libs/minikin/FontCollection.cpp - platform/frameworks/minikin - Git at Google

 /*
  * Copyright (C) 2013 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 VERBOSE_DEBUG

 #define LOG_TAG "Minikin"

 #include <algorithm>

 #include <log/log.h>
 #include "unicode/unistr.h"
 #include "unicode/unorm2.h"

 #include "FontLanguage.h"
 #include "FontLanguageListCache.h"
 #include "MinikinInternal.h"
 #include <minikin/Emoji.h>
 #include <minikin/FontCollection.h>

 using std::vector;

 namespace minikin {

 template <typename T>
 static inline T max(T a, T b) {
     return a>b ? a : b;
 }

 const uint32_t EMOJI_STYLE_VS = 0xFE0F;
 const uint32_t TEXT_STYLE_VS = 0xFE0E;

 uint32_t FontCollection::sNextId = 0;

 FontCollection::FontCollection(std::shared_ptr<FontFamily>&& typeface) : mMaxChar(0) {
     std::vector<std::shared_ptr<FontFamily>> typefaces;
     typefaces.push_back(typeface);
     init(typefaces);
 }

 FontCollection::FontCollection(const vector<std::shared_ptr<FontFamily>>& typefaces) :
     mMaxChar(0) {
     init(typefaces);
 }

 void FontCollection::init(const vector<std::shared_ptr<FontFamily>>& typefaces) {
     android::AutoMutex _l(gMinikinLock);
     mId = sNextId++;
     vector<uint32_t> lastChar;
     size_t nTypefaces = typefaces.size();
 #ifdef VERBOSE_DEBUG
     ALOGD("nTypefaces = %zd\n", nTypefaces);
 #endif
     const FontStyle defaultStyle;
     for (size_t i = 0; i < nTypefaces; i++) {
         const std::shared_ptr<FontFamily>& family = typefaces[i];
         if (family->getClosestMatch(defaultStyle).font == nullptr) {
             continue;
         }
         const SparseBitSet& coverage = family->getCoverage();
         mFamilies.push_back(family);  // emplace_back would be better
         if (family->hasVSTable()) {
             mVSFamilyVec.push_back(family);
         }
         mMaxChar = max(mMaxChar, coverage.length());
         lastChar.push_back(coverage.nextSetBit(0));

         const std::unordered_set<AxisTag>& supportedAxes = family->supportedAxes();
         mSupportedAxes.insert(supportedAxes.begin(), supportedAxes.end());
     }
     nTypefaces = mFamilies.size();
     LOG_ALWAYS_FATAL_IF(nTypefaces == 0,
         "Font collection must have at least one valid typeface");
     LOG_ALWAYS_FATAL_IF(nTypefaces > 254,
         "Font collection may only have up to 254 font families.");
     size_t nPages = (mMaxChar + kPageMask) >> kLogCharsPerPage;
     // TODO: Use variation selector map for mRanges construction.
     // A font can have a glyph for a base code point and variation selector pair but no glyph for
     // the base code point without variation selector. The family won't be listed in the range in
     // this case.
     for (size_t i = 0; i < nPages; i++) {
         Range dummy;
         mRanges.push_back(dummy);
         Range* range = &mRanges.back();
 #ifdef VERBOSE_DEBUG
         ALOGD("i=%zd: range start = %zd\n", i, offset);
 #endif
         range->start = mFamilyVec.size();
         for (size_t j = 0; j < nTypefaces; j++) {
             if (lastChar[j] < (i + 1) << kLogCharsPerPage) {
                 const std::shared_ptr<FontFamily>& family = mFamilies[j];
                 mFamilyVec.push_back(static_cast<uint8_t>(j));
                 uint32_t nextChar = family->getCoverage().nextSetBit((i + 1) << kLogCharsPerPage);
 #ifdef VERBOSE_DEBUG
                 ALOGD("nextChar = %d (j = %zd)\n", nextChar, j);
 #endif
                 lastChar[j] = nextChar;
             }
         }
         range->end = mFamilyVec.size();
     }
     // See the comment in Range for more details.
     LOG_ALWAYS_FATAL_IF(mFamilyVec.size() >= 0xFFFF,
         "Exceeded the maximum indexable cmap coverage.");
 }

 // Special scores for the font fallback.
 const uint32_t kUnsupportedFontScore = 0;
 const uint32_t kFirstFontScore = UINT32_MAX;

 // Calculates a font score.
 // The score of the font family is based on three subscores.
 //  - Coverage Score: How well the font family covers the given character or variation sequence.
 //  - Language Score: How well the font family is appropriate for the language.
 //  - Variant Score: Whether the font family matches the variant. Note that this variant is not the
 //    one in BCP47. This is our own font variant (e.g., elegant, compact).
 //
 // Then, there is a priority for these three subscores as follow:
 //   Coverage Score > Language Score > Variant Score
 // The returned score reflects this priority order.
 //
 // Note that there are two special scores.
 //  - kUnsupportedFontScore: When the font family doesn't support the variation sequence or even its
 //    base character.
 //  - kFirstFontScore: When the font is the first font family in the collection and it supports the
 //    given character or variation sequence.
 uint32_t FontCollection::calcFamilyScore(uint32_t ch, uint32_t vs, int variant, uint32_t langListId,
         const std::shared_ptr<FontFamily>& fontFamily) const {

     const uint32_t coverageScore = calcCoverageScore(ch, vs, fontFamily);
     if (coverageScore == kFirstFontScore || coverageScore == kUnsupportedFontScore) {
         // No need to calculate other scores.
         return coverageScore;
     }

     const uint32_t languageScore = calcLanguageMatchingScore(langListId, *fontFamily);
     const uint32_t variantScore = calcVariantMatchingScore(variant, *fontFamily);

     // Subscores are encoded into 31 bits representation to meet the subscore priority.
     // The highest 2 bits are for coverage score, then following 28 bits are for language score,
     // then the last 1 bit is for variant score.
     return coverageScore << 29 | languageScore << 1 | variantScore;
 }

 // Calculates a font score based on variation sequence coverage.
 // - Returns kUnsupportedFontScore if the font doesn't support the variation sequence or its base
 //   character.
 // - Returns kFirstFontScore if the font family is the first font family in the collection and it
 //   supports the given character or variation sequence.
 // - Returns 3 if the font family supports the variation sequence.
 // - Returns 2 if the vs is a color variation selector (U+FE0F) and if the font is an emoji font.
 // - Returns 2 if the vs is a text variation selector (U+FE0E) and if the font is not an emoji font.
 // - Returns 1 if the variation selector is not specified or if the font family only supports the
 //   variation sequence's base character.
 uint32_t FontCollection::calcCoverageScore(uint32_t ch, uint32_t vs,
         const std::shared_ptr<FontFamily>& fontFamily) const {
     const bool hasVSGlyph = (vs != 0) && fontFamily->hasGlyph(ch, vs);
     if (!hasVSGlyph && !fontFamily->getCoverage().get(ch)) {
         // The font doesn't support either variation sequence or even the base character.
         return kUnsupportedFontScore;
     }

     if ((vs == 0 || hasVSGlyph) && mFamilies[0] == fontFamily) {
         // If the first font family supports the given character or variation sequence, always use
         // it.
         return kFirstFontScore;
     }

     if (vs == 0) {
         return 1;
     }

     if (hasVSGlyph) {
         return 3;
     }

     if (vs == EMOJI_STYLE_VS || vs == TEXT_STYLE_VS) {
         const FontLanguages& langs = FontLanguageListCache::getById(fontFamily->langId());
         bool hasEmojiFlag = false;
         for (size_t i = 0; i < langs.size(); ++i) {
             if (langs[i].getEmojiStyle() == FontLanguage::EMSTYLE_EMOJI) {
                 hasEmojiFlag = true;
                 break;
             }
         }

         if (vs == EMOJI_STYLE_VS) {
             return hasEmojiFlag ? 2 : 1;
         } else {  // vs == TEXT_STYLE_VS
             return hasEmojiFlag ? 1 : 2;
         }
     }
     return 1;
 }

 // Calculate font scores based on the script matching, subtag matching and primary langauge matching.
 //
 // 1. If only the font's language matches or there is no matches between requested font and
 //    supported font, then the font obtains a score of 0.
 // 2. Without a match in language, considering subtag may change font's EmojiStyle over script,
 //    a match in subtag gets a score of 2 and a match in scripts gains a score of 1.
 // 3. Regarding to two elements matchings, language-and-subtag matching has a score of 4, while
 //    language-and-script obtains a socre of 3 with the same reason above.
 //
 // If two languages in the requested list have the same language score, the font matching with
 // higher priority language gets a higher score. For example, in the case the user requested
 // language list is "ja-Jpan,en-Latn". The score of for the font of "ja-Jpan" gets a higher score
 // than the font of "en-Latn".
 //
 // To achieve score calculation with priorities, the language score is determined as follows:
 //   LanguageScore = s(0) * 5^(m - 1) + s(1) * 5^(m - 2) + ... + s(m - 2) * 5 + s(m - 1)
 // Here, m is the maximum number of languages to be compared, and s(i) is the i-th language's
 // matching score. The possible values of s(i) are 0, 1, 2, 3 and 4.
 uint32_t FontCollection::calcLanguageMatchingScore(
         uint32_t userLangListId, const FontFamily& fontFamily) {
     const FontLanguages& langList = FontLanguageListCache::getById(userLangListId);
     const FontLanguages& fontLanguages = FontLanguageListCache::getById(fontFamily.langId());

     const size_t maxCompareNum = std::min(langList.size(), FONT_LANGUAGES_LIMIT);
     uint32_t score = 0;
     for (size_t i = 0; i < maxCompareNum; ++i) {
         score = score * 5u + langList[i].calcScoreFor(fontLanguages);
     }
     return score;
 }

 // Calculates a font score based on variant ("compact" or "elegant") matching.
 //  - Returns 1 if the font doesn't have variant or the variant matches with the text style.
 //  - No score if the font has a variant but it doesn't match with the text style.
 uint32_t FontCollection::calcVariantMatchingScore(int variant, const FontFamily& fontFamily) {
     return (fontFamily.variant() == 0 || fontFamily.variant() == variant) ? 1 : 0;
 }

 // Implement heuristic for choosing best-match font. Here are the rules:
 // 1. If first font in the collection has the character, it wins.
 // 2. Calculate a score for the font family. See comments in calcFamilyScore for the detail.
 // 3. Highest score wins, with ties resolved to the first font.
 // This method never returns nullptr.
 const std::shared_ptr<FontFamily>& FontCollection::getFamilyForChar(uint32_t ch, uint32_t vs,
             uint32_t langListId, int variant) const {
     if (ch >= mMaxChar) {
         return mFamilies[0];
     }

     Range range = mRanges[ch >> kLogCharsPerPage];

     if (vs != 0) {
         range = { 0, static_cast<uint16_t>(mFamilies.size()) };
     }

 #ifdef VERBOSE_DEBUG
     ALOGD("querying range %zd:%zd\n", range.start, range.end);
 #endif
     int bestFamilyIndex = -1;
     uint32_t bestScore = kUnsupportedFontScore;
     for (size_t i = range.start; i < range.end; i++) {
         const std::shared_ptr<FontFamily>& family =
                 vs == 0 ? mFamilies[mFamilyVec[i]] : mFamilies[i];
         const uint32_t score = calcFamilyScore(ch, vs, variant, langListId, family);
         if (score == kFirstFontScore) {
             // If the first font family supports the given character or variation sequence, always
             // use it.
             return family;
         }
         if (score > bestScore) {
             bestScore = score;
             bestFamilyIndex = i;
         }
     }
     if (bestFamilyIndex == -1) {
         UErrorCode errorCode = U_ZERO_ERROR;
         const UNormalizer2* normalizer = unorm2_getNFDInstance(&errorCode);
         if (U_SUCCESS(errorCode)) {
             UChar decomposed[4];
             int len = unorm2_getRawDecomposition(normalizer, ch, decomposed, 4, &errorCode);
             if (U_SUCCESS(errorCode) && len > 0) {
                 int off = 0;
                 U16_NEXT_UNSAFE(decomposed, off, ch);
                 return getFamilyForChar(ch, vs, langListId, variant);
             }
         }
         return mFamilies[0];
     }
     return vs == 0 ? mFamilies[mFamilyVec[bestFamilyIndex]] : mFamilies[bestFamilyIndex];
 }

 const uint32_t NBSP = 0x00A0;
 const uint32_t SOFT_HYPHEN = 0x00AD;
 const uint32_t ZWJ = 0x200C;
 const uint32_t ZWNJ = 0x200D;
 const uint32_t HYPHEN = 0x2010;
 const uint32_t NB_HYPHEN = 0x2011;
 const uint32_t NNBSP = 0x202F;
 const uint32_t FEMALE_SIGN = 0x2640;
 const uint32_t MALE_SIGN = 0x2642;
 const uint32_t STAFF_OF_AESCULAPIUS = 0x2695;

 // Characters where we want to continue using existing font run instead of
 // recomputing the best match in the fallback list.
 static const uint32_t stickyWhitelist[] = {
         '!', ',', '-', '.', ':', ';', '?', NBSP, ZWJ, ZWNJ,
         HYPHEN, NB_HYPHEN, NNBSP, FEMALE_SIGN, MALE_SIGN, STAFF_OF_AESCULAPIUS };

 static bool isStickyWhitelisted(uint32_t c) {
     for (size_t i = 0; i < sizeof(stickyWhitelist) / sizeof(stickyWhitelist[0]); i++) {
         if (stickyWhitelist[i] == c) return true;
     }
     return false;
 }

 bool FontCollection::hasVariationSelector(uint32_t baseCodepoint,
         uint32_t variationSelector) const {
     if (!isVariationSelector(variationSelector)) {
         return false;
     }
     if (baseCodepoint >= mMaxChar) {
         return false;
     }

     // Currently mRanges can not be used here since it isn't aware of the variation sequence.
     for (size_t i = 0; i < mVSFamilyVec.size(); i++) {
         if (mVSFamilyVec[i]->hasGlyph(baseCodepoint, variationSelector)) {
             return true;
         }
     }

     // TODO: We can remove this lock by precomputing color emoji information.
     android::AutoMutex _l(gMinikinLock);

     // Even if there is no cmap format 14 subtable entry for the given sequence, should return true
     // for <char, text presentation selector> case since we have special fallback rule for the
     // sequence. Note that we don't need to restrict this to already standardized variation
     // sequences, since Unicode is adding variation sequences more frequently now and may even move
     // towards allowing text and emoji variation selectors on any character.
     if (variationSelector == TEXT_STYLE_VS) {
         for (size_t i = 0; i < mFamilies.size(); ++i) {
             if (!mFamilies[i]->isColorEmojiFamily() && mFamilies[i]->hasGlyph(baseCodepoint, 0)) {
                 return true;
             }
         }
     }

     return false;
 }

 void FontCollection::itemize(const uint16_t *string, size_t string_size, FontStyle style,
         vector<Run>* result) const {
     const uint32_t langListId = style.getLanguageListId();
     int variant = style.getVariant();
     const FontFamily* lastFamily = nullptr;
     Run* run = NULL;

     if (string_size == 0) {
         return;
     }

     const uint32_t kEndOfString = 0xFFFFFFFF;

     uint32_t nextCh = 0;
     uint32_t prevCh = 0;
     size_t nextUtf16Pos = 0;
     size_t readLength = 0;
     U16_NEXT(string, readLength, string_size, nextCh);

     do {
         const uint32_t ch = nextCh;
         const size_t utf16Pos = nextUtf16Pos;
         nextUtf16Pos = readLength;
         if (readLength < string_size) {
             U16_NEXT(string, readLength, string_size, nextCh);
         } else {
             nextCh = kEndOfString;
         }

         bool shouldContinueRun = false;
         if (lastFamily != nullptr) {
             if (isStickyWhitelisted(ch)) {
                 // Continue using existing font as long as it has coverage and is whitelisted
                 shouldContinueRun = lastFamily->getCoverage().get(ch);
             } else if (ch == SOFT_HYPHEN || isVariationSelector(ch)) {
                 // Always continue if the character is the soft hyphen or a variation selector.
                 shouldContinueRun = true;
             }
         }

         if (!shouldContinueRun) {
             const std::shared_ptr<FontFamily>& family = getFamilyForChar(
                     ch, isVariationSelector(nextCh) ? nextCh : 0, langListId, variant);
             if (utf16Pos == 0 || family.get() != lastFamily) {
                 size_t start = utf16Pos;
                 // Workaround for combining marks and emoji modifiers until we implement
                 // per-cluster font selection: if a combining mark or an emoji modifier is found in
                 // a different font that also supports the previous character, attach previous
                 // character to the new run. U+20E3 COMBINING ENCLOSING KEYCAP, used in emoji, is
                 // handled properly by this since it's a combining mark too.
                 if (utf16Pos != 0 &&
                         ((U_GET_GC_MASK(ch) & U_GC_M_MASK) != 0 ||
                          (isEmojiModifier(ch) && isEmojiBase(prevCh))) &&
                         family != nullptr && family->getCoverage().get(prevCh)) {
                     const size_t prevChLength = U16_LENGTH(prevCh);
                     run->end -= prevChLength;
                     if (run->start == run->end) {
                         result->pop_back();
                     }
                     start -= prevChLength;
                 }
                 result->push_back({family->getClosestMatch(style), static_cast<int>(start), 0});
                 run = &result->back();
                 lastFamily = family.get();
             }
         }
         prevCh = ch;
         run->end = nextUtf16Pos;  // exclusive
     } while (nextCh != kEndOfString);
 }

 FakedFont FontCollection::baseFontFaked(FontStyle style) {
     return mFamilies[0]->getClosestMatch(style);
 }

 std::shared_ptr<FontCollection> FontCollection::createCollectionWithVariation(
         const std::vector<FontVariation>& variations) {
     if (variations.empty() || mSupportedAxes.empty()) {
         return nullptr;
     }

     bool hasSupportedAxis = false;
     for (const FontVariation& variation : variations) {
         if (mSupportedAxes.find(variation.axisTag) != mSupportedAxes.end()) {
             hasSupportedAxis = true;
             break;
         }
     }
     if (!hasSupportedAxis) {
         // None of variation axes are supported by this font collection.
         return nullptr;
     }

     std::vector<std::shared_ptr<FontFamily> > families;
     for (const std::shared_ptr<FontFamily>& family : mFamilies) {
         std::shared_ptr<FontFamily> newFamily = family->createFamilyWithVariation(variations);
         if (newFamily) {
             families.push_back(newFamily);
         } else {
             families.push_back(family);
         }
     }

     return std::shared_ptr<FontCollection>(new FontCollection(families));
 }

 uint32_t FontCollection::getId() const {
     return mId;
 }

 }  // namespace minikin
	/*
	* Copyright (C) 2013 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 VERBOSE_DEBUG

	#define LOG_TAG "Minikin"

	#include <algorithm>

	#include <log/log.h>
	#include "unicode/unistr.h"
	#include "unicode/unorm2.h"

	#include "FontLanguage.h"
	#include "FontLanguageListCache.h"
	#include "MinikinInternal.h"
	#include <minikin/Emoji.h>
	#include <minikin/FontCollection.h>

	using std::vector;

	namespace minikin {

	template <typename T>
	static inline T max(T a, T b) {
	return a>b ? a : b;
	}

	const uint32_t EMOJI_STYLE_VS = 0xFE0F;
	const uint32_t TEXT_STYLE_VS = 0xFE0E;

	uint32_t FontCollection::sNextId = 0;

	FontCollection::FontCollection(std::shared_ptr<FontFamily>&& typeface) : mMaxChar(0) {
	std::vector<std::shared_ptr<FontFamily>> typefaces;
	typefaces.push_back(typeface);
	init(typefaces);
	}

	FontCollection::FontCollection(const vector<std::shared_ptr<FontFamily>>& typefaces) :
	mMaxChar(0) {
	init(typefaces);
	}

	void FontCollection::init(const vector<std::shared_ptr<FontFamily>>& typefaces) {
	android::AutoMutex _l(gMinikinLock);
	mId = sNextId++;
	vector<uint32_t> lastChar;
	size_t nTypefaces = typefaces.size();
	#ifdef VERBOSE_DEBUG
	ALOGD("nTypefaces = %zd\n", nTypefaces);
	#endif
	const FontStyle defaultStyle;
	for (size_t i = 0; i < nTypefaces; i++) {
	const std::shared_ptr<FontFamily>& family = typefaces[i];
	if (family->getClosestMatch(defaultStyle).font == nullptr) {
	continue;
	}
	const SparseBitSet& coverage = family->getCoverage();
	mFamilies.push_back(family); // emplace_back would be better
	if (family->hasVSTable()) {
	mVSFamilyVec.push_back(family);
	}
	mMaxChar = max(mMaxChar, coverage.length());
	lastChar.push_back(coverage.nextSetBit(0));

	const std::unordered_set<AxisTag>& supportedAxes = family->supportedAxes();
	mSupportedAxes.insert(supportedAxes.begin(), supportedAxes.end());
	}
	nTypefaces = mFamilies.size();
	LOG_ALWAYS_FATAL_IF(nTypefaces == 0,
	"Font collection must have at least one valid typeface");
	LOG_ALWAYS_FATAL_IF(nTypefaces > 254,
	"Font collection may only have up to 254 font families.");
	size_t nPages = (mMaxChar + kPageMask) >> kLogCharsPerPage;
	// TODO: Use variation selector map for mRanges construction.
	// A font can have a glyph for a base code point and variation selector pair but no glyph for
	// the base code point without variation selector. The family won't be listed in the range in
	// this case.
	for (size_t i = 0; i < nPages; i++) {
	Range dummy;
	mRanges.push_back(dummy);
	Range* range = &mRanges.back();
	#ifdef VERBOSE_DEBUG
	ALOGD("i=%zd: range start = %zd\n", i, offset);
	#endif
	range->start = mFamilyVec.size();
	for (size_t j = 0; j < nTypefaces; j++) {
	if (lastChar[j] < (i + 1) << kLogCharsPerPage) {
	const std::shared_ptr<FontFamily>& family = mFamilies[j];
	mFamilyVec.push_back(static_cast<uint8_t>(j));
	uint32_t nextChar = family->getCoverage().nextSetBit((i + 1) << kLogCharsPerPage);
	#ifdef VERBOSE_DEBUG
	ALOGD("nextChar = %d (j = %zd)\n", nextChar, j);
	#endif
	lastChar[j] = nextChar;
	}
	}
	range->end = mFamilyVec.size();
	}
	// See the comment in Range for more details.
	LOG_ALWAYS_FATAL_IF(mFamilyVec.size() >= 0xFFFF,
	"Exceeded the maximum indexable cmap coverage.");
	}

	// Special scores for the font fallback.
	const uint32_t kUnsupportedFontScore = 0;
	const uint32_t kFirstFontScore = UINT32_MAX;

	// Calculates a font score.
	// The score of the font family is based on three subscores.
	// - Coverage Score: How well the font family covers the given character or variation sequence.
	// - Language Score: How well the font family is appropriate for the language.
	// - Variant Score: Whether the font family matches the variant. Note that this variant is not the
	// one in BCP47. This is our own font variant (e.g., elegant, compact).
	//
	// Then, there is a priority for these three subscores as follow:
	// Coverage Score > Language Score > Variant Score
	// The returned score reflects this priority order.
	//
	// Note that there are two special scores.
	// - kUnsupportedFontScore: When the font family doesn't support the variation sequence or even its
	// base character.
	// - kFirstFontScore: When the font is the first font family in the collection and it supports the
	// given character or variation sequence.
	uint32_t FontCollection::calcFamilyScore(uint32_t ch, uint32_t vs, int variant, uint32_t langListId,
	const std::shared_ptr<FontFamily>& fontFamily) const {

	const uint32_t coverageScore = calcCoverageScore(ch, vs, fontFamily);
	if (coverageScore == kFirstFontScore \|\| coverageScore == kUnsupportedFontScore) {
	// No need to calculate other scores.
	return coverageScore;
	}

	const uint32_t languageScore = calcLanguageMatchingScore(langListId, *fontFamily);
	const uint32_t variantScore = calcVariantMatchingScore(variant, *fontFamily);

	// Subscores are encoded into 31 bits representation to meet the subscore priority.
	// The highest 2 bits are for coverage score, then following 28 bits are for language score,
	// then the last 1 bit is for variant score.
	return coverageScore << 29 \| languageScore << 1 \| variantScore;
	}

	// Calculates a font score based on variation sequence coverage.
	// - Returns kUnsupportedFontScore if the font doesn't support the variation sequence or its base
	// character.
	// - Returns kFirstFontScore if the font family is the first font family in the collection and it
	// supports the given character or variation sequence.
	// - Returns 3 if the font family supports the variation sequence.
	// - Returns 2 if the vs is a color variation selector (U+FE0F) and if the font is an emoji font.
	// - Returns 2 if the vs is a text variation selector (U+FE0E) and if the font is not an emoji font.
	// - Returns 1 if the variation selector is not specified or if the font family only supports the
	// variation sequence's base character.
	uint32_t FontCollection::calcCoverageScore(uint32_t ch, uint32_t vs,
	const std::shared_ptr<FontFamily>& fontFamily) const {
	const bool hasVSGlyph = (vs != 0) && fontFamily->hasGlyph(ch, vs);
	if (!hasVSGlyph && !fontFamily->getCoverage().get(ch)) {
	// The font doesn't support either variation sequence or even the base character.
	return kUnsupportedFontScore;
	}

	if ((vs == 0 \|\| hasVSGlyph) && mFamilies[0] == fontFamily) {
	// If the first font family supports the given character or variation sequence, always use
	// it.
	return kFirstFontScore;
	}

	if (vs == 0) {
	return 1;
	}

	if (hasVSGlyph) {
	return 3;
	}

	if (vs == EMOJI_STYLE_VS \|\| vs == TEXT_STYLE_VS) {
	const FontLanguages& langs = FontLanguageListCache::getById(fontFamily->langId());
	bool hasEmojiFlag = false;
	for (size_t i = 0; i < langs.size(); ++i) {
	if (langs[i].getEmojiStyle() == FontLanguage::EMSTYLE_EMOJI) {
	hasEmojiFlag = true;
	break;
	}
	}

	if (vs == EMOJI_STYLE_VS) {
	return hasEmojiFlag ? 2 : 1;
	} else { // vs == TEXT_STYLE_VS
	return hasEmojiFlag ? 1 : 2;
	}
	}
	return 1;
	}

	// Calculate font scores based on the script matching, subtag matching and primary langauge matching.
	//
	// 1. If only the font's language matches or there is no matches between requested font and
	// supported font, then the font obtains a score of 0.
	// 2. Without a match in language, considering subtag may change font's EmojiStyle over script,
	// a match in subtag gets a score of 2 and a match in scripts gains a score of 1.
	// 3. Regarding to two elements matchings, language-and-subtag matching has a score of 4, while
	// language-and-script obtains a socre of 3 with the same reason above.
	//
	// If two languages in the requested list have the same language score, the font matching with
	// higher priority language gets a higher score. For example, in the case the user requested
	// language list is "ja-Jpan,en-Latn". The score of for the font of "ja-Jpan" gets a higher score
	// than the font of "en-Latn".
	//
	// To achieve score calculation with priorities, the language score is determined as follows:
	// LanguageScore = s(0) * 5^(m - 1) + s(1) * 5^(m - 2) + ... + s(m - 2) * 5 + s(m - 1)
	// Here, m is the maximum number of languages to be compared, and s(i) is the i-th language's
	// matching score. The possible values of s(i) are 0, 1, 2, 3 and 4.
	uint32_t FontCollection::calcLanguageMatchingScore(
	uint32_t userLangListId, const FontFamily& fontFamily) {
	const FontLanguages& langList = FontLanguageListCache::getById(userLangListId);
	const FontLanguages& fontLanguages = FontLanguageListCache::getById(fontFamily.langId());

	const size_t maxCompareNum = std::min(langList.size(), FONT_LANGUAGES_LIMIT);
	uint32_t score = 0;
	for (size_t i = 0; i < maxCompareNum; ++i) {
	score = score * 5u + langList[i].calcScoreFor(fontLanguages);
	}
	return score;
	}

	// Calculates a font score based on variant ("compact" or "elegant") matching.
	// - Returns 1 if the font doesn't have variant or the variant matches with the text style.
	// - No score if the font has a variant but it doesn't match with the text style.
	uint32_t FontCollection::calcVariantMatchingScore(int variant, const FontFamily& fontFamily) {
	return (fontFamily.variant() == 0 \|\| fontFamily.variant() == variant) ? 1 : 0;
	}

	// Implement heuristic for choosing best-match font. Here are the rules:
	// 1. If first font in the collection has the character, it wins.
	// 2. Calculate a score for the font family. See comments in calcFamilyScore for the detail.
	// 3. Highest score wins, with ties resolved to the first font.
	// This method never returns nullptr.
	const std::shared_ptr<FontFamily>& FontCollection::getFamilyForChar(uint32_t ch, uint32_t vs,
	uint32_t langListId, int variant) const {
	if (ch >= mMaxChar) {
	return mFamilies[0];
	}

	Range range = mRanges[ch >> kLogCharsPerPage];

	if (vs != 0) {
	range = { 0, static_cast<uint16_t>(mFamilies.size()) };
	}

	#ifdef VERBOSE_DEBUG
	ALOGD("querying range %zd:%zd\n", range.start, range.end);
	#endif
	int bestFamilyIndex = -1;
	uint32_t bestScore = kUnsupportedFontScore;
	for (size_t i = range.start; i < range.end; i++) {
	const std::shared_ptr<FontFamily>& family =
	vs == 0 ? mFamilies[mFamilyVec[i]] : mFamilies[i];
	const uint32_t score = calcFamilyScore(ch, vs, variant, langListId, family);
	if (score == kFirstFontScore) {
	// If the first font family supports the given character or variation sequence, always
	// use it.
	return family;
	}
	if (score > bestScore) {
	bestScore = score;
	bestFamilyIndex = i;
	}
	}
	if (bestFamilyIndex == -1) {
	UErrorCode errorCode = U_ZERO_ERROR;
	const UNormalizer2* normalizer = unorm2_getNFDInstance(&errorCode);
	if (U_SUCCESS(errorCode)) {
	UChar decomposed[4];
	int len = unorm2_getRawDecomposition(normalizer, ch, decomposed, 4, &errorCode);
	if (U_SUCCESS(errorCode) && len > 0) {
	int off = 0;
	U16_NEXT_UNSAFE(decomposed, off, ch);
	return getFamilyForChar(ch, vs, langListId, variant);
	}
	}
	return mFamilies[0];
	}
	return vs == 0 ? mFamilies[mFamilyVec[bestFamilyIndex]] : mFamilies[bestFamilyIndex];
	}

	const uint32_t NBSP = 0x00A0;
	const uint32_t SOFT_HYPHEN = 0x00AD;
	const uint32_t ZWJ = 0x200C;
	const uint32_t ZWNJ = 0x200D;
	const uint32_t HYPHEN = 0x2010;
	const uint32_t NB_HYPHEN = 0x2011;
	const uint32_t NNBSP = 0x202F;
	const uint32_t FEMALE_SIGN = 0x2640;
	const uint32_t MALE_SIGN = 0x2642;
	const uint32_t STAFF_OF_AESCULAPIUS = 0x2695;

	// Characters where we want to continue using existing font run instead of
	// recomputing the best match in the fallback list.
	static const uint32_t stickyWhitelist[] = {
	'!', ',', '-', '.', ':', ';', '?', NBSP, ZWJ, ZWNJ,
	HYPHEN, NB_HYPHEN, NNBSP, FEMALE_SIGN, MALE_SIGN, STAFF_OF_AESCULAPIUS };

	static bool isStickyWhitelisted(uint32_t c) {
	for (size_t i = 0; i < sizeof(stickyWhitelist) / sizeof(stickyWhitelist[0]); i++) {
	if (stickyWhitelist[i] == c) return true;
	}
	return false;
	}

	bool FontCollection::hasVariationSelector(uint32_t baseCodepoint,
	uint32_t variationSelector) const {
	if (!isVariationSelector(variationSelector)) {
	return false;
	}
	if (baseCodepoint >= mMaxChar) {
	return false;
	}

	// Currently mRanges can not be used here since it isn't aware of the variation sequence.
	for (size_t i = 0; i < mVSFamilyVec.size(); i++) {
	if (mVSFamilyVec[i]->hasGlyph(baseCodepoint, variationSelector)) {
	return true;
	}
	}

	// TODO: We can remove this lock by precomputing color emoji information.
	android::AutoMutex _l(gMinikinLock);

	// Even if there is no cmap format 14 subtable entry for the given sequence, should return true
	// for <char, text presentation selector> case since we have special fallback rule for the
	// sequence. Note that we don't need to restrict this to already standardized variation
	// sequences, since Unicode is adding variation sequences more frequently now and may even move
	// towards allowing text and emoji variation selectors on any character.
	if (variationSelector == TEXT_STYLE_VS) {
	for (size_t i = 0; i < mFamilies.size(); ++i) {
	if (!mFamilies[i]->isColorEmojiFamily() && mFamilies[i]->hasGlyph(baseCodepoint, 0)) {
	return true;
	}
	}
	}

	return false;
	}

	void FontCollection::itemize(const uint16_t *string, size_t string_size, FontStyle style,
	vector<Run>* result) const {
	const uint32_t langListId = style.getLanguageListId();
	int variant = style.getVariant();
	const FontFamily* lastFamily = nullptr;
	Run* run = NULL;

	if (string_size == 0) {
	return;
	}

	const uint32_t kEndOfString = 0xFFFFFFFF;

	uint32_t nextCh = 0;
	uint32_t prevCh = 0;
	size_t nextUtf16Pos = 0;
	size_t readLength = 0;
	U16_NEXT(string, readLength, string_size, nextCh);

	do {
	const uint32_t ch = nextCh;
	const size_t utf16Pos = nextUtf16Pos;
	nextUtf16Pos = readLength;
	if (readLength < string_size) {
	U16_NEXT(string, readLength, string_size, nextCh);
	} else {
	nextCh = kEndOfString;
	}

	bool shouldContinueRun = false;
	if (lastFamily != nullptr) {
	if (isStickyWhitelisted(ch)) {
	// Continue using existing font as long as it has coverage and is whitelisted
	shouldContinueRun = lastFamily->getCoverage().get(ch);
	} else if (ch == SOFT_HYPHEN \|\| isVariationSelector(ch)) {
	// Always continue if the character is the soft hyphen or a variation selector.
	shouldContinueRun = true;
	}
	}

	if (!shouldContinueRun) {
	const std::shared_ptr<FontFamily>& family = getFamilyForChar(
	ch, isVariationSelector(nextCh) ? nextCh : 0, langListId, variant);
	if (utf16Pos == 0 \|\| family.get() != lastFamily) {
	size_t start = utf16Pos;
	// Workaround for combining marks and emoji modifiers until we implement
	// per-cluster font selection: if a combining mark or an emoji modifier is found in
	// a different font that also supports the previous character, attach previous
	// character to the new run. U+20E3 COMBINING ENCLOSING KEYCAP, used in emoji, is
	// handled properly by this since it's a combining mark too.
	if (utf16Pos != 0 &&
	((U_GET_GC_MASK(ch) & U_GC_M_MASK) != 0 \|\|
	(isEmojiModifier(ch) && isEmojiBase(prevCh))) &&
	family != nullptr && family->getCoverage().get(prevCh)) {
	const size_t prevChLength = U16_LENGTH(prevCh);
	run->end -= prevChLength;
	if (run->start == run->end) {
	result->pop_back();
	}
	start -= prevChLength;
	}
	result->push_back({family->getClosestMatch(style), static_cast<int>(start), 0});
	run = &result->back();
	lastFamily = family.get();
	}
	}
	prevCh = ch;
	run->end = nextUtf16Pos; // exclusive
	} while (nextCh != kEndOfString);
	}

	FakedFont FontCollection::baseFontFaked(FontStyle style) {
	return mFamilies[0]->getClosestMatch(style);
	}

	std::shared_ptr<FontCollection> FontCollection::createCollectionWithVariation(
	const std::vector<FontVariation>& variations) {
	if (variations.empty() \|\| mSupportedAxes.empty()) {
	return nullptr;
	}

	bool hasSupportedAxis = false;
	for (const FontVariation& variation : variations) {
	if (mSupportedAxes.find(variation.axisTag) != mSupportedAxes.end()) {
	hasSupportedAxis = true;
	break;
	}
	}
	if (!hasSupportedAxis) {
	// None of variation axes are supported by this font collection.
	return nullptr;
	}

	std::vector<std::shared_ptr<FontFamily> > families;
	for (const std::shared_ptr<FontFamily>& family : mFamilies) {
	std::shared_ptr<FontFamily> newFamily = family->createFamilyWithVariation(variations);
	if (newFamily) {
	families.push_back(newFamily);
	} else {
	families.push_back(family);
	}
	}

	return std::shared_ptr<FontCollection>(new FontCollection(families));
	}

	uint32_t FontCollection::getId() const {
	return mId;
	}

	} // namespace minikin