gecko-dev/dom/canvas/WebGLContextState.cpp

/* -*- 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/. */

#include "WebGLContext.h"

#include "GLContext.h"
#include "GLScreenBuffer.h"
#include "mozilla/dom/ToJSValue.h"
#include "mozilla/Maybe.h"
#include "mozilla/Preferences.h"
#include "MozFramebuffer.h"
#include "nsString.h"
#include "WebGLBuffer.h"
#include "WebGLContextUtils.h"
#include "WebGLFramebuffer.h"
#include "WebGLProgram.h"
#include "WebGLRenderbuffer.h"
#include "WebGLShader.h"
#include "WebGLTexture.h"
#include "WebGLVertexArray.h"

namespace mozilla {

void
WebGLContext::SetEnabled(const char* const funcName, const GLenum cap, const bool enabled)
{
    if (IsContextLost())
        return;

    if (!ValidateCapabilityEnum(cap, funcName))
        return;

    const auto& slot = GetStateTrackingSlot(cap);
    if (slot) {
        *slot = enabled;
    }

    switch (cap) {
    case LOCAL_GL_DEPTH_TEST:
    case LOCAL_GL_STENCIL_TEST:
        break; // Lazily applied, so don't tell GL yet or we will desync.

    default:
        // Non-lazy caps.
        gl->SetEnabled(cap, enabled);
        break;
    }
}

bool
WebGLContext::GetStencilBits(GLint* const out_stencilBits) const
{
    *out_stencilBits = 0;
    if (mBoundDrawFramebuffer) {
        if (mBoundDrawFramebuffer->StencilAttachment().IsDefined() &&
            mBoundDrawFramebuffer->DepthStencilAttachment().IsDefined())
        {
            // Error, we don't know which stencil buffer's bits to use
            ErrorInvalidFramebufferOperation("getParameter: framebuffer has two stencil buffers bound");
            return false;
        }

        if (mBoundDrawFramebuffer->StencilAttachment().IsDefined() ||
            mBoundDrawFramebuffer->DepthStencilAttachment().IsDefined())
        {
            *out_stencilBits = 8;
        }
    } else if (mOptions.stencil) {
        *out_stencilBits = 8;
    }

    return true;
}

JS::Value
WebGLContext::GetParameter(JSContext* cx, GLenum pname, ErrorResult& rv)
{
    const char funcName[] = "getParameter";

    if (IsContextLost())
        return JS::NullValue();

    if (IsWebGL2() || 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 ret = LOCAL_GL_NONE;
            if (!mBoundDrawFramebuffer) {
                if (pname == LOCAL_GL_DRAW_BUFFER0) {
                    ret = mDefaultFB_DrawBuffer0;
                }
            } else {
                gl->fGetIntegerv(pname, &ret);
            }
            return JS::Int32Value(ret);
        }
    }

    if (IsWebGL2() || 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)) {
        switch (pname) {
        case LOCAL_GL_TIMESTAMP_EXT:
            {
                uint64_t val = 0;
                if (Has64BitTimestamps()) {
                    gl->fGetInteger64v(pname, (GLint64*)&val);
                } else {
                    gl->fGetIntegerv(pname, (GLint*)&val);
                }
                // TODO: JS doesn't support 64-bit integers. Be lossy and
                // cast to double (53 bits)
                return JS::NumberValue(val);
            }

        case LOCAL_GL_GPU_DISJOINT_EXT:
            {
                realGLboolean val = false; // Not disjoint by default.
                if (gl->IsExtensionSupported(gl::GLContext::EXT_disjoint_timer_query)) {
                    gl->fGetBooleanv(pname, &val);
                }
                return JS::BooleanValue(val);
            }

        default:
            break;
        }
    }

    // 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("GFX: 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 (IsWebGL2() || 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: {
            GLint i = 0;
            gl->fGetIntegerv(pname, &i);
            return JS::NumberValue(uint32_t(i));
        }

        case LOCAL_GL_GENERATE_MIPMAP_HINT:
            return JS::NumberValue(mGenerateMipmapHint);

        case LOCAL_GL_IMPLEMENTATION_COLOR_READ_FORMAT:
        case LOCAL_GL_IMPLEMENTATION_COLOR_READ_TYPE: {
            const webgl::FormatUsageInfo* usage;
            uint32_t width, height;
            if (!BindCurFBForColorRead(funcName, &usage, &width, &height))
                return JS::NullValue();

            const auto implPI = ValidImplementationColorReadPI(usage);

            GLenum ret;
            if (pname == LOCAL_GL_IMPLEMENTATION_COLOR_READ_FORMAT) {
                ret = implPI.format;
            } else {
                ret = implPI.type;
            }
            return JS::NumberValue(uint32_t(ret));
        }

        // 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_SAMPLE_BUFFERS:
        case LOCAL_GL_SAMPLES: {
            const auto& fb = mBoundDrawFramebuffer;
            auto samples = [&]() -> Maybe<uint32_t> {
                if (!fb) {
                    if (!EnsureDefaultFB(funcName))
                        return Nothing();
                    return Some(mDefaultFB->mSamples);
                }

                if (!fb->IsCheckFramebufferStatusComplete(funcName))
                    return Some(0);

                DoBindFB(fb, LOCAL_GL_FRAMEBUFFER);
                return Some(gl->GetIntAs<uint32_t>(LOCAL_GL_SAMPLES));
            }();
            if (samples && pname == LOCAL_GL_SAMPLE_BUFFERS) {
                samples = Some(uint32_t(bool(samples.value())));
            }
            if (!samples)
                return JS::NullValue();
            return JS::NumberValue(samples.value());
        }

        case LOCAL_GL_STENCIL_CLEAR_VALUE:
        case LOCAL_GL_UNPACK_ALIGNMENT:
        case LOCAL_GL_PACK_ALIGNMENT:
        case LOCAL_GL_SUBPIXEL_BITS: {
            GLint i = 0;
            gl->fGetIntegerv(pname, &i);
            return JS::Int32Value(i);
        }

        case LOCAL_GL_RED_BITS:
        case LOCAL_GL_GREEN_BITS:
        case LOCAL_GL_BLUE_BITS:
        case LOCAL_GL_ALPHA_BITS:
        case LOCAL_GL_DEPTH_BITS:
        case LOCAL_GL_STENCIL_BITS: {
            const auto format = [&]() -> const webgl::FormatInfo* {
                if (mBoundDrawFramebuffer) {
                    const auto& fb = *mBoundDrawFramebuffer;
                    const auto& attachment = [&]() -> const auto& {
                        switch (pname) {
                        case LOCAL_GL_DEPTH_BITS:
                            return fb.AnyDepthAttachment();

                        case LOCAL_GL_STENCIL_BITS:
                            return fb.AnyStencilAttachment();

                        default:
                            return fb.ColorAttachment0();
                        }
                    }();
                    if (!attachment.HasImage())
                        return nullptr;
                    return attachment.Format()->format;
                }

                auto effFormat = webgl::EffectiveFormat::RGB8;
                switch (pname) {
                case LOCAL_GL_DEPTH_BITS:
                    if (mOptions.depth) {
                        effFormat = webgl::EffectiveFormat::DEPTH24_STENCIL8;
                    }
                    break;

                case LOCAL_GL_STENCIL_BITS:
                    if (mOptions.stencil) {
                        effFormat = webgl::EffectiveFormat::DEPTH24_STENCIL8;
                    }
                    break;

                default:
                    if (mOptions.alpha) {
                        effFormat = webgl::EffectiveFormat::RGBA8;
                    }
                    break;
                }
                return webgl::GetFormat(effFormat);
            }();
            int32_t ret = 0;
            if (format) {
                switch (pname) {
                case LOCAL_GL_RED_BITS:
                    ret = format->r;
                    break;
                case LOCAL_GL_GREEN_BITS:
                    ret = format->g;
                    break;
                case LOCAL_GL_BLUE_BITS:
                    ret = format->b;
                    break;
                case LOCAL_GL_ALPHA_BITS:
                    ret = format->a;
                    break;
                case LOCAL_GL_DEPTH_BITS:
                    ret = format->d;
                    break;
                case LOCAL_GL_STENCIL_BITS:
                    ret = format->s;
                    break;
                }
            }
            return JS::Int32Value(ret);
        }

        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_TEXTURE_IMAGE_UNITS:
            return JS::Int32Value(mGLMaxVertexTextureImageUnits);

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

        case LOCAL_GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS:
            return JS::Int32Value(mGLMaxCombinedTextureImageUnits);

        case LOCAL_GL_MAX_VERTEX_ATTRIBS:
            return JS::Int32Value(mGLMaxVertexAttribs);

        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_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_LINE_WIDTH:
            return JS::DoubleValue(mLineWidth);

        case LOCAL_GL_DEPTH_CLEAR_VALUE:
        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_DEPTH_TEST:
            return JS::BooleanValue(mDepthTestEnabled);
        case LOCAL_GL_STENCIL_TEST:
            return JS::BooleanValue(mStencilTestEnabled);

        case LOCAL_GL_BLEND:
        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_SAMPLE_ALPHA_TO_COVERAGE:
        case LOCAL_GL_SAMPLE_COVERAGE:
        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(mPixelStore_FlipY);
        case UNPACK_PREMULTIPLY_ALPHA_WEBGL:
            return JS::BooleanValue(mPixelStore_PremultiplyAlpha);

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

        ////////////////////////////////
        // 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 };
            switch (pname) {
            case LOCAL_GL_ALIASED_POINT_SIZE_RANGE:
                fv[0] = mGLAliasedPointSizeRange[0];
                fv[1] = mGLAliasedPointSizeRange[1];
                break;
            case LOCAL_GL_ALIASED_LINE_WIDTH_RANGE:
                fv[0] = mGLAliasedLineWidthRange[0];
                fv[1] = mGLAliasedLineWidthRange[1];
                break;
            // case LOCAL_GL_DEPTH_RANGE:
            default:
                gl->fGetFloatv(pname, fv);
                break;
            }
            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] = { GLint(mGLMaxViewportDims[0]), GLint(mGLMaxViewportDims[1]) };
            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: {
            const bool vals[4] = { bool(mColorWriteMask & (1 << 0)),
                                   bool(mColorWriteMask & (1 << 1)),
                                   bool(mColorWriteMask & (1 << 2)),
                                   bool(mColorWriteMask & (1 << 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();
}

void
WebGLContext::GetParameterIndexed(JSContext* cx, GLenum pname, GLuint index,
                                  JS::MutableHandle<JS::Value> retval)
{
    if (IsContextLost()) {
        retval.setNull();
        return;
    }

    switch (pname) {
        case LOCAL_GL_TRANSFORM_FEEDBACK_BUFFER_BINDING:
        {
            if (index >= mGLMaxTransformFeedbackSeparateAttribs) {
                ErrorInvalidValue("getParameterIndexed: index should be less than MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS");
                retval.setNull();
                return;
            }
            retval.setNull(); // See bug 903594
            return;
        }

        default:
            break;
    }

    ErrorInvalidEnumInfo("getParameterIndexed: parameter", pname);
    retval.setNull();
}

bool
WebGLContext::IsEnabled(GLenum cap)
{
    if (IsContextLost())
        return false;

    if (!ValidateCapabilityEnum(cap, "isEnabled"))
        return false;

    const auto& slot = GetStateTrackingSlot(cap);
    if (slot)
        return *slot;

    return gl->fIsEnabled(cap);
}

bool
WebGLContext::ValidateCapabilityEnum(GLenum cap, const char* info)
{
    switch (cap) {
        case LOCAL_GL_BLEND:
        case LOCAL_GL_CULL_FACE:
        case LOCAL_GL_DEPTH_TEST:
        case LOCAL_GL_DITHER:
        case LOCAL_GL_POLYGON_OFFSET_FILL:
        case LOCAL_GL_SAMPLE_ALPHA_TO_COVERAGE:
        case LOCAL_GL_SAMPLE_COVERAGE:
        case LOCAL_GL_SCISSOR_TEST:
        case LOCAL_GL_STENCIL_TEST:
            return true;
        case LOCAL_GL_RASTERIZER_DISCARD:
            return IsWebGL2();
        default:
            ErrorInvalidEnumInfo(info, cap);
            return false;
    }
}

realGLboolean*
WebGLContext::GetStateTrackingSlot(GLenum cap)
{
    switch (cap) {
        case LOCAL_GL_DEPTH_TEST:
            return &mDepthTestEnabled;
        case LOCAL_GL_DITHER:
            return &mDitherEnabled;
        case LOCAL_GL_RASTERIZER_DISCARD:
            return &mRasterizerDiscardEnabled;
        case LOCAL_GL_SCISSOR_TEST:
            return &mScissorTestEnabled;
        case LOCAL_GL_STENCIL_TEST:
            return &mStencilTestEnabled;
    }

    return nullptr;
}

} // namespace mozilla