xref: /third_party/flutter/skia/src/gpu/gl/GrGLCaps.h

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#ifndef GrGLCaps_DEFINED
#define GrGLCaps_DEFINED

#include <functional>
#include "include/private/GrGLTypesPriv.h"
#include "include/private/SkChecksum.h"
#include "include/private/SkTArray.h"
#include "include/private/SkTHash.h"
#include "src/gpu/GrCaps.h"
#include "src/gpu/GrSwizzle.h"
#include "src/gpu/gl/GrGLStencilAttachment.h"
#include "src/gpu/gl/GrGLUtil.h"

class GrGLContextInfo;
class GrGLRenderTarget;

/**
 * Stores some capabilities of a GL context. Most are determined by the GL
 * version and the extensions string. It also tracks formats that have passed
 * the FBO completeness test.
 */
class GrGLCaps : public GrCaps {
public:
    typedef GrGLStencilAttachment::Format StencilFormat;

    /**
     * The type of MSAA for FBOs supported. Different extensions have different
     * semantics of how / when a resolve is performed.
     */
    enum MSFBOType {
        /**
         * no support for MSAA FBOs
         */
        kNone_MSFBOType = 0,
        /**
         * OpenGL 3.0+, OpenGL ES 3.0+, GL_ARB_framebuffer_object,
         * GL_CHROMIUM_framebuffer_multisample, GL_ANGLE_framebuffer_multisample,
         * or GL_EXT_framebuffer_multisample
         */
        kStandard_MSFBOType,
        /**
         * GL_APPLE_framebuffer_multisample ES extension
         */
        kES_Apple_MSFBOType,
        /**
         * GL_IMG_multisampled_render_to_texture. This variation does not have MSAA renderbuffers.
         * Instead the texture is multisampled when bound to the FBO and then resolved automatically
         * when read. It also defines an alternate value for GL_MAX_SAMPLES (which we call
         * GR_GL_MAX_SAMPLES_IMG).
         */
        kES_IMG_MsToTexture_MSFBOType,
        /**
         * GL_EXT_multisampled_render_to_texture. Same as the IMG one above but uses the standard
         * GL_MAX_SAMPLES value.
         */
        kES_EXT_MsToTexture_MSFBOType,

        kLast_MSFBOType = kES_EXT_MsToTexture_MSFBOType
    };

    enum BlitFramebufferFlags {
        kNoSupport_BlitFramebufferFlag                    = 1 << 0,
        kNoScalingOrMirroring_BlitFramebufferFlag         = 1 << 1,
        kResolveMustBeFull_BlitFrambufferFlag             = 1 << 2,
        kNoMSAADst_BlitFramebufferFlag                    = 1 << 3,
        kNoFormatConversion_BlitFramebufferFlag           = 1 << 4,
        kNoFormatConversionForMSAASrc_BlitFramebufferFlag = 1 << 5,
        kRectsMustMatchForMSAASrc_BlitFramebufferFlag     = 1 << 6,
    };

    enum InvalidateFBType {
        kNone_InvalidateFBType,
        kDiscard_InvalidateFBType,       //<! glDiscardFramebuffer()
        kInvalidate_InvalidateFBType,    //<! glInvalidateFramebuffer()

        kLast_InvalidateFBType = kInvalidate_InvalidateFBType
    };

    enum MapBufferType {
        kNone_MapBufferType,
        kMapBuffer_MapBufferType,         // glMapBuffer()
        kMapBufferRange_MapBufferType,    // glMapBufferRange()
        kChromium_MapBufferType,          // GL_CHROMIUM_map_sub

        kLast_MapBufferType = kChromium_MapBufferType,
    };

    enum TransferBufferType {
        kNone_TransferBufferType,
        kPBO_TransferBufferType,          // ARB_pixel_buffer_object
        kChromium_TransferBufferType,     // CHROMIUM_pixel_transfer_buffer_object

        kLast_TransferBufferType = kChromium_TransferBufferType,
    };

    /**
     * Initializes the GrGLCaps to the set of features supported in the current
     * OpenGL context accessible via ctxInfo.
     */
    GrGLCaps(const GrContextOptions& contextOptions, const GrGLContextInfo& ctxInfo,
             const GrGLInterface* glInterface);

    bool isFormatSRGB(const GrBackendFormat&) const override;
    bool isFormatCompressed(const GrBackendFormat&) const override;

    bool isFormatTexturableAndUploadable(GrColorType, const GrBackendFormat&) const override;
    bool isFormatTexturable(const GrBackendFormat&) const override;
    bool isFormatTexturable(GrGLFormat) const;

    bool isFormatAsColorTypeRenderable(GrColorType ct, const GrBackendFormat& format,
                                       int sampleCount = 1) const override;
    bool isFormatRenderable(const GrBackendFormat& format, int sampleCount) const override;
    bool isFormatRenderable(GrGLFormat format, int sampleCount) const {
        return sampleCount <= this->maxRenderTargetSampleCount(format);
    }

    int getRenderTargetSampleCount(int requestedCount,
                                   const GrBackendFormat& format) const override {
        return this->getRenderTargetSampleCount(requestedCount, format.asGLFormat());
    }
    int getRenderTargetSampleCount(int requestedCount, GrGLFormat) const;

    int maxRenderTargetSampleCount(const GrBackendFormat& format) const override {
        return this->maxRenderTargetSampleCount(format.asGLFormat());
    }
    int maxRenderTargetSampleCount(GrGLFormat) const;

    bool isFormatCopyable(const GrBackendFormat&) const override;

    bool canFormatBeFBOColorAttachment(GrGLFormat) const;

    GrGLFormat getFormatFromColorType(GrColorType colorType) const {
        int idx = static_cast<int>(colorType);
        return fColorTypeToFormatTable[idx];
    }

    GrGLenum formatSizedInternalFormat(GrGLFormat format) const {
        return this->getFormatInfo(format).fSizedInternalFormat;
    }

    void getTexImageFormats(GrGLFormat surfaceFormat, GrColorType surfaceColorType,
                            GrColorType memoryColorType, GrGLenum* internalFormat,
                            GrGLenum* externalFormat, GrGLenum* externalType) const;

    void getReadPixelsFormat(GrGLFormat surfaceFormat, GrColorType surfaceColorType,
                             GrColorType memoryColorType, GrGLenum* externalFormat,
                             GrGLenum* externalType) const;

    /**
    * Gets an array of legal stencil formats. These formats are not guaranteed
    * to be supported by the driver but are legal GLenum names given the GL
    * version and extensions supported.
    */
    const SkTArray<StencilFormat, true>& stencilFormats() const {
        return fStencilFormats;
    }

    bool formatSupportsTexStorage(GrGLFormat) const;

    /**
     * Gets the internal format to use with glTexImage...() and glTexStorage...(). May be sized or
     * base depending upon the GL. Not applicable to compressed textures.
     */
    GrGLenum getTexImageInternalFormat(GrGLFormat format) const {
        return this->getFormatInfo(format).fInternalFormatForTexImage;
    }

    /**
     * Gets the internal format to use with glRenderbufferStorageMultisample...(). May be sized or
     * base depending upon the GL. Not applicable to compressed textures.
     */
    GrGLenum getRenderbufferInternalFormat(GrGLFormat format) const {
        return this->getFormatInfo(format).fInternalFormatForRenderbuffer;
    }

    GrGLenum getSizedInternalFormat(GrGLFormat format) const {
        return this->getFormatInfo(format).fSizedInternalFormat;
    }

    GrGLenum getBaseInternalFormat(GrGLFormat format) const {
        return this->getFormatInfo(format).fBaseInternalFormat;
    }

    /**
     * Gets the default external type to use with glTex[Sub]Image... when the data pointer is null.
     */
    GrGLenum getFormatDefaultExternalType(GrGLFormat format) const {
        return this->getFormatInfo(format).fDefaultExternalType;
    }

    /**
     * Has a stencil format index been found for the format (or we've found that no format works).
     */
    bool hasStencilFormatBeenDeterminedForFormat(GrGLFormat format) const {
        return this->getFormatInfo(format).fStencilFormatIndex != FormatInfo::kUnknown_StencilIndex;
    }

    /**
     * Gets the stencil format index for the format. This assumes
     * hasStencilFormatBeenDeterminedForFormat has already been checked. Returns a value < 0 if
     * no stencil format is supported with the format. Otherwise, returned index refers to the array
     * returned by stencilFormats().
     */
    int getStencilFormatIndexForFormat(GrGLFormat format) const {
        SkASSERT(this->hasStencilFormatBeenDeterminedForFormat(format));
        return this->getFormatInfo(format).fStencilFormatIndex;
    }

    /**
     * If index is >= 0 this records an index into stencilFormats() as the best stencil format for
     * the format. If < 0 it records that the format has no supported stencil format index.
     */
    void setStencilFormatIndexForFormat(GrGLFormat, int index);

    /**
     * Call to note that a GrGLFormat has been verified as a valid color attachment. This may save
     * future calls to glCheckFramebufferStatus using isFormatVerifiedColorAttachment().
     */
    void markFormatAsValidColorAttachment(GrGLFormat format) {
        this->getFormatInfo(format).fVerifiedColorAttachment = true;
    }

    /**
     * Call to check whether a format has been verified as a valid color attachment.
     */
    bool isFormatVerifiedColorAttachment(GrGLFormat format) const {
        return this->getFormatInfo(format).fVerifiedColorAttachment;
    }

    /**
     * Reports the type of MSAA FBO support.
     */
    MSFBOType msFBOType() const { return fMSFBOType; }

    /**
     * Does the preferred MSAA FBO extension have MSAA renderbuffers?
     */
    bool usesMSAARenderBuffers() const {
        return kNone_MSFBOType != fMSFBOType &&
               kES_IMG_MsToTexture_MSFBOType != fMSFBOType &&
               kES_EXT_MsToTexture_MSFBOType != fMSFBOType;
    }

    /**
     * What functionality is supported by glBlitFramebuffer.
     */
    uint32_t blitFramebufferSupportFlags() const { return fBlitFramebufferFlags; }

    /**
     * Is the MSAA FBO extension one where the texture is multisampled when bound to an FBO and
     * then implicitly resolved when read.
     */
    bool usesImplicitMSAAResolve() const {
        return kES_IMG_MsToTexture_MSFBOType == fMSFBOType ||
               kES_EXT_MsToTexture_MSFBOType == fMSFBOType;
    }

    InvalidateFBType invalidateFBType() const { return fInvalidateFBType; }

    /// What type of buffer mapping is supported?
    MapBufferType mapBufferType() const { return fMapBufferType; }

    /// What type of transfer buffer is supported?
    TransferBufferType transferBufferType() const { return fTransferBufferType; }

    /// The maximum number of fragment uniform vectors (GLES has min. 16).
    int maxFragmentUniformVectors() const { return fMaxFragmentUniformVectors; }

    /// Is there support for GL_PACK_REVERSE_ROW_ORDER
    bool packFlipYSupport() const { return fPackFlipYSupport; }

    /// Is there support for texture parameter GL_TEXTURE_USAGE
    bool textureUsageSupport() const { return fTextureUsageSupport; }

    /// Is GL_ALPHA8 renderable
    bool alpha8IsRenderable() const { return fAlpha8IsRenderable; }

    /// Is GL_ARB_IMAGING supported
    bool imagingSupport() const { return fImagingSupport; }

    /// Is there support for Vertex Array Objects?
    bool vertexArrayObjectSupport() const { return fVertexArrayObjectSupport; }

    /// Is there support for GL_KHR_debug?
    bool debugSupport() const { return fDebugSupport; }

    /// Is there support for ES2 compatability?
    bool ES2CompatibilitySupport() const { return fES2CompatibilitySupport; }

    /// Is there support for glDraw*Instanced?
    bool drawInstancedSupport() const { return fDrawInstancedSupport; }

    /// Is there support for glDraw*Indirect? Note that the baseInstance fields of indirect draw
    /// commands cannot be used unless we have base instance support.
    bool drawIndirectSupport() const { return fDrawIndirectSupport; }

    /// Is there support for glMultiDraw*Indirect? Note that the baseInstance fields of indirect
    /// draw commands cannot be used unless we have base instance support.
    bool multiDrawIndirectSupport() const { return fMultiDrawIndirectSupport; }

    /// Is there support for glDrawRangeElements?
    bool drawRangeElementsSupport() const { return fDrawRangeElementsSupport; }

    /// Are the baseInstance fields supported in indirect draw commands?
    bool baseInstanceSupport() const { return fBaseInstanceSupport; }

    /// Use indices or vertices in CPU arrays rather than VBOs for dynamic content.
    bool useNonVBOVertexAndIndexDynamicData() const { return fUseNonVBOVertexAndIndexDynamicData; }

    SurfaceReadPixelsSupport surfaceSupportsReadPixels(const GrSurface*) const override;

    SupportedWrite supportedWritePixelsColorType(GrColorType surfaceColorType,
                                                 const GrBackendFormat& surfaceFormat,
                                                 GrColorType srcColorType) const override;

    bool isCoreProfile() const { return fIsCoreProfile; }

    bool bindFragDataLocationSupport() const { return fBindFragDataLocationSupport; }

    bool bindUniformLocationSupport() const { return fBindUniformLocationSupport; }

    /// Are textures with GL_TEXTURE_RECTANGLE type supported.
    bool rectangleTextureSupport() const { return fRectangleTextureSupport; }

    bool mipMapLevelAndLodControlSupport() const { return fMipMapLevelAndLodControlSupport; }

    bool doManualMipmapping() const { return fDoManualMipmapping; }

    void onDumpJSON(SkJSONWriter*) const override;

    bool rgba8888PixelsOpsAreSlow() const { return fRGBA8888PixelsOpsAreSlow; }
    bool partialFBOReadIsSlow() const { return fPartialFBOReadIsSlow; }
    bool rgbaToBgraReadbackConversionsAreSlow() const {
        return fRGBAToBGRAReadbackConversionsAreSlow;
    }

    bool useBufferDataNullHint() const { return fUseBufferDataNullHint; }

    // Certain Intel GPUs on Mac fail to clear if the glClearColor is made up of only 1s and 0s.
    bool clearToBoundaryValuesIsBroken() const { return fClearToBoundaryValuesIsBroken; }

    /// glClearTex(Sub)Image support
    bool clearTextureSupport() const { return fClearTextureSupport; }

    // Adreno/MSAA drops a draw on the imagefiltersbase GM if the base vertex param to
    // glDrawArrays is nonzero.
    // https://bugs.chromium.org/p/skia/issues/detail?id=6650
    bool drawArraysBaseVertexIsBroken() const { return fDrawArraysBaseVertexIsBroken; }

    // If true then we must use an intermediate surface to perform partial updates to unorm textures
    // that have ever been bound to a FBO.
    bool disallowTexSubImageForUnormConfigTexturesEverBoundToFBO() const {
        return fDisallowTexSubImageForUnormConfigTexturesEverBoundToFBO;
    }

    // Use an intermediate surface to write pixels (full or partial overwrite) to into a texture
    // that is bound to an FBO.
    bool useDrawInsteadOfAllRenderTargetWrites() const {
        return fUseDrawInsteadOfAllRenderTargetWrites;
    }

    // At least some Adreno 3xx drivers draw lines incorrectly after drawing non-lines. Toggling
    // face culling on and off seems to resolve this.
    bool requiresCullFaceEnableDisableWhenDrawingLinesAfterNonLines() const {
        return fRequiresCullFaceEnableDisableWhenDrawingLinesAfterNonLines;
    }

    // Some Adreno drivers refuse to ReadPixels from an MSAA buffer that has stencil attached.
    bool detachStencilFromMSAABuffersBeforeReadPixels() const {
        return fDetachStencilFromMSAABuffersBeforeReadPixels;
    }

    // Older Android versions seem to have an issue with setting GL_TEXTURE_BASE_LEVEL or
    // GL_TEXTURE_MAX_LEVEL for GL_TEXTURE_EXTERNAL_OES textures.
    bool dontSetBaseOrMaxLevelForExternalTextures() const {
        return fDontSetBaseOrMaxLevelForExternalTextures;
    }

    // PowerVRGX6250 drops every pixel if we modify the sample mask while color writes are disabled.
    bool neverDisableColorWrites() const { return fNeverDisableColorWrites; }

    // Returns the observed maximum number of instances the driver can handle in a single draw call
    // without crashing, or 'pendingInstanceCount' if this workaround is not necessary.
    // NOTE: the return value may be larger than pendingInstanceCount.
    int maxInstancesPerDrawWithoutCrashing(int pendingInstanceCount) const {
        return (fMaxInstancesPerDrawWithoutCrashing)
                ? fMaxInstancesPerDrawWithoutCrashing : pendingInstanceCount;
    }

    bool canCopyTexSubImage(GrGLFormat dstFormat, bool dstHasMSAARenderBuffer,
                            const GrTextureType* dstTypeIfTexture,
                            GrGLFormat srcFormat, bool srcHasMSAARenderBuffer,
                            const GrTextureType* srcTypeIfTexture) const;
    bool canCopyAsBlit(GrGLFormat dstFormat, int dstSampleCnt,
                       const GrTextureType* dstTypeIfTexture,
                       GrGLFormat srcFormat, int srcSampleCnt,
                       const GrTextureType* srcTypeIfTexture,
                       const SkRect& srcBounds, bool srcBoundsExact,
                       const SkIRect& srcRect, const SkIPoint& dstPoint) const;
    bool canCopyAsDraw(GrGLFormat dstFormat, bool srcIsTexturable) const;

    DstCopyRestrictions getDstCopyRestrictions(const GrRenderTargetProxy* src,
                                               GrColorType) const override;

    bool programBinarySupport() const { return fProgramBinarySupport; }
    bool programParameterSupport() const { return fProgramParameterSupport; }

    bool samplerObjectSupport() const { return fSamplerObjectSupport; }

    bool fbFetchRequiresEnablePerSample() const { return fFBFetchRequiresEnablePerSample; }

    GrColorType getYUVAColorTypeFromBackendFormat(const GrBackendFormat&,
                                                  bool isAlphaChannel) const override;

    GrBackendFormat getBackendFormatFromCompressionType(SkImage::CompressionType) const override;

    bool canClearTextureOnCreation() const override;

    GrSwizzle getTextureSwizzle(const GrBackendFormat&, GrColorType) const override;
    GrSwizzle getOutputSwizzle(const GrBackendFormat&, GrColorType) const override;

#if GR_TEST_UTILS
    GrGLStandard standard() const { return fStandard; }

    std::vector<TestFormatColorTypeCombination> getTestingCombinations() const override;
#endif

private:
    enum ExternalFormatUsage {
        kTexImage_ExternalFormatUsage,
        kReadPixels_ExternalFormatUsage,
    };
    void getExternalFormat(GrGLFormat surfaceFormat, GrColorType surfaceColorType,
                           GrColorType memoryColorType, ExternalFormatUsage usage,
                           GrGLenum* externalFormat, GrGLenum* externalType) const;

    void init(const GrContextOptions&, const GrGLContextInfo&, const GrGLInterface*);
    void initGLSL(const GrGLContextInfo&, const GrGLInterface*);
    bool hasPathRenderingSupport(const GrGLContextInfo&, const GrGLInterface*);

    struct FormatWorkarounds {
        bool fDisableTextureRedForMesa = false;
        bool fDisableSRGBRenderWithMSAAForMacAMD = false;
        bool fDisablePerFormatTextureStorageForCommandBufferES2 = false;
        bool fDisableNonRedSingleChannelTexStorageForANGLEGL = false;
        bool fDisableBGRATextureStorageForIntelWindowsES = false;
        bool fDisableRGB8ForMali400 = false;
        bool fDisableLuminance16F = false;
    };

    void applyDriverCorrectnessWorkarounds(const GrGLContextInfo&, const GrContextOptions&,
                                           GrShaderCaps*, FormatWorkarounds*);

    void onApplyOptionsOverrides(const GrContextOptions& options) override;

    bool onIsWindowRectanglesSupportedForRT(const GrBackendRenderTarget&) const override;

    void initFSAASupport(const GrContextOptions& contextOptions, const GrGLContextInfo&,
                         const GrGLInterface*);
    void initBlendEqationSupport(const GrGLContextInfo&);
    void initStencilSupport(const GrGLContextInfo&);
    // This must be called after initFSAASupport().
    void initFormatTable(const GrGLContextInfo&, const GrGLInterface*, const FormatWorkarounds&);
    void setupSampleCounts(const GrGLContextInfo&, const GrGLInterface*);
    bool onSurfaceSupportsWritePixels(const GrSurface*) const override;
    bool onCanCopySurface(const GrSurfaceProxy* dst, const GrSurfaceProxy* src,
                          const SkIRect& srcRect, const SkIPoint& dstPoint) const override;
    GrBackendFormat onGetDefaultBackendFormat(GrColorType, GrRenderable) const override;
    GrPixelConfig onGetConfigFromBackendFormat(const GrBackendFormat&, GrColorType) const override;
    bool onAreColorTypeAndFormatCompatible(GrColorType, const GrBackendFormat&) const override;

    SupportedRead onSupportedReadPixelsColorType(GrColorType, const GrBackendFormat&,
                                                 GrColorType) const override;

    GrGLStandard fStandard;

    SkTArray<StencilFormat, true> fStencilFormats;

    int fMaxFragmentUniformVectors;

    MSFBOType           fMSFBOType;
    InvalidateFBType    fInvalidateFBType;
    MapBufferType       fMapBufferType;
    TransferBufferType  fTransferBufferType;

    bool fPackFlipYSupport : 1;
    bool fTextureUsageSupport : 1;
    bool fAlpha8IsRenderable: 1;
    bool fImagingSupport  : 1;
    bool fVertexArrayObjectSupport : 1;
    bool fDebugSupport : 1;
    bool fES2CompatibilitySupport : 1;
    bool fDrawInstancedSupport : 1;
    bool fDrawIndirectSupport : 1;
    bool fDrawRangeElementsSupport : 1;
    bool fMultiDrawIndirectSupport : 1;
    bool fBaseInstanceSupport : 1;
    bool fUseNonVBOVertexAndIndexDynamicData : 1;
    bool fIsCoreProfile : 1;
    bool fBindFragDataLocationSupport : 1;
    bool fRGBA8888PixelsOpsAreSlow : 1;
    bool fPartialFBOReadIsSlow : 1;
    bool fBindUniformLocationSupport : 1;
    bool fRectangleTextureSupport : 1;
    bool fMipMapLevelAndLodControlSupport : 1;
    bool fRGBAToBGRAReadbackConversionsAreSlow : 1;
    bool fUseBufferDataNullHint                : 1;
    bool fClearTextureSupport : 1;
    bool fProgramBinarySupport : 1;
    bool fProgramParameterSupport : 1;
    bool fSamplerObjectSupport : 1;
    bool fFBFetchRequiresEnablePerSample : 1;

    // Driver workarounds
    bool fDoManualMipmapping : 1;
    bool fClearToBoundaryValuesIsBroken : 1;
    bool fDrawArraysBaseVertexIsBroken : 1;
    bool fDisallowTexSubImageForUnormConfigTexturesEverBoundToFBO : 1;
    bool fUseDrawInsteadOfAllRenderTargetWrites : 1;
    bool fRequiresCullFaceEnableDisableWhenDrawingLinesAfterNonLines : 1;
    bool fDetachStencilFromMSAABuffersBeforeReadPixels : 1;
    bool fDontSetBaseOrMaxLevelForExternalTextures : 1;
    bool fNeverDisableColorWrites : 1;
    int fMaxInstancesPerDrawWithoutCrashing;

    uint32_t fBlitFramebufferFlags;

    struct ReadPixelsFormat {
        ReadPixelsFormat() : fFormat(0), fType(0) {}
        GrGLenum fFormat;
        GrGLenum fType;
    };

    /** Number type of the components (with out considering number of bits.) */
    enum class FormatType {
        kUnknown,
        kNormalizedFixedPoint,
        kFloat,
    };

    // ColorTypeInfo for a specific format
    struct ColorTypeInfo {
        GrColorType fColorType = GrColorType::kUnknown;
        enum {
            kUploadData_Flag = 0x1,
            // Does Ganesh itself support rendering to this colorType & format pair. Renderability
            // still additionally depends on if the format can be an FBO color attachment.
            kRenderable_Flag = 0x2,
        };
        uint32_t fFlags = 0;

        GrSwizzle fTextureSwizzle;
        GrSwizzle fOutputSwizzle;

        struct ExternalIOFormats {
            GrColorType fColorType = GrColorType::kUnknown;

            /** The external format and type are to be used when uploading/downloading data using
                data of fColorType and uploading to a texture of a given GrGLFormat and its
                intended GrColorType. The fExternalTexImageFormat is the format to use for TexImage
                calls. The fExternalReadFormat is used when calling ReadPixels. If either is zero
                that signals that either TexImage or ReadPixels is not supported for the combination
                of format and color types. */
            GrGLenum fExternalType = 0;
            GrGLenum fExternalTexImageFormat = 0;
            GrGLenum fExternalReadFormat = 0;
        };

        GrGLenum externalFormat(GrColorType externalColorType, ExternalFormatUsage usage) const {
            for (int i = 0; i < fExternalIOFormatCount; ++i) {
                if (fExternalIOFormats[i].fColorType == externalColorType) {
                    if (usage == kTexImage_ExternalFormatUsage) {
                        return fExternalIOFormats[i].fExternalTexImageFormat;
                    } else {
                        SkASSERT(usage == kReadPixels_ExternalFormatUsage);
                        return fExternalIOFormats[i].fExternalReadFormat;
                    }
                }
            }
            return 0;
        }

        GrGLenum externalType(GrColorType externalColorType) const {
            for (int i = 0; i < fExternalIOFormatCount; ++i) {
                if (fExternalIOFormats[i].fColorType == externalColorType) {
                    return fExternalIOFormats[i].fExternalType;
                }
            }
            return 0;
        }

        std::unique_ptr<ExternalIOFormats[]> fExternalIOFormats;
        int fExternalIOFormatCount = 0;
    };

    struct FormatInfo {
        uint32_t colorTypeFlags(GrColorType colorType) const {
            for (int i = 0; i < fColorTypeInfoCount; ++i) {
                if (fColorTypeInfos[i].fColorType == colorType) {
                    return fColorTypeInfos[i].fFlags;
                }
            }
            return 0;
        }

        GrGLenum externalFormat(GrColorType surfaceColorType, GrColorType externalColorType,
                                ExternalFormatUsage usage) const {
            for (int i = 0; i < fColorTypeInfoCount; ++i) {
                if (fColorTypeInfos[i].fColorType == surfaceColorType) {
                    return fColorTypeInfos[i].externalFormat(externalColorType, usage);
                }
            }
            return 0;
        }

        GrGLenum externalType(GrColorType surfaceColorType, GrColorType externalColorType) const {
            for (int i = 0; i < fColorTypeInfoCount; ++i) {
                if (fColorTypeInfos[i].fColorType == surfaceColorType) {
                    return fColorTypeInfos[i].externalType(externalColorType);
                }
            }
            return 0;
        }

        enum {
            kTexturable_Flag                 = 0x1,
            /** kFBOColorAttachment means that even if the format cannot be a GrRenderTarget, we can
                still attach it to a FBO for blitting or reading pixels. */
            kFBOColorAttachment_Flag         = 0x2,
            kFBOColorAttachmentWithMSAA_Flag = 0x4,
            kCanUseTexStorage_Flag           = 0x8,
        };
        uint32_t fFlags = 0;

        FormatType fFormatType = FormatType::kUnknown;

        // Both compressed and uncompressed formats have base internal formats.
        GrGLenum fBaseInternalFormat = 0;

        // Not defined for compressed formats.
        GrGLenum fSizedInternalFormat = 0;

        // Not defined for uncompressed formats. Passed to glCompressedTexImage...
        GrGLenum fCompressedInternalFormat = 0;

        // Value to uses as the "internalformat" argument to glTexImage and glCompressedTexImage...
        // Usually one of fBaseInternalFormat or fSizedInternalFormat but may vary depending on the
        // particular format, GL version, extensions.
        GrGLenum fInternalFormatForTexImage = 0;

        // Value to uses as the "internalformat" argument to glRenderbufferStorageMultisample...
        // Usually one of fBaseInternalFormat or fSizedInternalFormat but may vary depending on the
        // particular format, GL version, extensions.
        GrGLenum fInternalFormatForRenderbuffer = 0;

        // Default value to use along with fBaseInternalFormat for functions such as glTexImage2D
        // when not input providing data (passing nullptr). Not defined for compressed formats.
        GrGLenum fDefaultExternalType = 0;

        enum {
            // This indicates that a stencil format has not yet been determined for the config.
            kUnknown_StencilIndex = -1,
            // This indicates that there is no supported stencil format for the config.
            kUnsupported_StencilFormatIndex = -2
        };

        // Index fStencilFormats.
        int fStencilFormatIndex = kUnknown_StencilIndex;

        SkTDArray<int> fColorSampleCounts;

        // verification of color attachment validity is done while flushing. Although only ever
        // used in the (sole) rendering thread it can cause races if it is glommed into fFlags.
        bool fVerifiedColorAttachment = false;

        std::unique_ptr<ColorTypeInfo[]> fColorTypeInfos;
        int fColorTypeInfoCount = 0;
    };

    FormatInfo fFormatTable[kGrGLFormatCount];

    FormatInfo& getFormatInfo(GrGLFormat format) { return fFormatTable[static_cast<int>(format)]; }
    const FormatInfo& getFormatInfo(GrGLFormat format) const {
        return fFormatTable[static_cast<int>(format)];
    }

    GrGLFormat fColorTypeToFormatTable[kGrColorTypeCnt];
    void setColorTypeFormat(GrColorType, GrGLFormat);

    typedef GrCaps INHERITED;
};

#endif