/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "include/core/SkBitmap.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkData.h"
#include "include/core/SkFontMetrics.h"
#include "include/core/SkPath.h"
#include "include/core/SkStream.h"
#include "include/core/SkString.h"
#include "include/private/SkColorData.h"
#include "include/private/SkMalloc.h"
#include "include/private/SkMutex.h"
#include "include/private/SkTPin.h"
#include "include/private/SkTemplates.h"
#include "include/private/SkTo.h"
#include "src/core/SkAdvancedTypefaceMetrics.h"
#include "src/core/SkDescriptor.h"
#include "src/core/SkFDot6.h"
#include "src/core/SkFontDescriptor.h"
#include "src/core/SkGlyph.h"
#include "src/core/SkMask.h"
#include "src/core/SkMaskGamma.h"
#include "src/core/SkScalerContext.h"
#include "src/ports/SkFontHost_FreeType_common.h"
#include "src/sfnt/SkOTUtils.h"
#include "src/utils/SkCallableTraits.h"
#include "src/utils/SkMatrix22.h"

#include <memory>

#include <ft2build.h>
#include FT_ADVANCES_H
#include FT_BITMAP_H
#ifdef FT_COLOR_H
#   include FT_COLOR_H
#endif
#include FT_FREETYPE_H
#include FT_LCD_FILTER_H
#include FT_MODULE_H
#include FT_MULTIPLE_MASTERS_H
#include FT_OUTLINE_H
#include FT_SIZES_H
#include FT_SYSTEM_H
#include FT_TRUETYPE_TABLES_H
#include FT_TYPE1_TABLES_H
#include FT_XFREE86_H

// SK_FREETYPE_MINIMUM_RUNTIME_VERSION 0x<major><minor><patch><flags>
// Flag SK_FREETYPE_DLOPEN: also try dlopen to get newer features.
#define SK_FREETYPE_DLOPEN (0x1)
#ifndef SK_FREETYPE_MINIMUM_RUNTIME_VERSION
#  if defined(SK_BUILD_FOR_ANDROID_FRAMEWORK) || defined (SK_BUILD_FOR_GOOGLE3)
#    define SK_FREETYPE_MINIMUM_RUNTIME_VERSION (((FREETYPE_MAJOR) << 24) | ((FREETYPE_MINOR) << 16) | ((FREETYPE_PATCH) << 8))
#  else
#    define SK_FREETYPE_MINIMUM_RUNTIME_VERSION ((2 << 24) | (3 << 16) | (11 << 8) | (SK_FREETYPE_DLOPEN))
#  endif
#endif
#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN
#  include <dlfcn.h>
#endif

// FT_LOAD_COLOR and the corresponding FT_Pixel_Mode::FT_PIXEL_MODE_BGRA
// were introduced in FreeType 2.5.0.
// The following may be removed once FreeType 2.5.0 is required to build.
#ifndef FT_LOAD_COLOR
#    define FT_LOAD_COLOR ( 1L << 20 )
#    define FT_PIXEL_MODE_BGRA 7
#endif

// FT_LOAD_BITMAP_METRICS_ONLY was introduced in FreeType 2.7.1
// The following may be removed once FreeType 2.7.1 is required to build.
#ifndef FT_LOAD_BITMAP_METRICS_ONLY
#    define FT_LOAD_BITMAP_METRICS_ONLY ( 1L << 22 )
#endif

// FT_VAR_AXIS_FLAG_HIDDEN was introduced in FreeType 2.8.1
// The variation axis should not be exposed to user interfaces.
#ifndef FT_VAR_AXIS_FLAG_HIDDEN
#    define FT_VAR_AXIS_FLAG_HIDDEN 1
#endif

//#define ENABLE_GLYPH_SPEW     // for tracing calls
//#define DUMP_STRIKE_CREATION
//#define SK_FONTHOST_FREETYPE_RUNTIME_VERSION
//#define SK_GAMMA_APPLY_TO_A8

#if 1
    #define LOG_INFO(...)
#else
    #define LOG_INFO SkDEBUGF
#endif

static bool isLCD(const SkScalerContextRec& rec) {
    return SkMask::kLCD16_Format == rec.fMaskFormat;
}

static SkScalar SkFT_FixedToScalar(FT_Fixed x) {
  return SkFixedToScalar(x);
}

using SkUniqueFTFace =
        std::unique_ptr<FT_FaceRec, SkFunctionWrapper<decltype(FT_Done_Face), FT_Done_Face>>;

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

using FT_Alloc_size_t = SkCallableTraits<FT_Alloc_Func>::argument<1>::type;
static_assert(std::is_same<FT_Alloc_size_t, long  >::value ||
              std::is_same<FT_Alloc_size_t, size_t>::value,"");

extern "C" {
    static void* sk_ft_alloc(FT_Memory, FT_Alloc_size_t size) {
        return sk_malloc_throw(size);
    }
    static void sk_ft_free(FT_Memory, void* block) {
        sk_free(block);
    }
    static void* sk_ft_realloc(FT_Memory, FT_Alloc_size_t cur_size,
                                          FT_Alloc_size_t new_size, void* block) {
        return sk_realloc_throw(block, new_size);
    }
};
FT_MemoryRec_ gFTMemory = { nullptr, sk_ft_alloc, sk_ft_free, sk_ft_realloc };

class FreeTypeLibrary : SkNoncopyable {
public:
    FreeTypeLibrary()
        : fGetVarDesignCoordinates(nullptr)
        , fGetVarAxisFlags(nullptr)
        , fLibrary(nullptr)
        , fIsLCDSupported(false)
        , fLightHintingIsYOnly(false)
        , fLCDExtra(0)
    {
        if (FT_New_Library(&gFTMemory, &fLibrary)) {
            return;
        }
        FT_Add_Default_Modules(fLibrary);

        // When using dlsym
        // *(void**)(&procPtr) = dlsym(self, "proc");
        // is non-standard, but safe for POSIX. Cannot write
        // *reinterpret_cast<void**>(&procPtr) = dlsym(self, "proc");
        // because clang has not implemented DR573. See http://clang.llvm.org/cxx_dr_status.html .

        FT_Int major, minor, patch;
        FT_Library_Version(fLibrary, &major, &minor, &patch);

#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02070100
        fGetVarDesignCoordinates = FT_Get_Var_Design_Coordinates;
#elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN
        if (major > 2 || ((major == 2 && minor > 7) || (major == 2 && minor == 7 && patch >= 0))) {
            //The FreeType library is already loaded, so symbols are available in process.
            void* self = dlopen(nullptr, RTLD_LAZY);
            if (self) {
                *(void**)(&fGetVarDesignCoordinates) = dlsym(self, "FT_Get_Var_Design_Coordinates");
                dlclose(self);
            }
        }
#endif

#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02070200
        FT_Set_Default_Properties(fLibrary);
#elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN
        if (major > 2 || ((major == 2 && minor > 7) || (major == 2 && minor == 7 && patch >= 1))) {
            //The FreeType library is already loaded, so symbols are available in process.
            void* self = dlopen(nullptr, RTLD_LAZY);
            if (self) {
                FT_Set_Default_PropertiesProc setDefaultProperties;
                *(void**)(&setDefaultProperties) = dlsym(self, "FT_Set_Default_Properties");
                dlclose(self);

                if (setDefaultProperties) {
                    setDefaultProperties(fLibrary);
                }
            }
        }
#endif

// The 'light' hinting is vertical only starting in 2.8.0.
#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02080000
        fLightHintingIsYOnly = true;
#else
        if (major > 2 || ((major == 2 && minor > 8) || (major == 2 && minor == 8 && patch >= 0))) {
            fLightHintingIsYOnly = true;
        }
#endif


#if SK_FREETYPE_MINIMUM_RUNTIME_VERSION >= 0x02080100
        fGetVarAxisFlags = FT_Get_Var_Axis_Flags;
#elif SK_FREETYPE_MINIMUM_RUNTIME_VERSION & SK_FREETYPE_DLOPEN
        if (major > 2 || ((major == 2 && minor > 7) || (major == 2 && minor == 7 && patch >= 0))) {
            //The FreeType library is already loaded, so symbols are available in process.
            void* self = dlopen(nullptr, RTLD_LAZY);
            if (self) {
                *(void**)(&fGetVarAxisFlags) = dlsym(self, "FT_Get_Var_Axis_Flags");
                dlclose(self);
            }
        }
#endif

        // Setup LCD filtering. This reduces color fringes for LCD smoothed glyphs.
        // The default has changed over time, so this doesn't mean the same thing to all users.
        if (FT_Library_SetLcdFilter(fLibrary, FT_LCD_FILTER_DEFAULT) == 0) {
            fIsLCDSupported = true;
            fLCDExtra = 2; //Using a filter adds one full pixel to each side.
        }
    }
    ~FreeTypeLibrary() {
        if (fLibrary) {
            FT_Done_Library(fLibrary);
        }
    }

    FT_Library library() { return fLibrary; }
    bool isLCDSupported() { return fIsLCDSupported; }
    int lcdExtra() { return fLCDExtra; }
    bool lightHintingIsYOnly() { return fLightHintingIsYOnly; }

    // FT_Get_{MM,Var}_{Blend,Design}_Coordinates were added in FreeType 2.7.1.
    // Prior to this there was no way to get the coordinates out of the FT_Face.
    // This wasn't too bad because you needed to specify them anyway, and the clamp was provided.
    // However, this doesn't work when face_index specifies named variations as introduced in 2.6.1.
    using FT_Get_Var_Blend_CoordinatesProc = FT_Error (*)(FT_Face, FT_UInt, FT_Fixed*);
    FT_Get_Var_Blend_CoordinatesProc fGetVarDesignCoordinates;

    // FT_Get_Var_Axis_Flags was introduced in FreeType 2.8.1
    // Get the ‘flags’ field of an OpenType Variation Axis Record.
    // Not meaningful for Adobe MM fonts (‘*flags’ is always zero).
    using FT_Get_Var_Axis_FlagsProc = FT_Error (*)(FT_MM_Var*, FT_UInt, FT_UInt*);
    FT_Get_Var_Axis_FlagsProc fGetVarAxisFlags;

private:
    FT_Library fLibrary;
    bool fIsLCDSupported;
    bool fLightHintingIsYOnly;
    int fLCDExtra;

    // FT_Library_SetLcdFilterWeights was introduced in FreeType 2.4.0.
    // The following platforms provide FreeType of at least 2.4.0.
    // Ubuntu >= 11.04 (previous deprecated April 2013)
    // Debian >= 6.0 (good)
    // OpenSuse >= 11.4 (previous deprecated January 2012 / Nov 2013 for Evergreen 11.2)
    // Fedora >= 14 (good)
    // Android >= Gingerbread (good)
    // RHEL >= 7 (6 has 2.3.11, EOL Nov 2020, Phase 3 May 2017)
    using FT_Library_SetLcdFilterWeightsProc = FT_Error (*)(FT_Library, unsigned char*);

    // FreeType added the ability to read global properties in 2.7.0. After 2.7.1 a means for users
    // of FT_New_Library to request these global properties to be read was added.
    using FT_Set_Default_PropertiesProc = void (*)(FT_Library);
};

struct SkFaceRec;

static SkMutex& f_t_mutex() {
    static SkMutex& mutex = *(new SkMutex);
    return mutex;
}

static FreeTypeLibrary* gFTLibrary;
static SkFaceRec* gFaceRecHead;

// Private to ref_ft_library and unref_ft_library
static int gFTCount;

// Caller must lock f_t_mutex() before calling this function.
static bool ref_ft_library() {
    f_t_mutex().assertHeld();
    SkASSERT(gFTCount >= 0);

    if (0 == gFTCount) {
        SkASSERT(nullptr == gFTLibrary);
        gFTLibrary = new FreeTypeLibrary;
    }
    ++gFTCount;
    return gFTLibrary->library();
}

// Caller must lock f_t_mutex() before calling this function.
static void unref_ft_library() {
    f_t_mutex().assertHeld();
    SkASSERT(gFTCount > 0);

    --gFTCount;
    if (0 == gFTCount) {
        SkASSERT(nullptr == gFaceRecHead);
        SkASSERT(nullptr != gFTLibrary);
        delete gFTLibrary;
        SkDEBUGCODE(gFTLibrary = nullptr;)
    }
}

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

struct SkFaceRec {
    SkFaceRec* fNext;
    SkUniqueFTFace fFace;
    FT_StreamRec fFTStream;
    std::unique_ptr<SkStreamAsset> fSkStream;
    uint32_t fRefCnt;
    uint32_t fFontID;

    // FreeType prior to 2.7.1 does not implement retreiving variation design metrics.
    // Cache the variation design metrics used to create the font if the user specifies them.
    SkAutoSTMalloc<4, SkFixed> fAxes;
    int fAxesCount;

    // FreeType from 2.6.1 (14d6b5d7) until 2.7.0 (ee3f36f6b38) uses font_index for both font index
    // and named variation index on input, but masks the named variation index part on output.
    // Manually keep track of when a named variation is requested for 2.6.1 until 2.7.1.
    bool fNamedVariationSpecified;

    SkFaceRec(std::unique_ptr<SkStreamAsset> stream, uint32_t fontID);
};

extern "C" {
    static unsigned long sk_ft_stream_io(FT_Stream ftStream,
                                         unsigned long offset,
                                         unsigned char* buffer,
                                         unsigned long count)
    {
        SkStreamAsset* stream = static_cast<SkStreamAsset*>(ftStream->descriptor.pointer);

        if (count) {
            if (!stream->seek(offset)) {
                return 0;
            }
            count = stream->read(buffer, count);
        }
        return count;
    }

    static void sk_ft_stream_close(FT_Stream) {}
}

SkFaceRec::SkFaceRec(std::unique_ptr<SkStreamAsset> stream, uint32_t fontID)
        : fNext(nullptr), fSkStream(std::move(stream)), fRefCnt(1), fFontID(fontID)
        , fAxesCount(0), fNamedVariationSpecified(false)
{
    sk_bzero(&fFTStream, sizeof(fFTStream));
    fFTStream.size = fSkStream->getLength();
    fFTStream.descriptor.pointer = fSkStream.get();
    fFTStream.read  = sk_ft_stream_io;
    fFTStream.close = sk_ft_stream_close;
}

static void ft_face_setup_axes(SkFaceRec* rec, const SkFontData& data) {
    if (!(rec->fFace->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS)) {
        return;
    }

    // If a named variation is requested, don't overwrite the named variation's position.
    if (data.getIndex() > 0xFFFF) {
        rec->fNamedVariationSpecified = true;
        return;
    }

    SkDEBUGCODE(
        FT_MM_Var* variations = nullptr;
        if (FT_Get_MM_Var(rec->fFace.get(), &variations)) {
            LOG_INFO("INFO: font %s claims variations, but none found.\n",
                     rec->fFace->family_name);
            return;
        }
        SkAutoFree autoFreeVariations(variations);

        if (static_cast<FT_UInt>(data.getAxisCount()) != variations->num_axis) {
            LOG_INFO("INFO: font %s has %d variations, but %d were specified.\n",
                     rec->fFace->family_name, variations->num_axis, data.getAxisCount());
            return;
        }
    )

    SkAutoSTMalloc<4, FT_Fixed> coords(data.getAxisCount());
    for (int i = 0; i < data.getAxisCount(); ++i) {
        coords[i] = data.getAxis()[i];
    }
    if (FT_Set_Var_Design_Coordinates(rec->fFace.get(), data.getAxisCount(), coords.get())) {
        LOG_INFO("INFO: font %s has variations, but specified variations could not be set.\n",
                 rec->fFace->family_name);
        return;
    }

    rec->fAxesCount = data.getAxisCount();
    rec->fAxes.reset(rec->fAxesCount);
    for (int i = 0; i < rec->fAxesCount; ++i) {
        rec->fAxes[i] = data.getAxis()[i];
    }
}

// Will return nullptr on failure
// Caller must lock f_t_mutex() before calling this function.
static SkFaceRec* ref_ft_face(const SkTypeface_FreeType* typeface) {
    f_t_mutex().assertHeld();

    const SkFontID fontID = typeface->uniqueID();
    SkFaceRec* cachedRec = gFaceRecHead;
    while (cachedRec) {
        if (cachedRec->fFontID == fontID) {
            SkASSERT(cachedRec->fFace);
            cachedRec->fRefCnt += 1;
            return cachedRec;
        }
        cachedRec = cachedRec->fNext;
    }

    std::unique_ptr<SkFontData> data = typeface->makeFontData();
    if (nullptr == data || !data->hasStream()) {
        return nullptr;
    }

    std::unique_ptr<SkFaceRec> rec(new SkFaceRec(data->detachStream(), fontID));

    FT_Open_Args args;
    memset(&args, 0, sizeof(args));
    const void* memoryBase = rec->fSkStream->getMemoryBase();
    if (memoryBase) {
        args.flags = FT_OPEN_MEMORY;
        args.memory_base = (const FT_Byte*)memoryBase;
        args.memory_size = rec->fSkStream->getLength();
    } else {
        args.flags = FT_OPEN_STREAM;
        args.stream = &rec->fFTStream;
    }

    {
        FT_Face rawFace;
        FT_Error err = FT_Open_Face(gFTLibrary->library(), &args, data->getIndex(), &rawFace);
        if (err) {
            SK_TRACEFTR(err, "unable to open font '%x'", fontID);
            return nullptr;
        }
        rec->fFace.reset(rawFace);
    }
    SkASSERT(rec->fFace);

    ft_face_setup_axes(rec.get(), *data);

    // FreeType will set the charmap to the "most unicode" cmap if it exists.
    // If there are no unicode cmaps, the charmap is set to nullptr.
    // However, "symbol" cmaps should also be considered "fallback unicode" cmaps
    // because they are effectively private use area only (even if they aren't).
    // This is the last on the fallback list at
    // https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6cmap.html
    if (!rec->fFace->charmap) {
        FT_Select_Charmap(rec->fFace.get(), FT_ENCODING_MS_SYMBOL);
    }

    rec->fNext = gFaceRecHead;
    gFaceRecHead = rec.get();
    return rec.release();
}

// Caller must lock f_t_mutex() before calling this function.
// Marked extern because vc++ does not support internal linkage template parameters.
extern /*static*/ void unref_ft_face(SkFaceRec* faceRec) {
    f_t_mutex().assertHeld();

    SkFaceRec*  rec = gFaceRecHead;
    SkFaceRec*  prev = nullptr;
    while (rec) {
        SkFaceRec* next = rec->fNext;
        if (rec->fFace == faceRec->fFace) {
            if (--rec->fRefCnt == 0) {
                if (prev) {
                    prev->fNext = next;
                } else {
                    gFaceRecHead = next;
                }
                delete rec;
            }
            return;
        }
        prev = rec;
        rec = next;
    }
    SkDEBUGFAIL("shouldn't get here, face not in list");
}

class AutoFTAccess {
public:
    AutoFTAccess(const SkTypeface_FreeType* tf) : fFaceRec(nullptr) {
        f_t_mutex().acquire();
        SkASSERT_RELEASE(ref_ft_library());
        fFaceRec = ref_ft_face(tf);
    }

    ~AutoFTAccess() {
        if (fFaceRec) {
            unref_ft_face(fFaceRec);
        }
        unref_ft_library();
        f_t_mutex().release();
    }

    FT_Face face() { return fFaceRec ? fFaceRec->fFace.get() : nullptr; }
    int getAxesCount() { return fFaceRec ? fFaceRec->fAxesCount : 0; }
    SkFixed* getAxes() { return fFaceRec ? fFaceRec->fAxes.get() : nullptr; }
    bool isNamedVariationSpecified() {
        return fFaceRec ? fFaceRec->fNamedVariationSpecified : false;
    }

private:
    SkFaceRec* fFaceRec;
};

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

class SkScalerContext_FreeType : public SkScalerContext_FreeType_Base {
public:
    SkScalerContext_FreeType(sk_sp<SkTypeface_FreeType>,
                             const SkScalerContextEffects&,
                             const SkDescriptor* desc);
    ~SkScalerContext_FreeType() override;

    bool success() const {
        return fFTSize != nullptr && fFace != nullptr;
    }

protected:
    unsigned generateGlyphCount() override;
    bool generateAdvance(SkGlyph* glyph) override;
    void generateMetrics(SkGlyph* glyph) override;
    void generateImage(const SkGlyph& glyph) override;
    bool generatePath(SkGlyphID glyphID, SkPath* path) override;
    void generateFontMetrics(SkFontMetrics*) override;

private:
    using UnrefFTFace = SkFunctionWrapper<decltype(unref_ft_face), unref_ft_face>;
    std::unique_ptr<SkFaceRec, UnrefFTFace> fFaceRec;

    FT_Face   fFace;  // Borrowed face from gFaceRecHead.
    FT_Size   fFTSize;  // The size on the fFace for this scaler.
    FT_Int    fStrikeIndex;

    /** The rest of the matrix after FreeType handles the size.
     *  With outline font rasterization this is handled by FreeType with FT_Set_Transform.
     *  With bitmap only fonts this matrix must be applied to scale the bitmap.
     */
    SkMatrix  fMatrix22Scalar;
    /** Same as fMatrix22Scalar, but in FreeType units and space. */
    FT_Matrix fMatrix22;
    /** The actual size requested. */
    SkVector  fScale;

    uint32_t  fLoadGlyphFlags;
    bool      fDoLinearMetrics;
    bool      fLCDIsVert;

    FT_Error setupSize();
    void getBBoxForCurrentGlyph(const SkGlyph* glyph, FT_BBox* bbox,
                                bool snapToPixelBoundary = false);
    bool getCBoxForLetter(char letter, FT_BBox* bbox);
    // Caller must lock f_t_mutex() before calling this function.
    void updateGlyphIfLCD(SkGlyph* glyph);
    // Caller must lock f_t_mutex() before calling this function.
    // update FreeType2 glyph slot with glyph emboldened
    void emboldenIfNeeded(FT_Face face, FT_GlyphSlot glyph, SkGlyphID gid);
    bool shouldSubpixelBitmap(const SkGlyph&, const SkMatrix&);
};

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

static bool canEmbed(FT_Face face) {
    FT_UShort fsType = FT_Get_FSType_Flags(face);
    return (fsType & (FT_FSTYPE_RESTRICTED_LICENSE_EMBEDDING |
                      FT_FSTYPE_BITMAP_EMBEDDING_ONLY)) == 0;
}

static bool canSubset(FT_Face face) {
    FT_UShort fsType = FT_Get_FSType_Flags(face);
    return (fsType & FT_FSTYPE_NO_SUBSETTING) == 0;
}

static SkAdvancedTypefaceMetrics::FontType get_font_type(FT_Face face) {
    const char* fontType = FT_Get_X11_Font_Format(face);
    static struct { const char* s; SkAdvancedTypefaceMetrics::FontType t; } values[] = {
        { "Type 1",     SkAdvancedTypefaceMetrics::kType1_Font    },
        { "CID Type 1", SkAdvancedTypefaceMetrics::kType1CID_Font },
        { "CFF",        SkAdvancedTypefaceMetrics::kCFF_Font      },
        { "TrueType",   SkAdvancedTypefaceMetrics::kTrueType_Font },
    };
    for(const auto& v : values) { if (strcmp(fontType, v.s) == 0) { return v.t; } }
    return SkAdvancedTypefaceMetrics::kOther_Font;
}

std::unique_ptr<SkAdvancedTypefaceMetrics> SkTypeface_FreeType::onGetAdvancedMetrics() const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return nullptr;
    }

    std::unique_ptr<SkAdvancedTypefaceMetrics> info(new SkAdvancedTypefaceMetrics);
    info->fPostScriptName.set(FT_Get_Postscript_Name(face));
    info->fFontName = info->fPostScriptName;

    if (FT_HAS_MULTIPLE_MASTERS(face)) {
        info->fFlags |= SkAdvancedTypefaceMetrics::kVariable_FontFlag;
    }
    if (!canEmbed(face)) {
        info->fFlags |= SkAdvancedTypefaceMetrics::kNotEmbeddable_FontFlag;
    }
    if (!canSubset(face)) {
        info->fFlags |= SkAdvancedTypefaceMetrics::kNotSubsettable_FontFlag;
    }

    info->fType = get_font_type(face);
    info->fStyle = (SkAdvancedTypefaceMetrics::StyleFlags)0;
    if (FT_IS_FIXED_WIDTH(face)) {
        info->fStyle |= SkAdvancedTypefaceMetrics::kFixedPitch_Style;
    }
    if (face->style_flags & FT_STYLE_FLAG_ITALIC) {
        info->fStyle |= SkAdvancedTypefaceMetrics::kItalic_Style;
    }

    PS_FontInfoRec psFontInfo;
    TT_Postscript* postTable;
    if (FT_Get_PS_Font_Info(face, &psFontInfo) == 0) {
        info->fItalicAngle = psFontInfo.italic_angle;
    } else if ((postTable = (TT_Postscript*)FT_Get_Sfnt_Table(face, ft_sfnt_post)) != nullptr) {
        info->fItalicAngle = SkFixedFloorToInt(postTable->italicAngle);
    } else {
        info->fItalicAngle = 0;
    }

    info->fAscent = face->ascender;
    info->fDescent = face->descender;

    TT_PCLT* pcltTable;
    TT_OS2* os2Table;
    if ((pcltTable = (TT_PCLT*)FT_Get_Sfnt_Table(face, ft_sfnt_pclt)) != nullptr) {
        info->fCapHeight = pcltTable->CapHeight;
        uint8_t serif_style = pcltTable->SerifStyle & 0x3F;
        if (2 <= serif_style && serif_style <= 6) {
            info->fStyle |= SkAdvancedTypefaceMetrics::kSerif_Style;
        } else if (9 <= serif_style && serif_style <= 12) {
            info->fStyle |= SkAdvancedTypefaceMetrics::kScript_Style;
        }
    } else if (((os2Table = (TT_OS2*)FT_Get_Sfnt_Table(face, ft_sfnt_os2)) != nullptr) &&
               // sCapHeight is available only when version 2 or later.
               os2Table->version != 0xFFFF &&
               os2Table->version >= 2)
    {
        info->fCapHeight = os2Table->sCapHeight;
    }
    info->fBBox = SkIRect::MakeLTRB(face->bbox.xMin, face->bbox.yMax,
                                    face->bbox.xMax, face->bbox.yMin);
    return info;
}

void SkTypeface_FreeType::getGlyphToUnicodeMap(SkUnichar* dstArray) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return;
    }

    FT_Long numGlyphs = face->num_glyphs;
    if (!dstArray) { SkASSERT(numGlyphs == 0); }
    sk_bzero(dstArray, sizeof(SkUnichar) * numGlyphs);

    FT_UInt glyphIndex;
    SkUnichar charCode = FT_Get_First_Char(face, &glyphIndex);
    while (glyphIndex) {
        SkASSERT(glyphIndex < SkToUInt(numGlyphs));
        // Use the first character that maps to this glyphID. https://crbug.com/359065
        if (0 == dstArray[glyphIndex]) {
            dstArray[glyphIndex] = charCode;
        }
        charCode = FT_Get_Next_Char(face, charCode, &glyphIndex);
    }
}

void SkTypeface_FreeType::getPostScriptGlyphNames(SkString* dstArray) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return;
    }

    FT_Long numGlyphs = face->num_glyphs;
    if (!dstArray) { SkASSERT(numGlyphs == 0); }

    if (FT_HAS_GLYPH_NAMES(face)) {
        for (int gID = 0; gID < numGlyphs; ++gID) {
            char glyphName[128];  // PS limit for names is 127 bytes.
            FT_Get_Glyph_Name(face, gID, glyphName, 128);
            dstArray[gID] = glyphName;
        }
    }
}

bool SkTypeface_FreeType::onGetPostScriptName(SkString* skPostScriptName) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return false;
    }

    const char* ftPostScriptName = FT_Get_Postscript_Name(face);
    if (!ftPostScriptName) {
        return false;
    }
    if (skPostScriptName) {
        *skPostScriptName = ftPostScriptName;
    }
    return true;
}

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

static bool bothZero(SkScalar a, SkScalar b) {
    return 0 == a && 0 == b;
}

// returns false if there is any non-90-rotation or skew
static bool isAxisAligned(const SkScalerContextRec& rec) {
    return 0 == rec.fPreSkewX &&
           (bothZero(rec.fPost2x2[0][1], rec.fPost2x2[1][0]) ||
            bothZero(rec.fPost2x2[0][0], rec.fPost2x2[1][1]));
}

SkScalerContext* SkTypeface_FreeType::onCreateScalerContext(const SkScalerContextEffects& effects,
                                                            const SkDescriptor* desc) const {
    auto c = std::make_unique<SkScalerContext_FreeType>(
            sk_ref_sp(const_cast<SkTypeface_FreeType*>(this)), effects, desc);
    if (!c->success()) {
        return SkScalerContext::MakeEmptyContext(
                sk_ref_sp(const_cast<SkTypeface_FreeType*>(this)), effects, desc);
    }
    return c.release();
}

std::unique_ptr<SkFontData> SkTypeface_FreeType::cloneFontData(const SkFontArguments& args) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return nullptr;
    }

    Scanner::AxisDefinitions axisDefinitions;
    if (!Scanner::GetAxes(face, &axisDefinitions)) {
        return nullptr;
    }

    SkString name;
    SkAutoSTMalloc<4, SkFixed> axisValues(axisDefinitions.count());
    Scanner::computeAxisValues(axisDefinitions, args.getVariationDesignPosition(),
                               axisValues, name);
    int ttcIndex;
    std::unique_ptr<SkStreamAsset> stream = this->openStream(&ttcIndex);
    return std::make_unique<SkFontData>(std::move(stream), ttcIndex, axisValues.get(),
                                          axisDefinitions.count());
}

void SkTypeface_FreeType::onFilterRec(SkScalerContextRec* rec) const {
    //BOGUS: http://code.google.com/p/chromium/issues/detail?id=121119
    //Cap the requested size as larger sizes give bogus values.
    //Remove when http://code.google.com/p/skia/issues/detail?id=554 is fixed.
    //Note that this also currently only protects against large text size requests,
    //the total matrix is not taken into account here.
    if (rec->fTextSize > SkIntToScalar(1 << 14)) {
        rec->fTextSize = SkIntToScalar(1 << 14);
    }

    if (isLCD(*rec)) {
        // TODO: re-work so that FreeType is set-up and selected by the SkFontMgr.
        SkAutoMutexExclusive ama(f_t_mutex());
        ref_ft_library();
        if (!gFTLibrary->isLCDSupported()) {
            // If the runtime Freetype library doesn't support LCD, disable it here.
            rec->fMaskFormat = SkMask::kA8_Format;
        }
        unref_ft_library();
    }

    SkFontHinting h = rec->getHinting();
    if (SkFontHinting::kFull == h && !isLCD(*rec)) {
        // collapse full->normal hinting if we're not doing LCD
        h = SkFontHinting::kNormal;
    }

    // rotated text looks bad with hinting, so we disable it as needed
    if (!isAxisAligned(*rec)) {
        h = SkFontHinting::kNone;
    }
    rec->setHinting(h);

#ifndef SK_GAMMA_APPLY_TO_A8
    if (!isLCD(*rec)) {
        // SRGBTODO: Is this correct? Do we want contrast boost?
        rec->ignorePreBlend();
    }
#endif
}

int SkTypeface_FreeType::GetUnitsPerEm(FT_Face face) {
    SkASSERT(face);

    SkScalar upem = SkIntToScalar(face->units_per_EM);
    // At least some versions of FreeType set face->units_per_EM to 0 for bitmap only fonts.
    if (upem == 0) {
        TT_Header* ttHeader = (TT_Header*)FT_Get_Sfnt_Table(face, ft_sfnt_head);
        if (ttHeader) {
            upem = SkIntToScalar(ttHeader->Units_Per_EM);
        }
    }
    return upem;
}

int SkTypeface_FreeType::onGetUPEM() const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return 0;
    }
    return GetUnitsPerEm(face);
}

bool SkTypeface_FreeType::onGetKerningPairAdjustments(const uint16_t glyphs[],
                                      int count, int32_t adjustments[]) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face || !FT_HAS_KERNING(face)) {
        return false;
    }

    for (int i = 0; i < count - 1; ++i) {
        FT_Vector delta;
        FT_Error err = FT_Get_Kerning(face, glyphs[i], glyphs[i+1],
                                      FT_KERNING_UNSCALED, &delta);
        if (err) {
            return false;
        }
        adjustments[i] = delta.x;
    }
    return true;
}

/** Returns the bitmap strike equal to or just larger than the requested size. */
static FT_Int chooseBitmapStrike(FT_Face face, FT_F26Dot6 scaleY) {
    if (face == nullptr) {
        LOG_INFO("chooseBitmapStrike aborted due to nullptr face.\n");
        return -1;
    }

    FT_Pos requestedPPEM = scaleY;  // FT_Bitmap_Size::y_ppem is in 26.6 format.
    FT_Int chosenStrikeIndex = -1;
    FT_Pos chosenPPEM = 0;
    for (FT_Int strikeIndex = 0; strikeIndex < face->num_fixed_sizes; ++strikeIndex) {
        FT_Pos strikePPEM = face->available_sizes[strikeIndex].y_ppem;
        if (strikePPEM == requestedPPEM) {
            // exact match - our search stops here
            return strikeIndex;
        } else if (chosenPPEM < requestedPPEM) {
            // attempt to increase chosenPPEM
            if (chosenPPEM < strikePPEM) {
                chosenPPEM = strikePPEM;
                chosenStrikeIndex = strikeIndex;
            }
        } else {
            // attempt to decrease chosenPPEM, but not below requestedPPEM
            if (requestedPPEM < strikePPEM && strikePPEM < chosenPPEM) {
                chosenPPEM = strikePPEM;
                chosenStrikeIndex = strikeIndex;
            }
        }
    }
    return chosenStrikeIndex;
}

SkScalerContext_FreeType::SkScalerContext_FreeType(sk_sp<SkTypeface_FreeType> typeface,
                                                   const SkScalerContextEffects& effects,
                                                   const SkDescriptor* desc)
    : SkScalerContext_FreeType_Base(std::move(typeface), effects, desc)
    , fFace(nullptr)
    , fFTSize(nullptr)
    , fStrikeIndex(-1)
{
    SkAutoMutexExclusive  ac(f_t_mutex());
    SkASSERT_RELEASE(ref_ft_library());

    fFaceRec.reset(ref_ft_face(static_cast<SkTypeface_FreeType*>(this->getTypeface())));

    // load the font file
    if (nullptr == fFaceRec) {
        LOG_INFO("Could not create FT_Face.\n");
        return;
    }

    fLCDIsVert = SkToBool(fRec.fFlags & SkScalerContext::kLCD_Vertical_Flag);

    // compute the flags we send to Load_Glyph
    bool linearMetrics = this->isLinearMetrics();
    {
        FT_Int32 loadFlags = FT_LOAD_DEFAULT;

        if (SkMask::kBW_Format == fRec.fMaskFormat) {
            // See http://code.google.com/p/chromium/issues/detail?id=43252#c24
            loadFlags = FT_LOAD_TARGET_MONO;
            if (fRec.getHinting() == SkFontHinting::kNone) {
                loadFlags = FT_LOAD_NO_HINTING;
                linearMetrics = true;
            }
        } else {
            switch (fRec.getHinting()) {
            case SkFontHinting::kNone:
                loadFlags = FT_LOAD_NO_HINTING;
                linearMetrics = true;
                break;
            case SkFontHinting::kSlight:
                loadFlags = FT_LOAD_TARGET_LIGHT;  // This implies FORCE_AUTOHINT
                if (gFTLibrary->lightHintingIsYOnly()) {
                    linearMetrics = true;
                }
                break;
            case SkFontHinting::kNormal:
                loadFlags = FT_LOAD_TARGET_NORMAL;
                break;
            case SkFontHinting::kFull:
                loadFlags = FT_LOAD_TARGET_NORMAL;
                if (isLCD(fRec)) {
                    if (fLCDIsVert) {
                        loadFlags = FT_LOAD_TARGET_LCD_V;
                    } else {
                        loadFlags = FT_LOAD_TARGET_LCD;
                    }
                }
                break;
            default:
                LOG_INFO("---------- UNKNOWN hinting %d\n", fRec.getHinting());
                break;
            }
        }

        if (fRec.fFlags & SkScalerContext::kForceAutohinting_Flag) {
            loadFlags |= FT_LOAD_FORCE_AUTOHINT;
#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
        } else {
            loadFlags |= FT_LOAD_NO_AUTOHINT;
#endif
        }

        if ((fRec.fFlags & SkScalerContext::kEmbeddedBitmapText_Flag) == 0) {
            loadFlags |= FT_LOAD_NO_BITMAP;
        }

        // Always using FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH to get correct
        // advances, as fontconfig and cairo do.
        // See http://code.google.com/p/skia/issues/detail?id=222.
        loadFlags |= FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH;

        // Use vertical layout if requested.
        if (this->isVertical()) {
            loadFlags |= FT_LOAD_VERTICAL_LAYOUT;
        }

        loadFlags |= FT_LOAD_COLOR;

        fLoadGlyphFlags = loadFlags;
    }

    using DoneFTSize = SkFunctionWrapper<decltype(FT_Done_Size), FT_Done_Size>;
    std::unique_ptr<std::remove_pointer_t<FT_Size>, DoneFTSize> ftSize([this]() -> FT_Size {
        FT_Size size;
        FT_Error err = FT_New_Size(fFaceRec->fFace.get(), &size);
        if (err != 0) {
            SK_TRACEFTR(err, "FT_New_Size(%s) failed.", fFaceRec->fFace->family_name);
            return nullptr;
        }
        return size;
    }());
    if (nullptr == ftSize) {
        LOG_INFO("Could not create FT_Size.\n");
        return;
    }

    FT_Error err = FT_Activate_Size(ftSize.get());
    if (err != 0) {
        SK_TRACEFTR(err, "FT_Activate_Size(%s) failed.", fFaceRec->fFace->family_name);
        return;
    }

    fRec.computeMatrices(SkScalerContextRec::kFull_PreMatrixScale, &fScale, &fMatrix22Scalar);
    FT_F26Dot6 scaleX = SkScalarToFDot6(fScale.fX);
    FT_F26Dot6 scaleY = SkScalarToFDot6(fScale.fY);

    if (FT_IS_SCALABLE(fFaceRec->fFace)) {
        err = FT_Set_Char_Size(fFaceRec->fFace.get(), scaleX, scaleY, 72, 72);
        if (err != 0) {
            SK_TRACEFTR(err, "FT_Set_CharSize(%s, %f, %f) failed.",
                        fFaceRec->fFace->family_name, fScale.fX, fScale.fY);
            return;
        }

        // Adjust the matrix to reflect the actually chosen scale.
        // FreeType currently does not allow requesting sizes less than 1, this allow for scaling.
        // Don't do this at all sizes as that will interfere with hinting.
        if (fScale.fX < 1 || fScale.fY < 1) {
            SkScalar upem = fFaceRec->fFace->units_per_EM;
            FT_Size_Metrics& ftmetrics = fFaceRec->fFace->size->metrics;
            SkScalar x_ppem = upem * SkFT_FixedToScalar(ftmetrics.x_scale) / 64.0f;
            SkScalar y_ppem = upem * SkFT_FixedToScalar(ftmetrics.y_scale) / 64.0f;
            fMatrix22Scalar.preScale(fScale.x() / x_ppem, fScale.y() / y_ppem);
        }

    } else if (FT_HAS_FIXED_SIZES(fFaceRec->fFace)) {
        fStrikeIndex = chooseBitmapStrike(fFaceRec->fFace.get(), scaleY);
        if (fStrikeIndex == -1) {
            LOG_INFO("No glyphs for font \"%s\" size %f.\n",
                     fFaceRec->fFace->family_name, fScale.fY);
            return;
        }

        err = FT_Select_Size(fFaceRec->fFace.get(), fStrikeIndex);
        if (err != 0) {
            SK_TRACEFTR(err, "FT_Select_Size(%s, %d) failed.",
                        fFaceRec->fFace->family_name, fStrikeIndex);
            fStrikeIndex = -1;
            return;
        }

        // Adjust the matrix to reflect the actually chosen scale.
        // It is likely that the ppem chosen was not the one requested, this allows for scaling.
        fMatrix22Scalar.preScale(fScale.x() / fFaceRec->fFace->size->metrics.x_ppem,
                                 fScale.y() / fFaceRec->fFace->size->metrics.y_ppem);

        // FreeType does not provide linear metrics for bitmap fonts.
        linearMetrics = false;

        // FreeType documentation says:
        // FT_LOAD_NO_BITMAP -- Ignore bitmap strikes when loading.
        // Bitmap-only fonts ignore this flag.
        //
        // However, in FreeType 2.5.1 color bitmap only fonts do not ignore this flag.
        // Force this flag off for bitmap only fonts.
        fLoadGlyphFlags &= ~FT_LOAD_NO_BITMAP;
    } else {
        LOG_INFO("Unknown kind of font \"%s\" size %f.\n", fFaceRec->fFace->family_name, fScale.fY);
        return;
    }

    fMatrix22.xx = SkScalarToFixed(fMatrix22Scalar.getScaleX());
    fMatrix22.xy = SkScalarToFixed(-fMatrix22Scalar.getSkewX());
    fMatrix22.yx = SkScalarToFixed(-fMatrix22Scalar.getSkewY());
    fMatrix22.yy = SkScalarToFixed(fMatrix22Scalar.getScaleY());

#ifdef FT_COLOR_H
    FT_Palette_Select(fFaceRec->fFace.get(), 0, nullptr);
#endif

    fFTSize = ftSize.release();
    fFace = fFaceRec->fFace.get();
    fDoLinearMetrics = linearMetrics;
}

SkScalerContext_FreeType::~SkScalerContext_FreeType() {
    SkAutoMutexExclusive  ac(f_t_mutex());

    if (fFTSize != nullptr) {
        FT_Done_Size(fFTSize);
    }

    fFaceRec = nullptr;

    unref_ft_library();
}

/*  We call this before each use of the fFace, since we may be sharing
    this face with other context (at different sizes).
*/
FT_Error SkScalerContext_FreeType::setupSize() {
    f_t_mutex().assertHeld();
    FT_Error err = FT_Activate_Size(fFTSize);
    if (err != 0) {
        return err;
    }
    FT_Set_Transform(fFace, &fMatrix22, nullptr);
    return 0;
}

unsigned SkScalerContext_FreeType::generateGlyphCount() {
    return fFace->num_glyphs;
}

bool SkScalerContext_FreeType::generateAdvance(SkGlyph* glyph) {
   /* unhinted and light hinted text have linearly scaled advances
    * which are very cheap to compute with some font formats...
    */
    if (!fDoLinearMetrics) {
        return false;
    }

    SkAutoMutexExclusive  ac(f_t_mutex());

    if (this->setupSize()) {
        glyph->zeroMetrics();
        return true;
    }

    FT_Error    error;
    FT_Fixed    advance;

    error = FT_Get_Advance( fFace, glyph->getGlyphID(),
                            fLoadGlyphFlags | FT_ADVANCE_FLAG_FAST_ONLY,
                            &advance );

    if (error != 0) {
        return false;
    }

    const SkScalar advanceScalar = SkFT_FixedToScalar(advance);
    glyph->fAdvanceX = SkScalarToFloat(fMatrix22Scalar.getScaleX() * advanceScalar);
    glyph->fAdvanceY = SkScalarToFloat(fMatrix22Scalar.getSkewY() * advanceScalar);
    return true;
}

void SkScalerContext_FreeType::getBBoxForCurrentGlyph(const SkGlyph* glyph,
                                                      FT_BBox* bbox,
                                                      bool snapToPixelBoundary) {

    FT_Outline_Get_CBox(&fFace->glyph->outline, bbox);

    if (this->isSubpixel()) {
        int dx = SkFixedToFDot6(glyph->getSubXFixed());
        int dy = SkFixedToFDot6(glyph->getSubYFixed());
        // negate dy since freetype-y-goes-up and skia-y-goes-down
        bbox->xMin += dx;
        bbox->yMin -= dy;
        bbox->xMax += dx;
        bbox->yMax -= dy;
    }

    // outset the box to integral boundaries
    if (snapToPixelBoundary) {
        bbox->xMin &= ~63;
        bbox->yMin &= ~63;
        bbox->xMax  = (bbox->xMax + 63) & ~63;
        bbox->yMax  = (bbox->yMax + 63) & ~63;
    }

    // Must come after snapToPixelBoundary so that the width and height are
    // consistent. Otherwise asserts will fire later on when generating the
    // glyph image.
    if (this->isVertical()) {
        FT_Vector vector;
        vector.x = fFace->glyph->metrics.vertBearingX - fFace->glyph->metrics.horiBearingX;
        vector.y = -fFace->glyph->metrics.vertBearingY - fFace->glyph->metrics.horiBearingY;
        FT_Vector_Transform(&vector, &fMatrix22);
        bbox->xMin += vector.x;
        bbox->xMax += vector.x;
        bbox->yMin += vector.y;
        bbox->yMax += vector.y;
    }
}

bool SkScalerContext_FreeType::getCBoxForLetter(char letter, FT_BBox* bbox) {
    const FT_UInt glyph_id = FT_Get_Char_Index(fFace, letter);
    if (!glyph_id) {
        return false;
    }
    if (FT_Load_Glyph(fFace, glyph_id, fLoadGlyphFlags) != 0) {
        return false;
    }
    emboldenIfNeeded(fFace, fFace->glyph, SkTo<SkGlyphID>(glyph_id));
    FT_Outline_Get_CBox(&fFace->glyph->outline, bbox);
    return true;
}

void SkScalerContext_FreeType::updateGlyphIfLCD(SkGlyph* glyph) {
    if (glyph->fMaskFormat == SkMask::kLCD16_Format) {
        if (fLCDIsVert) {
            glyph->fHeight += gFTLibrary->lcdExtra();
            glyph->fTop -= gFTLibrary->lcdExtra() >> 1;
        } else {
            glyph->fWidth += gFTLibrary->lcdExtra();
            glyph->fLeft -= gFTLibrary->lcdExtra() >> 1;
        }
    }
}

bool SkScalerContext_FreeType::shouldSubpixelBitmap(const SkGlyph& glyph, const SkMatrix& matrix) {
    // If subpixel rendering of a bitmap *can* be done.
    bool mechanism = fFace->glyph->format == FT_GLYPH_FORMAT_BITMAP &&
                     this->isSubpixel() &&
                     (glyph.getSubXFixed() || glyph.getSubYFixed());

    // If subpixel rendering of a bitmap *should* be done.
    // 1. If the face is not scalable then always allow subpixel rendering.
    //    Otherwise, if the font has an 8ppem strike 7 will subpixel render but 8 won't.
    // 2. If the matrix is already not identity the bitmap will already be resampled,
    //    so resampling slightly differently shouldn't make much difference.
    bool policy = !FT_IS_SCALABLE(fFace) || !matrix.isIdentity();

    return mechanism && policy;
}

void SkScalerContext_FreeType::generateMetrics(SkGlyph* glyph) {
    SkAutoMutexExclusive  ac(f_t_mutex());

    glyph->fMaskFormat = fRec.fMaskFormat;

    if (this->setupSize()) {
        glyph->zeroMetrics();
        return;
    }

    FT_Error    err;
    err = FT_Load_Glyph( fFace, glyph->getGlyphID(),
                         fLoadGlyphFlags | FT_LOAD_BITMAP_METRICS_ONLY );
    if (err != 0) {
        glyph->zeroMetrics();
        return;
    }
    emboldenIfNeeded(fFace, fFace->glyph, glyph->getGlyphID());

    if (fFace->glyph->format == FT_GLYPH_FORMAT_OUTLINE) {
        using FT_PosLimits = std::numeric_limits<FT_Pos>;
        FT_BBox bounds = { FT_PosLimits::max(), FT_PosLimits::max(),
                           FT_PosLimits::min(), FT_PosLimits::min() };
#ifdef FT_COLOR_H
        FT_Bool haveLayers = false;
        FT_LayerIterator layerIterator = { 0, 0, nullptr };
        FT_UInt layerGlyphIndex;
        FT_UInt layerColorIndex;
        while (FT_Get_Color_Glyph_Layer(fFace, glyph->getGlyphID(),
                                        &layerGlyphIndex, &layerColorIndex, &layerIterator))
        {
            haveLayers = true;
            err = FT_Load_Glyph(fFace, layerGlyphIndex,
                                fLoadGlyphFlags | FT_LOAD_BITMAP_METRICS_ONLY);
            if (err != 0) {
                glyph->zeroMetrics();
                return;
            }
            emboldenIfNeeded(fFace, fFace->glyph, layerGlyphIndex);

            if (0 < fFace->glyph->outline.n_contours) {
                FT_BBox bbox;
                getBBoxForCurrentGlyph(glyph, &bbox, true);

                // Union
                bounds.xMin = std::min(bbox.xMin, bounds.xMin);
                bounds.yMin = std::min(bbox.yMin, bounds.yMin);
                bounds.xMax = std::max(bbox.xMax, bounds.xMax);
                bounds.yMax = std::max(bbox.yMax, bounds.yMax);
            }
        }

        if (haveLayers) {
            glyph->fMaskFormat = SkMask::kARGB32_Format;
            if (!(bounds.xMin < bounds.xMax && bounds.yMin < bounds.yMax)) {
                bounds = { 0, 0, 0, 0 };
            }
        } else {
#endif
            if (0 < fFace->glyph->outline.n_contours) {
                getBBoxForCurrentGlyph(glyph, &bounds, true);
            } else {
                bounds = { 0, 0, 0, 0 };
            }
#ifdef FT_COLOR_H
        }
#endif
        // Round out, no longer dot6.
        bounds.xMin = SkFDot6Floor(bounds.xMin);
        bounds.yMin = SkFDot6Floor(bounds.yMin);
        bounds.xMax = SkFDot6Ceil (bounds.xMax);
        bounds.yMax = SkFDot6Ceil (bounds.yMax);

        FT_Pos width  =  bounds.xMax - bounds.xMin;
        FT_Pos height =  bounds.yMax - bounds.yMin;
        FT_Pos top    = -bounds.yMax;  // Freetype y-up, Skia y-down.
        FT_Pos left   =  bounds.xMin;
        if (!SkTFitsIn<decltype(glyph->fWidth )>(width ) ||
            !SkTFitsIn<decltype(glyph->fHeight)>(height) ||
            !SkTFitsIn<decltype(glyph->fTop   )>(top   ) ||
            !SkTFitsIn<decltype(glyph->fLeft  )>(left  )  )
        {
            width = height = top = left = 0;
        }

        glyph->fWidth  = SkToU16(width );
        glyph->fHeight = SkToU16(height);
        glyph->fTop    = SkToS16(top   );
        glyph->fLeft   = SkToS16(left  );
        updateGlyphIfLCD(glyph);

    } else if (fFace->glyph->format == FT_GLYPH_FORMAT_BITMAP) {
        if (this->isVertical()) {
            FT_Vector vector;
            vector.x = fFace->glyph->metrics.vertBearingX - fFace->glyph->metrics.horiBearingX;
            vector.y = -fFace->glyph->metrics.vertBearingY - fFace->glyph->metrics.horiBearingY;
            FT_Vector_Transform(&vector, &fMatrix22);
            fFace->glyph->bitmap_left += SkFDot6Floor(vector.x);
            fFace->glyph->bitmap_top  += SkFDot6Floor(vector.y);
        }

        if (fFace->glyph->bitmap.pixel_mode == FT_PIXEL_MODE_BGRA) {
            glyph->fMaskFormat = SkMask::kARGB32_Format;
        }

        {
            SkRect rect = SkRect::MakeXYWH(SkIntToScalar(fFace->glyph->bitmap_left),
                                          -SkIntToScalar(fFace->glyph->bitmap_top),
                                           SkIntToScalar(fFace->glyph->bitmap.width),
                                           SkIntToScalar(fFace->glyph->bitmap.rows));
            fMatrix22Scalar.mapRect(&rect);
            if (this->shouldSubpixelBitmap(*glyph, fMatrix22Scalar)) {
                rect.offset(SkFixedToScalar(glyph->getSubXFixed()),
                            SkFixedToScalar(glyph->getSubYFixed()));
            }
            SkIRect irect = rect.roundOut();
            glyph->fWidth   = SkToU16(irect.width());
            glyph->fHeight  = SkToU16(irect.height());
            glyph->fTop     = SkToS16(irect.top());
            glyph->fLeft    = SkToS16(irect.left());
        }
    } else {
        SkDEBUGFAIL("unknown glyph format");
        glyph->zeroMetrics();
        return;
    }

    if (this->isVertical()) {
        if (fDoLinearMetrics) {
            const SkScalar advanceScalar = SkFT_FixedToScalar(fFace->glyph->linearVertAdvance);
            glyph->fAdvanceX = SkScalarToFloat(fMatrix22Scalar.getSkewX() * advanceScalar);
            glyph->fAdvanceY = SkScalarToFloat(fMatrix22Scalar.getScaleY() * advanceScalar);
        } else {
            glyph->fAdvanceX = -SkFDot6ToFloat(fFace->glyph->advance.x);
            glyph->fAdvanceY = SkFDot6ToFloat(fFace->glyph->advance.y);
        }
    } else {
        if (fDoLinearMetrics) {
            const SkScalar advanceScalar = SkFT_FixedToScalar(fFace->glyph->linearHoriAdvance);
            glyph->fAdvanceX = SkScalarToFloat(fMatrix22Scalar.getScaleX() * advanceScalar);
            glyph->fAdvanceY = SkScalarToFloat(fMatrix22Scalar.getSkewY() * advanceScalar);
        } else {
            glyph->fAdvanceX = SkFDot6ToFloat(fFace->glyph->advance.x);
            glyph->fAdvanceY = -SkFDot6ToFloat(fFace->glyph->advance.y);
        }
    }

#ifdef ENABLE_GLYPH_SPEW
    LOG_INFO("Metrics(glyph:%d flags:0x%x) w:%d\n", glyph->getGlyphID(), fLoadGlyphFlags, glyph->fWidth);
#endif
}

void SkScalerContext_FreeType::generateImage(const SkGlyph& glyph) {
    SkAutoMutexExclusive  ac(f_t_mutex());

    if (this->setupSize()) {
        sk_bzero(glyph.fImage, glyph.imageSize());
        return;
    }

    FT_Error err = FT_Load_Glyph(fFace, glyph.getGlyphID(), fLoadGlyphFlags);
    if (err != 0) {
        SK_TRACEFTR(err, "SkScalerContext_FreeType::generateImage: FT_Load_Glyph(glyph:%d "
                     "width:%d height:%d rb:%d flags:%d) failed.",
                     glyph.getGlyphID(), glyph.width(), glyph.height(), glyph.rowBytes(),
                     fLoadGlyphFlags);
        sk_bzero(glyph.fImage, glyph.imageSize());
        return;
    }

    emboldenIfNeeded(fFace, fFace->glyph, glyph.getGlyphID());
    SkMatrix* bitmapMatrix = &fMatrix22Scalar;
    SkMatrix subpixelBitmapMatrix;
    if (this->shouldSubpixelBitmap(glyph, *bitmapMatrix)) {
        subpixelBitmapMatrix = fMatrix22Scalar;
        subpixelBitmapMatrix.postTranslate(SkFixedToScalar(glyph.getSubXFixed()),
                                           SkFixedToScalar(glyph.getSubYFixed()));
        bitmapMatrix = &subpixelBitmapMatrix;
    }
    generateGlyphImage(fFace, glyph, *bitmapMatrix);
}


bool SkScalerContext_FreeType::generatePath(SkGlyphID glyphID, SkPath* path) {
    SkASSERT(path);

    SkAutoMutexExclusive  ac(f_t_mutex());

    // FT_IS_SCALABLE is documented to mean the face contains outline glyphs.
    if (!FT_IS_SCALABLE(fFace) || this->setupSize()) {
        path->reset();
        return false;
    }

    uint32_t flags = fLoadGlyphFlags;
    flags |= FT_LOAD_NO_BITMAP; // ignore embedded bitmaps so we're sure to get the outline
    flags &= ~FT_LOAD_RENDER;   // don't scan convert (we just want the outline)

    FT_Error err = FT_Load_Glyph(fFace, glyphID, flags);
    if (err != 0 || fFace->glyph->format != FT_GLYPH_FORMAT_OUTLINE) {
        path->reset();
        return false;
    }
    emboldenIfNeeded(fFace, fFace->glyph, glyphID);

    if (!generateGlyphPath(fFace, path)) {
        path->reset();
        return false;
    }

    // The path's origin from FreeType is always the horizontal layout origin.
    // Offset the path so that it is relative to the vertical origin if needed.
    if (this->isVertical()) {
        FT_Vector vector;
        vector.x = fFace->glyph->metrics.vertBearingX - fFace->glyph->metrics.horiBearingX;
        vector.y = -fFace->glyph->metrics.vertBearingY - fFace->glyph->metrics.horiBearingY;
        FT_Vector_Transform(&vector, &fMatrix22);
        path->offset(SkFDot6ToScalar(vector.x), -SkFDot6ToScalar(vector.y));
    }
    return true;
}

void SkScalerContext_FreeType::generateFontMetrics(SkFontMetrics* metrics) {
    if (nullptr == metrics) {
        return;
    }

    SkAutoMutexExclusive ac(f_t_mutex());

    if (this->setupSize()) {
        sk_bzero(metrics, sizeof(*metrics));
        return;
    }

    FT_Face face = fFace;
    metrics->fFlags = 0;

    SkScalar upem = SkIntToScalar(SkTypeface_FreeType::GetUnitsPerEm(face));

    // use the os/2 table as a source of reasonable defaults.
    SkScalar x_height = 0.0f;
    SkScalar avgCharWidth = 0.0f;
    SkScalar cap_height = 0.0f;
    SkScalar strikeoutThickness = 0.0f, strikeoutPosition = 0.0f;
    TT_OS2* os2 = (TT_OS2*) FT_Get_Sfnt_Table(face, ft_sfnt_os2);
    if (os2) {
        x_height = SkIntToScalar(os2->sxHeight) / upem * fScale.y();
        avgCharWidth = SkIntToScalar(os2->xAvgCharWidth) / upem;
        strikeoutThickness = SkIntToScalar(os2->yStrikeoutSize) / upem;
        strikeoutPosition = -SkIntToScalar(os2->yStrikeoutPosition) / upem;
        metrics->fFlags |= SkFontMetrics::kStrikeoutThicknessIsValid_Flag;
        metrics->fFlags |= SkFontMetrics::kStrikeoutPositionIsValid_Flag;
        if (os2->version != 0xFFFF && os2->version >= 2) {
            cap_height = SkIntToScalar(os2->sCapHeight) / upem * fScale.y();
        }
    }

    // pull from format-specific metrics as needed
    SkScalar ascent, descent, leading, xmin, xmax, ymin, ymax;
    SkScalar underlineThickness, underlinePosition;
    if (face->face_flags & FT_FACE_FLAG_SCALABLE) { // scalable outline font
        // FreeType will always use HHEA metrics if they're not zero.
        // It completely ignores the OS/2 fsSelection::UseTypoMetrics bit.
        // It also ignores the VDMX tables, which are also of interest here
        // (and override everything else when they apply).
        static const int kUseTypoMetricsMask = (1 << 7);
        if (os2 && os2->version != 0xFFFF && (os2->fsSelection & kUseTypoMetricsMask)) {
            ascent = -SkIntToScalar(os2->sTypoAscender) / upem;
            descent = -SkIntToScalar(os2->sTypoDescender) / upem;
            leading = SkIntToScalar(os2->sTypoLineGap) / upem;
        } else {
            ascent = -SkIntToScalar(face->ascender) / upem;
            descent = -SkIntToScalar(face->descender) / upem;
            leading = SkIntToScalar(face->height + (face->descender - face->ascender)) / upem;
        }
        xmin = SkIntToScalar(face->bbox.xMin) / upem;
        xmax = SkIntToScalar(face->bbox.xMax) / upem;
        ymin = -SkIntToScalar(face->bbox.yMin) / upem;
        ymax = -SkIntToScalar(face->bbox.yMax) / upem;
        underlineThickness = SkIntToScalar(face->underline_thickness) / upem;
        underlinePosition = -SkIntToScalar(face->underline_position +
                                           face->underline_thickness / 2) / upem;

        metrics->fFlags |= SkFontMetrics::kUnderlineThicknessIsValid_Flag;
        metrics->fFlags |= SkFontMetrics::kUnderlinePositionIsValid_Flag;

        // we may be able to synthesize x_height and cap_height from outline
        if (!x_height) {
            FT_BBox bbox;
            if (getCBoxForLetter('x', &bbox)) {
                x_height = SkIntToScalar(bbox.yMax) / 64.0f;
            }
        }
        if (!cap_height) {
            FT_BBox bbox;
            if (getCBoxForLetter('H', &bbox)) {
                cap_height = SkIntToScalar(bbox.yMax) / 64.0f;
            }
        }
    } else if (fStrikeIndex != -1) { // bitmap strike metrics
        SkScalar xppem = SkIntToScalar(face->size->metrics.x_ppem);
        SkScalar yppem = SkIntToScalar(face->size->metrics.y_ppem);
        ascent = -SkIntToScalar(face->size->metrics.ascender) / (yppem * 64.0f);
        descent = -SkIntToScalar(face->size->metrics.descender) / (yppem * 64.0f);
        leading = (SkIntToScalar(face->size->metrics.height) / (yppem * 64.0f)) + ascent - descent;

        xmin = 0.0f;
        xmax = SkIntToScalar(face->available_sizes[fStrikeIndex].width) / xppem;
        ymin = descent;
        ymax = ascent;
        // The actual bitmaps may be any size and placed at any offset.
        metrics->fFlags |= SkFontMetrics::kBoundsInvalid_Flag;

        underlineThickness = 0;
        underlinePosition = 0;
        metrics->fFlags &= ~SkFontMetrics::kUnderlineThicknessIsValid_Flag;
        metrics->fFlags &= ~SkFontMetrics::kUnderlinePositionIsValid_Flag;

        TT_Postscript* post = (TT_Postscript*) FT_Get_Sfnt_Table(face, ft_sfnt_post);
        if (post) {
            underlineThickness = SkIntToScalar(post->underlineThickness) / upem;
            underlinePosition = -SkIntToScalar(post->underlinePosition) / upem;
            metrics->fFlags |= SkFontMetrics::kUnderlineThicknessIsValid_Flag;
            metrics->fFlags |= SkFontMetrics::kUnderlinePositionIsValid_Flag;
        }
    } else {
        sk_bzero(metrics, sizeof(*metrics));
        return;
    }

    // synthesize elements that were not provided by the os/2 table or format-specific metrics
    if (!x_height) {
        x_height = -ascent * fScale.y();
    }
    if (!avgCharWidth) {
        avgCharWidth = xmax - xmin;
    }
    if (!cap_height) {
      cap_height = -ascent * fScale.y();
    }

    // disallow negative linespacing
    if (leading < 0.0f) {
        leading = 0.0f;
    }

    metrics->fTop = ymax * fScale.y();
    metrics->fAscent = ascent * fScale.y();
    metrics->fDescent = descent * fScale.y();
    metrics->fBottom = ymin * fScale.y();
    metrics->fLeading = leading * fScale.y();
    metrics->fAvgCharWidth = avgCharWidth * fScale.y();
    metrics->fXMin = xmin * fScale.y();
    metrics->fXMax = xmax * fScale.y();
    metrics->fMaxCharWidth = metrics->fXMax - metrics->fXMin;
    metrics->fXHeight = x_height;
    metrics->fCapHeight = cap_height;
    metrics->fUnderlineThickness = underlineThickness * fScale.y();
    metrics->fUnderlinePosition = underlinePosition * fScale.y();
    metrics->fStrikeoutThickness = strikeoutThickness * fScale.y();
    metrics->fStrikeoutPosition = strikeoutPosition * fScale.y();

    if (face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS) {
        // The bounds are only valid for the default variation.
        metrics->fFlags |= SkFontMetrics::kBoundsInvalid_Flag;
    }
}

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

// hand-tuned value to reduce outline embolden strength
#ifndef SK_OUTLINE_EMBOLDEN_DIVISOR
    #ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
        #define SK_OUTLINE_EMBOLDEN_DIVISOR   34
    #else
        #define SK_OUTLINE_EMBOLDEN_DIVISOR   24
    #endif
#endif

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

void SkScalerContext_FreeType::emboldenIfNeeded(FT_Face face, FT_GlyphSlot glyph, SkGlyphID gid) {
    // check to see if the embolden bit is set
    if (0 == (fRec.fFlags & SkScalerContext::kEmbolden_Flag)) {
        return;
    }

    switch (glyph->format) {
        case FT_GLYPH_FORMAT_OUTLINE:
            FT_Pos strength;
            strength = FT_MulFix(face->units_per_EM, face->size->metrics.y_scale)
                       / SK_OUTLINE_EMBOLDEN_DIVISOR;
            FT_Outline_Embolden(&glyph->outline, strength);
            break;
        case FT_GLYPH_FORMAT_BITMAP:
            if (!fFace->glyph->bitmap.buffer) {
                FT_Load_Glyph(fFace, gid, fLoadGlyphFlags);
            }
            FT_GlyphSlot_Own_Bitmap(glyph);
            FT_Bitmap_Embolden(glyph->library, &glyph->bitmap, kBitmapEmboldenStrength, 0);
            break;
        default:
            SkDEBUGFAIL("unknown glyph format");
    }
}

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

#include "src/core/SkUtils.h"

// Just made up, so we don't end up storing 1000s of entries
constexpr int kMaxC2GCacheCount = 512;

void SkTypeface_FreeType::onCharsToGlyphs(const SkUnichar uni[], int count,
                                          SkGlyphID glyphs[]) const {
    // Try the cache first, *before* accessing freetype lib/face, as that
    // can be very slow. If we do need to compute a new glyphID, then
    // access those freetype objects and continue the loop.

    SkAutoMutexExclusive ama(fC2GCacheMutex);

    int i;
    for (i = 0; i < count; ++i) {
        int index = fC2GCache.findGlyphIndex(uni[i]);
        if (index < 0) {
            break;
        }
        glyphs[i] = SkToU16(index);
    }
    if (i == count) {
        // we're done, no need to access the freetype objects
        return;
    }

    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        sk_bzero(glyphs, count * sizeof(glyphs[0]));
        return;
    }

    for (; i < count; ++i) {
        SkUnichar c = uni[i];
        int index = fC2GCache.findGlyphIndex(c);
        if (index >= 0) {
            glyphs[i] = SkToU16(index);
        } else {
            glyphs[i] = SkToU16(FT_Get_Char_Index(face, c));
            fC2GCache.insertCharAndGlyph(~index, c, glyphs[i]);
        }
    }

    if (fC2GCache.count() > kMaxC2GCacheCount) {
        fC2GCache.reset();
    }
}

int SkTypeface_FreeType::onCountGlyphs() const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    return face ? face->num_glyphs : 0;
}

SkTypeface::LocalizedStrings* SkTypeface_FreeType::onCreateFamilyNameIterator() const {
    sk_sp<SkTypeface::LocalizedStrings> nameIter =
        SkOTUtils::LocalizedStrings_NameTable::MakeForFamilyNames(*this);
    if (!nameIter) {
        SkString familyName;
        this->getFamilyName(&familyName);
        SkString language("und"); //undetermined
        nameIter = sk_make_sp<SkOTUtils::LocalizedStrings_SingleName>(familyName, language);
    }
    return nameIter.release();
}

int SkTypeface_FreeType::onGetVariationDesignPosition(
    SkFontArguments::VariationPosition::Coordinate coordinates[], int coordinateCount) const
{
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return -1;
    }

    if (!(face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS)) {
        return 0;
    }

    FT_MM_Var* variations = nullptr;
    if (FT_Get_MM_Var(face, &variations)) {
        return -1;
    }
    SkAutoFree autoFreeVariations(variations);

    if (!coordinates || coordinateCount < SkToInt(variations->num_axis)) {
        return variations->num_axis;
    }

    SkAutoSTMalloc<4, FT_Fixed> coords(variations->num_axis);
    // FT_Get_{MM,Var}_{Blend,Design}_Coordinates were added in FreeType 2.7.1.
    if (gFTLibrary->fGetVarDesignCoordinates &&
        !gFTLibrary->fGetVarDesignCoordinates(face, variations->num_axis, coords.get()))
    {
        for (FT_UInt i = 0; i < variations->num_axis; ++i) {
            coordinates[i].axis = variations->axis[i].tag;
            coordinates[i].value = SkFixedToScalar(coords[i]);
        }
    } else if (static_cast<FT_UInt>(fta.getAxesCount()) == variations->num_axis) {
        for (FT_UInt i = 0; i < variations->num_axis; ++i) {
            coordinates[i].axis = variations->axis[i].tag;
            coordinates[i].value = SkFixedToScalar(fta.getAxes()[i]);
        }
    } else if (fta.isNamedVariationSpecified()) {
        // The font has axes, they cannot be retrieved, and some named axis was specified.
        return -1;
    } else {
        // The font has axes, they cannot be retrieved, but no named instance was specified.
        return 0;
    }

    return variations->num_axis;
}

int SkTypeface_FreeType::onGetVariationDesignParameters(
    SkFontParameters::Variation::Axis parameters[], int parameterCount) const
{
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return -1;
    }

    if (!(face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS)) {
        return 0;
    }

    FT_MM_Var* variations = nullptr;
    if (FT_Get_MM_Var(face, &variations)) {
        return -1;
    }
    SkAutoFree autoFreeVariations(variations);

    if (!parameters || parameterCount < SkToInt(variations->num_axis)) {
        return variations->num_axis;
    }

    for (FT_UInt i = 0; i < variations->num_axis; ++i) {
        parameters[i].tag = variations->axis[i].tag;
        parameters[i].min = SkFixedToScalar(variations->axis[i].minimum);
        parameters[i].def = SkFixedToScalar(variations->axis[i].def);
        parameters[i].max = SkFixedToScalar(variations->axis[i].maximum);
        FT_UInt flags = 0;
        bool hidden = gFTLibrary->fGetVarAxisFlags &&
            !gFTLibrary->fGetVarAxisFlags(variations, i, &flags) &&
            (flags & FT_VAR_AXIS_FLAG_HIDDEN);
        parameters[i].setHidden(hidden);
    }

    return variations->num_axis;
}

int SkTypeface_FreeType::onGetTableTags(SkFontTableTag tags[]) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return 0;
    }

    FT_ULong tableCount = 0;
    FT_Error error;

    // When 'tag' is nullptr, returns number of tables in 'length'.
    error = FT_Sfnt_Table_Info(face, 0, nullptr, &tableCount);
    if (error) {
        return 0;
    }

    if (tags) {
        for (FT_ULong tableIndex = 0; tableIndex < tableCount; ++tableIndex) {
            FT_ULong tableTag;
            FT_ULong tablelength;
            error = FT_Sfnt_Table_Info(face, tableIndex, &tableTag, &tablelength);
            if (error) {
                return 0;
            }
            tags[tableIndex] = static_cast<SkFontTableTag>(tableTag);
        }
    }
    return tableCount;
}

size_t SkTypeface_FreeType::onGetTableData(SkFontTableTag tag, size_t offset,
                                           size_t length, void* data) const
{
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return 0;
    }

    FT_ULong tableLength = 0;
    FT_Error error;

    // When 'length' is 0 it is overwritten with the full table length; 'offset' is ignored.
    error = FT_Load_Sfnt_Table(face, tag, 0, nullptr, &tableLength);
    if (error) {
        return 0;
    }

    if (offset > tableLength) {
        return 0;
    }
    FT_ULong size = std::min((FT_ULong)length, tableLength - (FT_ULong)offset);
    if (data) {
        error = FT_Load_Sfnt_Table(face, tag, offset, reinterpret_cast<FT_Byte*>(data), &size);
        if (error) {
            return 0;
        }
    }

    return size;
}

sk_sp<SkData> SkTypeface_FreeType::onCopyTableData(SkFontTableTag tag) const {
    AutoFTAccess fta(this);
    FT_Face face = fta.face();
    if (!face) {
        return nullptr;
    }

    FT_ULong tableLength = 0;
    FT_Error error;

    // When 'length' is 0 it is overwritten with the full table length; 'offset' is ignored.
    error = FT_Load_Sfnt_Table(face, tag, 0, nullptr, &tableLength);
    if (error) {
        return nullptr;
    }

    sk_sp<SkData> data = SkData::MakeUninitialized(tableLength);
    if (data) {
        error = FT_Load_Sfnt_Table(face, tag, 0,
                                   reinterpret_cast<FT_Byte*>(data->writable_data()), &tableLength);
        if (error) {
            data.reset();
        }
    }
    return data;
}

std::unique_ptr<SkFontData> SkTypeface_FreeType::makeFontData() const {
    return this->onMakeFontData();
}

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

SkTypeface_FreeType::Scanner::Scanner() : fLibrary(nullptr) {
    if (FT_New_Library(&gFTMemory, &fLibrary)) {
        return;
    }
    FT_Add_Default_Modules(fLibrary);
}
SkTypeface_FreeType::Scanner::~Scanner() {
    if (fLibrary) {
        FT_Done_Library(fLibrary);
    }
}

FT_Face SkTypeface_FreeType::Scanner::openFace(SkStreamAsset* stream, int ttcIndex,
                                               FT_Stream ftStream) const
{
    if (fLibrary == nullptr || stream == nullptr) {
        return nullptr;
    }

    FT_Open_Args args;
    memset(&args, 0, sizeof(args));

    const void* memoryBase = stream->getMemoryBase();

    if (memoryBase) {
        args.flags = FT_OPEN_MEMORY;
        args.memory_base = (const FT_Byte*)memoryBase;
        args.memory_size = stream->getLength();
    } else {
        memset(ftStream, 0, sizeof(*ftStream));
        ftStream->size = stream->getLength();
        ftStream->descriptor.pointer = stream;
        ftStream->read  = sk_ft_stream_io;
        ftStream->close = sk_ft_stream_close;

        args.flags = FT_OPEN_STREAM;
        args.stream = ftStream;
    }

    FT_Face face;
    if (FT_Open_Face(fLibrary, &args, ttcIndex, &face)) {
        return nullptr;
    }
    return face;
}

bool SkTypeface_FreeType::Scanner::recognizedFont(SkStreamAsset* stream, int* numFaces) const {
    SkAutoMutexExclusive libraryLock(fLibraryMutex);

    FT_StreamRec streamRec;
    SkUniqueFTFace face(this->openFace(stream, -1, &streamRec));
    if (!face) {
        return false;
    }

    *numFaces = face->num_faces;
    return true;
}

#include "src/core/SkTSearch.h"
bool SkTypeface_FreeType::Scanner::scanFont(
    SkStreamAsset* stream, int ttcIndex,
    SkString* name, SkFontStyle* style, bool* isFixedPitch, AxisDefinitions* axes) const
{
    SkAutoMutexExclusive libraryLock(fLibraryMutex);

    FT_StreamRec streamRec;
    SkUniqueFTFace face(this->openFace(stream, ttcIndex, &streamRec));
    if (!face) {
        return false;
    }

    int weight = SkFontStyle::kNormal_Weight;
    int width = SkFontStyle::kNormal_Width;
    SkFontStyle::Slant slant = SkFontStyle::kUpright_Slant;
    if (face->style_flags & FT_STYLE_FLAG_BOLD) {
        weight = SkFontStyle::kBold_Weight;
    }
    if (face->style_flags & FT_STYLE_FLAG_ITALIC) {
        slant = SkFontStyle::kItalic_Slant;
    }

    PS_FontInfoRec psFontInfo;
    TT_OS2* os2 = static_cast<TT_OS2*>(FT_Get_Sfnt_Table(face.get(), ft_sfnt_os2));
    if (os2 && os2->version != 0xffff) {
        weight = os2->usWeightClass;
        width = os2->usWidthClass;

        // OS/2::fsSelection bit 9 indicates oblique.
        if (SkToBool(os2->fsSelection & (1u << 9))) {
            slant = SkFontStyle::kOblique_Slant;
        }
    } else if (0 == FT_Get_PS_Font_Info(face.get(), &psFontInfo) && psFontInfo.weight) {
        static const struct {
            char const * const name;
            int const weight;
        } commonWeights [] = {
            // There are probably more common names, but these are known to exist.
            { "all", SkFontStyle::kNormal_Weight }, // Multiple Masters usually default to normal.
            { "black", SkFontStyle::kBlack_Weight },
            { "bold", SkFontStyle::kBold_Weight },
            { "book", (SkFontStyle::kNormal_Weight + SkFontStyle::kLight_Weight)/2 },
            { "demi", SkFontStyle::kSemiBold_Weight },
            { "demibold", SkFontStyle::kSemiBold_Weight },
            { "extra", SkFontStyle::kExtraBold_Weight },
            { "extrabold", SkFontStyle::kExtraBold_Weight },
            { "extralight", SkFontStyle::kExtraLight_Weight },
            { "hairline", SkFontStyle::kThin_Weight },
            { "heavy", SkFontStyle::kBlack_Weight },
            { "light", SkFontStyle::kLight_Weight },
            { "medium", SkFontStyle::kMedium_Weight },
            { "normal", SkFontStyle::kNormal_Weight },
            { "plain", SkFontStyle::kNormal_Weight },
            { "regular", SkFontStyle::kNormal_Weight },
            { "roman", SkFontStyle::kNormal_Weight },
            { "semibold", SkFontStyle::kSemiBold_Weight },
            { "standard", SkFontStyle::kNormal_Weight },
            { "thin", SkFontStyle::kThin_Weight },
            { "ultra", SkFontStyle::kExtraBold_Weight },
            { "ultrablack", SkFontStyle::kExtraBlack_Weight },
            { "ultrabold", SkFontStyle::kExtraBold_Weight },
            { "ultraheavy", SkFontStyle::kExtraBlack_Weight },
            { "ultralight", SkFontStyle::kExtraLight_Weight },
        };
        int const index = SkStrLCSearch(&commonWeights[0].name, SK_ARRAY_COUNT(commonWeights),
                                        psFontInfo.weight, sizeof(commonWeights[0]));
        if (index >= 0) {
            weight = commonWeights[index].weight;
        } else {
            LOG_INFO("Do not know weight for: %s (%s) \n", face->family_name, psFontInfo.weight);
        }
    }

    if (name != nullptr) {
        name->set(face->family_name);
    }
    if (style != nullptr) {
        *style = SkFontStyle(weight, width, slant);
    }
    if (isFixedPitch != nullptr) {
        *isFixedPitch = FT_IS_FIXED_WIDTH(face);
    }

    if (axes != nullptr && !GetAxes(face.get(), axes)) {
        return false;
    }
    return true;
}

bool SkTypeface_FreeType::Scanner::GetAxes(FT_Face face, AxisDefinitions* axes) {
    SkASSERT(face && axes);
    if (face->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS) {
        FT_MM_Var* variations = nullptr;
        FT_Error err = FT_Get_MM_Var(face, &variations);
        if (err) {
            LOG_INFO("INFO: font %s claims to have variations, but none found.\n",
                     face->family_name);
            return false;
        }
        SkAutoFree autoFreeVariations(variations);

        axes->reset(variations->num_axis);
        for (FT_UInt i = 0; i < variations->num_axis; ++i) {
            const FT_Var_Axis& ftAxis = variations->axis[i];
            (*axes)[i].fTag = ftAxis.tag;
            (*axes)[i].fMinimum = ftAxis.minimum;
            (*axes)[i].fDefault = ftAxis.def;
            (*axes)[i].fMaximum = ftAxis.maximum;
        }
    }
    return true;
}

/*static*/ void SkTypeface_FreeType::Scanner::computeAxisValues(
    AxisDefinitions axisDefinitions,
    const SkFontArguments::VariationPosition position,
    SkFixed* axisValues,
    const SkString& name)
{
    for (int i = 0; i < axisDefinitions.count(); ++i) {
        const Scanner::AxisDefinition& axisDefinition = axisDefinitions[i];
        const SkScalar axisMin = SkFixedToScalar(axisDefinition.fMinimum);
        const SkScalar axisMax = SkFixedToScalar(axisDefinition.fMaximum);
        axisValues[i] = axisDefinition.fDefault;
        // The position may be over specified. If there are multiple values for a given axis,
        // use the last one since that's what css-fonts-4 requires.
        for (int j = position.coordinateCount; j --> 0;) {
            const auto& coordinate = position.coordinates[j];
            if (axisDefinition.fTag == coordinate.axis) {
                const SkScalar axisValue = SkTPin(coordinate.value, axisMin, axisMax);
                if (coordinate.value != axisValue) {
                    LOG_INFO("Requested font axis value out of range: "
                             "%s '%c%c%c%c' %f; pinned to %f.\n",
                             name.c_str(),
                             (axisDefinition.fTag >> 24) & 0xFF,
                             (axisDefinition.fTag >> 16) & 0xFF,
                             (axisDefinition.fTag >>  8) & 0xFF,
                             (axisDefinition.fTag      ) & 0xFF,
                             SkScalarToDouble(coordinate.value),
                             SkScalarToDouble(axisValue));
                }
                axisValues[i] = SkScalarToFixed(axisValue);
                break;
            }
        }
        // TODO: warn on defaulted axis?
    }

    SkDEBUGCODE(
        // Check for axis specified, but not matched in font.
        for (int i = 0; i < position.coordinateCount; ++i) {
            SkFourByteTag skTag = position.coordinates[i].axis;
            bool found = false;
            for (int j = 0; j < axisDefinitions.count(); ++j) {
                if (skTag == axisDefinitions[j].fTag) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                LOG_INFO("Requested font axis not found: %s '%c%c%c%c'\n",
                         name.c_str(),
                         (skTag >> 24) & 0xFF,
                         (skTag >> 16) & 0xFF,
                         (skTag >>  8) & 0xFF,
                         (skTag)       & 0xFF);
            }
        }
    )
}