third_party/txt/src/minikin/FontCollection.cpp - mirrors/engine - 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 "unicode/utf16.h"

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

 // libtxt: return a locale string for a language list ID
 std::string GetFontLocale(uint32_t langListId) {
   const FontLanguages& langs = FontLanguageListCache::getById(langListId);
   return langs.size() ? langs[0].getString() : "";
 }

 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) {
   std::scoped_lock _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 language 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) {
     // libtxt: check if the fallback font provider can match this character
     if (mFallbackFontProvider) {
       const std::shared_ptr<FontFamily>& fallback =
           findFallbackFont(ch, vs, langListId);
       if (fallback) {
         return fallback;
       }
     }
     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) {
     // libtxt: check if the fallback font provider can match this character
     if (mFallbackFontProvider) {
       const std::shared_ptr<FontFamily>& fallback =
           findFallbackFont(ch, vs, langListId);
       if (fallback) {
         return fallback;
       }
     }

     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 std::shared_ptr<FontFamily>& FontCollection::findFallbackFont(
     uint32_t ch,
     uint32_t vs,
     uint32_t langListId) const {
   std::string locale = GetFontLocale(langListId);

   const auto it = mCachedFallbackFamilies.find(locale);
   if (it != mCachedFallbackFamilies.end()) {
     for (const auto& fallbackFamily : it->second) {
       if (calcCoverageScore(ch, vs, fallbackFamily)) {
         return fallbackFamily;
       }
     }
   }

   const std::shared_ptr<FontFamily>& fallback =
       mFallbackFontProvider->matchFallbackFont(ch, GetFontLocale(langListId));

   if (fallback) {
     mCachedFallbackFamilies[locale].push_back(fallback);
   }
   return fallback;
 }

 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 stickyAllowlist[] = {
     '!',   ',',         '-',       '.',
     ':',   ';',         '?',       NBSP,
     ZWJ,   ZWNJ,        HYPHEN,    NB_HYPHEN,
     NNBSP, FEMALE_SIGN, MALE_SIGN, STAFF_OF_AESCULAPIUS};

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

 static bool isVariationSelector(uint32_t c) {
   return (0xFE00 <= c && c <= 0xFE0F) || (0xE0100 <= c && c <= 0xE01EF);
 }

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

   std::scoped_lock _l(gMinikinLock);

   // 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;
     }
   }

   // 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 (isStickyAllowed(ch)) {
         // Continue using existing font as long as it has coverage and is
         // allowed.
         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 "unicode/utf16.h"

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

	// libtxt: return a locale string for a language list ID
	std::string GetFontLocale(uint32_t langListId) {
	const FontLanguages& langs = FontLanguageListCache::getById(langListId);
	return langs.size() ? langs[0].getString() : "";
	}

	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) {
	std::scoped_lock _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 language 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) {
	// libtxt: check if the fallback font provider can match this character
	if (mFallbackFontProvider) {
	const std::shared_ptr<FontFamily>& fallback =
	findFallbackFont(ch, vs, langListId);
	if (fallback) {
	return fallback;
	}
	}
	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) {
	// libtxt: check if the fallback font provider can match this character
	if (mFallbackFontProvider) {
	const std::shared_ptr<FontFamily>& fallback =
	findFallbackFont(ch, vs, langListId);
	if (fallback) {
	return fallback;
	}
	}

	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 std::shared_ptr<FontFamily>& FontCollection::findFallbackFont(
	uint32_t ch,
	uint32_t vs,
	uint32_t langListId) const {
	std::string locale = GetFontLocale(langListId);

	const auto it = mCachedFallbackFamilies.find(locale);
	if (it != mCachedFallbackFamilies.end()) {
	for (const auto& fallbackFamily : it->second) {
	if (calcCoverageScore(ch, vs, fallbackFamily)) {
	return fallbackFamily;
	}
	}
	}

	const std::shared_ptr<FontFamily>& fallback =
	mFallbackFontProvider->matchFallbackFont(ch, GetFontLocale(langListId));

	if (fallback) {
	mCachedFallbackFamilies[locale].push_back(fallback);
	}
	return fallback;
	}

	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 stickyAllowlist[] = {
	'!', ',', '-', '.',
	':', ';', '?', NBSP,
	ZWJ, ZWNJ, HYPHEN, NB_HYPHEN,
	NNBSP, FEMALE_SIGN, MALE_SIGN, STAFF_OF_AESCULAPIUS};

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

	static bool isVariationSelector(uint32_t c) {
	return (0xFE00 <= c && c <= 0xFE0F) \|\| (0xE0100 <= c && c <= 0xE01EF);
	}

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

	std::scoped_lock _l(gMinikinLock);

	// 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;
	}
	}

	// 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 (isStickyAllowed(ch)) {
	// Continue using existing font as long as it has coverage and is
	// allowed.
	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