                 GLuint elemOffset = 0, GLuint elemCountOverride = 0)  \
        {                                                                              \
            UniformNuiv("uniform" #N "uiv", N, loc, Uint32Arr::From(list), elemOffset, \
                        elemCountOverride);                                            \
        }

    FOO(1)
    FOO(2)
    FOO(3)
    FOO(4)

    #undef FOO

    //////

    #define FOO(X,A,B) \
        void UniformMatrix ## X ## fv(WebGLUniformLocation* loc, bool transpose,       \
                                      const Float32ListU& list, GLuint elemOffset = 0, \
                                      GLuint elemCountOverride = 0)                    \
        {                                                                              \
            UniformMatrixAxBfv("uniformMatrix" #X "fv", A, B, loc, transpose,          \
                               Float32Arr::From(list), elemOffset, elemCountOverride); \
        }

    FOO(2,2,2)
    FOO(2x3,2,3)
    FOO(2x4,2,4)

    FOO(3x2,3,2)
    FOO(3,3,3)
    FOO(3x4,3,4)

    FOO(4x2,4,2)
    FOO(4x3,4,3)
    FOO(4,4,4)

    #undef FOO

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

    void UseProgram(WebGLProgram* prog);

    bool ValidateAttribArraySetter(const char* name, uint32_t count,
                                   uint32_t arrayLength);
    bool ValidateUniformLocation(WebGLUniformLocation* loc, const char* funcName);
    bool ValidateUniformSetter(WebGLUniformLocation* loc, uint8_t setterSize,
                               GLenum setterType, const char* funcName);
    bool ValidateUniformArraySetter(WebGLUniformLocation* loc,
                                    uint8_t setterElemSize, GLenum setterType,
                                    uint32_t setterArraySize, const char* funcName,
                                    uint32_t* out_numElementsToUpload);
    bool ValidateUniformMatrixArraySetter(WebGLUniformLocation* loc,
                                          uint8_t setterCols,
                                          uint8_t setterRows,
                                          GLenum setterType,
                                          uint32_t setterArraySize,
                                          bool setterTranspose,
                                          const char* funcName,
                                          uint32_t* out_numElementsToUpload);
    void ValidateProgram(const WebGLProgram& prog);
    bool ValidateUniformLocation(const char* info, WebGLUniformLocation* loc);
    bool ValidateSamplerUniformSetter(const char* info,
                                      WebGLUniformLocation* loc, GLint value);
    void Viewport(GLint x, GLint y, GLsizei width, GLsizei height);
// -----------------------------------------------------------------------------
// WEBGL_lose_context
public:
    void LoseContext();
    void RestoreContext();

// -----------------------------------------------------------------------------
// Buffer Objects (WebGLContextBuffers.cpp)
    void BindBuffer(GLenum target, WebGLBuffer* buffer);
    void BindBufferBase(GLenum target, GLuint index, WebGLBuffer* buf);
    void BindBufferRange(GLenum target, GLuint index, WebGLBuffer* buf,
                         WebGLintptr offset, WebGLsizeiptr size);

private:
    void BufferDataImpl(GLenum target, size_t dataLen, const uint8_t* data, GLenum usage);

public:
    void BufferData(GLenum target, WebGLsizeiptr size, GLenum usage);
    void BufferData(GLenum target, const dom::Nullable<dom::ArrayBuffer>& maybeSrc,
                    GLenum usage);
    void BufferData(GLenum target, const dom::ArrayBufferView& srcData, GLenum usage,
                    GLuint srcElemOffset = 0, GLuint srcElemCountOverride = 0);

private:
    void BufferSubDataImpl(GLenum target, WebGLsizeiptr dstByteOffset,
                           size_t srcDataLen, const uint8_t* srcData);

public:
    void BufferSubData(GLenum target, WebGLsizeiptr dstByteOffset,
                       const dom::ArrayBufferView& src, GLuint srcElemOffset = 0,
                       GLuint srcElemCountOverride = 0);
    void BufferSubData(GLenum target, WebGLsizeiptr dstByteOffset,
                       const dom::ArrayBuffer& src);
    void BufferSubData(GLenum target, WebGLsizeiptr dstByteOffset,
                       const dom::SharedArrayBuffer& src);

    already_AddRefed<WebGLBuffer> CreateBuffer();
    void DeleteBuffer(WebGLBuffer* buf);
    bool IsBuffer(WebGLBuffer* buf);

protected:
    // bound buffer state
    WebGLRefPtr<WebGLBuffer> mBoundArrayBuffer;
    WebGLRefPtr<WebGLBuffer> mBoundCopyReadBuffer;
    WebGLRefPtr<WebGLBuffer> mBoundCopyWriteBuffer;
    WebGLRefPtr<WebGLBuffer> mBoundPixelPackBuffer;
    WebGLRefPtr<WebGLBuffer> mBoundPixelUnpackBuffer;
    WebGLRefPtr<WebGLBuffer> mBoundUniformBuffer;

    std::vector<IndexedBufferBinding> mIndexedUniformBufferBindings;

    WebGLRefPtr<WebGLBuffer>& GetBufferSlotByTarget(GLenum target);
    WebGLRefPtr<WebGLBuffer>& GetBufferSlotByTargetIndexed(GLenum target,
                                                           GLuint index);

// -----------------------------------------------------------------------------
// Queries (WebGL2ContextQueries.cpp)
protected:
    WebGLRefPtr<WebGLQuery> mQuerySlot_SamplesPassed;
    WebGLRefPtr<WebGLQuery> mQuerySlot_TFPrimsWritten;
    WebGLRefPtr<WebGLQuery> mQuerySlot_TimeElapsed;

    WebGLRefPtr<WebGLQuery>*
    ValidateQuerySlotByTarget(const char* funcName, GLenum target);

public:
    already_AddRefed<WebGLQuery> CreateQuery(const char* funcName = nullptr);
    void DeleteQuery(WebGLQuery* query, const char* funcName = nullptr);
    bool IsQuery(const WebGLQuery* query, const char* funcName = nullptr);
    void BeginQuery(GLenum target, WebGLQuery& query, const char* funcName = nullptr);
    void EndQuery(GLenum target, const char* funcName = nullptr);
    void GetQuery(JSContext* cx, GLenum target, GLenum pname,
                  JS::MutableHandleValue retval, const char* funcName = nullptr);
    void GetQueryParameter(JSContext* cx, const WebGLQuery& query, GLenum pname,
                           JS::MutableHandleValue retval, const char* funcName = nullptr);


// -----------------------------------------------------------------------------
// State and State Requests (WebGLContextState.cpp)
public:
    void Disable(GLenum cap);
    void Enable(GLenum cap);
    bool GetStencilBits(GLint* const out_stencilBits);
    bool GetChannelBits(const char* funcName, GLenum pname, GLint* const out_val);
    virtual JS::Value GetParameter(JSContext* cx, GLenum pname, ErrorResult& rv);

    void GetParameter(JSContext* cx, GLenum pname,
                      JS::MutableHandle<JS::Value> retval, ErrorResult& rv)
    {
        retval.set(GetParameter(cx, pname, rv));
    }

    void GetParameterIndexed(JSContext* cx, GLenum pname, GLuint index,
                             JS::MutableHandle<JS::Value> retval);
    bool IsEnabled(GLenum cap);

private:
    // State tracking slots
    realGLboolean mDitherEnabled;
    realGLboolean mRasterizerDiscardEnabled;
    realGLboolean mScissorTestEnabled;
    realGLboolean mDepthTestEnabled;
    realGLboolean mStencilTestEnabled;
    GLenum mGenerateMipmapHint;

    bool ValidateCapabilityEnum(GLenum cap, const char* info);
    realGLboolean* GetStateTrackingSlot(GLenum cap);

// -----------------------------------------------------------------------------
// Texture funcions (WebGLContextTextures.cpp)
public:
    void ActiveTexture(GLenum texUnit);
    void BindTexture(GLenum texTarget, WebGLTexture* tex);
    already_AddRefed<WebGLTexture> CreateTexture();
    void DeleteTexture(WebGLTexture* tex);
    void GenerateMipmap(GLenum texTarget);

    void GetTexParameter(JSContext*, GLenum texTarget, GLenum pname,
                         JS::MutableHandle<JS::Value> retval)
    {
        retval.set(GetTexParameter(texTarget, pname));
    }

    bool IsTexture(WebGLTexture* tex);

    void TexParameterf(GLenum texTarget, GLenum pname, GLfloat param) {
        TexParameter_base(texTarget, pname, FloatOrInt(param));
    }

    void TexParameteri(GLenum texTarget, GLenum pname, GLint param) {
        TexParameter_base(texTarget, pname, FloatOrInt(param));
    }

protected:
    JS::Value GetTexParameter(GLenum texTarget, GLenum pname);
    void TexParameter_base(GLenum texTarget, GLenum pname, const FloatOrInt& param);

    virtual bool IsTexParamValid(GLenum pname) const;

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

public:
    template<typename T>
    void CompressedTexImage2D(GLenum target, GLint level, GLenum internalFormat,
                              GLsizei width, GLsizei height, GLint border,
                              const T& anySrc, GLuint viewElemOffset = 0,
                              GLuint viewElemLengthOverride = 0)
    {
        const char funcName[] = "compressedTexImage2D";
        const uint8_t funcDims = 2;
        const GLsizei depth = 1;
        const TexImageSourceAdapter src(&anySrc, viewElemOffset, viewElemLengthOverride);
        CompressedTexImage(funcName, funcDims, target, level, internalFormat, width,
                           height, depth, border, src);
    }

    template<typename T>
    void CompressedTexSubImage2D(GLenum target, GLint level, GLint xOffset, GLint yOffset,
                                 GLsizei width, GLsizei height, GLenum unpackFormat,
                                 const T& anySrc, GLuint viewElemOffset = 0,
                                 GLuint viewElemLengthOverride = 0)
    {
        const char funcName[] = "compressedTexSubImage2D";
        const uint8_t funcDims = 2;
        const GLint zOffset = 0;
        const GLsizei depth = 1;
        const TexImageSourceAdapter src(&anySrc, viewElemOffset, viewElemLengthOverride);
        CompressedTexSubImage(funcName, funcDims, target, level, xOffset, yOffset,
                              zOffset, width, height, depth, unpackFormat, src);
    }

protected:
    void CompressedTexImage(const char* funcName, uint8_t funcDims, GLenum target,
                            GLint level, GLenum internalFormat, GLsizei width,
                            GLsizei height, GLsizei depth, GLint border,
                            const TexImageSource& src);

    void CompressedTexSubImage(const char* funcName, uint8_t funcDims, GLenum target,
                               GLint level, GLint xOffset, GLint yOffset, GLint zOffset,
                               GLsizei width, GLsizei height, GLsizei depth,
                               GLenum unpackFormat, const TexImageSource& src);

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

public:
    void CopyTexImage2D(GLenum target, GLint level, GLenum internalFormat, GLint x,
                        GLint y, GLsizei width, GLsizei height, GLint border);

    void CopyTexSubImage2D(GLenum target, GLint level, GLint xOffset,
                           GLint yOffset, GLint x, GLint y, GLsizei width,
                           GLsizei height)
    {
        const char funcName[] = "copyTexSubImage2D";
        const uint8_t funcDims = 2;
        const GLint zOffset = 0;
        CopyTexSubImage(funcName, funcDims, target, level, xOffset, yOffset, zOffset,
                        x, y, width, height);
    }

protected:
    void CopyTexSubImage(const char* funcName, uint8_t funcDims, GLenum target,
                         GLint level, GLint xOffset, GLint yOffset, GLint zOffset,
                         GLint x, GLint y, GLsizei width, GLsizei height);

    ////////////////////////////////////
    // TexImage

    // Implicit width/height uploads

public:
    template<typename T>
    void TexImage2D(GLenum target, GLint level, GLenum internalFormat,
                    GLenum unpackFormat, GLenum unpackType, const T& src,
                    ErrorResult& out_error)
    {
        GLsizei width = 0;
        GLsizei height = 0;
        GLint border = 0;
        TexImage2D(target, level, internalFormat, width, height, border, unpackFormat,
                   unpackType, src, out_error);
    }

    template<typename T>
    void TexSubImage2D(GLenum target, GLint level, GLint xOffset, GLint yOffset,
                       GLenum unpackFormat, GLenum unpackType, const T& src,
                       ErrorResult& out_error)
    {
        GLsizei width = 0;
        GLsizei height = 0;
        TexSubImage2D(target, level, xOffset, yOffset, width, height, unpackFormat,
                      unpackType, src, out_error);
    }

    ////

    template<typename T>
    void TexImage2D(GLenum target, GLint level, GLenum internalFormat, GLsizei width,
                    GLsizei height, GLint border, GLenum unpackFormat, GLenum unpackType,
                    const T& anySrc, ErrorResult& out_error)
    {
        const TexImageSourceAdapter src(&anySrc, &out_error);
        TexImage2D(target, level, internalFormat, width, height, border, unpackFormat,
                   unpackType, src);
    }

    void TexImage2D(GLenum target, GLint level, GLenum internalFormat, GLsizei width,
                    GLsizei height, GLint border, GLenum unpackFormat, GLenum unpackType,
                    const dom::ArrayBufferView& view, GLuint viewElemOffset,
                    ErrorResult&)
    {
        const TexImageSourceAdapter src(&view, viewElemOffset);
        TexImage2D(target, level, internalFormat, width, height, border, unpackFormat,
                   unpackType, src);
    }

protected:
    void TexImage2D(GLenum target, GLint level, GLenum internalFormat, GLsizei width,
                    GLsizei height, GLint border, GLenum unpackFormat,
                    GLenum unpackType, const TexImageSource& src)
    {
        const char funcName[] = "texImage2D";
        const uint8_t funcDims = 2;
        const GLsizei depth = 1;
        TexImage(funcName, funcDims, target, level, internalFormat, width, height, depth,
                 border, unpackFormat, unpackType, src);
    }

    void TexImage(const char* funcName, uint8_t funcDims, GLenum target, GLint level,
                  GLenum internalFormat, GLsizei width, GLsizei height, GLsizei depth,
                  GLint border, GLenum unpackFormat, GLenum unpackType,
                  const TexImageSource& src);

    ////

public:
    template<typename T>
    void TexSubImage2D(GLenum target, GLint level, GLint xOffset, GLint yOffset,
                       GLsizei width, GLsizei height, GLenum unpackFormat,
                       GLenum unpackType, const T& anySrc, ErrorResult& out_error)
    {
        const TexImageSourceAdapter src(&anySrc, &out_error);
        TexSubImage2D(target, level, xOffset, yOffset, width, height, unpackFormat,
                      unpackType, src);
    }

    void TexSubImage2D(GLenum target, GLint level, GLint xOffset, GLint yOffset,
                       GLsizei width, GLsizei height, GLenum unpackFormat,
                       GLenum unpackType, const dom::ArrayBufferView& view,
                       GLuint viewElemOffset, ErrorResult&)
    {
        const TexImageSourceAdapter src(&view, viewElemOffset);
        TexSubImage2D(target, level, xOffset, yOffset, width, height, unpackFormat,
                      unpackType, src);
    }

protected:
    void TexSubImage2D(GLenum target, GLint level, GLint xOffset, GLint yOffset,
                       GLsizei width, GLsizei height, GLenum unpackFormat,
                       GLenum unpackType, const TexImageSource& src)
    {
        const char funcName[] = "texSubImage2D";
        const uint8_t funcDims = 2;
        const GLint zOffset = 0;
        const GLsizei depth = 1;
        TexSubImage(funcName, funcDims, target, level, xOffset, yOffset, zOffset, width,
                    height, depth, unpackFormat, unpackType, src);
    }

    void TexSubImage(const char* funcName, uint8_t funcDims, GLenum target, GLint level,
                     GLint xOffset, GLint yOffset, GLint zOffset, GLsizei width,
                     GLsizei height, GLsizei depth, GLenum unpackFormat,
                     GLenum unpackType, const TexImageSource& src);

    ////////////////////////////////////
    // WebGLTextureUpload.cpp
public:
    UniquePtr<webgl::TexUnpackBlob>
    From(const char* funcName, TexImageTarget target, GLsizei rawWidth, GLsizei rawHeight,
         GLsizei rawDepth, GLint border, const TexImageSource& src,
         dom::Uint8ClampedArray* const scopedArr);

protected:
    bool ValidateTexImageSpecification(const char* funcName, uint8_t funcDims,
                                       GLenum texImageTarget, GLint level,
                                       GLsizei width, GLsizei height, GLsizei depth,
                                       GLint border,
                                       TexImageTarget* const out_target,
                                       WebGLTexture** const out_texture,
                                       WebGLTexture::ImageInfo** const out_imageInfo);
    bool ValidateTexImageSelection(const char* funcName, uint8_t funcDims,
                                   GLenum texImageTarget, GLint level, GLint xOffset,
                                   GLint yOffset, GLint zOffset, GLsizei width,
                                   GLsizei height, GLsizei depth,
                                   TexImageTarget* const out_target,
                                   WebGLTexture** const out_texture,
                                   WebGLTexture::ImageInfo** const out_imageInfo);
    bool ValidateUnpackInfo(const char* funcName, bool usePBOs, GLenum format,
                            GLenum type, webgl::PackingInfo* const out);

    UniquePtr<webgl::TexUnpackBlob>
    FromDomElem(const char* funcName, TexImageTarget target, uint32_t width,
                uint32_t height, uint32_t depth, const dom::Element& elem,
                ErrorResult* const out_error);

    UniquePtr<webgl::TexUnpackBytes>
    FromCompressed(const char* funcName, TexImageTarget target, GLsizei rawWidth,
                   GLsizei rawHeight, GLsizei rawDepth, GLint border,
                   const TexImageSource& src);

// -----------------------------------------------------------------------------
// Vertices Feature (WebGLContextVertices.cpp)
    GLenum mPrimRestartTypeBytes;

public:
    void DrawArrays(GLenum mode, GLint first, GLsizei count);
    void DrawArraysInstanced(GLenum mode, GLint first, GLsizei count,
                             GLsizei primcount);
    void DrawElements(GLenum mode, GLsizei count, GLenum type,
                      WebGLintptr byteOffset, const char* funcName = nullptr);
    void DrawElementsInstanced(GLenum mode, GLsizei count, GLenum type,
                               WebGLintptr byteOffset, GLsizei primcount);

    void EnableVertexAttribArray(GLuint index);
    void DisableVertexAttribArray(GLuint index);

    JS::Value GetVertexAttrib(JSContext* cx, GLuint index, GLenum pname,
                              ErrorResult& rv);

    void GetVertexAttrib(JSContext* cx, GLuint index, GLenum pname,
                         JS::MutableHandle<JS::Value> retval, ErrorResult& rv)
    {
        retval.set(GetVertexAttrib(cx, index, pname, rv));
    }

    WebGLsizeiptr GetVertexAttribOffset(GLuint index, GLenum pname);

    ////

    void VertexAttrib4f(GLuint index, GLfloat x, GLfloat y, GLfloat z, GLfloat w,
                        const char* funcName = nullptr);

    ////

    void VertexAttrib1f(GLuint index, GLfloat x) {
        VertexAttrib4f(index, x, 0, 0, 1, "vertexAttrib1f");
    }
    void VertexAttrib2f(GLuint index, GLfloat x, GLfloat y) {
        VertexAttrib4f(index, x, y, 0, 1, "vertexAttrib2f");
    }
    void VertexAttrib3f(GLuint index, GLfloat x, GLfloat y, GLfloat z) {
        VertexAttrib4f(index, x, y, z, 1, "vertexAttrib3f");
    }

    ////

    void VertexAttrib1fv(GLuint index, const Float32ListU& list) {
        const char funcName[] = "vertexAttrib1fv";
        const auto& arr = Float32Arr::From(list);
        if (!ValidateAttribArraySetter(funcName, 1, arr.elemCount))
            return;

        VertexAttrib4f(index, arr.elemBytes[0], 0, 0, 1, funcName);
    }

    void VertexAttrib2fv(GLuint index, const Float32ListU& list) {
        const char funcName[] = "vertexAttrib2fv";
        const auto& arr = Float32Arr::From(list);
        if (!ValidateAttribArraySetter(funcName, 2, arr.elemCount))
            return;

        VertexAttrib4f(index, arr.elemBytes[0], arr.elemBytes[1], 0, 1, funcName);
    }

    void VertexAttrib3fv(GLuint index, const Float32ListU& list) {
        const char funcName[] = "vertexAttrib3fv";
        const auto& arr = Float32Arr::From(list);
        if (!ValidateAttribArraySetter(funcName, 3, arr.elemCount))
            return;

        VertexAttrib4f(index, arr.elemBytes[0], arr.elemBytes[1], arr.elemBytes[2], 1,
                       funcName);
    }

    void VertexAttrib4fv(GLuint index, const Float32ListU& list) {
        const char funcName[] = "vertexAttrib4fv";
        const auto& arr = Float32Arr::From(list);
        if (!ValidateAttribArraySetter(funcName, 4, arr.elemCount))
            return;

        VertexAttrib4f(index, arr.elemBytes[0], arr.elemBytes[1], arr.elemBytes[2],
                       arr.elemBytes[3], funcName);
    }

    ////

    void VertexAttribPointer(GLuint index, GLint size, GLenum type,
                             WebGLboolean normalized, GLsizei stride,
                             WebGLintptr byteOffset);
    void VertexAttribDivisor(GLuint index, GLuint divisor);

private:
    // Cache the max number of vertices and instances that can be read from
    // bound VBOs (result of ValidateBuffers).
    bool mBufferFetchingIsVerified;
    bool mBufferFetchingHasPerVertex;
    uint32_t mMaxFetchedVertices;
    uint32_t mMaxFetchedInstances;
    bool mBufferFetch_IsAttrib0Active;

    bool DrawArrays_check(const char* funcName, GLenum mode, GLint first,
                          GLsizei vertCount, GLsizei instanceCount);
    bool DrawElements_check(const char* funcName, GLenum mode, GLsizei vertCount,
                            GLenum type, WebGLintptr byteOffset,
                            GLsizei instanceCount);
    bool DrawInstanced_check(const char* info);
    void Draw_cleanup(const char* funcName);

    void VertexAttrib1fv_base(GLuint index, uint32_t arrayLength,
                              const GLfloat* ptr);
    void VertexAttrib2fv_base(GLuint index, uint32_t arrayLength,
                              const GLfloat* ptr);
    void VertexAttrib3fv_base(GLuint index, uint32_t arrayLength,
                              const GLfloat* ptr);
    void VertexAttrib4fv_base(GLuint index, uint32_t arrayLength,
                              const GLfloat* ptr);

    bool ValidateBufferFetching(const char* info);
    bool BindArrayAttribToLocation0(WebGLProgram* prog);

// -----------------------------------------------------------------------------
// PROTECTED
protected:
    WebGLVertexAttrib0Status WhatDoesVertexAttrib0Need() const;
    bool DoFakeVertexAttrib0(const char* funcName, GLuint vertexCount);
    void UndoFakeVertexAttrib0();

    inline void InvalidateBufferFetching()
    {
        mBufferFetchingIsVerified = false;
        mBufferFetchingHasPerVertex = false;
        mMaxFetchedVertices = 0;
        mMaxFetchedInstances = 0;
    }

    CheckedUint32 mGeneration;

    WebGLContextOptions mOptions;

    bool mInvalidated;
    bool mCapturedFrameInvalidated;
    bool mResetLayer;
    bool mLayerIsMirror;
    bool mOptionsFrozen;
    bool mMinCapability;
    bool mDisableExtensions;
    bool mIsMesa;
    bool mLoseContextOnMemoryPressure;
    bool mCanLoseContextInForeground;
    bool mRestoreWhenVisible;
    bool mShouldPresent;
    bool mBackbufferNeedsClear;
    bool mDisableFragHighP;

    template<typename WebGLObjectType>
    void DeleteWebGLObjectsArray(nsTArray<WebGLObjectType>& array);

    GLuint mActiveTexture;
    GLenum mDefaultFB_DrawBuffer0;

    // glGetError sources:
    bool mEmitContextLostErrorOnce;
    GLenum mWebGLError;
    GLenum mUnderlyingGLError;
    GLenum GetAndFlushUnderlyingGLErrors();

    bool mBypassShaderValidation;

    webgl::ShaderValidator* CreateShaderValidator(GLenum shaderType) const;

    // some GL constants
    uint32_t mGLMaxVertexAttribs;
    int32_t mGLMaxTextureUnits;
    int32_t mGLMaxTextureImageUnits;
    int32_t mGLMaxVertexTextureImageUnits;
    int32_t mGLMaxVaryingVectors;
    int32_t mGLMaxFragmentUniformVectors;
    int32_t mGLMaxVertexUniformVectors;
    uint32_t  mGLMaxTransformFeedbackSeparateAttribs;
    GLuint  mGLMaxUniformBufferBindings;

    // What is supported:
    uint32_t mGLMaxColorAttachments;
    uint32_t mGLMaxDrawBuffers;
    // What we're allowing:
    uint32_t mImplMaxColorAttachments;
    uint32_t mImplMaxDrawBuffers;

    uint32_t mImplMaxViewportDims[2];

public:
    GLenum LastColorAttachmentEnum() const {
        return LOCAL_GL_COLOR_ATTACHMENT0 + mImplMaxColorAttachments - 1;
    }

    const decltype(mOptions)& Options() const { return mOptions; }

protected:

    // Texture sizes are often not actually the GL values. Let's be explicit that these
    // are implementation limits.
    uint32_t mImplMaxTextureSize;
    uint32_t mImplMaxCubeMapTextureSize;
    uint32_t mImplMax3DTextureSize;
    uint32_t mImplMaxArrayTextureLayers;
    uint32_t mImplMaxRenderbufferSize;

public:
    GLuint MaxVertexAttribs() const {
        return mGLMaxVertexAttribs;
    }

    GLuint GLMaxTextureUnits() const {
        return mGLMaxTextureUnits;
    }

    bool IsFormatValidForFB(TexInternalFormat format) const;

protected:
    // Represents current status of the context with respect to context loss.
    // That is, whether the context is lost, and what part of the context loss
    // process we currently are at.
    // This is used to support the WebGL spec's asyncronous nature in handling
    // context loss.
    enum ContextStatus {
        // The context is stable; there either are none or we don't know of any.
        ContextNotLost,
        // The context has been lost, but we have not yet sent an event to the
        // script informing it of this.
        ContextLostAwaitingEvent,
        // The context has been lost, and we have sent the script an event
        // informing it of this.
        ContextLost,
        // The context is lost, an event has been sent to the script, and the
        // script correctly handled the event. We are waiting for the context to
        // be restored.
        ContextLostAwaitingRestore
    };

    // -------------------------------------------------------------------------
    // WebGL extensions (implemented in WebGLContextExtensions.cpp)
    typedef EnumeratedArray<WebGLExtensionID, WebGLExtensionID::Max,
                            RefPtr<WebGLExtensionBase>> ExtensionsArrayType;

    ExtensionsArrayType mExtensions;

    // enable an extension. the extension should not be enabled before.
    void EnableExtension(WebGLExtensionID ext);

    // Enable an extension if it's supported. Return the extension on success.
    WebGLExtensionBase* EnableSupportedExtension(dom::CallerType callerType,
                                                 WebGLExtensionID ext);

public:
    // returns true if the extension has been enabled by calling getExtension.
    bool IsExtensionEnabled(WebGLExtensionID ext) const;

protected:
    // returns true if the extension is supported for this caller type (this decides what getSupportedExtensions exposes)
    bool IsExtensionSupported(dom::CallerType callerType,
                              WebGLExtensionID ext) const;
    bool IsExtensionSupported(WebGLExtensionID ext) const;

    static const char* GetExtensionString(WebGLExtensionID ext);

    nsTArray<GLenum> mCompressedTextureFormats;

    // -------------------------------------------------------------------------
    // WebGL 2 specifics (implemented in WebGL2Context.cpp)
public:
    virtual bool IsWebGL2() const = 0;

    struct FailureReason {
        nsCString key; // For reporting.
        nsCString info;

        FailureReason() { }

        template<typename A, typename B>
        FailureReason(const A& _key, const B& _info)
            : key(nsCString(_key))
            , info(nsCString(_info))
        { }
    };
protected:
    bool InitWebGL2(FailureReason* const out_failReason);

    bool CreateAndInitGL(bool forceEnabled,
                         std::vector<FailureReason>* const out_failReasons);

    bool ResizeBackbuffer(uint32_t width, uint32_t height);

    typedef already_AddRefed<gl::GLContext> FnCreateGL_T(const gl::SurfaceCaps& caps,
                                                         gl::CreateContextFlags flags,
                                                         WebGLContext* webgl,
                                                         std::vector<FailureReason>* const out_failReasons);

    bool CreateAndInitGLWith(FnCreateGL_T fnCreateGL, const gl::SurfaceCaps& baseCaps,
                             gl::CreateContextFlags flags,
                             std::vector<FailureReason>* const out_failReasons);

    void ThrowEvent_WebGLContextCreationError(const nsACString& text);

    // -------------------------------------------------------------------------
    // Validation functions (implemented in WebGLContextValidate.cpp)
    bool InitAndValidateGL(FailureReason* const out_failReason);

    bool ValidateBlendEquationEnum(GLenum cap, const char* info);
    bool ValidateBlendFuncDstEnum(GLenum mode, const char* info);
    bool ValidateBlendFuncSrcEnum(GLenum mode, const char* info);
    bool ValidateBlendFuncEnumsCompatibility(GLenum sfactor, GLenum dfactor,
                                             const char* info);
    bool ValidateComparisonEnum(GLenum target, const char* info);
    bool ValidateStencilOpEnum(GLenum action, const char* info);
    bool ValidateFaceEnum(GLenum face, const char* info);
    bool ValidateTexInputData(GLenum type, js::Scalar::Type jsArrayType,
                              WebGLTexImageFunc func, WebGLTexDimensions dims);
    bool ValidateDrawModeEnum(GLenum mode, const char* info);
    bool ValidateAttribIndex(GLuint index, const char* info);
    bool ValidateAttribPointer(bool integerMode, GLuint index, GLint size, GLenum type,
                               WebGLboolean normalized, GLsizei stride,
                               WebGLintptr byteOffset, const char* info);
    bool ValidateStencilParamsForDrawCall();

    bool ValidateCopyTexImage(TexInternalFormat srcFormat, TexInternalFormat dstformat,
                              WebGLTexImageFunc func, WebGLTexDimensions dims);

    bool ValidateTexImage(TexImageTarget texImageTarget,
                          GLint level, GLenum internalFormat,
                          GLint xoffset, GLint yoffset, GLint zoffset,
                          GLint width, GLint height, GLint depth,
                          GLint border, GLenum format, GLenum type,
                          WebGLTexImageFunc func, WebGLTexDimensions dims);
    bool ValidateTexImageFormat(GLenum internalFormat, WebGLTexImageFunc func,
                                WebGLTexDimensions dims);
    bool ValidateTexImageType(GLenum type, WebGLTexImageFunc func,
                              WebGLTexDimensions dims);
    bool ValidateTexImageFormatAndType(GLenum format, GLenum type,
                                       WebGLTexImageFunc func,
                                       WebGLTexDimensions dims);
    bool ValidateCompTexImageInternalFormat(GLenum format,
                                            WebGLTexImageFunc func,
                                            WebGLTexDimensions dims);
    bool ValidateCopyTexImageInternalFormat(GLenum format,
                                            WebGLTexImageFunc func,
                                            WebGLTexDimensions dims);
    bool ValidateTexImageSize(TexImageTarget texImageTarget, GLint level,
                              GLint width, GLint height, GLint depth,
                              WebGLTexImageFunc func, WebGLTexDimensions dims);
    bool ValidateTexSubImageSize(GLint x, GLint y, GLint z, GLsizei width,
                                 GLsizei height, GLsizei depth,
                                 GLsizei baseWidth, GLsizei baseHeight,
                                 GLsizei baseDepth, WebGLTexImageFunc func,
                                 WebGLTexDimensions dims);
    bool ValidateCompTexImageSize(GLint level, GLenum internalFormat,
                                  GLint xoffset, GLint yoffset, GLsizei width,
                                  GLsizei height, GLsizei levelWidth,
                                  GLsizei levelHeight, WebGLTexImageFunc func,
                                  WebGLTexDimensions dims);
    bool ValidateCompTexImageDataSize(GLint level, GLenum internalFormat,
                                      GLsizei width, GLsizei height,
                                      uint32_t byteLength,
                                      WebGLTexImageFunc func,
                                      WebGLTexDimensions dims);

    bool ValidateUniformLocationForProgram(WebGLUniformLocation* location,
                                           WebGLProgram* program,
                                           const char* funcName);

    bool ValidateCurFBForRead(const char* funcName,
                              const webgl::FormatUsageInfo** const out_format,
                              uint32_t* const out_width, uint32_t* const out_height);

    bool HasDrawBuffers() const {
        return IsWebGL2() ||
               IsExtensionEnabled(WebGLExtensionID::WEBGL_draw_buffers);
    }

    WebGLRefPtr<WebGLBuffer>* ValidateBufferSlot(const char* funcName, GLenum target);
public:
    WebGLBuffer* ValidateBufferSelection(const char* funcName, GLenum target);
protected:
    IndexedBufferBinding* ValidateIndexedBufferSlot(const char* funcName, GLenum target,
                                                    GLuint index);

    bool ValidateIndexedBufferBinding(const char* funcName, GLenum target, GLuint index,
                                      WebGLRefPtr<WebGLBuffer>** const out_genericBinding,
                                      IndexedBufferBinding** const out_indexedBinding);

    bool ValidateNonNegative(const char* funcName, const char* argName, int64_t val) {
        if (MOZ_UNLIKELY(val < 0)) {
            ErrorInvalidValue("%s: `%s` must be non-negative.", funcName, argName);
            return false;
        }
        return true;
    }

public:
    template<typename T>
    bool ValidateNonNull(const char* funcName, const dom::Nullable<T>& maybe) {
        if (maybe.IsNull()) {
            ErrorInvalidValue("%s: `null` is invalid.", funcName);
            return false;
        }
        return true;
    }

    bool ValidateArrayBufferView(const char* funcName, const dom::ArrayBufferView& view,
                                 GLuint elemOffset, GLuint elemCountOverride,
                                 uint8_t** const out_bytes, size_t* const out_byteLen);

protected:
    ////

    void Invalidate();
    void DestroyResourcesAndContext();

    void MakeContextCurrent() const;

    // helpers

    bool ConvertImage(size_t width, size_t height, size_t srcStride,
                      size_t dstStride, const uint8_t* src, uint8_t* dst,
                      WebGLTexelFormat srcFormat, bool srcPremultiplied,
                      WebGLTexelFormat dstFormat, bool dstPremultiplied,
                      size_t dstTexelSize);

    //////
public:
    bool ValidateObjectAllowDeleted(const char* funcName,
                                    const WebGLContextBoundObject& object)
    {
        if (!object.IsCompatibleWithContext(this)) {
            ErrorInvalidOperation("%s: Object from different WebGL context (or older"
                                  " generation of this one) passed as argument.",
                                  funcName);
            return false;
        }

        return true;
    }

    bool ValidateObject(const char* funcName, const WebGLDeletableObject& object,
                        bool isShaderOrProgram = false)
    {
        if (!ValidateObjectAllowDeleted(funcName, object))
            return false;

        if (isShaderOrProgram) {
            /* GLES 3.0.5 p45:
             * "Commands that accept shader or program object names will generate the
             *  error INVALID_VALUE if the provided name is not the name of either a
             *  shader or program object[.]"
             * Further, shaders and programs appear to be different from other objects,
             * in that their lifetimes are better defined. However, they also appear to
             * allow use of objects marked for deletion, and only reject
             * actually-destroyed objects.
             */
            if (object.IsDeleted()) {
                ErrorInvalidValue("%s: Shader or program object argument cannot have been"
                                  " deleted.",
                                  funcName);
                return false;
            }
        } else {
            if (object.IsDeleteRequested()) {
                ErrorInvalidOperation("%s: Object argument cannot have been marked for"
                                      " deletion.",
                                      funcName);
                return false;
            }
        }

        return true;
    }

    ////

    bool ValidateObject(const char* funcName, const WebGLProgram& object);
    bool ValidateObject(const char* funcName, const WebGLShader& object);

    ////

    bool ValidateIsObject(const char* funcName,
                          const WebGLDeletableObject* object) const
    {
        if (IsContextLost())
            return false;

        if (!object)
            return false;

        if (!object->IsCompatibleWithContext(this))
            return false;

        if (object->IsDeleted())
            return false;

        return true;
    }

    bool ValidateDeleteObject(const char* funcName, const WebGLDeletableObject* object) {
        if (IsContextLost())
            return false;

        if (!object)
            return false;

        if (!ValidateObjectAllowDeleted(funcName, *object))
            return false;

        if (object->IsDeleteRequested())
            return false;

        return true;
    }

    ////

private:
    // -------------------------------------------------------------------------
    // Context customization points
    virtual WebGLVertexArray* CreateVertexArrayImpl();

    virtual bool ValidateAttribPointerType(bool integerMode, GLenum type, uint32_t* alignment, const char* info) = 0;
    virtual bool ValidateUniformMatrixTranspose(bool transpose, const char* info) = 0;

public:
    void ForceLoseContext(bool simulateLoss = false);

protected:
    void ForceRestoreContext();

    nsTArray<WebGLRefPtr<WebGLTexture> > mBound2DTextures;
    nsTArray<WebGLRefPtr<WebGLTexture> > mBoundCubeMapTextures;
    nsTArray<WebGLRefPtr<WebGLTexture> > mBound3DTextures;
    nsTArray<WebGLRefPtr<WebGLTexture> > mBound2DArrayTextures;
    nsTArray<WebGLRefPtr<WebGLSampler> > mBoundSamplers;

    void ResolveTexturesForDraw() const;

    WebGLRefPtr<WebGLProgram> mCurrentProgram;
    RefPtr<const webgl::LinkedProgramInfo> mActiveProgramLinkInfo;

    bool ValidateFramebufferTarget(GLenum target, const char* const info);
    bool ValidateInvalidateFramebuffer(const char* funcName, GLenum target,
                                       const dom::Sequence<GLenum>& attachments,
                                       ErrorResult* const out_rv,
                                       std::vector<GLenum>* const scopedVector,
                                       GLsizei* const out_glNumAttachments,
                                       const GLenum** const out_glAttachments);

    WebGLRefPtr<WebGLFramebuffer> mBoundDrawFramebuffer;
    WebGLRefPtr<WebGLFramebuffer> mBoundReadFramebuffer;
    WebGLRefPtr<WebGLRenderbuffer> mBoundRenderbuffer;
    WebGLRefPtr<WebGLTransformFeedback> mBoundTransformFeedback;
    WebGLRefPtr<WebGLVertexArray> mBoundVertexArray;

    LinkedList<WebGLBuffer> mBuffers;
    LinkedList<WebGLFramebuffer> mFramebuffers;
    LinkedList<WebGLProgram> mPrograms;
    LinkedList<WebGLQuery> mQueries;
    LinkedList<WebGLRenderbuffer> mRenderbuffers;
    LinkedList<WebGLSampler> mSamplers;
    LinkedList<WebGLShader> mShaders;
    LinkedList<WebGLSync> mSyncs;
    LinkedList<WebGLTexture> mTextures;
    LinkedList<WebGLTransformFeedback> mTransformFeedbacks;
    LinkedList<WebGLVertexArray> mVertexArrays;

    WebGLRefPtr<WebGLTransformFeedback> mDefaultTransformFeedback;
    WebGLRefPtr<WebGLVertexArray> mDefaultVertexArray;

    // PixelStore parameters
    uint32_t mPixelStore_UnpackImageHeight;
    uint32_t mPixelStore_UnpackSkipImages;
    uint32_t mPixelStore_UnpackRowLength;
    uint32_t mPixelStore_UnpackSkipRows;
    uint32_t mPixelStore_UnpackSkipPixels;
    uint32_t mPixelStore_UnpackAlignment;
    uint32_t mPixelStore_PackRowLength;
    uint32_t mPixelStore_PackSkipRows;
    uint32_t mPixelStore_PackSkipPixels;
    uint32_t mPixelStore_PackAlignment;

    CheckedUint32 GetUnpackSize(bool isFunc3D, uint32_t width, uint32_t height,
                                uint32_t depth, uint8_t bytesPerPixel);

    bool ValidatePackSize(const char* funcName, uint32_t width, uint32_t height,
                          uint8_t bytesPerPixel, uint32_t* const out_rowStride,
                          uint32_t* const out_endOffset);

    GLenum mPixelStore_ColorspaceConversion;
    bool mPixelStore_FlipY;
    bool mPixelStore_PremultiplyAlpha;

    ////////////////////////////////////
    class FakeBlackTexture {
    public:
        static UniquePtr<FakeBlackTexture> Create(gl::GLContext* gl,
                                                  TexTarget target,
                                                  FakeBlackType type);
        gl::GLContext* const mGL;
        const GLuint mGLName;

        ~FakeBlackTexture();
    protected:
        explicit FakeBlackTexture(gl::GLContext* gl);
    };

    UniquePtr<FakeBlackTexture> mFakeBlack_2D_0000;
    UniquePtr<FakeBlackTexture> mFakeBlack_2D_0001;
    UniquePtr<FakeBlackTexture> mFakeBlack_CubeMap_0000;
    UniquePtr<FakeBlackTexture> mFakeBlack_CubeMap_0001;
    UniquePtr<FakeBlackTexture> mFakeBlack_3D_0000;
    UniquePtr<FakeBlackTexture> mFakeBlack_3D_0001;
    UniquePtr<FakeBlackTexture> mFakeBlack_2D_Array_0000;
    UniquePtr<FakeBlackTexture> mFakeBlack_2D_Array_0001;

    bool BindFakeBlack(uint32_t texUnit, TexTarget target, FakeBlackType fakeBlack);

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

protected:
    GLuint mEmptyTFO;

    // Generic Vertex Attributes
    // Though CURRENT_VERTEX_ATTRIB is listed under "Vertex Shader State" in the spec
    // state tables, this isn't vertex shader /object/ state. This array is merely state
    // useful to vertex shaders, but is global state.
    UniquePtr<GLenum[]> mGenericVertexAttribTypes;
    uint8_t mGenericVertexAttrib0Data[sizeof(float) * 4];

    GLuint mFakeVertexAttrib0BufferObject;
    size_t mFakeVertexAttrib0BufferObjectSize;
    bool mFakeVertexAttrib0DataDefined;
    uint8_t mFakeVertexAttrib0Data[sizeof(float) * 4];

    JSObject* GetVertexAttribFloat32Array(JSContext* cx, GLuint index);
    JSObject* GetVertexAttribInt32Array(JSContext* cx, GLuint index);
    JSObject* GetVertexAttribUint32Array(JSContext* cx, GLuint index);

    GLint mStencilRefFront;
    GLint mStencilRefBack;
    GLuint mStencilValueMaskFront;
    GLuint mStencilValueMaskBack;
    GLuint mStencilWriteMaskFront;
    GLuint mStencilWriteMaskBack;
    realGLboolean mColorWriteMask[4];
    realGLboolean mDepthWriteMask;
    GLfloat mColorClearValue[4];
    GLint mStencilClearValue;
    GLfloat mDepthClearValue;

    GLint mViewportX;
    GLint mViewportY;
    GLsizei mViewportWidth;
    GLsizei mViewportHeight;
    bool mAlreadyWarnedAboutViewportLargerThanDest;

    GLfloat mLineWidth;

    WebGLContextLossHandler mContextLossHandler;
    bool mAllowContextRestore;
    bool mLastLossWasSimulated;
    ContextStatus mContextStatus;
    bool mContextLostErrorSet;

    // Used for some hardware (particularly Tegra 2 and 4) that likes to
    // be Flushed while doing hundreds of draw calls.
    int mDrawCallsSinceLastFlush;

    int mAlreadyGeneratedWarnings;
    int mMaxWarnings;
    bool mAlreadyWarnedAboutFakeVertexAttrib0;

    bool ShouldGenerateWarnings() const;

    uint64_t mLastUseIndex;

    bool mNeedsFakeNoAlpha;
    bool mNeedsFakeNoDepth;
    bool mNeedsFakeNoStencil;
    bool mNeedsEmulatedLoneDepthStencil;

    const bool mAllowFBInvalidation;

    bool Has64BitTimestamps() const;

    struct ScopedDrawCallWrapper final {
        WebGLContext& mWebGL;
        const bool mFakeNoAlpha;
        const bool mFakeNoDepth;
        const bool mFakeNoStencil;

        static bool ShouldFakeNoAlpha(WebGLContext& webgl) {
            // We should only be doing this if we're about to draw to the backbuffer, but
            // the backbuffer needs to have this fake-no-alpha workaround.
            return !webgl.mBoundDrawFramebuffer &&
                   webgl.mNeedsFakeNoAlpha &&
                   webgl.mColorWriteMask[3] != false;
        }

        static bool ShouldFakeNoDepth(WebGLContext& webgl) {
            // We should only be doing this if we're about to draw to the backbuffer.
            return !webgl.mBoundDrawFramebuffer &&
                   webgl.mNeedsFakeNoDepth &&
                   webgl.mDepthTestEnabled;
        }

        static bool HasDepthButNoStencil(const WebGLFramebuffer* fb);

        static bool ShouldFakeNoStencil(WebGLContext& webgl) {
            if (!webgl.mStencilTestEnabled)
                return false;

            if (!webgl.mBoundDrawFramebuffer) {
                if (webgl.mNeedsFakeNoStencil)
                    return true;

                if (webgl.mNeedsEmulatedLoneDepthStencil &&
                    webgl.mOptions.depth && !webgl.mOptions.stencil)
                {
                    return true;
                }

                return false;
            }

            if (webgl.mNeedsEmulatedLoneDepthStencil &&
                HasDepthButNoStencil(webgl.mBoundDrawFramebuffer))
            {
                return true;
            }

            return false;
        }

        ////

        explicit ScopedDrawCallWrapper(WebGLContext& webgl);
        ~ScopedDrawCallWrapper();
    };

    void OnBeforeReadCall();

    void LoseOldestWebGLContextIfLimitExceeded();
    void UpdateLastUseIndex();

    template <typename WebGLObjectType>
    JS::Value WebGLObjectAsJSValue(JSContext* cx, const WebGLObjectType*,
                                   ErrorResult& rv) const;
    template <typename WebGLObjectType>
    JSObject* WebGLObjectAsJSObject(JSContext* cx, const WebGLObjectType*,
                                    ErrorResult& rv) const;

#ifdef XP_MACOSX
    // see bug 713305. This RAII helper guarantees that we're on the discrete GPU, during its lifetime
    // Debouncing note: we don't want to switch GPUs too frequently, so try to not create and destroy
    // these objects at high frequency. Having WebGLContext's hold one such object seems fine,
    // because WebGLContext objects only go away during GC, which shouldn't happen too frequently.
    // If in the future GC becomes much more frequent, we may have to revisit then (maybe use a timer).
    ForceDiscreteGPUHelperCGL mForceDiscreteGPUHelper;
#endif

public:
    // console logging helpers
    void GenerateWarning(const char* fmt, ...);
    void GenerateWarning(const char* fmt, va_list ap);

public:
    UniquePtr<webgl::FormatUsageAuthority> mFormatUsage;

    virtual UniquePtr<webgl::FormatUsageAuthority>
    CreateFormatUsage(gl::GLContext* gl) const = 0;


    const decltype(mBound2DTextures)* TexListForElemType(GLenum elemType) const;

    // Friend list
    friend class ScopedCopyTexImageSource;
    friend class ScopedResolveTexturesForDraw;
    friend class ScopedUnpackReset;
    friend class webgl::TexUnpackBlob;
    friend class webgl::TexUnpackBytes;
    friend class webgl::TexUnpackImage;
    friend class webgl::TexUnpackSurface;
    friend struct webgl::UniformInfo;
    friend class WebGLTexture;
    friend class WebGLFBAttachPoint;
    friend class WebGLFramebuffer;
    friend class WebGLRenderbuffer;
    friend class WebGLProgram;
    friend class WebGLQuery;
    friend class WebGLBuffer;
    friend class WebGLSampler;
    friend class WebGLShader;
    friend class WebGLSync;
    friend class WebGLTransformFeedback;
    friend class WebGLUniformLocation;
    friend class WebGLVertexArray;
    friend class WebGLVertexArrayFake;
    friend class WebGLVertexArrayGL;
};

// used by DOM bindings in conjunction with GetParentObject
inline nsISupports*
ToSupports(WebGLContext* webgl)
{
    return static_cast<nsIDOMWebGLRenderingContext*>(webgl);
}

// Returns `value` rounded to the next highest multiple of `multiple`.
// AKA PadToAlignment, StrideForAlignment.
template<typename V, typename M>
V
RoundUpToMultipleOf(const V& value, const M& multiple)
{
    return ((value + multiple - 1) / multiple) * multiple;
}

bool
ValidateTexTarget(WebGLContext* webgl, const char* funcName, uint8_t funcDims,
                  GLenum rawTexTarget, TexTarget* const out_texTarget,
                  WebGLTexture** const out_tex);
bool
ValidateTexImageTarget(WebGLContext* webgl, const char* funcName, uint8_t funcDims,
                       GLenum rawTexImageTarget, TexImageTarget* const out_texImageTarget,
                       WebGLTexture** const out_tex);

class UniqueBuffer
{
    // Like UniquePtr<>, but for void* and malloc/calloc/free.
    void* mBuffer;

public:
    UniqueBuffer()
        : mBuffer(nullptr)
    { }

    MOZ_IMPLICIT UniqueBuffer(void* buffer)
        : mBuffer(buffer)
    { }

    ~UniqueBuffer() {
        free(mBuffer);
    }

    UniqueBuffer(UniqueBuffer&& other) {
        this->mBuffer = other.mBuffer;
        other.mBuffer = nullptr;
    }

    UniqueBuffer& operator =(UniqueBuffer&& other) {
        free(this->mBuffer);
        this->mBuffer = other.mBuffer;
        other.mBuffer = nullptr;
        return *this;
    }

    UniqueBuffer& operator =(void* newBuffer) {
        free(this->mBuffer);
        this->mBuffer = newBuffer;
        return *this;
    }

    explicit operator bool() const { return bool(mBuffer); }

    void* get() const { return mBuffer; }

    UniqueBuffer(const UniqueBuffer& other) = delete; // construct using Move()!
    void operator =(const UniqueBuffer& other) = delete; // assign using Move()!
};

class ScopedUnpackReset final
    : public gl::ScopedGLWrapper<ScopedUnpackReset>
{
    friend struct gl::ScopedGLWrapper<ScopedUnpackReset>;

private:
    WebGLContext* const mWebGL;

public:
    explicit ScopedUnpackReset(WebGLContext* webgl);

private:
    void UnwrapImpl();
};

class ScopedFBRebinder final
    : public gl::ScopedGLWrapper<ScopedFBRebinder>
{
    friend struct gl::ScopedGLWrapper<ScopedFBRebinder>;

private:
    WebGLContext* const mWebGL;

public:
    explicit ScopedFBRebinder(WebGLContext* webgl)
        : ScopedGLWrapper<ScopedFBRebinder>(webgl->gl)
        , mWebGL(webgl)
    { }

private:
    void UnwrapImpl();
};

class ScopedLazyBind final
    : public gl::ScopedGLWrapper<ScopedLazyBind>
{
    friend struct gl::ScopedGLWrapper<ScopedLazyBind>;

    const GLenum mTarget;
    const WebGLBuffer* const mBuf;

public:
    ScopedLazyBind(gl::GLContext* gl, GLenum target, const WebGLBuffer* buf);

private:
    void UnwrapImpl();
};

////

bool
Intersect(int32_t srcSize, int32_t read0, int32_t readSize, int32_t* out_intRead0,
          int32_t* out_intWrite0, int32_t* out_intSize);

////

void
ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& callback,
                            const std::vector<IndexedBufferBinding>& field,
                            const char* name, uint32_t flags = 0);

void
ImplCycleCollectionUnlink(std::vector<IndexedBufferBinding>& field);

} // namespace mozilla

#endif
