SkPDF: Subset Type3 (fallback) font

src/pdf/SkPDFFont.cpp

Index: src/pdf/SkPDFFont.cpp
diff --git a/src/pdf/SkPDFFont.cpp b/src/pdf/SkPDFFont.cpp
index ff1dd2d76d594de616b15d074ac19ebe083089fb..cc71a893d92c4abcbc5060ae843e7120079955b1 100644
--- a/src/pdf/SkPDFFont.cpp
+++ b/src/pdf/SkPDFFont.cpp
@@ -60,7 +60,7 @@ public:
                    SkTypeface* typeface);
     virtual ~SkPDFType0Font();
     bool multiByteGlyphs() const override { return true; }
-    SkPDFFont* getFontSubset(const SkPDFGlyphSet* usage) override;
+    sk_sp<SkPDFObject> getFontSubset(const SkPDFGlyphSet* usage) override;
 #ifdef SK_DEBUG
     void emitObject(SkWStream*,
                     const SkPDFObjNumMap&,
@@ -108,11 +108,14 @@ public:
     SkPDFType3Font(const SkAdvancedTypefaceMetrics* info,
                    SkTypeface* typeface,
                    uint16_t glyphID);
-    virtual ~SkPDFType3Font();
+    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; }
-
-private:
-    bool populate(uint16_t glyphID);
 };
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -335,7 +338,7 @@ SkScalar scaleFromFontUnits(int16_t val, uint16_t emSize) {
 
 
 void setGlyphWidthAndBoundingBox(SkScalar width, SkIRect box,
-                                 SkWStream* content) {
+                                 SkDynamicMemoryWStream* content) {
     // Specify width and bounding box for the glyph.
     SkPDFUtils::AppendScalar(width, content);
     content->writeText(" 0 ");
@@ -559,7 +562,7 @@ SkPDFFont* SkPDFFont::GetFontResource(SkPDFCanon* canon,
     return font;
 }
 
-SkPDFFont* SkPDFFont::getFontSubset(const SkPDFGlyphSet*) {
+sk_sp<SkPDFObject> SkPDFFont::getFontSubset(const SkPDFGlyphSet*) {
     return nullptr;  // Default: no support.
 }
 
@@ -571,12 +574,13 @@ SkPDFFont::SkPDFFont(const SkAdvancedTypefaceMetrics* info,
     , fFirstGlyphID(1)
     , fLastGlyphID(info ? info->fLastGlyphID : 0)
     , fFontInfo(SkSafeRef(info))
-    , fDescriptor(SkSafeRef(relatedFontDescriptor)) {
-    if (info == nullptr ||
-            info->fFlags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag) {
-        fFontType = SkAdvancedTypefaceMetrics::kOther_Font;
-    } else {
-        fFontType = info->fType;
+    , fDescriptor(SkSafeRef(relatedFontDescriptor))
+    , fFontType((!info || info->fFlags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag)
+                ? SkAdvancedTypefaceMetrics::kOther_Font
+                : info->fType) {
+    if (0 == fLastGlyphID) {
+        SkAutoResolveDefaultTypeface face(typeface);
+        fLastGlyphID = SkToU16(face->countGlyphs() - 1);
     }
 }
 
@@ -588,23 +592,29 @@ SkPDFFont* SkPDFFont::Create(SkPDFCanon* canon,
                              SkPDFDict* relatedFontDescriptor) {
     SkAdvancedTypefaceMetrics::FontType type =
         info ? info->fType : SkAdvancedTypefaceMetrics::kOther_Font;
-
-    if (info && (info->fFlags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag)) {
+    SkAdvancedTypefaceMetrics::FontFlags flags =
+        info ? info->fFlags : SkAdvancedTypefaceMetrics::kEmpty_FontFlag;
+    if (SkToBool(flags & SkAdvancedTypefaceMetrics::kMultiMaster_FontFlag) ||
+        SkToBool(flags & SkAdvancedTypefaceMetrics::kNotEmbeddable_FontFlag)) {
         return new SkPDFType3Font(info, typeface, glyphID);
     }
-    if (type == SkAdvancedTypefaceMetrics::kType1CID_Font ||
-        type == SkAdvancedTypefaceMetrics::kTrueType_Font) {
-        SkASSERT(relatedFontDescriptor == nullptr);
-        return new SkPDFType0Font(info, typeface);
-    }
-    if (type == SkAdvancedTypefaceMetrics::kType1_Font) {
-        return new SkPDFType1Font(info, typeface, glyphID, relatedFontDescriptor);
+    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);
     }
-
-    SkASSERT(type == SkAdvancedTypefaceMetrics::kCFF_Font ||
-             type == SkAdvancedTypefaceMetrics::kOther_Font);
-
-    return new SkPDFType3Font(info, typeface, glyphID);
+    SkDEBUGFAIL("invalid SkAdvancedTypefaceMetrics::FontType");
+    return nullptr;
 }
 
 const SkAdvancedTypefaceMetrics* SkPDFFont::fontInfo() {
@@ -703,11 +713,11 @@ SkPDFType0Font::SkPDFType0Font(const SkAdvancedTypefaceMetrics* info, SkTypeface
 
 SkPDFType0Font::~SkPDFType0Font() {}
 
-SkPDFFont* SkPDFType0Font::getFontSubset(const SkPDFGlyphSet* subset) {
+sk_sp<SkPDFObject>  SkPDFType0Font::getFontSubset(const SkPDFGlyphSet* subset) {
     if (!canSubset()) {
         return nullptr;
     }
-    SkPDFType0Font* newSubset = new SkPDFType0Font(fontInfo(), typeface());
+    auto newSubset = sk_make_sp<SkPDFType0Font>(fontInfo(), typeface());
     newSubset->populate(subset);
     return newSubset;
 }
@@ -878,7 +888,8 @@ void set_glyph_widths(SkTypeface* tf,
     tmpPaint.setHinting(SkPaint::kNo_Hinting);
     tmpPaint.setTypeface(sk_ref_sp(tf));
     tmpPaint.setTextSize((SkScalar)tf->getUnitsPerEm());
-    SkAutoGlyphCache autoGlyphCache(tmpPaint, nullptr, nullptr);
+    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 {
@@ -1017,7 +1028,8 @@ bool SkPDFType1Font::populate(int16_t glyphID) {
         tmpPaint.setHinting(SkPaint::kNo_Hinting);
         tmpPaint.setTypeface(sk_ref_sp(this->typeface()));
         tmpPaint.setTextSize((SkScalar)this->typeface()->getUnitsPerEm());
-        SkAutoGlyphCache glyphCache(tmpPaint, nullptr, nullptr);
+        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;
@@ -1054,84 +1066,178 @@ bool SkPDFType1Font::populate(int16_t glyphID) {
 // class SkPDFType3Font
 ///////////////////////////////////////////////////////////////////////////////
 
-SkPDFType3Font::SkPDFType3Font(const SkAdvancedTypefaceMetrics* info,
-                               SkTypeface* typeface,
-                               uint16_t glyphID)
-    : SkPDFFont(info, typeface, nullptr) {
-    this->populate(glyphID);
+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;
+            fValue = (uint16_t)fCurrent;  // may overflow
+        }
+        const SkGlyphID& operator*() const { return fValue; }
+        bool operator!=(const Iter& rhs) const {
+            return fCurrent != rhs.fCurrent;
+        }
+        Iter(SkGlyphID f, int c)
+            : fFirst(f), fValue((uint16_t)c), fCurrent(c) {}
+    private:
+        const SkGlyphID fFirst;
+        SkGlyphID fValue;
+        int fCurrent; // must be int to make fLast+1 to fit

[bungeman-skia, 2016/08/11 16:19:56]

While half open ranges have great properties on the low side, they do have this
annoying property of requiring at least one otherwise unusable value to
represent one past the end.

I think operator* should return either a SkGlyphId values (and cast) or const
int& (and update gID below). Before I was just commenting that usually operator*
returns a reference, but in the case of input iterators (which this can be
considered to be) operator* may return a value. For example, see
std::istreambuf_iterator. As a result, it would probably be cleaner to just do
this the way you were doing it before, but with at least a comment so we dont'
forget this

// This is an input_iterator
SkGlyphID operator*() const { return static_cast<SkGlyphID>(fCurrent); }

This is at least cleaner than having an extra field sitting around and the extra
complexity of managing it.

[hal.canary, 2016/08/11 17:49:47]

Done.

+    };
+    Iter begin() const { return Iter(fFirst, 0); }
+    Iter end() const { return Iter(fFirst, (int)fLast + 1); }
+private:
+    const SkGlyphID fFirst;
+    const SkGlyphID fLast;
+};
 }
 
-SkPDFType3Font::~SkPDFType3Font() {}
-
-bool SkPDFType3Font::populate(uint16_t glyphID) {
+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.setTypeface(sk_ref_sp(this->typeface()));
-    paint.setTextSize(1000);
+    paint.setHinting(SkPaint::kNo_Hinting);
+    paint.setTypeface(sk_ref_sp(typeface));
+    paint.setTextSize(emSize);
     const SkSurfaceProps props(0, kUnknown_SkPixelGeometry);
-    SkAutoGlyphCache autoCache(paint, &props, nullptr);
-    SkGlyphCache* cache = autoCache.getCache();
-    // If fLastGlyphID isn't set (because there is not fFontInfo), look it up.
-    if (lastGlyphID() == 0) {
-        setLastGlyphID(cache->getGlyphCount() - 1);
-    }
+    SkAutoGlyphCache cache(paint, &props, nullptr);
 
-    adjustGlyphRangeForSingleByteEncoding(glyphID);
-
-    insertName("Subtype", "Type3");
-    // Flip about the x-axis and scale by 1/1000.
+    font->insertName("Subtype", "Type3");
+    // Flip about the x-axis and scale by 1/emSize.
     SkMatrix fontMatrix;
-    fontMatrix.setScale(SkScalarInvert(1000), -SkScalarInvert(1000));
-    this->insertObject("FontMatrix", SkPDFUtils::MatrixToArray(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>();
-    encDiffs->reserve(lastGlyphID() - firstGlyphID() + 2);
-    encDiffs->appendInt(1);
+    // lenth(firstGlyphID .. lastGlyphID) ==  lastGlyphID - firstGlyphID + 1

[bungeman-skia, 2016/08/11 16:19:56]

s/lenth/length

[hal.canary, 2016/08/11 17:49:47]

Done.

+    // 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();
-    for (int gID = firstGlyphID(); gID <= lastGlyphID(); gID++) {
+
+    sk_sp<SkPDFStream> emptyStream;
+    for (SkGlyphID gID : SingleByteGlyphIdIterator(firstGlyphID, lastGlyphID)) {
+        bool skipGlyph = subset && gID != 0 && !subset->has(gID);
         SkString characterName;
-        characterName.printf("gid%d", gID);
+        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);
+                content.writeText("f"); // ::kFill_Style, ::kWinding_FillType
+                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);
+    }
 
-        const SkGlyph& glyph = cache->getGlyphIDMetrics(gID);
-        widthArray->appendScalar(SkFloatToScalar(glyph.fAdvanceX));
-        SkIRect glyphBBox = SkIRect::MakeXYWH(glyph.fLeft, glyph.fTop,
-                                              glyph.fWidth, glyph.fHeight);
-        bbox.join(glyphBBox);
-
-        SkDynamicMemoryWStream content;
-        setGlyphWidthAndBoundingBox(SkFloatToScalar(glyph.fAdvanceX), glyphBBox,
-                                    &content);
-        const SkPath* path = cache->findPath(glyph);
-        if (path) {
-            SkPDFUtils::EmitPath(*path, paint.getStyle(), &content);
-            SkPDFUtils::PaintPath(paint.getStyle(), path->getFillType(),
-                                  &content);
+    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->appendScalar(bbox.left());
+    fontBBox->appendScalar(bbox.bottom());
+    fontBBox->appendScalar(bbox.right());
+    fontBBox->appendScalar(bbox.top());
+    font->insertObject("FontBBox", std::move(fontBBox));
+//FIXME
+    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);
+            }
         }
-        charProcs->insertObjRef(
-                characterName, sk_make_sp<SkPDFStream>(
-                        std::unique_ptr<SkStreamAsset>(content.detachAsStream())));
+        subset->exportTo(&subsetList);
+        metrics = SkPDFFont::GetFontMetricsWithToUnicode(typeface, subsetList.begin(),
+                                                         subsetList.count());
+    } else {
+        metrics = SkPDFFont::GetFontMetricsWithToUnicode(typeface, nullptr, 0);
     }
+    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));
+}
 
-    encoding->insertObject("Differences", std::move(encDiffs));
+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);
+}
 
-    this->insertObject("CharProcs", std::move(charProcs));
-    this->insertObject("Encoding", std::move(encoding));
+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;
+}
 
-    this->insertObject("FontBBox", makeFontBBox(bbox, 1000));
-    this->insertInt("FirstChar", 1);
-    this->insertInt("LastChar", lastGlyphID() - firstGlyphID() + 1);
-    this->insertObject("Widths", std::move(widthArray));
-    this->insertName("CIDToGIDMap", "Identity");
 
-    this->populateToUnicodeTable(nullptr);
-    return true;
-}
+////////////////////////////////////////////////////////////////////////////////
 
 SkPDFFont::Match SkPDFFont::IsMatch(SkPDFFont* existingFont,
                                     uint32_t existingFontID,