src/pdf/SkPDFFont.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkData.h"
#include "SkGlyphCache.h"
#include "SkPaint.h"
#include "SkPDFCanon.h"
#include "SkPDFConvertType1FontStream.h"
#include "SkPDFDevice.h"
#include "SkPDFMakeToUnicodeCmap.h"
#include "SkPDFFont.h"
#include "SkPDFUtils.h"
#include "SkRefCnt.h"
#include "SkScalar.h"
#include "SkStream.h"
#include "SkTypefacePriv.h"
#include "SkTypes.h"
#include "SkUtils.h"

#if defined (SK_SFNTLY_SUBSETTER)
    #if defined (GOOGLE3)
        // #including #defines doesn't work with this build system.
        #include "typography/font/sfntly/src/sample/chromium/font_subsetter.h"
    #else
        #include SK_SFNTLY_SUBSETTER
    #endif
#endif

namespace {

// PDF's notion of symbolic vs non-symbolic is related to the character set, not
// symbols vs. characters.  Rarely is a font the right character set to call it
// non-symbolic, so always call it symbolic.  (PDF 1.4 spec, section 5.7.1)
static const int kPdfSymbolic = 4;

struct AdvanceMetric {
    enum MetricType {
        kDefault,  // Default advance: fAdvance.count = 1
        kRange,    // Advances for a range: fAdvance.count = fEndID-fStartID
        kRun       // fStartID-fEndID have same advance: fAdvance.count = 1
    };
    MetricType fType;
    uint16_t fStartId;
    uint16_t fEndId;
    SkTDArray<int16_t> fAdvance;
    AdvanceMetric(uint16_t startId) : fStartId(startId) {}
    AdvanceMetric(AdvanceMetric&&) = default;
    AdvanceMetric& operator=(AdvanceMetric&& other) = default;
    AdvanceMetric(const AdvanceMetric&) = delete;
    AdvanceMetric& operator=(const AdvanceMetric&) = delete;
};

class SkPDFType0Font final : public SkPDFFont {
public:
    SkPDFType0Font(const SkAdvancedTypefaceMetrics* info,
                   SkTypeface* typeface);
    virtual ~SkPDFType0Font();
    bool multiByteGlyphs() const override { return true; }
    sk_sp<SkPDFObject> getFontSubset(const SkPDFGlyphSet* usage) override;
#ifdef SK_DEBUG
    void emitObject(SkWStream*,
                    const SkPDFObjNumMap&,
                    const SkPDFSubstituteMap&) const override;
#endif

private:
#ifdef SK_DEBUG
    bool fPopulated;
#endif
    bool populate(const SkPDFGlyphSet* subset);
    typedef SkPDFDict INHERITED;
};

class SkPDFCIDFont final : public SkPDFFont {
public:
    SkPDFCIDFont(const SkAdvancedTypefaceMetrics* info,
                 SkTypeface* typeface,
                 const SkPDFGlyphSet* subset);
    virtual ~SkPDFCIDFont();
    bool multiByteGlyphs() const override { return true; }

private:
    bool populate(const SkPDFGlyphSet* subset);
    bool addFontDescriptor(int16_t defaultWidth,
                           const SkTDArray<uint32_t>* subset);
};

class SkPDFType1Font final : public SkPDFFont {
public:
    SkPDFType1Font(const SkAdvancedTypefaceMetrics* info,
                   SkTypeface* typeface,
                   uint16_t glyphID,
                   SkPDFDict* relatedFontDescriptor);
    virtual ~SkPDFType1Font();
    bool multiByteGlyphs() const override { return false; }

private:
    bool populate(int16_t glyphID);
    bool addFontDescriptor(int16_t defaultWidth);
};

class SkPDFType3Font final : public SkPDFFont {
public:
    SkPDFType3Font(const SkAdvancedTypefaceMetrics* info,
                   SkTypeface* typeface,
                   uint16_t glyphID);
    virtual ~SkPDFType3Font() {}
    void emitObject(SkWStream*,
                    const SkPDFObjNumMap&,
                    const SkPDFSubstituteMap&) const override {
        SkDEBUGFAIL("should call getFontSubset!");
    }
    sk_sp<SkPDFObject> getFontSubset(const SkPDFGlyphSet* usage) override;
    bool multiByteGlyphs() const override { return false; }
};

///////////////////////////////////////////////////////////////////////////////
// File-Local Functions
///////////////////////////////////////////////////////////////////////////////

const int16_t kInvalidAdvance = SK_MinS16;
const int16_t kDontCareAdvance = SK_MinS16 + 1;

static void stripUninterestingTrailingAdvancesFromRange(
        AdvanceMetric* range) {
    SkASSERT(range);

    int expectedAdvanceCount = range->fEndId - range->fStartId + 1;
    if (range->fAdvance.count() < expectedAdvanceCount) {
        return;
    }

    for (int i = expectedAdvanceCount - 1; i >= 0; --i) {
        if (range->fAdvance[i] != kDontCareAdvance &&
            range->fAdvance[i] != kInvalidAdvance &&
            range->fAdvance[i] != 0) {
            range->fEndId = range->fStartId + i;
            break;
        }
    }
}

static void zeroWildcardsInRange(AdvanceMetric* range) {
    SkASSERT(range);
    if (range->fType != AdvanceMetric::kRange) {
        return;
    }
    SkASSERT(range->fAdvance.count() == range->fEndId - range->fStartId + 1);

    // Zero out wildcards.
    for (int i = 0; i < range->fAdvance.count(); ++i) {
        if (range->fAdvance[i] == kDontCareAdvance) {
            range->fAdvance[i] = 0;
        }
    }
}

static void FinishRange(
        AdvanceMetric* range,
        int endId,
        AdvanceMetric::MetricType type) {
    range->fEndId = endId;
    range->fType = type;
    stripUninterestingTrailingAdvancesFromRange(range);
    int newLength;
    if (type == AdvanceMetric::kRange) {
        newLength = range->fEndId - range->fStartId + 1;
    } else {
        if (range->fEndId == range->fStartId) {
            range->fType = AdvanceMetric::kRange;
        }
        newLength = 1;
    }
    SkASSERT(range->fAdvance.count() >= newLength);
    range->fAdvance.setCount(newLength);
    zeroWildcardsInRange(range);
}


/** Retrieve advance data for glyphs. Used by the PDF backend.
    @param num_glyphs    Total number of glyphs in the given font.
    @param glyphIDs      For per-glyph info, specify subset of the
                         font by giving glyph ids.  Each integer
                         represents a glyph id.  Passing nullptr
                         means all glyphs in the font.
    @param glyphIDsCount Number of elements in subsetGlyphIds.
                         Ignored if glyphIDs is nullptr.
*/
// TODO(halcanary): this function is complex enough to need its logic
// tested with unit tests.  On the other hand, I want to do another
// round of re-factoring before figuring out how to mock this.
// TODO(halcanary): this function should be combined with
// composeAdvanceData() so that we don't need to produce a linked list
// of intermediate values.  Or we could make the intermediate value
// something other than a linked list.
static void get_glyph_widths(SkSinglyLinkedList<AdvanceMetric>* glyphWidths,
                             int num_glyphs,
                             const uint32_t* subsetGlyphIDs,
                             uint32_t subsetGlyphIDsLength,
                             SkGlyphCache* glyphCache) {
    // Assuming that on average, the ASCII representation of an advance plus
    // a space is 8 characters and the ASCII representation of a glyph id is 3
    // characters, then the following cut offs for using different range types
    // apply:
    // The cost of stopping and starting the range is 7 characers
    //  a. Removing 4 0's or don't care's is a win
    // The cost of stopping and starting the range plus a run is 22
    // characters
    //  b. Removing 3 repeating advances is a win
    //  c. Removing 2 repeating advances and 3 don't cares is a win
    // When not currently in a range the cost of a run over a range is 16
    // characaters, so:
    //  d. Removing a leading 0/don't cares is a win because it is omitted
    //  e. Removing 2 repeating advances is a win

    AdvanceMetric* prevRange = nullptr;
    int16_t lastAdvance = kInvalidAdvance;
    int repeatedAdvances = 0;
    int wildCardsInRun = 0;
    int trailingWildCards = 0;
    uint32_t subsetIndex = 0;

    // Limit the loop count to glyph id ranges provided.
    int firstIndex = 0;
    int lastIndex = num_glyphs;
    if (subsetGlyphIDs) {
        firstIndex = static_cast<int>(subsetGlyphIDs[0]);
        lastIndex =
                static_cast<int>(subsetGlyphIDs[subsetGlyphIDsLength - 1]) + 1;
    }
    AdvanceMetric curRange(firstIndex);

    for (int gId = firstIndex; gId <= lastIndex; gId++) {
        int16_t advance = kInvalidAdvance;
        if (gId < lastIndex) {
            // Get glyph id only when subset is nullptr, or the id is in subset.
            SkASSERT(!subsetGlyphIDs || (subsetIndex < subsetGlyphIDsLength &&
                    static_cast<uint32_t>(gId) <= subsetGlyphIDs[subsetIndex]));
            if (!subsetGlyphIDs ||
                (subsetIndex < subsetGlyphIDsLength &&
                 static_cast<uint32_t>(gId) == subsetGlyphIDs[subsetIndex])) {
                advance = (int16_t)glyphCache->getGlyphIDAdvance(gId).fAdvanceX;
                ++subsetIndex;
            } else {
                advance = kDontCareAdvance;
            }
        }
        if (advance == lastAdvance) {
            repeatedAdvances++;
            trailingWildCards = 0;
        } else if (advance == kDontCareAdvance) {
            wildCardsInRun++;
            trailingWildCards++;
        } else if (curRange.fAdvance.count() ==
                   repeatedAdvances + 1 + wildCardsInRun) {  // All in run.
            if (lastAdvance == 0) {
                curRange.fStartId = gId;  // reset
                curRange.fAdvance.setCount(0);
                trailingWildCards = 0;
            } else if (repeatedAdvances + 1 >= 2 || trailingWildCards >= 4) {
                FinishRange(&curRange, gId - 1, AdvanceMetric::kRun);
                prevRange = glyphWidths->emplace_back(std::move(curRange));
                curRange = AdvanceMetric(gId);
                trailingWildCards = 0;
            }
            repeatedAdvances = 0;
            wildCardsInRun = trailingWildCards;
            trailingWildCards = 0;
        } else {
            if (lastAdvance == 0 &&
                    repeatedAdvances + 1 + wildCardsInRun >= 4) {
                FinishRange(&curRange,
                            gId - repeatedAdvances - wildCardsInRun - 2,
                            AdvanceMetric::kRange);
                prevRange = glyphWidths->emplace_back(std::move(curRange));
                curRange = AdvanceMetric(gId);
                trailingWildCards = 0;
            } else if (trailingWildCards >= 4 && repeatedAdvances + 1 < 2) {
                FinishRange(&curRange, gId - trailingWildCards - 1,
                            AdvanceMetric::kRange);
                prevRange = glyphWidths->emplace_back(std::move(curRange));
                curRange = AdvanceMetric(gId);
                trailingWildCards = 0;
            } else if (lastAdvance != 0 &&
                       (repeatedAdvances + 1 >= 3 ||
                        (repeatedAdvances + 1 >= 2 && wildCardsInRun >= 3))) {
                FinishRange(&curRange,
                            gId - repeatedAdvances - wildCardsInRun - 2,
                            AdvanceMetric::kRange);
                (void)glyphWidths->emplace_back(std::move(curRange));
                curRange =
                        AdvanceMetric(gId - repeatedAdvances - wildCardsInRun - 1);
                curRange.fAdvance.append(1, &lastAdvance);
                FinishRange(&curRange, gId - 1, AdvanceMetric::kRun);
                prevRange = glyphWidths->emplace_back(std::move(curRange));
                curRange = AdvanceMetric(gId);
                trailingWildCards = 0;
            }
            repeatedAdvances = 0;
            wildCardsInRun = trailingWildCards;
            trailingWildCards = 0;
        }
        curRange.fAdvance.append(1, &advance);
        if (advance != kDontCareAdvance) {
            lastAdvance = advance;
        }
    }
    if (curRange.fStartId == lastIndex) {
        if (!prevRange) {
            glyphWidths->reset();
            return;  // https://crbug.com/567031
        }
    } else {
        FinishRange(&curRange, lastIndex - 1, AdvanceMetric::kRange);
        glyphWidths->emplace_back(std::move(curRange));
    }
}

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


// scale from em-units to base-1000, returning as a SkScalar
SkScalar from_font_units(SkScalar scaled, uint16_t emSize) {
    if (emSize == 1000) {
        return scaled;
    } else {
        return SkScalarMulDiv(scaled, 1000, emSize);
    }
}

SkScalar scaleFromFontUnits(int16_t val, uint16_t emSize) {
    return from_font_units(SkIntToScalar(val), emSize);
}


void setGlyphWidthAndBoundingBox(SkScalar width, SkIRect box,
                                 SkDynamicMemoryWStream* content) {
    // Specify width and bounding box for the glyph.
    SkPDFUtils::AppendScalar(width, content);
    content->writeText(" 0 ");
    content->writeDecAsText(box.fLeft);
    content->writeText(" ");
    content->writeDecAsText(box.fTop);
    content->writeText(" ");
    content->writeDecAsText(box.fRight);
    content->writeText(" ");
    content->writeDecAsText(box.fBottom);
    content->writeText(" d1\n");
}

static sk_sp<SkPDFArray> makeFontBBox(SkIRect glyphBBox, uint16_t emSize) {
    auto bbox = sk_make_sp<SkPDFArray>();
    bbox->reserve(4);
    bbox->appendScalar(scaleFromFontUnits(glyphBBox.fLeft, emSize));
    bbox->appendScalar(scaleFromFontUnits(glyphBBox.fBottom, emSize));
    bbox->appendScalar(scaleFromFontUnits(glyphBBox.fRight, emSize));
    bbox->appendScalar(scaleFromFontUnits(glyphBBox.fTop, emSize));
    return bbox;
}

sk_sp<SkPDFArray> composeAdvanceData(
        const SkSinglyLinkedList<AdvanceMetric>& advanceInfo,
        uint16_t emSize,
        int16_t* defaultAdvance) {
    auto result = sk_make_sp<SkPDFArray>();
    for (const AdvanceMetric& range : advanceInfo) {
        switch (range.fType) {
            case AdvanceMetric::kDefault: {
                SkASSERT(range.fAdvance.count() == 1);
                *defaultAdvance = range.fAdvance[0];
                break;
            }
            case AdvanceMetric::kRange: {
                auto advanceArray = sk_make_sp<SkPDFArray>();
                for (int j = 0; j < range.fAdvance.count(); j++)
                    advanceArray->appendScalar(
                            scaleFromFontUnits(range.fAdvance[j], emSize));
                result->appendInt(range.fStartId);
                result->appendObject(std::move(advanceArray));
                break;
            }
            case AdvanceMetric::kRun: {
                SkASSERT(range.fAdvance.count() == 1);
                result->appendInt(range.fStartId);
                result->appendInt(range.fEndId);
                result->appendScalar(
                        scaleFromFontUnits(range.fAdvance[0], emSize));
                break;
            }
        }
    }
    return result;
}

}  // namespace


///////////////////////////////////////////////////////////////////////////////
// class SkPDFGlyphSet
///////////////////////////////////////////////////////////////////////////////

SkPDFGlyphSet::SkPDFGlyphSet() : fBitSet(SK_MaxU16 + 1) {
}

void SkPDFGlyphSet::set(const uint16_t* glyphIDs, int numGlyphs) {
    for (int i = 0; i < numGlyphs; ++i) {
        fBitSet.setBit(glyphIDs[i], true);
    }
}

bool SkPDFGlyphSet::has(uint16_t glyphID) const {
    return fBitSet.isBitSet(glyphID);
}

void SkPDFGlyphSet::exportTo(SkTDArray<unsigned int>* glyphIDs) const {
    fBitSet.exportTo(glyphIDs);
}

///////////////////////////////////////////////////////////////////////////////
// class SkPDFGlyphSetMap
///////////////////////////////////////////////////////////////////////////////

SkPDFGlyphSetMap::SkPDFGlyphSetMap() {}

SkPDFGlyphSetMap::~SkPDFGlyphSetMap() {
    fMap.reset();
}

void SkPDFGlyphSetMap::noteGlyphUsage(SkPDFFont* font, const uint16_t* glyphIDs,
                                      int numGlyphs) {
    SkPDFGlyphSet* subset = getGlyphSetForFont(font);
    if (subset) {
        subset->set(glyphIDs, numGlyphs);
    }
}

SkPDFGlyphSet* SkPDFGlyphSetMap::getGlyphSetForFont(SkPDFFont* font) {
    int index = fMap.count();
    for (int i = 0; i < index; ++i) {
        if (fMap[i].fFont == font) {
            return &fMap[i].fGlyphSet;
        }
    }
    FontGlyphSetPair& pair = fMap.push_back();
    pair.fFont = font;
    return &pair.fGlyphSet;
}

///////////////////////////////////////////////////////////////////////////////
// class SkPDFFont
///////////////////////////////////////////////////////////////////////////////

/* Font subset design: It would be nice to be able to subset fonts
 * (particularly type 3 fonts), but it's a lot of work and not a priority.
 *
 * Resources are canonicalized and uniqueified by pointer so there has to be
 * some additional state indicating which subset of the font is used.  It
 * must be maintained at the page granularity and then combined at the document
 * granularity. a) change SkPDFFont to fill in its state on demand, kind of
 * like SkPDFGraphicState.  b) maintain a per font glyph usage class in each
 * page/pdf device. c) in the document, retrieve the per font glyph usage
 * from each page and combine it and ask for a resource with that subset.
 */

SkPDFFont::~SkPDFFont() {}

SkTypeface* SkPDFFont::typeface() {
    return fTypeface.get();
}

SkAdvancedTypefaceMetrics::FontType SkPDFFont::getType() {
    return fFontType;
}

bool SkPDFFont::canEmbed() const {
    if (!fFontInfo.get()) {
        SkASSERT(fFontType == SkAdvancedTypefaceMetrics::kOther_Font);
        return true;
    }
    return (fFontInfo->fFlags &
            SkAdvancedTypefaceMetrics::kNotEmbeddable_FontFlag) == 0;
}

bool SkPDFFont::canSubset() const {
    if (!fFontInfo.get()) {
        SkASSERT(fFontType == SkAdvancedTypefaceMetrics::kOther_Font);
        return true;
    }
    return (fFontInfo->fFlags &
            SkAdvancedTypefaceMetrics::kNotSubsettable_FontFlag) == 0;
}

bool SkPDFFont::hasGlyph(uint16_t id) {
    return (id >= fFirstGlyphID && id <= fLastGlyphID) || id == 0;
}

int SkPDFFont::glyphsToPDFFontEncoding(SkGlyphID* glyphIDs, int numGlyphs) const {
    // A font with multibyte glyphs will support all glyph IDs in a single font.
    if (this->multiByteGlyphs()) {
        return numGlyphs;
    }

    for (int i = 0; i < numGlyphs; i++) {
        if (glyphIDs[i] == 0) {
            continue;
        }
        if (glyphIDs[i] < fFirstGlyphID || glyphIDs[i] > fLastGlyphID) {
            return i;
        }
        glyphIDs[i] -= (fFirstGlyphID - 1);
    }

    return numGlyphs;
}

int SkPDFFont::glyphsToPDFFontEncodingCount(const SkGlyphID* glyphIDs,
                                            int numGlyphs) const {
    if (this->multiByteGlyphs()) {    // A font with multibyte glyphs will
        return numGlyphs;             // support all glyph IDs in a single font.
    }
    for (int i = 0; i < numGlyphs; i++) {
        if (glyphIDs[i] != 0 &&
            (glyphIDs[i] < fFirstGlyphID || glyphIDs[i] > fLastGlyphID)) {
            return i;
        }
    }
    return numGlyphs;
}

// static
SkPDFFont* SkPDFFont::GetFontResource(SkPDFCanon* canon,
                                      SkTypeface* typeface,
                                      uint16_t glyphID) {
    SkASSERT(canon);
    const uint32_t fontID = SkTypeface::UniqueID(typeface);
    SkPDFFont* relatedFont;
    if (SkPDFFont* pdfFont = canon->findFont(fontID, glyphID, &relatedFont)) {
        return SkRef(pdfFont);
    }
    SkAutoResolveDefaultTypeface autoResolve(typeface);
    typeface = autoResolve.get();
    SkASSERT(typeface);
    int glyphCount = typeface->countGlyphs();
    if (glyphCount < 1 ||  // typeface lacks even a NOTDEF glyph.
        glyphCount > 1 + SK_MaxU16 ||  // invalid glyphCount
        glyphID >= glyphCount) {  // invalid glyph
        return nullptr;
    }
    sk_sp<const SkAdvancedTypefaceMetrics> fontMetrics;
    SkPDFDict* relatedFontDescriptor = nullptr;
    if (relatedFont) {
        fontMetrics.reset(SkSafeRef(relatedFont->fontInfo()));
        relatedFontDescriptor = relatedFont->getFontDescriptor();

        // This only is to catch callers who pass invalid glyph ids.
        // If glyph id is invalid, then we will create duplicate entries
        // for TrueType fonts.
        SkAdvancedTypefaceMetrics::FontType fontType =
            fontMetrics.get() ? fontMetrics.get()->fType :
                                SkAdvancedTypefaceMetrics::kOther_Font;

        if (fontType == SkAdvancedTypefaceMetrics::kType1CID_Font ||
            fontType == SkAdvancedTypefaceMetrics::kTrueType_Font) {
            return SkRef(relatedFont);
        }
    } else {
        SkTypeface::PerGlyphInfo info =
            SkTBitOr(SkTypeface::kGlyphNames_PerGlyphInfo,
                     SkTypeface::kToUnicode_PerGlyphInfo);
        fontMetrics.reset(
            typeface->getAdvancedTypefaceMetrics(info, nullptr, 0));
    }

    SkPDFFont* font = SkPDFFont::Create(canon, fontMetrics.get(), typeface,
                                        glyphID, relatedFontDescriptor);
    canon->addFont(font, fontID, font->fFirstGlyphID);
    return font;
}

sk_sp<SkPDFObject> SkPDFFont::getFontSubset(const SkPDFGlyphSet*) {
    return nullptr;  // Default: no support.
}

// TODO: take a sk_sp<SkAdvancedTypefaceMetrics> and sk_sp<SkTypeface>
SkPDFFont::SkPDFFont(const SkAdvancedTypefaceMetrics* info,
                     SkTypeface* typeface,
                     SkPDFDict* relatedFontDescriptor)
    : SkPDFDict("Font")
    , fTypeface(ref_or_default(typeface))
    , fFirstGlyphID(1)
    , fLastGlyphID(info ? info->fLastGlyphID : 0)
    , fFontInfo(SkSafeRef(info))
    , fDescriptor(SkSafeRef(relatedFontDescriptor))
    , fFontType((!info || info->fFlags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag)
                ? SkAdvancedTypefaceMetrics::kOther_Font
                : info->fType) {
    SkASSERT(fTypeface);
    if (0 == fLastGlyphID) {
        fLastGlyphID = SkToU16(fTypeface->countGlyphs() - 1);
    }
}

// static
SkPDFFont* SkPDFFont::Create(SkPDFCanon* canon,
                             const SkAdvancedTypefaceMetrics* info,
                             SkTypeface* typeface,
                             uint16_t glyphID,
                             SkPDFDict* relatedFontDescriptor) {
    SkAdvancedTypefaceMetrics::FontType type =
        info ? info->fType : SkAdvancedTypefaceMetrics::kOther_Font;
    SkAdvancedTypefaceMetrics::FontFlags flags =
        info ? info->fFlags : SkAdvancedTypefaceMetrics::kEmpty_FontFlag;
    if (SkToBool(flags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag)) {
        return new SkPDFType3Font(info, typeface, glyphID);
    }
    switch (type) {
        case SkAdvancedTypefaceMetrics::kType1CID_Font:
        case SkAdvancedTypefaceMetrics::kTrueType_Font:
            SkASSERT(relatedFontDescriptor == nullptr);
            SkASSERT(info != nullptr);
            return new SkPDFType0Font(info, typeface);
        case SkAdvancedTypefaceMetrics::kType1_Font:
            SkASSERT(info != nullptr);
            return new SkPDFType1Font(info, typeface, glyphID, relatedFontDescriptor);
        case SkAdvancedTypefaceMetrics::kCFF_Font:
            SkASSERT(info != nullptr);
            // fallthrough
        case SkAdvancedTypefaceMetrics::kOther_Font:
            return new SkPDFType3Font(info, typeface, glyphID);
    }
    SkDEBUGFAIL("invalid SkAdvancedTypefaceMetrics::FontType");
    return nullptr;
}

const SkAdvancedTypefaceMetrics* SkPDFFont::fontInfo() {
    return fFontInfo.get();
}

void SkPDFFont::setFontInfo(const SkAdvancedTypefaceMetrics* info) {
    if (info == nullptr || info == fFontInfo.get()) {
        return;
    }
    fFontInfo.reset(info);
    SkSafeRef(info);
}

uint16_t SkPDFFont::firstGlyphID() const {
    return fFirstGlyphID;
}

uint16_t SkPDFFont::lastGlyphID() const {
    return fLastGlyphID;
}

void SkPDFFont::setLastGlyphID(uint16_t glyphID) {
    fLastGlyphID = glyphID;
}

SkPDFDict* SkPDFFont::getFontDescriptor() {
    return fDescriptor.get();
}

void SkPDFFont::setFontDescriptor(SkPDFDict* descriptor) {
    fDescriptor.reset(descriptor);
    SkSafeRef(descriptor);
}

bool SkPDFFont::addCommonFontDescriptorEntries(int16_t defaultWidth) {
    if (fDescriptor.get() == nullptr) {
        return false;
    }

    const uint16_t emSize = fFontInfo->fEmSize;

    fDescriptor->insertName("FontName", fFontInfo->fFontName);
    fDescriptor->insertInt("Flags", fFontInfo->fStyle | kPdfSymbolic);
    fDescriptor->insertScalar("Ascent",
            scaleFromFontUnits(fFontInfo->fAscent, emSize));
    fDescriptor->insertScalar("Descent",
            scaleFromFontUnits(fFontInfo->fDescent, emSize));
    fDescriptor->insertScalar("StemV",
            scaleFromFontUnits(fFontInfo->fStemV, emSize));

    fDescriptor->insertScalar("CapHeight",
            scaleFromFontUnits(fFontInfo->fCapHeight, emSize));
    fDescriptor->insertInt("ItalicAngle", fFontInfo->fItalicAngle);
    fDescriptor->insertObject(
            "FontBBox", makeFontBBox(fFontInfo->fBBox, fFontInfo->fEmSize));

    if (defaultWidth > 0) {
        fDescriptor->insertScalar("MissingWidth",
                scaleFromFontUnits(defaultWidth, emSize));
    }
    return true;
}

void SkPDFFont::adjustGlyphRangeForSingleByteEncoding(uint16_t glyphID) {
    // Single byte glyph encoding supports a max of 255 glyphs.
    fFirstGlyphID = glyphID - (glyphID - 1) % 255;
    if (fLastGlyphID > fFirstGlyphID + 255 - 1) {
        fLastGlyphID = fFirstGlyphID + 255 - 1;
    }
}

void SkPDFFont::populateToUnicodeTable(const SkPDFGlyphSet* subset) {
    if (fFontInfo == nullptr || fFontInfo->fGlyphToUnicode.begin() == nullptr) {
        return;
    }
    this->insertObjRef("ToUnicode",
                       SkPDFMakeToUnicodeCmap(fFontInfo->fGlyphToUnicode,
                                              subset,
                                              multiByteGlyphs(),
                                              firstGlyphID(),
                                              lastGlyphID()));
}

///////////////////////////////////////////////////////////////////////////////
// class SkPDFType0Font
///////////////////////////////////////////////////////////////////////////////

SkPDFType0Font::SkPDFType0Font(const SkAdvancedTypefaceMetrics* info, SkTypeface* typeface)
    : SkPDFFont(info, typeface, nullptr) {
    SkDEBUGCODE(fPopulated = false);
    if (!canSubset()) {
        this->populate(nullptr);
    }
}

SkPDFType0Font::~SkPDFType0Font() {}

sk_sp<SkPDFObject>  SkPDFType0Font::getFontSubset(const SkPDFGlyphSet* subset) {
    if (!canSubset()) {
        return nullptr;
    }
    auto newSubset = sk_make_sp<SkPDFType0Font>(fontInfo(), typeface());
    newSubset->populate(subset);
    return newSubset;
}

#ifdef SK_DEBUG
void SkPDFType0Font::emitObject(SkWStream* stream,
                                const SkPDFObjNumMap& objNumMap,
                                const SkPDFSubstituteMap& substitutes) const {
    SkASSERT(fPopulated);
    return INHERITED::emitObject(stream, objNumMap, substitutes);
}
#endif

bool SkPDFType0Font::populate(const SkPDFGlyphSet* subset) {
    insertName("Subtype", "Type0");
    insertName("BaseFont", fontInfo()->fFontName);
    insertName("Encoding", "Identity-H");

    sk_sp<SkPDFCIDFont> newCIDFont(
            new SkPDFCIDFont(fontInfo(), typeface(), subset));
    auto descendantFonts = sk_make_sp<SkPDFArray>();
    descendantFonts->appendObjRef(std::move(newCIDFont));
    this->insertObject("DescendantFonts", std::move(descendantFonts));

    this->populateToUnicodeTable(subset);

    SkDEBUGCODE(fPopulated = true);
    return true;
}

///////////////////////////////////////////////////////////////////////////////
// class SkPDFCIDFont
///////////////////////////////////////////////////////////////////////////////

SkPDFCIDFont::SkPDFCIDFont(const SkAdvancedTypefaceMetrics* info,
                           SkTypeface* typeface,
                           const SkPDFGlyphSet* subset)
    : SkPDFFont(info, typeface, nullptr) {
    this->populate(subset);
}

SkPDFCIDFont::~SkPDFCIDFont() {}

#ifdef SK_SFNTLY_SUBSETTER
// if possible, make no copy.
static sk_sp<SkData> stream_to_data(std::unique_ptr<SkStreamAsset> stream) {
    SkASSERT(stream);
    (void)stream->rewind();
    SkASSERT(stream->hasLength());
    size_t size = stream->getLength();
    if (const void* base = stream->getMemoryBase()) {
        SkData::ReleaseProc proc =
            [](const void*, void* ctx) { delete (SkStream*)ctx; };
        return SkData::MakeWithProc(base, size, proc, stream.release());
    }
    return SkData::MakeFromStream(stream.get(), size);
}

static sk_sp<SkPDFObject> get_subset_font_stream(
        std::unique_ptr<SkStreamAsset> fontAsset,
        const SkTDArray<uint32_t>& subset,
        const char* fontName) {
    // sfntly requires unsigned int* to be passed in,
    // as far as we know, unsigned int is equivalent
    // to uint32_t on all platforms.
    static_assert(sizeof(unsigned) == sizeof(uint32_t), "");

    // TODO(halcanary): Use ttcIndex, not fontName.

    unsigned char* subsetFont{nullptr};
    int subsetFontSize{0};
    {
        sk_sp<SkData> fontData(stream_to_data(std::move(fontAsset)));
        subsetFontSize =
            SfntlyWrapper::SubsetFont(fontName,
                                      fontData->bytes(),
                                      fontData->size(),
                                      subset.begin(),
                                      subset.count(),
                                      &subsetFont);
    }
    SkASSERT(subsetFontSize > 0 || subsetFont == nullptr);
    if (subsetFontSize < 1) {
        return nullptr;
    }
    SkASSERT(subsetFont != nullptr);
    auto subsetStream = sk_make_sp<SkPDFStream>(
            SkData::MakeWithProc(
                    subsetFont, subsetFontSize,
                    [](const void* p, void*) { delete[] (unsigned char*)p; },
                    nullptr));
    subsetStream->dict()->insertInt("Length1", subsetFontSize);
    return subsetStream;
}
#endif  // SK_SFNTLY_SUBSETTER

bool SkPDFCIDFont::addFontDescriptor(int16_t defaultWidth,
                                     const SkTDArray<uint32_t>* subset) {
    auto descriptor = sk_make_sp<SkPDFDict>("FontDescriptor");
    setFontDescriptor(descriptor.get());
    if (!addCommonFontDescriptorEntries(defaultWidth)) {
        this->insertObjRef("FontDescriptor", std::move(descriptor));
        return false;
    }
    SkASSERT(this->canEmbed());

    switch (getType()) {
        case SkAdvancedTypefaceMetrics::kTrueType_Font: {
            int ttcIndex;
            std::unique_ptr<SkStreamAsset> fontAsset(
                    this->typeface()->openStream(&ttcIndex));
            SkASSERT(fontAsset);
            if (!fontAsset) {
                return false;
            }
            size_t fontSize = fontAsset->getLength();
            SkASSERT(fontSize > 0);
            if (fontSize == 0) {
                return false;
            }

            #ifdef SK_SFNTLY_SUBSETTER
            if (this->canSubset() && subset) {
                sk_sp<SkPDFObject> subsetStream = get_subset_font_stream(
                        std::move(fontAsset), *subset, fontInfo()->fFontName.c_str());
                if (subsetStream) {
                    descriptor->insertObjRef("FontFile2", std::move(subsetStream));
                    break;
                }
                // If subsetting fails, fall back to original font data.
                fontAsset.reset(this->typeface()->openStream(&ttcIndex));
            }
            #endif  // SK_SFNTLY_SUBSETTER
            auto fontStream = sk_make_sp<SkPDFSharedStream>(std::move(fontAsset));
            fontStream->dict()->insertInt("Length1", fontSize);
            descriptor->insertObjRef("FontFile2", std::move(fontStream));
            break;
        }
        case SkAdvancedTypefaceMetrics::kCFF_Font:
        case SkAdvancedTypefaceMetrics::kType1CID_Font: {
            std::unique_ptr<SkStreamAsset> fontData(
                    this->typeface()->openStream(nullptr));
            SkASSERT(fontData);
            SkASSERT(fontData->getLength() > 0);
            if (!fontData || 0 == fontData->getLength()) {
                return false;
            }
            auto fontStream = sk_make_sp<SkPDFSharedStream>(std::move(fontData));
            if (getType() == SkAdvancedTypefaceMetrics::kCFF_Font) {
                fontStream->dict()->insertName("Subtype", "Type1C");
            } else {
                fontStream->dict()->insertName("Subtype", "CIDFontType0c");
            }
            descriptor->insertObjRef("FontFile3", std::move(fontStream));
            break;
        }
        default:
            SkASSERT(false);
    }
    this->insertObjRef("FontDescriptor", std::move(descriptor));
    return true;
}

void set_glyph_widths(SkTypeface* tf,
                      const SkTDArray<uint32_t>* glyphIDs,
                      SkSinglyLinkedList<AdvanceMetric>* dst) {
    SkPaint tmpPaint;
    tmpPaint.setHinting(SkPaint::kNo_Hinting);
    tmpPaint.setTypeface(sk_ref_sp(tf));
    tmpPaint.setTextSize((SkScalar)tf->getUnitsPerEm());
    const SkSurfaceProps props(0, kUnknown_SkPixelGeometry);
    SkAutoGlyphCache autoGlyphCache(tmpPaint, &props, nullptr);
    if (!glyphIDs || glyphIDs->isEmpty()) {
        get_glyph_widths(dst, tf->countGlyphs(), nullptr, 0, autoGlyphCache.get());
    } else {
        get_glyph_widths(dst, tf->countGlyphs(), glyphIDs->begin(),
                         glyphIDs->count(), autoGlyphCache.get());
    }
}

sk_sp<const SkAdvancedTypefaceMetrics> SkPDFFont::GetFontMetricsWithGlyphNames(
        SkTypeface* typeface, uint32_t* glyphs, uint32_t glyphsCount) {
    return sk_sp<const SkAdvancedTypefaceMetrics>(
            typeface->getAdvancedTypefaceMetrics(
                    SkTypeface::kGlyphNames_PerGlyphInfo, glyphs, glyphsCount));
}

sk_sp<const SkAdvancedTypefaceMetrics> SkPDFFont::GetFontMetricsWithToUnicode(
        SkTypeface* typeface, uint32_t* glyphs, uint32_t glyphsCount) {
    return sk_sp<const SkAdvancedTypefaceMetrics>(
            typeface->getAdvancedTypefaceMetrics(
                    SkTypeface::kToUnicode_PerGlyphInfo, glyphs, glyphsCount));
}

bool SkPDFCIDFont::populate(const SkPDFGlyphSet* subset) {
    // Generate new font metrics with advance info for true type fonts.
    // Generate glyph id array.
    SkTDArray<uint32_t> glyphIDs;
    if (subset) {
        if (!subset->has(0)) {
            glyphIDs.push(0);  // Always include glyph 0.
        }
        subset->exportTo(&glyphIDs);
    }
    if (fontInfo()->fType == SkAdvancedTypefaceMetrics::kTrueType_Font) {
        uint32_t* glyphs = (glyphIDs.count() == 0) ? nullptr : glyphIDs.begin();
        uint32_t glyphsCount = glyphs ? glyphIDs.count() : 0;
        sk_sp<const SkAdvancedTypefaceMetrics> fontMetrics =
            SkPDFFont::GetFontMetricsWithGlyphNames(this->typeface(), glyphs, glyphsCount);
        this->setFontInfo(fontMetrics.get());
        this->addFontDescriptor(0, &glyphIDs);
    } else {
        // Other CID fonts
        addFontDescriptor(0, nullptr);
    }

    insertName("BaseFont", fontInfo()->fFontName);

    if (getType() == SkAdvancedTypefaceMetrics::kType1CID_Font) {
        insertName("Subtype", "CIDFontType0");
    } else if (getType() == SkAdvancedTypefaceMetrics::kTrueType_Font) {
        insertName("Subtype", "CIDFontType2");
        insertName("CIDToGIDMap", "Identity");
    } else {
        SkASSERT(false);
    }

    auto sysInfo = sk_make_sp<SkPDFDict>();
    sysInfo->insertString("Registry", "Adobe");
    sysInfo->insertString("Ordering", "Identity");
    sysInfo->insertInt("Supplement", 0);
    this->insertObject("CIDSystemInfo", std::move(sysInfo));

    SkSinglyLinkedList<AdvanceMetric> tmpMetrics;
    set_glyph_widths(this->typeface(), &glyphIDs, &tmpMetrics);
    int16_t defaultWidth = 0;
    uint16_t emSize = (uint16_t)this->fontInfo()->fEmSize;
    sk_sp<SkPDFArray> widths = composeAdvanceData(tmpMetrics, emSize, &defaultWidth);
    if (widths->size()) {
        this->insertObject("W", std::move(widths));
    }

    this->insertScalar(
            "DW", scaleFromFontUnits(defaultWidth, emSize));
    return true;
}

///////////////////////////////////////////////////////////////////////////////
// class SkPDFType1Font
///////////////////////////////////////////////////////////////////////////////

SkPDFType1Font::SkPDFType1Font(const SkAdvancedTypefaceMetrics* info,
                               SkTypeface* typeface,
                               uint16_t glyphID,
                               SkPDFDict* relatedFontDescriptor)
    : SkPDFFont(info, typeface, relatedFontDescriptor) {
    this->populate(glyphID);
}

SkPDFType1Font::~SkPDFType1Font() {}

bool SkPDFType1Font::addFontDescriptor(int16_t defaultWidth) {
    if (SkPDFDict* descriptor = getFontDescriptor()) {
        this->insertObjRef("FontDescriptor",
                           sk_ref_sp(descriptor));
        return true;
    }

    auto descriptor = sk_make_sp<SkPDFDict>("FontDescriptor");
    setFontDescriptor(descriptor.get());

    int ttcIndex;
    size_t header SK_INIT_TO_AVOID_WARNING;
    size_t data SK_INIT_TO_AVOID_WARNING;
    size_t trailer SK_INIT_TO_AVOID_WARNING;
    std::unique_ptr<SkStreamAsset> rawFontData(typeface()->openStream(&ttcIndex));
    sk_sp<SkData> fontData = SkPDFConvertType1FontStream(std::move(rawFontData),
                                                         &header, &data, &trailer);
    if (!fontData) {
        return false;
    }
    SkASSERT(this->canEmbed());
    auto fontStream = sk_make_sp<SkPDFStream>(std::move(fontData));
    fontStream->dict()->insertInt("Length1", header);
    fontStream->dict()->insertInt("Length2", data);
    fontStream->dict()->insertInt("Length3", trailer);
    descriptor->insertObjRef("FontFile", std::move(fontStream));

    this->insertObjRef("FontDescriptor", std::move(descriptor));

    return addCommonFontDescriptorEntries(defaultWidth);
}

bool SkPDFType1Font::populate(int16_t glyphID) {
    this->insertName("Subtype", "Type1");
    this->insertName("BaseFont", fontInfo()->fFontName);
    adjustGlyphRangeForSingleByteEncoding(glyphID);
    SkGlyphID firstGlyphID = this->firstGlyphID();
    SkGlyphID lastGlyphID = this->lastGlyphID();

    // glyphCount not including glyph 0
    unsigned glyphCount = 1 + lastGlyphID - firstGlyphID;
    SkASSERT(glyphCount > 0 && glyphCount <= 255);
    this->insertInt("FirstChar", (size_t)0);
    this->insertInt("LastChar", (size_t)glyphCount);
    {
        SkPaint tmpPaint;
        tmpPaint.setHinting(SkPaint::kNo_Hinting);
        tmpPaint.setTypeface(sk_ref_sp(this->typeface()));
        tmpPaint.setTextSize((SkScalar)this->typeface()->getUnitsPerEm());
        const SkSurfaceProps props(0, kUnknown_SkPixelGeometry);
        SkAutoGlyphCache glyphCache(tmpPaint, &props, nullptr);
        auto widths = sk_make_sp<SkPDFArray>();
        SkScalar advance = glyphCache->getGlyphIDAdvance(0).fAdvanceX;
        const uint16_t emSize = this->fontInfo()->fEmSize;
        widths->appendScalar(from_font_units(advance, emSize));
        for (unsigned gID = firstGlyphID; gID <= lastGlyphID; gID++) {
            advance = glyphCache->getGlyphIDAdvance(gID).fAdvanceX;
            widths->appendScalar(from_font_units(advance, emSize));
        }
        this->insertObject("Widths", std::move(widths));
    }
    if (!addFontDescriptor(0)) {
        return false;
    }
    auto encDiffs = sk_make_sp<SkPDFArray>();
    encDiffs->reserve(lastGlyphID - firstGlyphID + 3);
    encDiffs->appendInt(0);
    const SkTArray<SkString>& glyphNames = this->fontInfo()->fGlyphNames;
    SkASSERT(glyphNames.count() > lastGlyphID);
    encDiffs->appendName(glyphNames[0].c_str());
    const SkString unknown("UNKNOWN");
    for (int gID = firstGlyphID; gID <= lastGlyphID; gID++) {
        const bool valid = gID < glyphNames.count() && !glyphNames[gID].isEmpty();
        const SkString& name = valid ? glyphNames[gID] : unknown;
        encDiffs->appendName(name);
    }

    auto encoding = sk_make_sp<SkPDFDict>("Encoding");
    encoding->insertObject("Differences", std::move(encDiffs));
    this->insertObject("Encoding", std::move(encoding));
    return true;
}

///////////////////////////////////////////////////////////////////////////////
// class SkPDFType3Font
///////////////////////////////////////////////////////////////////////////////

namespace {
// returns [0, first, first+1, ... last-1,  last]
struct SingleByteGlyphIdIterator {
    SingleByteGlyphIdIterator(SkGlyphID first, SkGlyphID last)
        : fFirst(first), fLast(last) {
        SkASSERT(fFirst > 0);
        SkASSERT(fLast >= first);
    }
    struct Iter {
        void operator++() {
            fCurrent = (0 == fCurrent) ? fFirst : fCurrent + 1;
        }
        // This is an input_iterator
        SkGlyphID operator*() const { return (SkGlyphID)fCurrent; }
        bool operator!=(const Iter& rhs) const {
            return fCurrent != rhs.fCurrent;
        }
        Iter(SkGlyphID f, int c) : fFirst(f), fCurrent(c) {}
    private:
        const SkGlyphID fFirst;
        int fCurrent; // must be int to make fLast+1 to fit
    };
    Iter begin() const { return Iter(fFirst, 0); }
    Iter end() const { return Iter(fFirst, (int)fLast + 1); }
private:
    const SkGlyphID fFirst;
    const SkGlyphID fLast;
};
}

static void add_type3_font_info(SkPDFDict* font,
                                SkTypeface* typeface,
                                SkScalar emSize,
                                const SkPDFGlyphSet* subset,
                                SkGlyphID firstGlyphID,
                                SkGlyphID lastGlyphID) {
    SkASSERT(lastGlyphID >= firstGlyphID);
    SkPaint paint;
    paint.setHinting(SkPaint::kNo_Hinting);
    paint.setTypeface(sk_ref_sp(typeface));
    paint.setTextSize(emSize);
    const SkSurfaceProps props(0, kUnknown_SkPixelGeometry);
    SkAutoGlyphCache cache(paint, &props, nullptr);

    font->insertName("Subtype", "Type3");
    // Flip about the x-axis and scale by 1/emSize.
    SkMatrix fontMatrix;
    fontMatrix.setScale(SkScalarInvert(emSize), -SkScalarInvert(emSize));
    font->insertObject("FontMatrix", SkPDFUtils::MatrixToArray(fontMatrix));

    auto charProcs = sk_make_sp<SkPDFDict>();
    auto encoding = sk_make_sp<SkPDFDict>("Encoding");

    auto encDiffs = sk_make_sp<SkPDFArray>();
    // length(firstGlyphID .. lastGlyphID) ==  lastGlyphID - firstGlyphID + 1
    // plus 1 for glyph 0;
    SkASSERT(firstGlyphID > 0);
    SkASSERT(lastGlyphID >= firstGlyphID);
    int glyphCount = lastGlyphID - firstGlyphID + 2;
    // one other entry for the index of first glyph.
    encDiffs->reserve(glyphCount + 1);
    encDiffs->appendInt(0);  // index of first glyph

    auto widthArray = sk_make_sp<SkPDFArray>();
    widthArray->reserve(glyphCount);

    SkIRect bbox = SkIRect::MakeEmpty();

    sk_sp<SkPDFStream> emptyStream;
    for (SkGlyphID gID : SingleByteGlyphIdIterator(firstGlyphID, lastGlyphID)) {
        bool skipGlyph = subset && gID != 0 && !subset->has(gID);
        SkString characterName;
        SkScalar advance = 0.0f;
        SkIRect glyphBBox;
        if (skipGlyph) {
            characterName.set("g0");
        } else {
            characterName.printf("g%X", gID);
            const SkGlyph& glyph = cache->getGlyphIDMetrics(gID);
            advance = SkFloatToScalar(glyph.fAdvanceX);
            glyphBBox = SkIRect::MakeXYWH(glyph.fLeft, glyph.fTop,
                                          glyph.fWidth, glyph.fHeight);
            bbox.join(glyphBBox);
            const SkPath* path = cache->findPath(glyph);
            if (path && !path->isEmpty()) {
                SkDynamicMemoryWStream content;
                setGlyphWidthAndBoundingBox(SkFloatToScalar(glyph.fAdvanceX), glyphBBox,
                                            &content);
                SkPDFUtils::EmitPath(*path, SkPaint::kFill_Style, &content);
                SkPDFUtils::PaintPath(SkPaint::kFill_Style, path->getFillType(),
                                      &content);
                charProcs->insertObjRef(
                    characterName, sk_make_sp<SkPDFStream>(
                            std::unique_ptr<SkStreamAsset>(content.detachAsStream())));
            } else {
                if (!emptyStream) {
                    emptyStream = sk_make_sp<SkPDFStream>(
                            std::unique_ptr<SkStreamAsset>(
                                    new SkMemoryStream((size_t)0)));
                }
                charProcs->insertObjRef(characterName, emptyStream);
            }
        }
        encDiffs->appendName(characterName.c_str());
        widthArray->appendScalar(advance);
    }

    encoding->insertObject("Differences", std::move(encDiffs));
    font->insertInt("FirstChar", 0);
    font->insertInt("LastChar", lastGlyphID - firstGlyphID + 1);
    /* FontBBox: "A rectangle expressed in the glyph coordinate
      system, specifying the font bounding box. This is the smallest
      rectangle enclosing the shape that would result if all of the
      glyphs of the font were placed with their origins coincident and
      then filled." */
    auto fontBBox = sk_make_sp<SkPDFArray>();
    fontBBox->reserve(4);
    fontBBox->appendInt(bbox.left());
    fontBBox->appendInt(bbox.bottom());
    fontBBox->appendInt(bbox.right());
    fontBBox->appendInt(bbox.top());
    font->insertObject("FontBBox", std::move(fontBBox));
    font->insertName("CIDToGIDMap", "Identity");
    sk_sp<const SkAdvancedTypefaceMetrics> metrics;
    if (subset) {
        SkTDArray<uint32_t> subsetList;
        for (SkGlyphID gID : SingleByteGlyphIdIterator(firstGlyphID, lastGlyphID)) {
            if (gID == 0 || subset->has(gID)) {  // Always include glyph 0.
                subsetList.push(0);
            }
        }
        subset->exportTo(&subsetList);
        metrics = SkPDFFont::GetFontMetricsWithToUnicode(typeface, subsetList.begin(),
                                                         subsetList.count());
    } else {
        metrics = SkPDFFont::GetFontMetricsWithToUnicode(typeface, nullptr, 0);
    }
    if (metrics) {
        font->insertObjRef("ToUnicode",
                           SkPDFMakeToUnicodeCmap(metrics->fGlyphToUnicode,
                                                  subset,
                                                  false,
                                                  firstGlyphID,
                                                  lastGlyphID));
    }
    font->insertObject("Widths", std::move(widthArray));
    font->insertObject("Encoding", std::move(encoding));
    font->insertObject("CharProcs", std::move(charProcs));
}

SkPDFType3Font::SkPDFType3Font(const SkAdvancedTypefaceMetrics* info,
                               SkTypeface* typeface,
                               uint16_t glyphID)
    : SkPDFFont(info, typeface, nullptr) {
    // If fLastGlyphID isn't set (because there is not fFontInfo), look it up.
    this->setLastGlyphID(SkToU16(typeface->countGlyphs() - 1));
    this->adjustGlyphRangeForSingleByteEncoding(glyphID);
}

sk_sp<SkPDFObject> SkPDFType3Font::getFontSubset(const SkPDFGlyphSet* usage) {
    // All fonts are subset before serialization.
    // TODO(halcanary): all fonts should follow this pattern.
    auto font = sk_make_sp<SkPDFDict>("Font");
    const SkAdvancedTypefaceMetrics* info = this->fontInfo();
    uint16_t emSize = info && info->fEmSize > 0 ? info->fEmSize : 1000;
    add_type3_font_info(font.get(), this->typeface(), (SkScalar)emSize, usage,
                        this->firstGlyphID(), this->lastGlyphID());
    return font;
}


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

SkPDFFont::Match SkPDFFont::IsMatch(SkPDFFont* existingFont,
                                    uint32_t existingFontID,
                                    uint16_t existingGlyphID,
                                    uint32_t searchFontID,
                                    uint16_t searchGlyphID) {
    if (existingFontID != searchFontID) {
        return SkPDFFont::kNot_Match;
    }
    if (existingGlyphID == 0 || searchGlyphID == 0) {
        return SkPDFFont::kExact_Match;
    }
    if (existingFont != nullptr) {
        return (existingFont->fFirstGlyphID <= searchGlyphID &&
                searchGlyphID <= existingFont->fLastGlyphID)
                       ? SkPDFFont::kExact_Match
                       : SkPDFFont::kRelated_Match;
    }
    return (existingGlyphID == searchGlyphID) ? SkPDFFont::kExact_Match
                                              : SkPDFFont::kRelated_Match;
}

//  Since getAdvancedTypefaceMetrics is expensive, cache the result.
bool SkPDFFont::CanEmbedTypeface(SkTypeface* typeface, SkPDFCanon* canon) {
    SkFontID id = SkTypeface::UniqueID(typeface);
    if (bool* value = canon->fCanEmbedTypeface.find(id)) {
        return *value;
    }
    SkAutoResolveDefaultTypeface face(typeface);
    bool canEmbed = true;
    sk_sp<const SkAdvancedTypefaceMetrics> fontMetrics(
            face->getAdvancedTypefaceMetrics(
                    SkTypeface::kNo_PerGlyphInfo, nullptr, 0));
    if (fontMetrics) {
        canEmbed = !SkToBool(
                fontMetrics->fFlags &
                SkAdvancedTypefaceMetrics::kNotEmbeddable_FontFlag);
    }
    return *canon->fCanEmbedTypeface.set(id, canEmbed);
}

void SkPDFFont::drop() {
    fTypeface = nullptr;
    fFontInfo = nullptr;
    fDescriptor = nullptr;
    this->SkPDFDict::drop();
}