Make SkShaper a module

Change-Id: I3709e49ba865f14260660cc07a762b9ac837cb3c
Reviewed-on: https://skia-review.googlesource.com/130602
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Herb Derby <herb@google.com>

4 files changed, 891 insertions, 0 deletions

diff --git a/modules/skshaper/BUILD.gn b/modules/skshaper/BUILD.gn
new file mode 100644
index 0000000000..eb67f90790
--- /dev/null
+++ b/modules/skshaper/BUILD.gn
@@ -0,0 +1,40 @@
+# Copyright 2018 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+declare_args() {
+  skia_enable_skshaper = true
+}
+
+config("public_config") {
+  if (skia_enable_skshaper) {
+    include_dirs = [ "include" ]
+  }
+}
+
+source_set("skshaper") {
+  if (skia_enable_skshaper) {
+    public_configs = [ ":public_config" ]
+    public = [ "include/SkShaper.h" ]
+    deps = [
+      "../..:skia",
+    ]
+    if (target_cpu == "wasm") {
+      sources = [
+        "src/SkShaper_primitive.cpp",
+      ]
+    } else {
+      sources = [
+        "src/SkShaper_harfbuzz.cpp",
+      ]
+      deps += [
+        "//third_party/harfbuzz",
+        "//third_party/icu",
+      ]
+    }
+    configs += [ "../../:skia_private" ]
+
+  }
+}
+
diff --git a/modules/skshaper/include/SkShaper.h b/modules/skshaper/include/SkShaper.h
new file mode 100644
index 0000000000..190a4d834e
--- /dev/null
+++ b/modules/skshaper/include/SkShaper.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkShaper_DEFINED
+#define SkShaper_DEFINED
+
+#include <memory>
+
+#include "SkPoint.h"
+#include "SkTypeface.h"
+
+class SkPaint;
+class SkTextBlobBuilder;
+
+/**
+   Shapes text using HarfBuzz and places the shaped text into a
+   TextBlob.
+
+   If compiled without HarfBuzz, fall back on SkPaint::textToGlyphs.
+ */
+class SkShaper {
+public:
+    SkShaper(sk_sp<SkTypeface> face);
+    ~SkShaper();
+
+    bool good() const;
+    SkPoint shape(SkTextBlobBuilder* dest,
+                   const SkPaint& srcPaint,
+                   const char* utf8text,
+                   size_t textBytes,
+                   bool leftToRight,
+                   SkPoint point,
+                   SkScalar width) const;
+
+private:
+    SkShaper(const SkShaper&) = delete;
+    SkShaper& operator=(const SkShaper&) = delete;
+
+    struct Impl;
+    std::unique_ptr<Impl> fImpl;
+};
+
+#endif  // SkShaper_DEFINED
diff --git a/modules/skshaper/src/SkShaper_harfbuzz.cpp b/modules/skshaper/src/SkShaper_harfbuzz.cpp
new file mode 100644
index 0000000000..40414d9a79
--- /dev/null
+++ b/modules/skshaper/src/SkShaper_harfbuzz.cpp
@@ -0,0 +1,728 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <hb-ot.h>
+#include <unicode/brkiter.h>
+#include <unicode/locid.h>
+#include <unicode/stringpiece.h>
+#include <unicode/ubidi.h>
+#include <unicode/uchriter.h>
+#include <unicode/unistr.h>
+#include <unicode/uscript.h>
+
+#include "SkFontMgr.h"
+#include "SkLoadICU.h"
+#include "SkOnce.h"
+#include "SkShaper.h"
+#include "SkStream.h"
+#include "SkTDPQueue.h"
+#include "SkTLazy.h"
+#include "SkTemplates.h"
+#include "SkTextBlob.h"
+#include "SkTypeface.h"
+#include "SkUtils.h"
+
+namespace {
+template <class T, void(*P)(T*)> using resource = std::unique_ptr<T, SkFunctionWrapper<void, T, P>>;
+using HBBlob   = resource<hb_blob_t  , hb_blob_destroy  >;
+using HBFace   = resource<hb_face_t  , hb_face_destroy  >;
+using HBFont   = resource<hb_font_t  , hb_font_destroy  >;
+using HBBuffer = resource<hb_buffer_t, hb_buffer_destroy>;
+using ICUBiDi  = resource<UBiDi      , ubidi_close      >;
+
+HBBlob stream_to_blob(std::unique_ptr<SkStreamAsset> asset) {
+    size_t size = asset->getLength();
+    HBBlob blob;
+    if (const void* base = asset->getMemoryBase()) {
+        blob.reset(hb_blob_create((char*)base, SkToUInt(size),
+                                  HB_MEMORY_MODE_READONLY, asset.release(),
+                                  [](void* p) { delete (SkStreamAsset*)p; }));
+    } else {
+        // SkDebugf("Extra SkStreamAsset copy\n");
+        void* ptr = size ? sk_malloc_throw(size) : nullptr;
+        asset->read(ptr, size);
+        blob.reset(hb_blob_create((char*)ptr, SkToUInt(size),
+                                  HB_MEMORY_MODE_READONLY, ptr, sk_free));
+    }
+    SkASSERT(blob);
+    hb_blob_make_immutable(blob.get());
+    return blob;
+}
+
+HBFont create_hb_font(SkTypeface* tf) {
+    int index;
+    HBBlob blob(stream_to_blob(std::unique_ptr<SkStreamAsset>(tf->openStream(&index))));
+    HBFace face(hb_face_create(blob.get(), (unsigned)index));
+    SkASSERT(face);
+    if (!face) {
+        return nullptr;
+    }
+    hb_face_set_index(face.get(), (unsigned)index);
+    hb_face_set_upem(face.get(), tf->getUnitsPerEm());
+
+    HBFont font(hb_font_create(face.get()));
+    SkASSERT(font);
+    if (!font) {
+        return nullptr;
+    }
+    hb_ot_font_set_funcs(font.get());
+    int axis_count = tf->getVariationDesignPosition(nullptr, 0);
+    if (axis_count > 0) {
+        SkAutoSTMalloc<4, SkFontArguments::VariationPosition::Coordinate> axis_values(axis_count);
+        if (tf->getVariationDesignPosition(axis_values, axis_count) == axis_count) {
+            hb_font_set_variations(font.get(),
+                                   reinterpret_cast<hb_variation_t*>(axis_values.get()),
+                                   axis_count);
+        }
+    }
+    return font;
+}
+
+class RunIterator {
+public:
+    virtual ~RunIterator() {}
+    virtual void consume() = 0;
+    // Pointer one past the last (utf8) element in the current run.
+    virtual const char* endOfCurrentRun() const = 0;
+    virtual bool atEnd() const = 0;
+    bool operator<(const RunIterator& that) const {
+        return this->endOfCurrentRun() < that.endOfCurrentRun();
+    }
+};
+
+class BiDiRunIterator : public RunIterator {
+public:
+    static SkTLazy<BiDiRunIterator> Make(const char* utf8, size_t utf8Bytes, UBiDiLevel level) {
+        SkTLazy<BiDiRunIterator> ret;
+
+        // ubidi only accepts utf16 (though internally it basically works on utf32 chars).
+        // We want an ubidi_setPara(UBiDi*, UText*, UBiDiLevel, UBiDiLevel*, UErrorCode*);
+        if (!SkTFitsIn<int32_t>(utf8Bytes)) {
+            SkDebugf("Bidi error: text too long");
+            return ret;
+        }
+        icu::UnicodeString utf16 = icu::UnicodeString::fromUTF8(icu::StringPiece(utf8, utf8Bytes));
+
+        UErrorCode status = U_ZERO_ERROR;
+        ICUBiDi bidi(ubidi_openSized(utf16.length(), 0, &status));
+        if (U_FAILURE(status)) {
+            SkDebugf("Bidi error: %s", u_errorName(status));
+            return ret;
+        }
+        SkASSERT(bidi);
+
+        // The required lifetime of utf16 isn't well documented.
+        // It appears it isn't used after ubidi_setPara except through ubidi_getText.
+        ubidi_setPara(bidi.get(), utf16.getBuffer(), utf16.length(), level, nullptr, &status);
+        if (U_FAILURE(status)) {
+            SkDebugf("Bidi error: %s", u_errorName(status));
+            return ret;
+        }
+
+        ret.init(utf8, std::move(bidi));
+        return ret;
+    }
+    BiDiRunIterator(const char* utf8, ICUBiDi bidi)
+        : fBidi(std::move(bidi))
+        , fEndOfCurrentRun(utf8)
+        , fUTF16LogicalPosition(0)
+        , fLevel(UBIDI_DEFAULT_LTR)
+    {}
+    void consume() override {
+        SkASSERT(fUTF16LogicalPosition < ubidi_getLength(fBidi.get()));
+        int32_t endPosition = ubidi_getLength(fBidi.get());
+        fLevel = ubidi_getLevelAt(fBidi.get(), fUTF16LogicalPosition);
+        SkUnichar u = SkUTF8_NextUnichar(&fEndOfCurrentRun);
+        fUTF16LogicalPosition += SkUTF16_FromUnichar(u);
+        UBiDiLevel level;
+        while (fUTF16LogicalPosition < endPosition) {
+            level = ubidi_getLevelAt(fBidi.get(), fUTF16LogicalPosition);
+            if (level != fLevel) {
+                break;
+            }
+            u = SkUTF8_NextUnichar(&fEndOfCurrentRun);
+            fUTF16LogicalPosition += SkUTF16_FromUnichar(u);
+        }
+    }
+    const char* endOfCurrentRun() const override {
+        return fEndOfCurrentRun;
+    }
+    bool atEnd() const override {
+        return fUTF16LogicalPosition == ubidi_getLength(fBidi.get());
+    }
+
+    UBiDiLevel currentLevel() const {
+        return fLevel;
+    }
+private:
+    ICUBiDi fBidi;
+    const char* fEndOfCurrentRun;
+    int32_t fUTF16LogicalPosition;
+    UBiDiLevel fLevel;
+};
+
+class ScriptRunIterator : public RunIterator {
+public:
+    static SkTLazy<ScriptRunIterator> Make(const char* utf8, size_t utf8Bytes,
+                                           hb_unicode_funcs_t* hbUnicode)
+    {
+        SkTLazy<ScriptRunIterator> ret;
+        ret.init(utf8, utf8Bytes, hbUnicode);
+        return ret;
+    }
+    ScriptRunIterator(const char* utf8, size_t utf8Bytes, hb_unicode_funcs_t* hbUnicode)
+        : fCurrent(utf8), fEnd(fCurrent + utf8Bytes)
+        , fHBUnicode(hbUnicode)
+        , fCurrentScript(HB_SCRIPT_UNKNOWN)
+    {}
+    void consume() override {
+        SkASSERT(fCurrent < fEnd);
+        SkUnichar u = SkUTF8_NextUnichar(&fCurrent);
+        fCurrentScript = hb_unicode_script(fHBUnicode, u);
+        while (fCurrent < fEnd) {
+            const char* prev = fCurrent;
+            u = SkUTF8_NextUnichar(&fCurrent);
+            const hb_script_t script = hb_unicode_script(fHBUnicode, u);
+            if (script != fCurrentScript) {
+                if (fCurrentScript == HB_SCRIPT_INHERITED || fCurrentScript == HB_SCRIPT_COMMON) {
+                    fCurrentScript = script;
+                } else if (script == HB_SCRIPT_INHERITED || script == HB_SCRIPT_COMMON) {
+                    continue;
+                } else {
+                    fCurrent = prev;
+                    break;
+                }
+            }
+        }
+        if (fCurrentScript == HB_SCRIPT_INHERITED) {
+            fCurrentScript = HB_SCRIPT_COMMON;
+        }
+    }
+    const char* endOfCurrentRun() const override {
+        return fCurrent;
+    }
+    bool atEnd() const override {
+        return fCurrent == fEnd;
+    }
+
+    hb_script_t currentScript() const {
+        return fCurrentScript;
+    }
+private:
+    const char* fCurrent;
+    const char* fEnd;
+    hb_unicode_funcs_t* fHBUnicode;
+    hb_script_t fCurrentScript;
+};
+
+class FontRunIterator : public RunIterator {
+public:
+    static SkTLazy<FontRunIterator> Make(const char* utf8, size_t utf8Bytes,
+                                         sk_sp<SkTypeface> typeface,
+                                         hb_font_t* hbFace,
+                                         sk_sp<SkFontMgr> fallbackMgr)
+    {
+        SkTLazy<FontRunIterator> ret;
+        ret.init(utf8, utf8Bytes, std::move(typeface), hbFace, std::move(fallbackMgr));
+        return ret;
+    }
+    FontRunIterator(const char* utf8, size_t utf8Bytes, sk_sp<SkTypeface> typeface,
+                    hb_font_t* hbFace, sk_sp<SkFontMgr> fallbackMgr)
+        : fCurrent(utf8), fEnd(fCurrent + utf8Bytes)
+        , fFallbackMgr(std::move(fallbackMgr))
+        , fHBFont(hbFace), fTypeface(std::move(typeface))
+        , fFallbackHBFont(nullptr), fFallbackTypeface(nullptr)
+        , fCurrentHBFont(fHBFont), fCurrentTypeface(fTypeface.get())
+    {}
+    void consume() override {
+        SkASSERT(fCurrent < fEnd);
+        SkUnichar u = SkUTF8_NextUnichar(&fCurrent);
+        // If the starting typeface can handle this character, use it.
+        if (fTypeface->charsToGlyphs(&u, SkTypeface::kUTF32_Encoding, nullptr, 1)) {
+            fFallbackTypeface.reset();
+        // If not, try to find a fallback typeface
+        } else {
+            fFallbackTypeface.reset(fFallbackMgr->matchFamilyStyleCharacter(
+                nullptr, fTypeface->fontStyle(), nullptr, 0, u));
+        }
+
+        if (fFallbackTypeface) {
+            fFallbackHBFont = create_hb_font(fFallbackTypeface.get());
+            fCurrentTypeface = fFallbackTypeface.get();
+            fCurrentHBFont = fFallbackHBFont.get();
+        } else {
+            fFallbackHBFont.reset();
+            fCurrentTypeface = fTypeface.get();
+            fCurrentHBFont = fHBFont;
+        }
+
+        while (fCurrent < fEnd) {
+            const char* prev = fCurrent;
+            u = SkUTF8_NextUnichar(&fCurrent);
+
+            // If using a fallback and the initial typeface has this character, stop fallback.
+            if (fFallbackTypeface &&
+                fTypeface->charsToGlyphs(&u, SkTypeface::kUTF32_Encoding, nullptr, 1))
+            {
+                fCurrent = prev;
+                return;
+            }
+            // If the current typeface cannot handle this character, stop using it.
+            if (!fCurrentTypeface->charsToGlyphs(&u, SkTypeface::kUTF32_Encoding, nullptr, 1)) {
+                fCurrent = prev;
+                return;
+            }
+        }
+    }
+    const char* endOfCurrentRun() const override {
+        return fCurrent;
+    }
+    bool atEnd() const override {
+        return fCurrent == fEnd;
+    }
+
+    SkTypeface* currentTypeface() const {
+        return fCurrentTypeface;
+    }
+    hb_font_t* currentHBFont() const {
+        return fCurrentHBFont;
+    }
+private:
+    const char* fCurrent;
+    const char* fEnd;
+    sk_sp<SkFontMgr> fFallbackMgr;
+    hb_font_t* fHBFont;
+    sk_sp<SkTypeface> fTypeface;
+    HBFont fFallbackHBFont;
+    sk_sp<SkTypeface> fFallbackTypeface;
+    hb_font_t* fCurrentHBFont;
+    SkTypeface* fCurrentTypeface;
+};
+
+class RunIteratorQueue {
+public:
+    void insert(RunIterator* runIterator) {
+        fRunIterators.insert(runIterator);
+    }
+
+    bool advanceRuns() {
+        const RunIterator* leastRun = fRunIterators.peek();
+        if (leastRun->atEnd()) {
+            SkASSERT(this->allRunsAreAtEnd());
+            return false;
+        }
+        const char* leastEnd = leastRun->endOfCurrentRun();
+        RunIterator* currentRun = nullptr;
+        SkDEBUGCODE(const char* previousEndOfCurrentRun);
+        while ((currentRun = fRunIterators.peek())->endOfCurrentRun() <= leastEnd) {
+            fRunIterators.pop();
+            SkDEBUGCODE(previousEndOfCurrentRun = currentRun->endOfCurrentRun());
+            currentRun->consume();
+            SkASSERT(previousEndOfCurrentRun < currentRun->endOfCurrentRun());
+            fRunIterators.insert(currentRun);
+        }
+        return true;
+    }
+
+    const char* endOfCurrentRun() const {
+        return fRunIterators.peek()->endOfCurrentRun();
+    }
+
+private:
+    bool allRunsAreAtEnd() const {
+        for (int i = 0; i < fRunIterators.count(); ++i) {
+            if (!fRunIterators.at(i)->atEnd()) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    static bool CompareRunIterator(RunIterator* const& a, RunIterator* const& b) {
+        return *a < *b;
+    }
+    SkTDPQueue<RunIterator*, CompareRunIterator> fRunIterators;
+};
+
+struct ShapedGlyph {
+    SkGlyphID fID;
+    uint32_t fCluster;
+    SkPoint fOffset;
+    SkVector fAdvance;
+    bool fMayLineBreakBefore;
+    bool fMustLineBreakBefore;
+    bool fHasVisual;
+};
+struct ShapedRun {
+    ShapedRun(const char* utf8Start, const char* utf8End, int numGlyphs, const SkPaint& paint,
+              UBiDiLevel level, std::unique_ptr<ShapedGlyph[]> glyphs)
+        : fUtf8Start(utf8Start), fUtf8End(utf8End), fNumGlyphs(numGlyphs), fPaint(paint)
+        , fLevel(level), fGlyphs(std::move(glyphs))
+    {}
+
+    const char* fUtf8Start;
+    const char* fUtf8End;
+    int fNumGlyphs;
+    SkPaint fPaint;
+    UBiDiLevel fLevel;
+    std::unique_ptr<ShapedGlyph[]> fGlyphs;
+};
+
+static constexpr bool is_LTR(UBiDiLevel level) {
+    return (level & 1) == 0;
+}
+
+static void append(SkTextBlobBuilder* b, const ShapedRun& run, int start, int end, SkPoint* p) {
+    unsigned len = end - start;
+    auto runBuffer = b->allocRunTextPos(run.fPaint, len, run.fUtf8End - run.fUtf8Start, SkString());
+    memcpy(runBuffer.utf8text, run.fUtf8Start, run.fUtf8End - run.fUtf8Start);
+
+    for (unsigned i = 0; i < len; i++) {
+        // Glyphs are in logical order, but output ltr since PDF readers seem to expect that.
+        const ShapedGlyph& glyph = run.fGlyphs[is_LTR(run.fLevel) ? start + i : end - 1 - i];
+        runBuffer.glyphs[i] = glyph.fID;
+        runBuffer.clusters[i] = glyph.fCluster;
+        reinterpret_cast<SkPoint*>(runBuffer.pos)[i] =
+                SkPoint::Make(p->fX + glyph.fOffset.fX, p->fY - glyph.fOffset.fY);
+        p->fX += glyph.fAdvance.fX;
+        p->fY += glyph.fAdvance.fY;
+    }
+}
+
+struct ShapedRunGlyphIterator {
+    ShapedRunGlyphIterator(const SkTArray<ShapedRun>& origRuns)
+        : fRuns(&origRuns), fRunIndex(0), fGlyphIndex(0)
+    { }
+
+    ShapedRunGlyphIterator(const ShapedRunGlyphIterator& that) = default;
+    ShapedRunGlyphIterator& operator=(const ShapedRunGlyphIterator& that) = default;
+    bool operator==(const ShapedRunGlyphIterator& that) const {
+        return fRuns == that.fRuns &&
+               fRunIndex == that.fRunIndex &&
+               fGlyphIndex == that.fGlyphIndex;
+    }
+    bool operator!=(const ShapedRunGlyphIterator& that) const {
+        return fRuns != that.fRuns ||
+               fRunIndex != that.fRunIndex ||
+               fGlyphIndex != that.fGlyphIndex;
+    }
+
+    ShapedGlyph* next() {
+        const SkTArray<ShapedRun>& runs = *fRuns;
+        SkASSERT(fRunIndex < runs.count());
+        SkASSERT(fGlyphIndex < runs[fRunIndex].fNumGlyphs);
+
+        ++fGlyphIndex;
+        if (fGlyphIndex == runs[fRunIndex].fNumGlyphs) {
+            fGlyphIndex = 0;
+            ++fRunIndex;
+            if (fRunIndex >= runs.count()) {
+                return nullptr;
+            }
+        }
+        return &runs[fRunIndex].fGlyphs[fGlyphIndex];
+    }
+
+    ShapedGlyph* current() {
+        const SkTArray<ShapedRun>& runs = *fRuns;
+        if (fRunIndex >= runs.count()) {
+            return nullptr;
+        }
+        return &runs[fRunIndex].fGlyphs[fGlyphIndex];
+    }
+
+    const SkTArray<ShapedRun>* fRuns;
+    int fRunIndex;
+    int fGlyphIndex;
+};
+
+}  // namespace
+
+struct SkShaper::Impl {
+    HBFont fHarfBuzzFont;
+    HBBuffer fBuffer;
+    sk_sp<SkTypeface> fTypeface;
+    std::unique_ptr<icu::BreakIterator> fBreakIterator;
+};
+
+SkShaper::SkShaper(sk_sp<SkTypeface> tf) : fImpl(new Impl) {
+    SkOnce once;
+    once([] { SkLoadICU(); });
+
+    fImpl->fTypeface = tf ? std::move(tf) : SkTypeface::MakeDefault();
+    fImpl->fHarfBuzzFont = create_hb_font(fImpl->fTypeface.get());
+    SkASSERT(fImpl->fHarfBuzzFont);
+    fImpl->fBuffer.reset(hb_buffer_create());
+    SkASSERT(fImpl->fBuffer);
+
+    icu::Locale thai("th");
+    UErrorCode status = U_ZERO_ERROR;
+    fImpl->fBreakIterator.reset(icu::BreakIterator::createLineInstance(thai, status));
+    if (U_FAILURE(status)) {
+        SkDebugf("Could not create break iterator: %s", u_errorName(status));
+        SK_ABORT("");
+    }
+}
+
+SkShaper::~SkShaper() {}
+
+bool SkShaper::good() const {
+    return fImpl->fHarfBuzzFont &&
+           fImpl->fBuffer &&
+           fImpl->fTypeface &&
+           fImpl->fBreakIterator;
+}
+
+SkPoint SkShaper::shape(SkTextBlobBuilder* builder,
+                        const SkPaint& srcPaint,
+                        const char* utf8,
+                        size_t utf8Bytes,
+                        bool leftToRight,
+                        SkPoint point,
+                        SkScalar width) const {
+    sk_sp<SkFontMgr> fontMgr = SkFontMgr::RefDefault();
+    SkASSERT(builder);
+    UBiDiLevel defaultLevel = leftToRight ? UBIDI_DEFAULT_LTR : UBIDI_DEFAULT_RTL;
+    //hb_script_t script = ...
+
+    SkTArray<ShapedRun> runs;
+{
+    RunIteratorQueue runSegmenter;
+
+    SkTLazy<BiDiRunIterator> maybeBidi(BiDiRunIterator::Make(utf8, utf8Bytes, defaultLevel));
+    BiDiRunIterator* bidi = maybeBidi.getMaybeNull();
+    if (!bidi) {
+        return point;
+    }
+    runSegmenter.insert(bidi);
+
+    hb_unicode_funcs_t* hbUnicode = hb_buffer_get_unicode_funcs(fImpl->fBuffer.get());
+    SkTLazy<ScriptRunIterator> maybeScript(ScriptRunIterator::Make(utf8, utf8Bytes, hbUnicode));
+    ScriptRunIterator* script = maybeScript.getMaybeNull();
+    if (!script) {
+        return point;
+    }
+    runSegmenter.insert(script);
+
+    SkTLazy<FontRunIterator> maybeFont(FontRunIterator::Make(utf8, utf8Bytes,
+                                                             fImpl->fTypeface,
+                                                             fImpl->fHarfBuzzFont.get(),
+                                                             std::move(fontMgr)));
+    FontRunIterator* font = maybeFont.getMaybeNull();
+    if (!font) {
+        return point;
+    }
+    runSegmenter.insert(font);
+
+    icu::BreakIterator& breakIterator = *fImpl->fBreakIterator;
+    {
+        UErrorCode status = U_ZERO_ERROR;
+        UText utf8UText = UTEXT_INITIALIZER;
+        utext_openUTF8(&utf8UText, utf8, utf8Bytes, &status);
+        std::unique_ptr<UText, SkFunctionWrapper<UText*, UText, utext_close>> autoClose(&utf8UText);
+        if (U_FAILURE(status)) {
+            SkDebugf("Could not create utf8UText: %s", u_errorName(status));
+            return point;
+        }
+        breakIterator.setText(&utf8UText, status);
+        //utext_close(&utf8UText);
+        if (U_FAILURE(status)) {
+            SkDebugf("Could not setText on break iterator: %s", u_errorName(status));
+            return point;
+        }
+    }
+
+    const char* utf8Start = nullptr;
+    const char* utf8End = utf8;
+    while (runSegmenter.advanceRuns()) {
+        utf8Start = utf8End;
+        utf8End = runSegmenter.endOfCurrentRun();
+
+        hb_buffer_t* buffer = fImpl->fBuffer.get();
+        SkAutoTCallVProc<hb_buffer_t, hb_buffer_clear_contents> autoClearBuffer(buffer);
+        hb_buffer_set_content_type(buffer, HB_BUFFER_CONTENT_TYPE_UNICODE);
+        hb_buffer_set_cluster_level(buffer, HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS);
+
+        // Populate the hb_buffer directly with utf8 cluster indexes.
+        const char* utf8Current = utf8Start;
+        while (utf8Current < utf8End) {
+            unsigned int cluster = utf8Current - utf8Start;
+            hb_codepoint_t u = SkUTF8_NextUnichar(&utf8Current);
+            hb_buffer_add(buffer, u, cluster);
+        }
+
+        size_t utf8runLength = utf8End - utf8Start;
+        if (!SkTFitsIn<int>(utf8runLength)) {
+            SkDebugf("Shaping error: utf8 too long");
+            return point;
+        }
+        hb_buffer_set_script(buffer, script->currentScript());
+        hb_direction_t direction = is_LTR(bidi->currentLevel()) ? HB_DIRECTION_LTR:HB_DIRECTION_RTL;
+        hb_buffer_set_direction(buffer, direction);
+        // TODO: language
+        hb_buffer_guess_segment_properties(buffer);
+        // TODO: features
+        hb_shape(font->currentHBFont(), buffer, nullptr, 0);
+        unsigned len = hb_buffer_get_length(buffer);
+        if (len == 0) {
+            continue;
+        }
+
+        if (direction == HB_DIRECTION_RTL) {
+            // Put the clusters back in logical order.
+            // Note that the advances remain ltr.
+            hb_buffer_reverse(buffer);
+        }
+        hb_glyph_info_t* info = hb_buffer_get_glyph_infos(buffer, nullptr);
+        hb_glyph_position_t* pos = hb_buffer_get_glyph_positions(buffer, nullptr);
+
+        if (!SkTFitsIn<int>(len)) {
+            SkDebugf("Shaping error: too many glyphs");
+            return point;
+        }
+
+        SkPaint paint(srcPaint);
+        paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
+        paint.setTypeface(sk_ref_sp(font->currentTypeface()));
+        ShapedRun& run = runs.emplace_back(utf8Start, utf8End, len, paint, bidi->currentLevel(),
+                                           std::unique_ptr<ShapedGlyph[]>(new ShapedGlyph[len]));
+        int scaleX, scaleY;
+        hb_font_get_scale(font->currentHBFont(), &scaleX, &scaleY);
+        double textSizeY = run.fPaint.getTextSize() / scaleY;
+        double textSizeX = run.fPaint.getTextSize() / scaleX * run.fPaint.getTextScaleX();
+        for (unsigned i = 0; i < len; i++) {
+            ShapedGlyph& glyph = run.fGlyphs[i];
+            glyph.fID = info[i].codepoint;
+            glyph.fCluster = info[i].cluster;
+            glyph.fOffset.fX = pos[i].x_offset * textSizeX;
+            glyph.fOffset.fY = pos[i].y_offset * textSizeY;
+            glyph.fAdvance.fX = pos[i].x_advance * textSizeX;
+            glyph.fAdvance.fY = pos[i].y_advance * textSizeY;
+            glyph.fHasVisual = true; //!font->currentTypeface()->glyphBoundsAreZero(glyph.fID);
+            //info->mask safe_to_break;
+            glyph.fMustLineBreakBefore = false;
+        }
+
+        int32_t clusterOffset = utf8Start - utf8;
+        uint32_t previousCluster = 0xFFFFFFFF;
+        for (unsigned i = 0; i < len; ++i) {
+            ShapedGlyph& glyph = run.fGlyphs[i];
+            int32_t glyphCluster = glyph.fCluster + clusterOffset;
+            int32_t breakIteratorCurrent = breakIterator.current();
+            while (breakIteratorCurrent != icu::BreakIterator::DONE &&
+                   breakIteratorCurrent < glyphCluster)
+            {
+                breakIteratorCurrent = breakIterator.next();
+            }
+            glyph.fMayLineBreakBefore = glyph.fCluster != previousCluster &&
+                                        breakIteratorCurrent == glyphCluster;
+            previousCluster = glyph.fCluster;
+        }
+    }
+}
+
+// Iterate over the glyphs in logical order to mark line endings.
+{
+    SkScalar widthSoFar = 0;
+    bool previousBreakValid = false; // Set when previousBreak is set to a valid candidate break.
+    bool canAddBreakNow = false; // Disallow line breaks before the first glyph of a run.
+    ShapedRunGlyphIterator previousBreak(runs);
+    ShapedRunGlyphIterator glyphIterator(runs);
+    while (ShapedGlyph* glyph = glyphIterator.current()) {
+        if (canAddBreakNow && glyph->fMayLineBreakBefore) {
+            previousBreakValid = true;
+            previousBreak = glyphIterator;
+        }
+        SkScalar glyphWidth = glyph->fAdvance.fX;
+        if (widthSoFar + glyphWidth < width) {
+            widthSoFar += glyphWidth;
+            glyphIterator.next();
+            canAddBreakNow = true;
+            continue;
+        }
+
+        if (widthSoFar == 0) {
+            // Adding just this glyph is too much, just break with this glyph
+            glyphIterator.next();
+            previousBreak = glyphIterator;
+        } else if (!previousBreakValid) {
+            // No break opprotunity found yet, just break without this glyph
+            previousBreak = glyphIterator;
+        }
+        glyphIterator = previousBreak;
+        glyph = glyphIterator.current();
+        if (glyph) {
+            glyph->fMustLineBreakBefore = true;
+        }
+        widthSoFar = 0;
+        previousBreakValid = false;
+        canAddBreakNow = false;
+    }
+}
+
+// Reorder the runs and glyphs per line and write them out.
+    SkPoint currentPoint = point;
+{
+    ShapedRunGlyphIterator previousBreak(runs);
+    ShapedRunGlyphIterator glyphIterator(runs);
+    SkScalar maxAscent = 0;
+    SkScalar maxDescent = 0;
+    SkScalar maxLeading = 0;
+    int previousRunIndex = -1;
+    while (glyphIterator.current()) {
+        int runIndex = glyphIterator.fRunIndex;
+        int glyphIndex = glyphIterator.fGlyphIndex;
+        ShapedGlyph* nextGlyph = glyphIterator.next();
+
+        if (previousRunIndex != runIndex) {
+            SkPaint::FontMetrics metrics;
+            runs[runIndex].fPaint.getFontMetrics(&metrics);
+            maxAscent = SkTMin(maxAscent, metrics.fAscent);
+            maxDescent = SkTMax(maxDescent, metrics.fDescent);
+            maxLeading = SkTMax(maxLeading, metrics.fLeading);
+            previousRunIndex = runIndex;
+        }
+
+        // Nothing can be written until the baseline is known.
+        if (!(nextGlyph == nullptr || nextGlyph->fMustLineBreakBefore)) {
+            continue;
+        }
+
+        currentPoint.fY -= maxAscent;
+
+        int numRuns = runIndex - previousBreak.fRunIndex + 1;
+        SkAutoSTMalloc<4, UBiDiLevel> runLevels(numRuns);
+        for (int i = 0; i < numRuns; ++i) {
+            runLevels[i] = runs[previousBreak.fRunIndex + i].fLevel;
+        }
+        SkAutoSTMalloc<4, int32_t> logicalFromVisual(numRuns);
+        ubidi_reorderVisual(runLevels, numRuns, logicalFromVisual);
+
+        for (int i = 0; i < numRuns; ++i) {
+            int logicalIndex = previousBreak.fRunIndex + logicalFromVisual[i];
+
+            int startGlyphIndex = (logicalIndex == previousBreak.fRunIndex)
+                                ? previousBreak.fGlyphIndex
+                                : 0;
+            int endGlyphIndex = (logicalIndex == runIndex)
+                              ? glyphIndex + 1
+                              : runs[logicalIndex].fNumGlyphs;
+            append(builder, runs[logicalIndex], startGlyphIndex, endGlyphIndex, &currentPoint);
+        }
+
+        currentPoint.fY += maxDescent + maxLeading;
+        currentPoint.fX = point.fX;
+        maxAscent = 0;
+        maxDescent = 0;
+        maxLeading = 0;
+        previousRunIndex = -1;
+        previousBreak = glyphIterator;
+    }
+}
+
+    return currentPoint;
+}
diff --git a/modules/skshaper/src/SkShaper_primitive.cpp b/modules/skshaper/src/SkShaper_primitive.cpp
new file mode 100644
index 0000000000..06a8bec41c
--- /dev/null
+++ b/modules/skshaper/src/SkShaper_primitive.cpp
@@ -0,0 +1,76 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "SkShaper.h"
+#include "SkStream.h"
+#include "SkTextBlob.h"
+#include "SkTypeface.h"
+
+struct SkShaper::Impl {
+    sk_sp<SkTypeface> fTypeface;
+};
+
+SkShaper::SkShaper(sk_sp<SkTypeface> tf) : fImpl(new Impl) {
+    fImpl->fTypeface = tf ? std::move(tf) : SkTypeface::MakeDefault();
+}
+
+SkShaper::~SkShaper() {}
+
+bool SkShaper::good() const { return true; }
+
+// This example only uses public API, so we don't use SkUTF8_NextUnichar.
+unsigned utf8_lead_byte_to_count(const char* ptr) {
+    uint8_t c = *(const uint8_t*)ptr;
+    SkASSERT(c <= 0xF7);
+    SkASSERT((c & 0xC0) != 0x80);
+    return (((0xE5 << 24) >> ((unsigned)c >> 4 << 1)) & 3) + 1;
+}
+
+SkPoint SkShaper::shape(SkTextBlobBuilder* builder,
+                        const SkPaint& srcPaint,
+                        const char* utf8text,
+                        size_t textBytes,
+                        bool leftToRight,
+                        SkPoint point,
+                        SkScalar width) const {
+    sk_ignore_unused_variable(leftToRight);
+
+    SkPaint paint(srcPaint);
+    paint.setTypeface(fImpl->fTypeface);
+    paint.setTextEncoding(SkPaint::kUTF8_TextEncoding);
+    int glyphCount = paint.countText(utf8text, textBytes);
+    if (glyphCount <= 0) {
+        return point;
+    }
+    SkRect bounds;
+    SkPaint::FontMetrics metrics;
+    paint.getFontMetrics(&metrics);
+    point.fY -= metrics.fAscent;
+    (void)paint.measureText(utf8text, textBytes, &bounds);
+    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
+    const SkTextBlobBuilder::RunBuffer& runBuffer =
+        builder->allocRunTextPosH(paint, glyphCount, point.y(), textBytes, SkString(), &bounds);
+    memcpy(runBuffer.utf8text, utf8text, textBytes);
+    const char* txtPtr = utf8text;
+    for (int i = 0; i < glyphCount; ++i) {
+        // Each charater maps to exactly one glyph via SkGlyphCache::unicharToGlyph().
+        runBuffer.clusters[i] = SkToU32(txtPtr - utf8text);
+        txtPtr += utf8_lead_byte_to_count(txtPtr);
+        SkASSERT(txtPtr <= utf8text + textBytes);
+    }
+    paint.setTextEncoding(SkPaint::kUTF8_TextEncoding);
+    (void)paint.textToGlyphs(utf8text, textBytes, runBuffer.glyphs);
+    (void)paint.getTextWidths(utf8text, textBytes, runBuffer.pos);
+    SkScalar x = point.x();
+    for (int i = 0; i < glyphCount; ++i) {
+        SkScalar w = runBuffer.pos[i];
+        runBuffer.pos[i] = x;
+        x += w;
+    }
+    point.fY += metrics.fDescent + metrics.fLeading;
+
+    return point;
+}