/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "TextLayoutCache"

#include "TextLayoutCache.h"
#include "TextLayout.h"
#include "SkFontHost.h"
#include "SkTypeface_android.h"
#include <unicode/unistr.h>
#include <unicode/normlzr.h>
#include <unicode/uchar.h>

extern "C" {
  #include "harfbuzz-unicode.h"
}

namespace android {

//--------------------------------------------------------------------------------------------------

ANDROID_SINGLETON_STATIC_INSTANCE(TextLayoutEngine);

//--------------------------------------------------------------------------------------------------

TextLayoutCache::TextLayoutCache(TextLayoutShaper* shaper) :
        mShaper(shaper),
        mCache(GenerationCache<TextLayoutCacheKey, sp<TextLayoutValue> >::kUnlimitedCapacity),
        mSize(0), mMaxSize(MB(DEFAULT_TEXT_LAYOUT_CACHE_SIZE_IN_MB)),
        mCacheHitCount(0), mNanosecondsSaved(0) {
    init();
}

TextLayoutCache::~TextLayoutCache() {
    mCache.clear();
}

void TextLayoutCache::init() {
    mCache.setOnEntryRemovedListener(this);

    mDebugLevel = readRtlDebugLevel();
    mDebugEnabled = mDebugLevel & kRtlDebugCaches;
    ALOGD("Using debug level = %d - Debug Enabled = %d", mDebugLevel, mDebugEnabled);

    mCacheStartTime = systemTime(SYSTEM_TIME_MONOTONIC);

    if (mDebugEnabled) {
        ALOGD("Initialization is done - Start time = %lld", mCacheStartTime);
    }

    mInitialized = true;
}

/**
 *  Callbacks
 */
void TextLayoutCache::operator()(TextLayoutCacheKey& text, sp<TextLayoutValue>& desc) {
    size_t totalSizeToDelete = text.getSize() + desc->getSize();
    mSize -= totalSizeToDelete;
    if (mDebugEnabled) {
        ALOGD("Cache value %p deleted, size = %d", desc.get(), totalSizeToDelete);
    }
}

/*
 * Cache clearing
 */
void TextLayoutCache::purgeCaches() {
    AutoMutex _l(mLock);
    mCache.clear();
    mShaper->purgeCaches();
}

/*
 * Caching
 */
sp<TextLayoutValue> TextLayoutCache::getValue(const SkPaint* paint,
            const jchar* text, jint start, jint count, jint contextCount, jint dirFlags) {
    AutoMutex _l(mLock);
    nsecs_t startTime = 0;
    if (mDebugEnabled) {
        startTime = systemTime(SYSTEM_TIME_MONOTONIC);
    }

    // Create the key
    TextLayoutCacheKey key(paint, text, start, count, contextCount, dirFlags);

    // Get value from cache if possible
    sp<TextLayoutValue> value = mCache.get(key);

    // Value not found for the key, we need to add a new value in the cache
    if (value == NULL) {
        if (mDebugEnabled) {
            startTime = systemTime(SYSTEM_TIME_MONOTONIC);
        }

        value = new TextLayoutValue(contextCount);

        // Compute advances and store them
        mShaper->computeValues(value.get(), paint,
                reinterpret_cast<const UChar*>(key.getText()), start, count,
                size_t(contextCount), int(dirFlags));

        if (mDebugEnabled) {
            value->setElapsedTime(systemTime(SYSTEM_TIME_MONOTONIC) - startTime);
        }

        // Don't bother to add in the cache if the entry is too big
        size_t size = key.getSize() + value->getSize();
        if (size <= mMaxSize) {
            // Cleanup to make some room if needed
            if (mSize + size > mMaxSize) {
                if (mDebugEnabled) {
                    ALOGD("Need to clean some entries for making some room for a new entry");
                }
                while (mSize + size > mMaxSize) {
                    // This will call the callback
                    bool removedOne = mCache.removeOldest();
                    LOG_ALWAYS_FATAL_IF(!removedOne, "The cache is non-empty but we "
                            "failed to remove the oldest entry.  "
                            "mSize = %u, size = %u, mMaxSize = %u, mCache.size() = %u",
                            mSize, size, mMaxSize, mCache.size());
                }
            }

            // Update current cache size
            mSize += size;

            bool putOne = mCache.put(key, value);
            LOG_ALWAYS_FATAL_IF(!putOne, "Failed to put an entry into the cache.  "
                    "This indicates that the cache already has an entry with the "
                    "same key but it should not since we checked earlier!"
                    " - start = %d, count = %d, contextCount = %d - Text = '%s'",
                    start, count, contextCount, String8(key.getText() + start, count).string());

            if (mDebugEnabled) {
                nsecs_t totalTime = systemTime(SYSTEM_TIME_MONOTONIC) - startTime;
                ALOGD("CACHE MISS: Added entry %p "
                        "with start = %d, count = %d, contextCount = %d, "
                        "entry size %d bytes, remaining space %d bytes"
                        " - Compute time %0.6f ms - Put time %0.6f ms - Text = '%s'",
                        value.get(), start, count, contextCount, size, mMaxSize - mSize,
                        value->getElapsedTime() * 0.000001f,
                        (totalTime - value->getElapsedTime()) * 0.000001f,
                        String8(key.getText() + start, count).string());
            }
        } else {
            if (mDebugEnabled) {
                ALOGD("CACHE MISS: Calculated but not storing entry because it is too big "
                        "with start = %d, count = %d, contextCount = %d, "
                        "entry size %d bytes, remaining space %d bytes"
                        " - Compute time %0.6f ms - Text = '%s'",
                        start, count, contextCount, size, mMaxSize - mSize,
                        value->getElapsedTime() * 0.000001f,
                        String8(key.getText() + start, count).string());
            }
        }
    } else {
        // This is a cache hit, just log timestamp and user infos
        if (mDebugEnabled) {
            nsecs_t elapsedTimeThruCacheGet = systemTime(SYSTEM_TIME_MONOTONIC) - startTime;
            mNanosecondsSaved += (value->getElapsedTime() - elapsedTimeThruCacheGet);
            ++mCacheHitCount;

            if (value->getElapsedTime() > 0) {
                float deltaPercent = 100 * ((value->getElapsedTime() - elapsedTimeThruCacheGet)
                        / ((float)value->getElapsedTime()));
                ALOGD("CACHE HIT #%d with start = %d, count = %d, contextCount = %d"
                        "- Compute time %0.6f ms - "
                        "Cache get time %0.6f ms - Gain in percent: %2.2f - Text = '%s'",
                        mCacheHitCount, start, count, contextCount,
                        value->getElapsedTime() * 0.000001f,
                        elapsedTimeThruCacheGet * 0.000001f,
                        deltaPercent,
                        String8(key.getText() + start, count).string());
            }
            if (mCacheHitCount % DEFAULT_DUMP_STATS_CACHE_HIT_INTERVAL == 0) {
                dumpCacheStats();
            }
        }
    }
    return value;
}

void TextLayoutCache::dumpCacheStats() {
    float remainingPercent = 100 * ((mMaxSize - mSize) / ((float)mMaxSize));
    float timeRunningInSec = (systemTime(SYSTEM_TIME_MONOTONIC) - mCacheStartTime) / 1000000000;

    size_t bytes = 0;
    size_t cacheSize = mCache.size();
    for (size_t i = 0; i < cacheSize; i++) {
        bytes += mCache.getKeyAt(i).getSize() + mCache.getValueAt(i)->getSize();
    }

    ALOGD("------------------------------------------------");
    ALOGD("Cache stats");
    ALOGD("------------------------------------------------");
    ALOGD("pid       : %d", getpid());
    ALOGD("running   : %.0f seconds", timeRunningInSec);
    ALOGD("entries   : %d", cacheSize);
    ALOGD("max size  : %d bytes", mMaxSize);
    ALOGD("used      : %d bytes according to mSize, %d bytes actual", mSize, bytes);
    ALOGD("remaining : %d bytes or %2.2f percent", mMaxSize - mSize, remainingPercent);
    ALOGD("hits      : %d", mCacheHitCount);
    ALOGD("saved     : %0.6f ms", mNanosecondsSaved * 0.000001f);
    ALOGD("------------------------------------------------");
}

/**
 * TextLayoutCacheKey
 */
TextLayoutCacheKey::TextLayoutCacheKey(): start(0), count(0), contextCount(0),
        dirFlags(0), typeface(NULL), textSize(0), textSkewX(0), textScaleX(0), flags(0),
        hinting(SkPaint::kNo_Hinting), variant(SkPaint::kDefault_Variant), language()  {
}

TextLayoutCacheKey::TextLayoutCacheKey(const SkPaint* paint, const UChar* text,
        size_t start, size_t count, size_t contextCount, int dirFlags) :
            start(start), count(count), contextCount(contextCount),
            dirFlags(dirFlags) {
    textCopy.setTo(text, contextCount);
    typeface = paint->getTypeface();
    textSize = paint->getTextSize();
    textSkewX = paint->getTextSkewX();
    textScaleX = paint->getTextScaleX();
    flags = paint->getFlags();
    hinting = paint->getHinting();
    variant = paint->getFontVariant();
    language = paint->getLanguage();
}

TextLayoutCacheKey::TextLayoutCacheKey(const TextLayoutCacheKey& other) :
        textCopy(other.textCopy),
        start(other.start),
        count(other.count),
        contextCount(other.contextCount),
        dirFlags(other.dirFlags),
        typeface(other.typeface),
        textSize(other.textSize),
        textSkewX(other.textSkewX),
        textScaleX(other.textScaleX),
        flags(other.flags),
        hinting(other.hinting),
        variant(other.variant),
        language(other.language) {
}

int TextLayoutCacheKey::compare(const TextLayoutCacheKey& lhs, const TextLayoutCacheKey& rhs) {
    int deltaInt = lhs.start - rhs.start;
    if (deltaInt != 0) return (deltaInt);

    deltaInt = lhs.count - rhs.count;
    if (deltaInt != 0) return (deltaInt);

    deltaInt = lhs.contextCount - rhs.contextCount;
    if (deltaInt != 0) return (deltaInt);

    if (lhs.typeface < rhs.typeface) return -1;
    if (lhs.typeface > rhs.typeface) return +1;

    if (lhs.textSize < rhs.textSize) return -1;
    if (lhs.textSize > rhs.textSize) return +1;

    if (lhs.textSkewX < rhs.textSkewX) return -1;
    if (lhs.textSkewX > rhs.textSkewX) return +1;

    if (lhs.textScaleX < rhs.textScaleX) return -1;
    if (lhs.textScaleX > rhs.textScaleX) return +1;

    deltaInt = lhs.flags - rhs.flags;
    if (deltaInt != 0) return (deltaInt);

    deltaInt = lhs.hinting - rhs.hinting;
    if (deltaInt != 0) return (deltaInt);

    deltaInt = lhs.dirFlags - rhs.dirFlags;
    if (deltaInt) return (deltaInt);

    deltaInt = lhs.variant - rhs.variant;
    if (deltaInt) return (deltaInt);

    if (lhs.language < rhs.language) return -1;
    if (lhs.language > rhs.language) return +1;

    return memcmp(lhs.getText(), rhs.getText(), lhs.contextCount * sizeof(UChar));
}

size_t TextLayoutCacheKey::getSize() const {
    return sizeof(TextLayoutCacheKey) + sizeof(UChar) * contextCount;
}

/**
 * TextLayoutCacheValue
 */
TextLayoutValue::TextLayoutValue(size_t contextCount) :
        mTotalAdvance(0), mElapsedTime(0) {
    // Give a hint for advances and glyphs vectors size
    mAdvances.setCapacity(contextCount);
    mGlyphs.setCapacity(contextCount);
    mPos.setCapacity(contextCount * 2);
}

size_t TextLayoutValue::getSize() const {
    return sizeof(TextLayoutValue) + sizeof(jfloat) * mAdvances.capacity() +
            sizeof(jchar) * mGlyphs.capacity() + sizeof(jfloat) * mPos.capacity();
}

void TextLayoutValue::setElapsedTime(uint32_t time) {
    mElapsedTime = time;
}

uint32_t TextLayoutValue::getElapsedTime() {
    return mElapsedTime;
}

TextLayoutShaper::TextLayoutShaper() : mShaperItemGlyphArraySize(0) {
    init();

    mFontRec.klass = &harfbuzzSkiaClass;
    mFontRec.userData = 0;

    // Note that the scaling values (x_ and y_ppem, x_ and y_scale) will be set
    // below, when the paint transform and em unit of the actual shaping font
    // are known.

    memset(&mShaperItem, 0, sizeof(mShaperItem));

    mShaperItem.font = &mFontRec;
    mShaperItem.font->userData = &mShapingPaint;
}

void TextLayoutShaper::init() {
    mDefaultTypeface = SkFontHost::CreateTypeface(NULL, NULL, NULL, 0, SkTypeface::kNormal);
}

void TextLayoutShaper::unrefTypefaces() {
    SkSafeUnref(mDefaultTypeface);
}

TextLayoutShaper::~TextLayoutShaper() {
    unrefTypefaces();
    deleteShaperItemGlyphArrays();
}

void TextLayoutShaper::computeValues(TextLayoutValue* value, const SkPaint* paint, const UChar* chars,
        size_t start, size_t count, size_t contextCount, int dirFlags) {

    computeValues(paint, chars, start, count, contextCount, dirFlags,
            &value->mAdvances, &value->mTotalAdvance, &value->mGlyphs, &value->mPos);
#if DEBUG_ADVANCES
    ALOGD("Advances - start = %d, count = %d, contextCount = %d, totalAdvance = %f", start, count,
            contextCount, value->mTotalAdvance);
#endif
}

void TextLayoutShaper::computeValues(const SkPaint* paint, const UChar* chars,
        size_t start, size_t count, size_t contextCount, int dirFlags,
        Vector<jfloat>* const outAdvances, jfloat* outTotalAdvance,
        Vector<jchar>* const outGlyphs, Vector<jfloat>* const outPos) {
        *outTotalAdvance = 0;
        if (!count) {
            return;
        }

        UBiDiLevel bidiReq = 0;
        bool forceLTR = false;
        bool forceRTL = false;

        switch (dirFlags) {
            case kBidi_LTR: bidiReq = 0; break; // no ICU constant, canonical LTR level
            case kBidi_RTL: bidiReq = 1; break; // no ICU constant, canonical RTL level
            case kBidi_Default_LTR: bidiReq = UBIDI_DEFAULT_LTR; break;
            case kBidi_Default_RTL: bidiReq = UBIDI_DEFAULT_RTL; break;
            case kBidi_Force_LTR: forceLTR = true; break; // every char is LTR
            case kBidi_Force_RTL: forceRTL = true; break; // every char is RTL
        }

        bool useSingleRun = false;
        bool isRTL = forceRTL;
        if (forceLTR || forceRTL) {
            useSingleRun = true;
        } else {
            UBiDi* bidi = ubidi_open();
            if (bidi) {
                UErrorCode status = U_ZERO_ERROR;
#if DEBUG_GLYPHS
                ALOGD("******** ComputeValues -- start");
                ALOGD("      -- string = '%s'", String8(chars + start, count).string());
                ALOGD("      -- start = %d", start);
                ALOGD("      -- count = %d", count);
                ALOGD("      -- contextCount = %d", contextCount);
                ALOGD("      -- bidiReq = %d", bidiReq);
#endif
                ubidi_setPara(bidi, chars, contextCount, bidiReq, NULL, &status);
                if (U_SUCCESS(status)) {
                    int paraDir = ubidi_getParaLevel(bidi) & kDirection_Mask; // 0 if ltr, 1 if rtl
                    ssize_t rc = ubidi_countRuns(bidi, &status);
#if DEBUG_GLYPHS
                    ALOGD("      -- dirFlags = %d", dirFlags);
                    ALOGD("      -- paraDir = %d", paraDir);
                    ALOGD("      -- run-count = %d", int(rc));
#endif
                    if (U_SUCCESS(status) && rc == 1) {
                        // Normal case: one run, status is ok
                        isRTL = (paraDir == 1);
                        useSingleRun = true;
                    } else if (!U_SUCCESS(status) || rc < 1) {
                        ALOGW("Need to force to single run -- string = '%s',"
                                " status = %d, rc = %d",
                                String8(chars + start, count).string(), status, int(rc));
                        isRTL = (paraDir == 1);
                        useSingleRun = true;
                    } else {
                        int32_t end = start + count;
                        for (size_t i = 0; i < size_t(rc); ++i) {
                            int32_t startRun = -1;
                            int32_t lengthRun = -1;
                            UBiDiDirection runDir = ubidi_getVisualRun(bidi, i, &startRun, &lengthRun);

                            if (startRun == -1 || lengthRun == -1) {
                                // Something went wrong when getting the visual run, need to clear
                                // already computed data before doing a single run pass
                                ALOGW("Visual run is not valid");
                                outGlyphs->clear();
                                outAdvances->clear();
                                outPos->clear();
                                *outTotalAdvance = 0;
                                isRTL = (paraDir == 1);
                                useSingleRun = true;
                                break;
                            }

                            if (startRun >= end) {
                                continue;
                            }
                            int32_t endRun = startRun + lengthRun;
                            if (endRun <= int32_t(start)) {
                                continue;
                            }
                            if (startRun < int32_t(start)) {
                                startRun = int32_t(start);
                            }
                            if (endRun > end) {
                                endRun = end;
                            }

                            lengthRun = endRun - startRun;
                            isRTL = (runDir == UBIDI_RTL);
#if DEBUG_GLYPHS
                            ALOGD("Processing Bidi Run = %d -- run-start = %d, run-len = %d, isRTL = %d",
                                    i, startRun, lengthRun, isRTL);
#endif
                            computeRunValues(paint, chars + startRun, lengthRun, isRTL,
                                    outAdvances, outTotalAdvance, outGlyphs, outPos);

                        }
                    }
                } else {
                    ALOGW("Cannot set Para");
                    useSingleRun = true;
                    isRTL = (bidiReq = 1) || (bidiReq = UBIDI_DEFAULT_RTL);
                }
                ubidi_close(bidi);
            } else {
                ALOGW("Cannot ubidi_open()");
                useSingleRun = true;
                isRTL = (bidiReq = 1) || (bidiReq = UBIDI_DEFAULT_RTL);
            }
        }

        // Default single run case
        if (useSingleRun){
#if DEBUG_GLYPHS
            ALOGD("Using a SINGLE BiDi Run "
                    "-- run-start = %d, run-len = %d, isRTL = %d", start, count, isRTL);
#endif
            computeRunValues(paint, chars + start, count, isRTL,
                    outAdvances, outTotalAdvance, outGlyphs, outPos);
        }

#if DEBUG_GLYPHS
        ALOGD("      -- Total returned glyphs-count = %d", outGlyphs->size());
        ALOGD("******** ComputeValues -- end");
#endif
}

static void logGlyphs(HB_ShaperItem shaperItem) {
    ALOGD("         -- glyphs count=%d", shaperItem.num_glyphs);
    for (size_t i = 0; i < shaperItem.num_glyphs; i++) {
        ALOGD("         -- glyph[%d] = %d, offset.x = %0.2f, offset.y = %0.2f", i,
                shaperItem.glyphs[i],
                HBFixedToFloat(shaperItem.offsets[i].x),
                HBFixedToFloat(shaperItem.offsets[i].y));
    }
}

void TextLayoutShaper::computeRunValues(const SkPaint* paint, const UChar* chars,
        size_t count, bool isRTL,
        Vector<jfloat>* const outAdvances, jfloat* outTotalAdvance,
        Vector<jchar>* const outGlyphs, Vector<jfloat>* const outPos) {
    if (!count) {
        // We cannot shape an empty run.
        return;
    }

    // To be filled in later
    for (size_t i = 0; i < count; i++) {
        outAdvances->add(0);
    }
    UErrorCode error = U_ZERO_ERROR;
    bool useNormalizedString = false;
    for (ssize_t i = count - 1; i >= 0; --i) {
        UChar ch1 = chars[i];
        if (::ublock_getCode(ch1) == UBLOCK_COMBINING_DIACRITICAL_MARKS) {
            // So we have found a diacritic, let's get now the main code point which is paired
            // with it. As we can have several diacritics in a row, we need to iterate back again
#if DEBUG_GLYPHS
            ALOGD("The BiDi run '%s' is containing a Diacritic at position %d",
                    String8(chars, count).string(), int(i));
#endif
            ssize_t j = i - 1;
            for (; j >= 0;  --j) {
                UChar ch2 = chars[j];
                if (::ublock_getCode(ch2) != UBLOCK_COMBINING_DIACRITICAL_MARKS) {
                    break;
                }
            }

            // We could not found the main code point, so we will just use the initial chars
            if (j < 0) {
                break;
            }

#if DEBUG_GLYPHS
            ALOGD("Found main code point at index %d", int(j));
#endif
            // We found the main code point, so we can normalize the "chunk" and fill
            // the remaining with ZWSP so that the Paint.getTextWidth() APIs will still be able
            // to get one advance per char
            mBuffer.remove();
            Normalizer::normalize(UnicodeString(chars + j, i - j + 1),
                    UNORM_NFC, 0 /* no options */, mBuffer, error);
            if (U_SUCCESS(error)) {
                if (!useNormalizedString) {
                    useNormalizedString = true;
                    mNormalizedString.setTo(false /* not terminated*/, chars, count);
                }
                // Set the normalized chars
                for (ssize_t k = j; k < j + mBuffer.length(); ++k) {
                    mNormalizedString.setCharAt(k, mBuffer.charAt(k - j));
                }
                // Fill the remain part with ZWSP (ZWNJ and ZWJ would lead to weird results
                // because some fonts are missing those glyphs)
                for (ssize_t k = j + mBuffer.length(); k <= i; ++k) {
                    mNormalizedString.setCharAt(k, UNICODE_ZWSP);
                }
            }
            i = j - 1;
        }
    }

    // Reverse "BiDi mirrored chars" in RTL mode only
    // See: http://www.unicode.org/Public/6.0.0/ucd/extracted/DerivedBinaryProperties.txt
    // This is a workaround because Harfbuzz is not able to do mirroring in all cases and
    // script-run splitting with Harfbuzz is splitting on parenthesis
    if (isRTL) {
        for (ssize_t i = 0; i < ssize_t(count); i++) {
            UChar32 ch = chars[i];
            if (!u_isMirrored(ch)) continue;
            if (!useNormalizedString) {
                useNormalizedString = true;
                mNormalizedString.setTo(false /* not terminated*/, chars, count);
            }
            UChar result =  (UChar) u_charMirror(ch);
            mNormalizedString.setCharAt(i, result);
#if DEBUG_GLYPHS
            ALOGD("Rewriting codepoint '%d' to '%d' at position %d",
                    ch, mNormalizedString[i], int(i));
#endif
        }
    }

#if DEBUG_GLYPHS
    if (useNormalizedString) {
        ALOGD("Will use normalized string '%s', length = %d",
                    String8(mNormalizedString.getTerminatedBuffer(),
                            mNormalizedString.length()).string(),
                    mNormalizedString.length());
    } else {
        ALOGD("Normalization is not needed or cannot be done, using initial string");
    }
#endif

    assert(mNormalizedString.length() == count);

    // Set the string properties
    mShaperItem.string = useNormalizedString ? mNormalizedString.getTerminatedBuffer() : chars;
    mShaperItem.stringLength = count;

    // Define shaping paint properties
    mShapingPaint.setTextSize(paint->getTextSize());
    float skewX = paint->getTextSkewX();
    mShapingPaint.setTextSkewX(skewX);
    mShapingPaint.setTextScaleX(paint->getTextScaleX());
    mShapingPaint.setFlags(paint->getFlags());
    mShapingPaint.setHinting(paint->getHinting());
    mShapingPaint.setFontVariant(paint->getFontVariant());
    mShapingPaint.setLanguage(paint->getLanguage());

    // Split the BiDi run into Script runs. Harfbuzz will populate the pos, length and script
    // into the shaperItem
    ssize_t indexFontRun = isRTL ? mShaperItem.stringLength - 1 : 0;
    unsigned numCodePoints = 0;
    jfloat totalAdvance = *outTotalAdvance;
    while ((isRTL) ?
            hb_utf16_script_run_prev(&numCodePoints, &mShaperItem.item, mShaperItem.string,
                    mShaperItem.stringLength, &indexFontRun):
            hb_utf16_script_run_next(&numCodePoints, &mShaperItem.item, mShaperItem.string,
                    mShaperItem.stringLength, &indexFontRun)) {

        ssize_t startScriptRun = mShaperItem.item.pos;
        size_t countScriptRun = mShaperItem.item.length;
        ssize_t endScriptRun = startScriptRun + countScriptRun;

#if DEBUG_GLYPHS
        ALOGD("-------- Start of Script Run --------");
        ALOGD("Shaping Script Run with");
        ALOGD("         -- isRTL = %d", isRTL);
        ALOGD("         -- HB script = %d", mShaperItem.item.script);
        ALOGD("         -- startFontRun = %d", int(startScriptRun));
        ALOGD("         -- endFontRun = %d", int(endScriptRun));
        ALOGD("         -- countFontRun = %d", countScriptRun);
        ALOGD("         -- run = '%s'", String8(chars + startScriptRun, countScriptRun).string());
        ALOGD("         -- string = '%s'", String8(chars, count).string());
#endif

        // Initialize Harfbuzz Shaper and get the base glyph count for offsetting the glyphIDs
        // and shape the Font run
        size_t glyphBaseCount = shapeFontRun(paint, isRTL);

#if DEBUG_GLYPHS
        ALOGD("Got from Harfbuzz");
        ALOGD("         -- glyphBaseCount = %d", glyphBaseCount);
        ALOGD("         -- num_glypth = %d", mShaperItem.num_glyphs);
        ALOGD("         -- kerning_applied = %d", mShaperItem.kerning_applied);
        ALOGD("         -- isDevKernText = %d", paint->isDevKernText());

        logGlyphs(mShaperItem);
#endif

        if (mShaperItem.advances == NULL || mShaperItem.num_glyphs == 0) {
#if DEBUG_GLYPHS
            ALOGD("Advances array is empty or num_glypth = 0");
#endif
            continue;
        }

#if DEBUG_GLYPHS
        ALOGD("Returned logclusters");
        for (size_t i = 0; i < mShaperItem.num_glyphs; i++) {
            ALOGD("         -- lc[%d] = %d, hb-adv[%d] = %0.2f", i, mShaperItem.log_clusters[i],
                    i, HBFixedToFloat(mShaperItem.advances[i]));
        }
#endif
        jfloat totalFontRunAdvance = 0;
        size_t clusterStart = 0;
        for (size_t i = 0; i < countScriptRun; i++) {
            size_t cluster = mShaperItem.log_clusters[i];
            size_t clusterNext = i == countScriptRun - 1 ? mShaperItem.num_glyphs :
                mShaperItem.log_clusters[i + 1];
            if (cluster != clusterNext) {
                jfloat advance = 0;
                // The advance for the cluster is the sum of the advances of all glyphs within
                // the cluster.
                for (size_t j = cluster; j < clusterNext; j++) {
                    advance += HBFixedToFloat(mShaperItem.advances[j]);
                }
                totalFontRunAdvance += advance;
                outAdvances->replaceAt(advance, startScriptRun + clusterStart);
                clusterStart = i + 1;
            }
        }

#if DEBUG_ADVANCES
        ALOGD("Returned advances");
        for (size_t i = 0; i < countScriptRun; i++) {
            ALOGD("         -- hb-adv[%d] = %0.2f, log_clusters = %d, total = %0.2f", i,
                    (*outAdvances)[i], mShaperItem.log_clusters[i], totalFontRunAdvance);
        }
#endif

        // Get Glyphs and reverse them in place if RTL
        if (outGlyphs) {
            size_t countGlyphs = mShaperItem.num_glyphs;
#if DEBUG_GLYPHS
            ALOGD("Returned script run glyphs -- count = %d", countGlyphs);
#endif
            for (size_t i = 0; i < countGlyphs; i++) {
                jchar glyph = glyphBaseCount +
                        (jchar) mShaperItem.glyphs[(!isRTL) ? i : countGlyphs - 1 - i];
#if DEBUG_GLYPHS
                ALOGD("         -- glyph[%d] = %d", i, glyph);
#endif
                outGlyphs->add(glyph);
            }
        }

        // Get glyph positions (and reverse them in place if RTL)
        if (outPos) {
            size_t countGlyphs = mShaperItem.num_glyphs;
            jfloat x = totalAdvance;
            for (size_t i = 0; i < countGlyphs; i++) {
                size_t index = (!isRTL) ? i : countGlyphs - 1 - i;
                float xo = HBFixedToFloat(mShaperItem.offsets[index].x);
                float yo = HBFixedToFloat(mShaperItem.offsets[index].y);
                // Apply skewX component of transform to position offsets. Note
                // that scale has already been applied through x_ and y_scale
                // set in the mFontRec.
                outPos->add(x + xo + yo * skewX);
                outPos->add(yo);
#if DEBUG_GLYPHS
                ALOGD("         -- hb adv[%d] = %f, log_cluster[%d] = %d",
                        index, HBFixedToFloat(mShaperItem.advances[index]),
                        index, mShaperItem.log_clusters[index]);
#endif
                x += HBFixedToFloat(mShaperItem.advances[index]);
            }
        }

        totalAdvance += totalFontRunAdvance;
    }

    *outTotalAdvance = totalAdvance;

#if DEBUG_GLYPHS
    ALOGD("-------- End of Script Run --------");
#endif
}

/**
 * Return the first typeface in the logical change, starting with this typeface,
 * that contains the specified unichar, or NULL if none is found.
 * 
 * Note that this function does _not_ increment the reference count on the typeface, as the
 * assumption is that its lifetime is managed elsewhere - in particular, the fallback typefaces
 * for the default font live in a global cache.
 */
SkTypeface* TextLayoutShaper::typefaceForScript(const SkPaint* paint, SkTypeface* typeface,
        HB_Script script) {
    SkTypeface::Style currentStyle = SkTypeface::kNormal;
    if (typeface) {
        currentStyle = typeface->style();
    }
    typeface = SkCreateTypefaceForScript(script, currentStyle);
#if DEBUG_GLYPHS
    ALOGD("Using Harfbuzz Script %d, Style %d", script, currentStyle);
#endif
    return typeface;
}

bool TextLayoutShaper::isComplexScript(HB_Script script) {
    switch (script) {
    case HB_Script_Common:
    case HB_Script_Greek:
    case HB_Script_Cyrillic:
    case HB_Script_Hangul:
    case HB_Script_Inherited:
        return false;
    default:
        return true;
    }
}

size_t TextLayoutShaper::shapeFontRun(const SkPaint* paint, bool isRTL) {
    // Reset kerning
    mShaperItem.kerning_applied = false;

    // Update Harfbuzz Shaper
    mShaperItem.item.bidiLevel = isRTL;

    SkTypeface* typeface = paint->getTypeface();

    // Get the glyphs base count for offsetting the glyphIDs returned by Harfbuzz
    // This is needed as the Typeface used for shaping can be not the default one
    // when we are shaping any script that needs to use a fallback Font.
    // If we are a "common" script we dont need to shift
    size_t baseGlyphCount = 0;
    SkUnichar firstUnichar = 0;
    if (isComplexScript(mShaperItem.item.script)) {
        const uint16_t* text16 = (const uint16_t*) (mShaperItem.string + mShaperItem.item.pos);
        const uint16_t* text16End = text16 + mShaperItem.item.length;
        firstUnichar = SkUTF16_NextUnichar(&text16);
        while (firstUnichar == ' ' && text16 < text16End) {
            firstUnichar = SkUTF16_NextUnichar(&text16);
        }
        baseGlyphCount = paint->getBaseGlyphCount(firstUnichar);
    }

    if (baseGlyphCount != 0) {
        typeface = typefaceForScript(paint, typeface, mShaperItem.item.script);
        if (!typeface) {
            typeface = mDefaultTypeface;
            SkSafeRef(typeface);
#if DEBUG_GLYPHS
            ALOGD("Using Default Typeface");
#endif
        }
    } else {
        if (!typeface) {
            typeface = mDefaultTypeface;
#if DEBUG_GLYPHS
            ALOGD("Using Default Typeface");
#endif
        }
        SkSafeRef(typeface);
    }

    mShapingPaint.setTypeface(typeface);
    mShaperItem.face = getCachedHBFace(typeface);

    int textSize = paint->getTextSize();
    float scaleX = paint->getTextScaleX();
    mFontRec.x_ppem = floor(scaleX * textSize + 0.5);
    mFontRec.y_ppem = textSize;
    uint32_t unitsPerEm = SkFontHost::GetUnitsPerEm(typeface->uniqueID());
    // x_ and y_scale are the conversion factors from font design space
    // (unitsPerEm) to 1/64th of device pixels in 16.16 format.
    const int kDevicePixelFraction = 64;
    const int kMultiplyFor16Dot16 = 1 << 16;
    float emScale = kDevicePixelFraction * kMultiplyFor16Dot16 / (float)unitsPerEm;
    mFontRec.x_scale = emScale * scaleX * textSize;
    mFontRec.y_scale = emScale * textSize;

#if DEBUG_GLYPHS
    ALOGD("Run typeface = %p, uniqueID = %d, hb_face = %p",
            typeface, typeface->uniqueID(), mShaperItem.face);
#endif
    SkSafeUnref(typeface);

    // Shape
    assert(mShaperItem.item.length > 0); // Harfbuzz will overwrite other memory if length is 0.
    size_t size = mShaperItem.item.length * 3 / 2;
    while (!doShaping(size)) {
        // We overflowed our glyph arrays. Resize and retry.
        // HB_ShapeItem fills in shaperItem.num_glyphs with the needed size.
        size = mShaperItem.num_glyphs * 2;
    }
    return baseGlyphCount;
}

bool TextLayoutShaper::doShaping(size_t size) {
    if (size > mShaperItemGlyphArraySize) {
        deleteShaperItemGlyphArrays();
        createShaperItemGlyphArrays(size);
    }
    mShaperItem.num_glyphs = mShaperItemGlyphArraySize;
    memset(mShaperItem.offsets, 0, mShaperItem.num_glyphs * sizeof(HB_FixedPoint));
    return HB_ShapeItem(&mShaperItem);
}

void TextLayoutShaper::createShaperItemGlyphArrays(size_t size) {
#if DEBUG_GLYPHS
    ALOGD("Creating Glyph Arrays with size = %d", size);
#endif
    mShaperItemGlyphArraySize = size;

    // These arrays are all indexed by glyph.
    mShaperItem.glyphs = new HB_Glyph[size];
    mShaperItem.attributes = new HB_GlyphAttributes[size];
    mShaperItem.advances = new HB_Fixed[size];
    mShaperItem.offsets = new HB_FixedPoint[size];

    // Although the log_clusters array is indexed by character, Harfbuzz expects that
    // it is big enough to hold one element per glyph.  So we allocate log_clusters along
    // with the other glyph arrays above.
    mShaperItem.log_clusters = new unsigned short[size];
}

void TextLayoutShaper::deleteShaperItemGlyphArrays() {
    delete[] mShaperItem.glyphs;
    delete[] mShaperItem.attributes;
    delete[] mShaperItem.advances;
    delete[] mShaperItem.offsets;
    delete[] mShaperItem.log_clusters;
}

HB_Face TextLayoutShaper::getCachedHBFace(SkTypeface* typeface) {
    SkFontID fontId = typeface->uniqueID();
    ssize_t index = mCachedHBFaces.indexOfKey(fontId);
    if (index >= 0) {
        return mCachedHBFaces.valueAt(index);
    }
    HB_Face face = HB_NewFace(typeface, harfbuzzSkiaGetTable);
    if (face) {
#if DEBUG_GLYPHS
        ALOGD("Created HB_NewFace %p from paint typeface = %p", face, typeface);
#endif
        mCachedHBFaces.add(fontId, face);
    }
    return face;
}

void TextLayoutShaper::purgeCaches() {
    size_t cacheSize = mCachedHBFaces.size();
    for (size_t i = 0; i < cacheSize; i++) {
        HB_FreeFace(mCachedHBFaces.valueAt(i));
    }
    mCachedHBFaces.clear();
    unrefTypefaces();
    init();
}

TextLayoutEngine::TextLayoutEngine() {
    mShaper = new TextLayoutShaper();
#if USE_TEXT_LAYOUT_CACHE
    mTextLayoutCache = new TextLayoutCache(mShaper);
#else
    mTextLayoutCache = NULL;
#endif
}

TextLayoutEngine::~TextLayoutEngine() {
    delete mTextLayoutCache;
    delete mShaper;
}

sp<TextLayoutValue> TextLayoutEngine::getValue(const SkPaint* paint, const jchar* text,
        jint start, jint count, jint contextCount, jint dirFlags) {
    sp<TextLayoutValue> value;
#if USE_TEXT_LAYOUT_CACHE
    value = mTextLayoutCache->getValue(paint, text, start, count,
            contextCount, dirFlags);
    if (value == NULL) {
        ALOGE("Cannot get TextLayoutCache value for text = '%s'",
                String8(text + start, count).string());
    }
#else
    value = new TextLayoutValue(count);
    mShaper->computeValues(value.get(), paint,
            reinterpret_cast<const UChar*>(text), start, count, contextCount, dirFlags);
#endif
    return value;
}

void TextLayoutEngine::purgeCaches() {
#if USE_TEXT_LAYOUT_CACHE
    mTextLayoutCache->purgeCaches();
#if DEBUG_GLYPHS
    ALOGD("Purged TextLayoutEngine caches");
#endif
#endif
}


} // namespace android