path: root/chromium/third_party/WebKit/Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp

/*
 * Copyright (c) 2012 Google Inc. All rights reserved.
 * Copyright (C) 2013 BlackBerry Limited. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "platform/fonts/harfbuzz/HarfBuzzShaper.h"

#include "hb.h"
#include "platform/LayoutUnit.h"
#include "platform/RuntimeEnabledFeatures.h"
#include "platform/fonts/Character.h"
#include "platform/fonts/Font.h"
#include "platform/fonts/GlyphBuffer.h"
#include "platform/fonts/harfbuzz/HarfBuzzFace.h"
#include "platform/text/SurrogatePairAwareTextIterator.h"
#include "platform/text/TextBreakIterator.h"
#include "wtf/Compiler.h"
#include "wtf/MathExtras.h"
#include "wtf/unicode/Unicode.h"
#include <unicode/normlzr.h>
#include <unicode/uchar.h>
#include <unicode/uscript.h>

#include <list>
#include <map>
#include <string>

namespace WebCore {

template<typename T>
class HarfBuzzScopedPtr {
public:
    typedef void (*DestroyFunction)(T*);

    HarfBuzzScopedPtr(T* ptr, DestroyFunction destroy)
        : m_ptr(ptr)
        , m_destroy(destroy)
    {
        ASSERT(m_destroy);
    }
    ~HarfBuzzScopedPtr()
    {
        if (m_ptr)
            (*m_destroy)(m_ptr);
    }

    T* get() { return m_ptr; }
    void set(T* ptr) { m_ptr = ptr; }
private:
    T* m_ptr;
    DestroyFunction m_destroy;
};


static const unsigned cHarfBuzzCacheMaxSize = 256;

struct CachedShapingResultsLRUNode;
struct CachedShapingResults;
typedef std::map<std::wstring, CachedShapingResults*> CachedShapingResultsMap;
typedef std::list<CachedShapingResultsLRUNode*> CachedShapingResultsLRU;

struct CachedShapingResults {
    CachedShapingResults(hb_buffer_t* harfBuzzBuffer, const Font* runFont, hb_direction_t runDir, const String& newLocale);
    ~CachedShapingResults();

    hb_buffer_t* buffer;
    Font font;
    hb_direction_t dir;
    String locale;
    CachedShapingResultsLRU::iterator lru;
};

struct CachedShapingResultsLRUNode {
    CachedShapingResultsLRUNode(const CachedShapingResultsMap::iterator& cacheEntry);
    ~CachedShapingResultsLRUNode();

    CachedShapingResultsMap::iterator entry;
};

CachedShapingResults::CachedShapingResults(hb_buffer_t* harfBuzzBuffer, const Font* fontData, hb_direction_t dirData, const String& newLocale)
    : buffer(harfBuzzBuffer)
    , font(*fontData)
    , dir(dirData)
    , locale(newLocale)
{
}

CachedShapingResults::~CachedShapingResults()
{
    hb_buffer_destroy(buffer);
}

CachedShapingResultsLRUNode::CachedShapingResultsLRUNode(const CachedShapingResultsMap::iterator& cacheEntry)
    : entry(cacheEntry)
{
}

CachedShapingResultsLRUNode::~CachedShapingResultsLRUNode()
{
}

class HarfBuzzRunCache {
public:
    HarfBuzzRunCache();
    ~HarfBuzzRunCache();

    CachedShapingResults* find(const std::wstring& key) const;
    void remove(CachedShapingResults* node);
    void moveToBack(CachedShapingResults* node);
    bool insert(const std::wstring& key, CachedShapingResults* run);

private:
    CachedShapingResultsMap m_harfBuzzRunMap;
    CachedShapingResultsLRU m_harfBuzzRunLRU;
};


HarfBuzzRunCache::HarfBuzzRunCache()
{
}

HarfBuzzRunCache::~HarfBuzzRunCache()
{
    for (CachedShapingResultsMap::iterator it = m_harfBuzzRunMap.begin(); it != m_harfBuzzRunMap.end(); ++it)
        delete it->second;
    for (CachedShapingResultsLRU::iterator it = m_harfBuzzRunLRU.begin(); it != m_harfBuzzRunLRU.end(); ++it)
        delete *it;
}

bool HarfBuzzRunCache::insert(const std::wstring& key, CachedShapingResults* data)
{
    std::pair<CachedShapingResultsMap::iterator, bool> results =
        m_harfBuzzRunMap.insert(CachedShapingResultsMap::value_type(key, data));

    if (!results.second)
        return false;

    CachedShapingResultsLRUNode* node = new CachedShapingResultsLRUNode(results.first);

    m_harfBuzzRunLRU.push_back(node);
    data->lru = --m_harfBuzzRunLRU.end();

    if (m_harfBuzzRunMap.size() > cHarfBuzzCacheMaxSize) {
        CachedShapingResultsLRUNode* lru = m_harfBuzzRunLRU.front();
        CachedShapingResults* foo = lru->entry->second;
        m_harfBuzzRunMap.erase(lru->entry);
        m_harfBuzzRunLRU.pop_front();
        delete foo;
        delete lru;
    }

    return true;
}

inline CachedShapingResults* HarfBuzzRunCache::find(const std::wstring& key) const
{
    CachedShapingResultsMap::const_iterator it = m_harfBuzzRunMap.find(key);

    return it != m_harfBuzzRunMap.end() ? it->second : 0;
}

inline void HarfBuzzRunCache::remove(CachedShapingResults* node)
{
    CachedShapingResultsLRUNode* lruNode = *node->lru;

    m_harfBuzzRunLRU.erase(node->lru);
    m_harfBuzzRunMap.erase(lruNode->entry);
    delete lruNode;
    delete node;
}

inline void HarfBuzzRunCache::moveToBack(CachedShapingResults* node)
{
    CachedShapingResultsLRUNode* lruNode = *node->lru;
    m_harfBuzzRunLRU.erase(node->lru);
    m_harfBuzzRunLRU.push_back(lruNode);
    node->lru = --m_harfBuzzRunLRU.end();
}

HarfBuzzRunCache& harfBuzzRunCache()
{
    DEFINE_STATIC_LOCAL(HarfBuzzRunCache, globalHarfBuzzRunCache, ());
    return globalHarfBuzzRunCache;
}

static inline float harfBuzzPositionToFloat(hb_position_t value)
{
    return static_cast<float>(value) / (1 << 16);
}

static inline unsigned countGraphemesInCluster(const UChar* normalizedBuffer, unsigned normalizedBufferLength, uint16_t startIndex, uint16_t endIndex)
{
    if (startIndex > endIndex) {
        uint16_t tempIndex = startIndex;
        startIndex = endIndex;
        endIndex = tempIndex;
    }
    uint16_t length = endIndex - startIndex;
    ASSERT(static_cast<unsigned>(startIndex + length) <= normalizedBufferLength);
    TextBreakIterator* cursorPosIterator = cursorMovementIterator(&normalizedBuffer[startIndex], length);

    int cursorPos = cursorPosIterator->current();
    int numGraphemes = -1;
    while (0 <= cursorPos) {
        cursorPos = cursorPosIterator->next();
        numGraphemes++;
    }
    return numGraphemes < 0 ? 0 : numGraphemes;
}

inline HarfBuzzShaper::HarfBuzzRun::HarfBuzzRun(const SimpleFontData* fontData, unsigned startIndex, unsigned numCharacters, TextDirection direction, hb_script_t script)
    : m_fontData(fontData)
    , m_startIndex(startIndex)
    , m_numCharacters(numCharacters)
    , m_numGlyphs(0)
    , m_direction(direction)
    , m_script(script)
    , m_width(0)
{
}

inline HarfBuzzShaper::HarfBuzzRun::HarfBuzzRun(const HarfBuzzRun& rhs)
    : m_fontData(rhs.m_fontData)
    , m_startIndex(rhs.m_startIndex)
    , m_numCharacters(rhs.m_numCharacters)
    , m_numGlyphs(rhs.m_numGlyphs)
    , m_direction(rhs.m_direction)
    , m_script(rhs.m_script)
    , m_glyphs(rhs.m_glyphs)
    , m_advances(rhs.m_advances)
    , m_glyphToCharacterIndexes(rhs.m_glyphToCharacterIndexes)
    , m_offsets(rhs.m_offsets)
    , m_width(rhs.m_width)
{
}

HarfBuzzShaper::HarfBuzzRun::~HarfBuzzRun()
{
}

inline void HarfBuzzShaper::HarfBuzzRun::applyShapeResult(hb_buffer_t* harfBuzzBuffer)
{
    m_numGlyphs = hb_buffer_get_length(harfBuzzBuffer);
    m_glyphs.resize(m_numGlyphs);
    m_advances.resize(m_numGlyphs);
    m_glyphToCharacterIndexes.resize(m_numGlyphs);
    m_offsets.resize(m_numGlyphs);
}

inline void HarfBuzzShaper::HarfBuzzRun::copyShapeResultAndGlyphPositions(const HarfBuzzRun& run)
{
    m_numGlyphs = run.m_numGlyphs;
    m_glyphs = run.m_glyphs;
    m_advances = run.m_advances;
    m_glyphToCharacterIndexes = run.m_glyphToCharacterIndexes;
    m_offsets = run.m_offsets;
    m_width = run.m_width;
}

inline void HarfBuzzShaper::HarfBuzzRun::setGlyphAndPositions(unsigned index, uint16_t glyphId, float advance, float offsetX, float offsetY)
{
    m_glyphs[index] = glyphId;
    m_advances[index] = advance;
    m_offsets[index] = FloatPoint(offsetX, offsetY);
}

int HarfBuzzShaper::HarfBuzzRun::characterIndexForXPosition(float targetX)
{
    ASSERT(targetX <= m_width);
    float currentX = 0;
    float currentAdvance = m_advances[0];
    unsigned glyphIndex = 0;

    // Sum up advances that belong to a character.
    while (glyphIndex < m_numGlyphs - 1 && m_glyphToCharacterIndexes[glyphIndex] == m_glyphToCharacterIndexes[glyphIndex + 1])
        currentAdvance += m_advances[++glyphIndex];
    currentAdvance = currentAdvance / 2.0;
    if (targetX <= currentAdvance)
        return rtl() ? m_numCharacters : 0;

    ++glyphIndex;
    while (glyphIndex < m_numGlyphs) {
        unsigned prevCharacterIndex = m_glyphToCharacterIndexes[glyphIndex - 1];
        float prevAdvance = currentAdvance;
        currentAdvance = m_advances[glyphIndex];
        while (glyphIndex < m_numGlyphs - 1 && m_glyphToCharacterIndexes[glyphIndex] == m_glyphToCharacterIndexes[glyphIndex + 1])
            currentAdvance += m_advances[++glyphIndex];
        currentAdvance = currentAdvance / 2.0;
        float nextX = currentX + prevAdvance + currentAdvance;
        if (currentX <= targetX && targetX <= nextX)
            return rtl() ? prevCharacterIndex : m_glyphToCharacterIndexes[glyphIndex];
        currentX = nextX;
        ++glyphIndex;
    }

    return rtl() ? 0 : m_numCharacters;
}

float HarfBuzzShaper::HarfBuzzRun::xPositionForOffset(unsigned offset)
{
    ASSERT(offset < m_numCharacters);
    unsigned glyphIndex = 0;
    float position = 0;
    if (rtl()) {
        while (glyphIndex < m_numGlyphs && m_glyphToCharacterIndexes[glyphIndex] > offset) {
            position += m_advances[glyphIndex];
            ++glyphIndex;
        }
        // For RTL, we need to return the right side boundary of the character.
        // Add advance of glyphs which are part of the character.
        while (glyphIndex < m_numGlyphs - 1 && m_glyphToCharacterIndexes[glyphIndex] == m_glyphToCharacterIndexes[glyphIndex + 1]) {
            position += m_advances[glyphIndex];
            ++glyphIndex;
        }
        position += m_advances[glyphIndex];
    } else {
        while (glyphIndex < m_numGlyphs && m_glyphToCharacterIndexes[glyphIndex] < offset) {
            position += m_advances[glyphIndex];
            ++glyphIndex;
        }
    }
    return position;
}

static void normalizeCharacters(const TextRun& run, unsigned length, UChar* destination, unsigned* destinationLength)
{
    unsigned position = 0;
    bool error = false;
    const UChar* source;
    String stringFor8BitRun;
    if (run.is8Bit()) {
        stringFor8BitRun = String::make16BitFrom8BitSource(run.characters8(), run.length());
        source = stringFor8BitRun.characters16();
    } else
        source = run.characters16();

    *destinationLength = 0;
    while (position < length) {
        UChar32 character;
        U16_NEXT(source, position, length, character);
        // Don't normalize tabs as they are not treated as spaces for word-end.
        if (Character::treatAsSpace(character) && character != '\t')
            character = ' ';
        else if (Character::treatAsZeroWidthSpaceInComplexScript(character))
            character = zeroWidthSpace;
        U16_APPEND(destination, *destinationLength, length, character, error);
        ASSERT_UNUSED(error, !error);
    }
}

HarfBuzzShaper::HarfBuzzShaper(const Font* font, const TextRun& run, ForTextEmphasisOrNot forTextEmphasis)
    : m_font(font)
    , m_normalizedBufferLength(0)
    , m_run(run)
    , m_wordSpacingAdjustment(font->fontDescription().wordSpacing())
    , m_padding(0)
    , m_padPerWordBreak(0)
    , m_padError(0)
    , m_letterSpacing(font->fontDescription().letterSpacing())
    , m_fromIndex(0)
    , m_toIndex(m_run.length())
    , m_forTextEmphasis(forTextEmphasis)
    , m_glyphBoundingBox(std::numeric_limits<float>::max(), std::numeric_limits<float>::min(), std::numeric_limits<float>::min(), std::numeric_limits<float>::max())
{
    m_normalizedBuffer = adoptArrayPtr(new UChar[m_run.length() + 1]);
    normalizeCharacters(m_run, m_run.length(), m_normalizedBuffer.get(), &m_normalizedBufferLength);
    setPadding(m_run.expansion());
    setFontFeatures();
}

bool HarfBuzzShaper::isWordEnd(unsigned index)
{
    // This could refer a high-surrogate, but should work.
    return index && isCodepointSpace(m_normalizedBuffer[index]);
}

int HarfBuzzShaper::determineWordBreakSpacing()
{
    int wordBreakSpacing = m_wordSpacingAdjustment;

    if (m_padding > 0) {
        int toPad = roundf(m_padPerWordBreak + m_padError);
        m_padError += m_padPerWordBreak - toPad;

        if (m_padding < toPad)
            toPad = m_padding;
        m_padding -= toPad;
        wordBreakSpacing += toPad;
    }
    return wordBreakSpacing;
}

// setPadding sets a number of pixels to be distributed across the TextRun.
// WebKit uses this to justify text.
void HarfBuzzShaper::setPadding(int padding)
{
    m_padding = padding;
    m_padError = 0;
    if (!m_padding)
        return;

    // If we have padding to distribute, then we try to give an equal
    // amount to each space. The last space gets the smaller amount, if
    // any.
    unsigned numWordEnds = 0;

    for (unsigned i = 0; i < m_normalizedBufferLength; i++) {
        if (isWordEnd(i))
            numWordEnds++;
    }

    if (numWordEnds)
        m_padPerWordBreak = m_padding / numWordEnds;
    else
        m_padPerWordBreak = 0;
}


void HarfBuzzShaper::setDrawRange(int from, int to)
{
    ASSERT_WITH_SECURITY_IMPLICATION(from >= 0);
    ASSERT_WITH_SECURITY_IMPLICATION(to <= m_run.length());
    m_fromIndex = from;
    m_toIndex = to;
}

void HarfBuzzShaper::setFontFeatures()
{
    const FontDescription& description = m_font->fontDescription();
    if (description.orientation() == Vertical) {
        static hb_feature_t vert = { HarfBuzzFace::vertTag, 1, 0, static_cast<unsigned>(-1) };
        static hb_feature_t vrt2 = { HarfBuzzFace::vrt2Tag, 1, 0, static_cast<unsigned>(-1) };
        m_features.append(vert);
        m_features.append(vrt2);
    }

    static hb_feature_t noKern = { HB_TAG('k', 'e', 'r', 'n'), 0, 0, static_cast<unsigned>(-1) };
    static hb_feature_t noVkrn = { HB_TAG('v', 'k', 'r', 'n'), 0, 0, static_cast<unsigned>(-1) };
    switch (description.kerning()) {
    case FontDescription::NormalKerning:
        // kern/vkrn are enabled by default
        break;
    case FontDescription::NoneKerning:
        m_features.append(description.orientation() == Vertical ? noVkrn : noKern);
        break;
    case FontDescription::AutoKerning:
        break;
    }

    static hb_feature_t noClig = { HB_TAG('c', 'l', 'i', 'g'), 0, 0, static_cast<unsigned>(-1) };
    static hb_feature_t noLiga = { HB_TAG('l', 'i', 'g', 'a'), 0, 0, static_cast<unsigned>(-1) };
    switch (description.commonLigaturesState()) {
    case FontDescription::DisabledLigaturesState:
        m_features.append(noLiga);
        m_features.append(noClig);
        break;
    case FontDescription::EnabledLigaturesState:
        // liga and clig are on by default
        break;
    case FontDescription::NormalLigaturesState:
        break;
    }
    static hb_feature_t dlig = { HB_TAG('d', 'l', 'i', 'g'), 1, 0, static_cast<unsigned>(-1) };
    switch (description.discretionaryLigaturesState()) {
    case FontDescription::DisabledLigaturesState:
        // dlig is off by default
        break;
    case FontDescription::EnabledLigaturesState:
        m_features.append(dlig);
        break;
    case FontDescription::NormalLigaturesState:
        break;
    }
    static hb_feature_t hlig = { HB_TAG('h', 'l', 'i', 'g'), 1, 0, static_cast<unsigned>(-1) };
    switch (description.historicalLigaturesState()) {
    case FontDescription::DisabledLigaturesState:
        // hlig is off by default
        break;
    case FontDescription::EnabledLigaturesState:
        m_features.append(hlig);
        break;
    case FontDescription::NormalLigaturesState:
        break;
    }
    static hb_feature_t noCalt = { HB_TAG('c', 'a', 'l', 't'), 0, 0, static_cast<unsigned>(-1) };
    switch (description.contextualLigaturesState()) {
    case FontDescription::DisabledLigaturesState:
        m_features.append(noCalt);
        break;
    case FontDescription::EnabledLigaturesState:
        // calt is on by default
        break;
    case FontDescription::NormalLigaturesState:
        break;
    }

    FontFeatureSettings* settings = description.featureSettings();
    if (!settings)
        return;

    unsigned numFeatures = settings->size();
    for (unsigned i = 0; i < numFeatures; ++i) {
        hb_feature_t feature;
        const AtomicString& tag = settings->at(i).tag();
        feature.tag = HB_TAG(tag[0], tag[1], tag[2], tag[3]);
        feature.value = settings->at(i).value();
        feature.start = 0;
        feature.end = static_cast<unsigned>(-1);
        m_features.append(feature);
    }
}

bool HarfBuzzShaper::shape(GlyphBuffer* glyphBuffer)
{
    if (!createHarfBuzzRuns())
        return false;

    m_totalWidth = 0;
    if (!shapeHarfBuzzRuns())
        return false;

    if (!RuntimeEnabledFeatures::subpixelFontScalingEnabled())
        m_totalWidth = roundf(m_totalWidth);

    if (m_harfBuzzRuns.last()->hasGlyphToCharacterIndexes()
        && glyphBuffer && !fillGlyphBuffer(glyphBuffer))
        return false;

    return true;
}

FloatPoint HarfBuzzShaper::adjustStartPoint(const FloatPoint& point)
{
    return point + m_startOffset;
}

static inline int handleMultipleUChar(
    UChar32 character,
    unsigned clusterLength,
    const SimpleFontData* currentFontData,
    const UChar* currentCharacterPosition,
    const UChar* markCharactersEnd,
    const UChar* normalizedBufferEnd)
{
    if (U_GET_GC_MASK(character) & U_GC_M_MASK) {
        int markLength = clusterLength;
        while (markCharactersEnd < normalizedBufferEnd) {
            UChar32 nextCharacter;
            int nextCharacterLength = 0;
            U16_NEXT(markCharactersEnd, nextCharacterLength, normalizedBufferEnd - markCharactersEnd, nextCharacter);
            if (!(U_GET_GC_MASK(nextCharacter) & U_GC_M_MASK))
                break;
            markLength += nextCharacterLength;
            markCharactersEnd += nextCharacterLength;
        }

        if (currentFontData->canRenderCombiningCharacterSequence(currentCharacterPosition, markCharactersEnd - currentCharacterPosition)) {
            return markLength;
        }
    }
    return 0;
}

struct CandidateRun {
    UChar32 character;
    unsigned start;
    unsigned end;
    const SimpleFontData* fontData;
    UScriptCode script;
};

static inline bool collectCandidateRuns(const UChar* normalizedBuffer,
    size_t bufferLength, const Font* font, Vector<CandidateRun>* runs)
{
    const UChar* normalizedBufferEnd = normalizedBuffer + bufferLength;
    SurrogatePairAwareTextIterator iterator(normalizedBuffer, 0, bufferLength, bufferLength);
    UChar32 character;
    unsigned clusterLength = 0;
    unsigned startIndexOfCurrentRun = 0;
    if (!iterator.consume(character, clusterLength))
        return false;

    const SimpleFontData* nextFontData = font->glyphDataForCharacter(character, false).fontData;
    UErrorCode errorCode = U_ZERO_ERROR;
    UScriptCode nextScript = uscript_getScript(character, &errorCode);
    if (U_FAILURE(errorCode))
        return false;

    do {
        const UChar* currentCharacterPosition = iterator.characters();
        const SimpleFontData* currentFontData = nextFontData;
        UScriptCode currentScript = nextScript;

        UChar32 lastCharacter = character;
        for (iterator.advance(clusterLength); iterator.consume(character, clusterLength); iterator.advance(clusterLength)) {
            if (Character::treatAsZeroWidthSpace(character))
                continue;

            int length = handleMultipleUChar(character, clusterLength, currentFontData, currentCharacterPosition, iterator.characters() + clusterLength, normalizedBufferEnd);
            if (length) {
                clusterLength = length;
                continue;
            }

            nextFontData = font->glyphDataForCharacter(character, false).fontData;
            nextScript = uscript_getScript(character, &errorCode);
            if (U_FAILURE(errorCode))
                return false;
            if (lastCharacter == zeroWidthJoiner)
                currentFontData = nextFontData;
            if ((nextFontData != currentFontData) || ((currentScript != nextScript) && (nextScript != USCRIPT_INHERITED) && (!uscript_hasScript(character, currentScript))))
                break;
            currentCharacterPosition = iterator.characters();
            lastCharacter = character;
        }

        CandidateRun run = { character, startIndexOfCurrentRun, iterator.currentCharacter(), currentFontData, currentScript };
        runs->append(run);

        startIndexOfCurrentRun = iterator.currentCharacter();
    } while (iterator.consume(character, clusterLength));

    return true;
}

static inline bool matchesAdjacentRun(UScriptCode* scriptExtensions, int length,
    CandidateRun& adjacentRun)
{
    for (int i = 0; i < length; i++) {
        if (scriptExtensions[i] == adjacentRun.script)
            return true;
    }
    return false;
}

static inline void resolveRunBasedOnScriptExtensions(Vector<CandidateRun>& runs,
    CandidateRun& run, size_t i, size_t length, UScriptCode* scriptExtensions,
    int extensionsLength, size_t& nextResolvedRun)
{
    // If uscript_getScriptExtensions returns 1 it only contains the script value,
    // we only care about ScriptExtensions which is indicated by a value >= 2.
    if (extensionsLength <= 1)
        return;

    if (i > 0 && matchesAdjacentRun(scriptExtensions, extensionsLength, runs[i - 1])) {
        run.script = runs[i - 1].script;
        return;
    }

    for (size_t j = i + 1; j < length; j++) {
        if (runs[j].script != USCRIPT_COMMON
            && runs[j].script != USCRIPT_INHERITED
            && matchesAdjacentRun(scriptExtensions, extensionsLength, runs[j])) {
            nextResolvedRun = j;
            break;
        }
    }
}

static inline void resolveRunBasedOnScriptValue(Vector<CandidateRun>& runs,
    CandidateRun& run, size_t i, size_t length, size_t& nextResolvedRun)
{
    if (run.script != USCRIPT_COMMON)
        return;

    if (i > 0 && runs[i - 1].script != USCRIPT_COMMON) {
        run.script = runs[i - 1].script;
        return;
    }

    for (size_t j = i + 1; j < length; j++) {
        if (runs[j].script != USCRIPT_COMMON
            && runs[j].script != USCRIPT_INHERITED) {
            nextResolvedRun = j;
            break;
        }
    }
}

static inline bool resolveCandidateRuns(Vector<CandidateRun>& runs)
{
    UScriptCode scriptExtensions[8];
    UErrorCode errorCode = U_ZERO_ERROR;
    size_t length = runs.size();
    size_t nextResolvedRun = 0;
    for (size_t i = 0; i < length; i++) {
        CandidateRun& run = runs[i];
        nextResolvedRun = 0;

        if (run.script == USCRIPT_INHERITED)
            run.script = i > 0 ? runs[i - 1].script : USCRIPT_COMMON;

        int extensionsLength = uscript_getScriptExtensions(run.character,
            scriptExtensions, sizeof(scriptExtensions), &errorCode);
        if (U_FAILURE(errorCode))
            return false;

        resolveRunBasedOnScriptExtensions(runs, run, i, length,
            scriptExtensions, extensionsLength, nextResolvedRun);
        resolveRunBasedOnScriptValue(runs, run, i, length,
            nextResolvedRun);
        for (size_t j = i; j < nextResolvedRun; j++)
            runs[j].script = runs[nextResolvedRun].script;

        i = std::max(i, nextResolvedRun);
    }
    return true;
}

bool HarfBuzzShaper::createHarfBuzzRuns()
{
    Vector<CandidateRun> candidateRuns;
    if (!collectCandidateRuns(m_normalizedBuffer.get(),
        m_normalizedBufferLength, m_font, &candidateRuns))
        return false;

    if (!resolveCandidateRuns(candidateRuns))
        return false;

    size_t length = candidateRuns.size();
    for (size_t i = 0; i < length; ) {
        CandidateRun& run = candidateRuns[i];
        CandidateRun lastMatchingRun = run;
        for (i++; i < length; i++) {
            if (candidateRuns[i].script != run.script
                || candidateRuns[i].fontData != run.fontData)
                break;
            lastMatchingRun = candidateRuns[i];
        }
        addHarfBuzzRun(run.start, lastMatchingRun.end, run.fontData, run.script);
    }
    return !m_harfBuzzRuns.isEmpty();
}

// A port of hb_icu_script_to_script because harfbuzz on CrOS is built
// without hb-icu. See http://crbug.com/356929
static inline hb_script_t ICUScriptToHBScript(UScriptCode script)
{
    if (UNLIKELY(script == USCRIPT_INVALID_CODE))
        return HB_SCRIPT_INVALID;

    return hb_script_from_string(uscript_getShortName(script), -1);
}


void HarfBuzzShaper::addHarfBuzzRun(unsigned startCharacter,
    unsigned endCharacter, const SimpleFontData* fontData,
    UScriptCode script)
{
    ASSERT(endCharacter > startCharacter);
    ASSERT(script != USCRIPT_INVALID_CODE);
    return m_harfBuzzRuns.append(HarfBuzzRun::create(fontData,
        startCharacter, endCharacter - startCharacter,
        m_run.direction(), ICUScriptToHBScript(script)));
}

static const uint16_t* toUint16(const UChar* src)
{
    // FIXME: This relies on undefined behavior however it works on the
    // current versions of all compilers we care about and avoids making
    // a copy of the string.
    COMPILE_ASSERT(sizeof(UChar) == sizeof(uint16_t), UChar_is_the_same_size_as_uint16_t);
    return reinterpret_cast<const uint16_t*>(src);
}

bool HarfBuzzShaper::shapeHarfBuzzRuns()
{
    HarfBuzzScopedPtr<hb_buffer_t> harfBuzzBuffer(hb_buffer_create(), hb_buffer_destroy);

    HarfBuzzRunCache& runCache = harfBuzzRunCache();
    const FontDescription& fontDescription = m_font->fontDescription();
    const String& localeString = fontDescription.locale();
    CString locale = localeString.latin1();

    for (unsigned i = 0; i < m_harfBuzzRuns.size(); ++i) {
        unsigned runIndex = m_run.rtl() ? m_harfBuzzRuns.size() - i - 1 : i;
        HarfBuzzRun* currentRun = m_harfBuzzRuns[runIndex].get();
        const SimpleFontData* currentFontData = currentRun->fontData();
        if (currentFontData->isSVGFont())
            return false;

        FontPlatformData* platformData = const_cast<FontPlatformData*>(&currentFontData->platformData());
        HarfBuzzFace* face = platformData->harfBuzzFace();
        if (!face)
            return false;

        hb_buffer_set_language(harfBuzzBuffer.get(), hb_language_from_string(locale.data(), locale.length()));
        hb_buffer_set_script(harfBuzzBuffer.get(), currentRun->script());
        hb_buffer_set_direction(harfBuzzBuffer.get(), currentRun->rtl() ? HB_DIRECTION_RTL : HB_DIRECTION_LTR);

        hb_segment_properties_t props;
        hb_buffer_get_segment_properties(harfBuzzBuffer.get(), &props);

        const UChar* src = m_normalizedBuffer.get() + currentRun->startIndex();
        std::wstring key(src, src + currentRun->numCharacters());

        CachedShapingResults* cachedResults = runCache.find(key);
        if (cachedResults) {
            if (cachedResults->dir == props.direction && cachedResults->font == *m_font && cachedResults->locale == localeString) {
                currentRun->applyShapeResult(cachedResults->buffer);
                setGlyphPositionsForHarfBuzzRun(currentRun, cachedResults->buffer);

                hb_buffer_clear_contents(harfBuzzBuffer.get());

                runCache.moveToBack(cachedResults);

                continue;
            }

            runCache.remove(cachedResults);
        }

        // Add a space as pre-context to the buffer. This prevents showing dotted-circle
        // for combining marks at the beginning of runs.
        static const uint16_t preContext = ' ';
        hb_buffer_add_utf16(harfBuzzBuffer.get(), &preContext, 1, 1, 0);

        if (fontDescription.variant() == FontVariantSmallCaps && u_islower(m_normalizedBuffer[currentRun->startIndex()])) {
            String upperText = String(m_normalizedBuffer.get() + currentRun->startIndex(), currentRun->numCharacters()).upper();
            ASSERT(!upperText.is8Bit()); // m_normalizedBuffer is 16 bit, therefore upperText is 16 bit, even after we call makeUpper().
            hb_buffer_add_utf16(harfBuzzBuffer.get(), toUint16(upperText.characters16()), currentRun->numCharacters(), 0, currentRun->numCharacters());
        } else {
            hb_buffer_add_utf16(harfBuzzBuffer.get(), toUint16(m_normalizedBuffer.get() + currentRun->startIndex()), currentRun->numCharacters(), 0, currentRun->numCharacters());
        }

        if (fontDescription.orientation() == Vertical)
            face->setScriptForVerticalGlyphSubstitution(harfBuzzBuffer.get());

        HarfBuzzScopedPtr<hb_font_t> harfBuzzFont(face->createFont(), hb_font_destroy);

        hb_shape(harfBuzzFont.get(), harfBuzzBuffer.get(), m_features.isEmpty() ? 0 : m_features.data(), m_features.size());
        currentRun->applyShapeResult(harfBuzzBuffer.get());
        setGlyphPositionsForHarfBuzzRun(currentRun, harfBuzzBuffer.get());

        runCache.insert(key, new CachedShapingResults(harfBuzzBuffer.get(), m_font, props.direction, localeString));

        harfBuzzBuffer.set(hb_buffer_create());
    }

    return true;
}

void HarfBuzzShaper::setGlyphPositionsForHarfBuzzRun(HarfBuzzRun* currentRun, hb_buffer_t* harfBuzzBuffer)
{
    const SimpleFontData* currentFontData = currentRun->fontData();
    hb_glyph_info_t* glyphInfos = hb_buffer_get_glyph_infos(harfBuzzBuffer, 0);
    hb_glyph_position_t* glyphPositions = hb_buffer_get_glyph_positions(harfBuzzBuffer, 0);

    if (!currentRun->hasGlyphToCharacterIndexes()) {
        // FIXME: https://crbug.com/337886
        ASSERT_NOT_REACHED();
        return;
    }

    unsigned numGlyphs = currentRun->numGlyphs();
    uint16_t* glyphToCharacterIndexes = currentRun->glyphToCharacterIndexes();
    float totalAdvance = 0;
    FloatPoint glyphOrigin;

    // HarfBuzz returns the shaping result in visual order. We need not to flip for RTL.
    for (size_t i = 0; i < numGlyphs; ++i) {
        bool runEnd = i + 1 == numGlyphs;
        uint16_t glyph = glyphInfos[i].codepoint;
        float offsetX = harfBuzzPositionToFloat(glyphPositions[i].x_offset);
        float offsetY = -harfBuzzPositionToFloat(glyphPositions[i].y_offset);
        float advance = harfBuzzPositionToFloat(glyphPositions[i].x_advance);

        unsigned currentCharacterIndex = currentRun->startIndex() + glyphInfos[i].cluster;
        bool isClusterEnd = runEnd || glyphInfos[i].cluster != glyphInfos[i + 1].cluster;
        float spacing = 0;

        glyphToCharacterIndexes[i] = glyphInfos[i].cluster;

        if (isClusterEnd && !Character::treatAsZeroWidthSpace(m_normalizedBuffer[currentCharacterIndex]))
            spacing += m_letterSpacing;

        if (isClusterEnd && isWordEnd(currentCharacterIndex))
            spacing += determineWordBreakSpacing();

        if (currentFontData->isZeroWidthSpaceGlyph(glyph)) {
            currentRun->setGlyphAndPositions(i, glyph, 0, 0, 0);
            continue;
        }

        advance += spacing;
        if (m_run.rtl()) {
            // In RTL, spacing should be added to left side of glyphs.
            offsetX += spacing;
            if (!isClusterEnd)
                offsetX += m_letterSpacing;
        }

        currentRun->setGlyphAndPositions(i, glyph, advance, offsetX, offsetY);

        FloatRect glyphBounds = currentFontData->boundsForGlyph(glyph);
        glyphBounds.move(glyphOrigin.x(), glyphOrigin.y());
        m_glyphBoundingBox.unite(glyphBounds);
        glyphOrigin += FloatSize(advance + offsetX, offsetY);

        totalAdvance += advance;
    }
    currentRun->setWidth(totalAdvance > 0.0 ? totalAdvance : 0.0);
    m_totalWidth += currentRun->width();
}

void HarfBuzzShaper::fillGlyphBufferFromHarfBuzzRun(GlyphBuffer* glyphBuffer, HarfBuzzRun* currentRun, FloatPoint& firstOffsetOfNextRun)
{
    FloatPoint* offsets = currentRun->offsets();
    uint16_t* glyphs = currentRun->glyphs();
    float* advances = currentRun->advances();
    unsigned numGlyphs = currentRun->numGlyphs();
    uint16_t* glyphToCharacterIndexes = currentRun->glyphToCharacterIndexes();
    for (unsigned i = 0; i < numGlyphs; ++i) {
        uint16_t currentCharacterIndex = currentRun->startIndex() + glyphToCharacterIndexes[i];
        FloatPoint& currentOffset = offsets[i];
        FloatPoint& nextOffset = (i == numGlyphs - 1) ? firstOffsetOfNextRun : offsets[i + 1];
        float glyphAdvanceX = advances[i] + nextOffset.x() - currentOffset.x();
        float glyphAdvanceY = nextOffset.y() - currentOffset.y();
        if (m_run.rtl()) {
            if (currentCharacterIndex >= m_toIndex)
                m_startOffset.move(glyphAdvanceX, glyphAdvanceY);
            else if (currentCharacterIndex >= m_fromIndex)
                glyphBuffer->add(glyphs[i], currentRun->fontData(), FloatSize(glyphAdvanceX, glyphAdvanceY));
        } else {
            if (currentCharacterIndex < m_fromIndex)
                m_startOffset.move(glyphAdvanceX, glyphAdvanceY);
            else if (currentCharacterIndex < m_toIndex)
                glyphBuffer->add(glyphs[i], currentRun->fontData(), FloatSize(glyphAdvanceX, glyphAdvanceY));
        }
    }
}

void HarfBuzzShaper::fillGlyphBufferForTextEmphasis(GlyphBuffer* glyphBuffer, HarfBuzzRun* currentRun)
{
    // FIXME: Instead of generating a synthetic GlyphBuffer here which is then used by the
    // drawEmphasisMarks method of FontFastPath, we should roll our own emphasis mark drawing function.

    float* advances = currentRun->advances();
    unsigned numGlyphs = currentRun->numGlyphs();
    uint16_t* glyphToCharacterIndexes = currentRun->glyphToCharacterIndexes();
    unsigned graphemesInCluster = 1;
    float clusterAdvance = 0;
    uint16_t clusterStart;

    // A "cluster" in this context means a cluster as it is used by HarfBuzz:
    // The minimal group of characters and corresponding glyphs, that cannot be broken
    // down further from a text shaping point of view.
    // A cluster can contain multiple glyphs and grapheme clusters, with mutually
    // overlapping boundaries. Below we count grapheme clusters per HarfBuzz clusters,
    // then linearly split the sum of corresponding glyph advances by the number of
    // grapheme clusters in order to find positions for emphasis mark drawing.

    if (m_run.rtl())
        clusterStart = currentRun->startIndex() + currentRun->numCharacters();
    else
        clusterStart = currentRun->startIndex() + glyphToCharacterIndexes[0];

    for (unsigned i = 0; i < numGlyphs; ++i) {
        uint16_t currentCharacterIndex = currentRun->startIndex() + glyphToCharacterIndexes[i];
        bool isRunEnd = (i + 1 == numGlyphs);
        bool isClusterEnd =  isRunEnd || (currentRun->startIndex() + glyphToCharacterIndexes[i + 1] != currentCharacterIndex);
        clusterAdvance += advances[i];

        if (isClusterEnd) {
            uint16_t clusterEnd;
            if (m_run.rtl())
                clusterEnd = currentCharacterIndex;
            else
                clusterEnd = isRunEnd ? currentRun->startIndex() + currentRun->numCharacters() : currentRun->startIndex() + glyphToCharacterIndexes[i + 1];

            graphemesInCluster = countGraphemesInCluster(m_normalizedBuffer.get(), m_normalizedBufferLength, clusterStart, clusterEnd);
            if (!graphemesInCluster || !clusterAdvance)
                continue;

            float glyphAdvanceX = clusterAdvance / graphemesInCluster;
            for (unsigned j = 0; j < graphemesInCluster; ++j) {
                // Do not put emphasis marks on space, separator, and control characters.
                Glyph glyphToAdd = Character::canReceiveTextEmphasis(m_run[currentCharacterIndex]) ? 1 : 0;
                glyphBuffer->add(glyphToAdd, currentRun->fontData(), glyphAdvanceX);
            }
            clusterStart = clusterEnd;
            clusterAdvance = 0;
        }
    }
}

bool HarfBuzzShaper::fillGlyphBuffer(GlyphBuffer* glyphBuffer)
{
    unsigned numRuns = m_harfBuzzRuns.size();
    if (m_run.rtl()) {
        m_startOffset = m_harfBuzzRuns.last()->offsets()[0];
        for (int runIndex = numRuns - 1; runIndex >= 0; --runIndex) {
            HarfBuzzRun* currentRun = m_harfBuzzRuns[runIndex].get();
            if (!currentRun->hasGlyphToCharacterIndexes()) {
                // FIXME: bug 337886, 359664
                continue;
            }
            FloatPoint firstOffsetOfNextRun = !runIndex ? FloatPoint() : m_harfBuzzRuns[runIndex - 1]->offsets()[0];
            if (m_forTextEmphasis == ForTextEmphasis)
                fillGlyphBufferForTextEmphasis(glyphBuffer, currentRun);
            else
                fillGlyphBufferFromHarfBuzzRun(glyphBuffer, currentRun, firstOffsetOfNextRun);
        }
    } else {
        m_startOffset = m_harfBuzzRuns.first()->offsets()[0];
        for (unsigned runIndex = 0; runIndex < numRuns; ++runIndex) {
            HarfBuzzRun* currentRun = m_harfBuzzRuns[runIndex].get();
            if (!currentRun->hasGlyphToCharacterIndexes()) {
                // FIXME: bug 337886, 359664
                continue;
            }
            FloatPoint firstOffsetOfNextRun = runIndex == numRuns - 1 ? FloatPoint() : m_harfBuzzRuns[runIndex + 1]->offsets()[0];
            if (m_forTextEmphasis == ForTextEmphasis)
                fillGlyphBufferForTextEmphasis(glyphBuffer, currentRun);
            else
                fillGlyphBufferFromHarfBuzzRun(glyphBuffer, currentRun, firstOffsetOfNextRun);
        }
    }
    return glyphBuffer->size();
}

int HarfBuzzShaper::offsetForPosition(float targetX)
{
    int charactersSoFar = 0;
    float currentX = 0;

    if (m_run.rtl()) {
        charactersSoFar = m_normalizedBufferLength;
        for (int i = m_harfBuzzRuns.size() - 1; i >= 0; --i) {
            charactersSoFar -= m_harfBuzzRuns[i]->numCharacters();
            float nextX = currentX + m_harfBuzzRuns[i]->width();
            float offsetForRun = targetX - currentX;
            if (offsetForRun >= 0 && offsetForRun <= m_harfBuzzRuns[i]->width()) {
                // The x value in question is within this script run.
                const unsigned index = m_harfBuzzRuns[i]->characterIndexForXPosition(offsetForRun);
                return charactersSoFar + index;
            }
            currentX = nextX;
        }
    } else {
        for (unsigned i = 0; i < m_harfBuzzRuns.size(); ++i) {
            float nextX = currentX + m_harfBuzzRuns[i]->width();
            float offsetForRun = targetX - currentX;
            if (offsetForRun >= 0 && offsetForRun <= m_harfBuzzRuns[i]->width()) {
                const unsigned index = m_harfBuzzRuns[i]->characterIndexForXPosition(offsetForRun);
                return charactersSoFar + index;
            }
            charactersSoFar += m_harfBuzzRuns[i]->numCharacters();
            currentX = nextX;
        }
    }

    return charactersSoFar;
}

FloatRect HarfBuzzShaper::selectionRect(const FloatPoint& point, int height, int from, int to)
{
    float currentX = 0;
    float fromX = 0;
    float toX = 0;
    bool foundFromX = false;
    bool foundToX = false;

    if (m_run.rtl())
        currentX = m_totalWidth;
    for (unsigned i = 0; i < m_harfBuzzRuns.size(); ++i) {
        if (m_run.rtl())
            currentX -= m_harfBuzzRuns[i]->width();
        int numCharacters = m_harfBuzzRuns[i]->numCharacters();
        if (!foundFromX && from >= 0 && from < numCharacters) {
            fromX = m_harfBuzzRuns[i]->xPositionForOffset(from) + currentX;
            foundFromX = true;
        } else
            from -= numCharacters;

        if (!foundToX && to >= 0 && to < numCharacters) {
            toX = m_harfBuzzRuns[i]->xPositionForOffset(to) + currentX;
            foundToX = true;
        } else
            to -= numCharacters;

        if (foundFromX && foundToX)
            break;
        if (!m_run.rtl())
            currentX += m_harfBuzzRuns[i]->width();
    }

    // The position in question might be just after the text.
    if (!foundFromX)
        fromX = 0;
    if (!foundToX)
        toX = m_run.rtl() ? 0 : m_totalWidth;

    if (fromX < toX) {
        return Font::pixelSnappedSelectionRect(
            point.x() + fromX, point.x() + toX,
            point.y(), height);
    }

    return Font::pixelSnappedSelectionRect(
        point.x() + toX, point.x() + fromX,
        point.y(), height);
}

} // namespace WebCore