third_party/txt/src/minikin/LineBreaker.cpp - external/github.com/flutter/engine - Git at Google

 /*
  * Copyright (C) 2015 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 0

 #define LOG_TAG "Minikin"

 #include <algorithm>
 #include <limits>

 #include <log/log.h>

 #include <minikin/Layout.h>
 #include <minikin/LineBreaker.h>
 #include <utils/WindowsUtils.h>
 #include "LayoutUtils.h"

 using std::vector;

 namespace minikin {

 // Large scores in a hierarchy; we prefer desperate breaks to an overfull line.
 // All these constants are larger than any reasonable actual width score.
 const float SCORE_INFTY = std::numeric_limits<float>::max();
 const float SCORE_OVERFULL = 1e12f;
 const float SCORE_DESPERATE = 1e10f;

 // Multiplier for hyphen penalty on last line.
 const float LAST_LINE_PENALTY_MULTIPLIER = 4.0f;
 // Penalty assigned to each line break (to try to minimize number of lines)
 // TODO: when we implement full justification (so spaces can shrink and
 // stretch), this is probably not the most appropriate method.
 const float LINE_PENALTY_MULTIPLIER = 2.0f;

 // Penalty assigned to shrinking the whitepsace.
 const float SHRINK_PENALTY_MULTIPLIER = 4.0f;

 // Very long words trigger O(n^2) behavior in hyphenation, so we disable
 // hyphenation for unreasonably long words. This is somewhat of a heuristic
 // because extremely long words are possible in some languages. This does mean
 // that very long real words can get broken by desperate breaks, with no
 // hyphens.
 const size_t LONGEST_HYPHENATED_WORD = 45;

 // When the text buffer is within this limit, capacity of vectors is retained at
 // finish(), to avoid allocation.
 const size_t MAX_TEXT_BUF_RETAIN = 32678;

 // Maximum amount that spaces can shrink, in justified text.
 const float SHRINKABILITY = 1.0 / 3.0;

 void LineBreaker::setLocale(const icu::Locale& locale, Hyphenator* hyphenator) {
   mWordBreaker.setLocale(locale);
   mLocale = locale;
   mHyphenator = hyphenator;
 }

 void LineBreaker::setText() {
   mWordBreaker.setText(mTextBuf.data(), mTextBuf.size());

   // handle initial break here because addStyleRun may never be called
   mWordBreaker.next();
   mCandidates.clear();
   Candidate cand = {0,   0, 0.0, 0.0, 0.0,
                     0.0, 0, 0,   0,   HyphenationType::DONT_BREAK};
   mCandidates.push_back(cand);

   // reset greedy breaker state
   mBreaks.clear();
   mWidths.clear();
   mFlags.clear();
   mLastBreak = 0;
   mBestBreak = 0;
   mBestScore = SCORE_INFTY;
   mPreBreak = 0;
   mLastHyphenation = HyphenEdit::NO_EDIT;
   mFirstTabIndex = INT_MAX;
   mSpaceCount = 0;
 }

 void LineBreaker::setLineWidths(float firstWidth,
                                 int firstWidthLineCount,
                                 float restWidth) {
   mLineWidths.setWidths(firstWidth, firstWidthLineCount, restWidth);
 }

 void LineBreaker::setIndents(const std::vector<float>& indents) {
   mLineWidths.setIndents(indents);
 }

 // This function determines whether a character is a space that disappears at
 // end of line. It is the Unicode set:
 // [[:General_Category=Space_Separator:]-[:Line_Break=Glue:]], plus '\n'. Note:
 // all such characters are in the BMP, so it's ok to use code units for this.
 bool isLineEndSpace(uint16_t c) {
   return c == '\n' || c == ' ' || c == 0x1680 ||
          (0x2000 <= c && c <= 0x200A && c != 0x2007) || c == 0x205F ||
          c == 0x3000;
 }

 // Ordinarily, this method measures the text in the range given. However, when
 // paint is nullptr, it assumes the widths have already been calculated and
 // stored in the width buffer. This method finds the candidate word breaks
 // (using the ICU break iterator) and sends them to addCandidate.
 float LineBreaker::addStyleRun(MinikinPaint* paint,
                                const std::shared_ptr<FontCollection>& typeface,
                                FontStyle style,
                                size_t start,
                                size_t end,
                                bool isRtl) {
   float width = 0.0f;

   float hyphenPenalty = 0.0;
   if (paint != nullptr) {
     width = Layout::measureText(mTextBuf.data(), start, end - start,
                                 mTextBuf.size(), isRtl, style, *paint, typeface,
                                 mCharWidths.data() + start);

     // a heuristic that seems to perform well
     hyphenPenalty =
         0.5 * paint->size * paint->scaleX * mLineWidths.getLineWidth(0);
     if (mHyphenationFrequency == kHyphenationFrequency_Normal) {
       hyphenPenalty *=
           4.0;  // TODO: Replace with a better value after some testing
     }

     if (mJustified) {
       // Make hyphenation more aggressive for fully justified text (so that
       // "normal" in justified mode is the same as "full" in ragged-right).
       hyphenPenalty *= 0.25;
     } else {
       // Line penalty is zero for justified text.
       mLinePenalty =
           std::max(mLinePenalty, hyphenPenalty * LINE_PENALTY_MULTIPLIER);
     }
   }

   size_t current = (size_t)mWordBreaker.current();
   size_t afterWord = start;
   size_t lastBreak = start;
   ParaWidth lastBreakWidth = mWidth;
   ParaWidth postBreak = mWidth;
   size_t postSpaceCount = mSpaceCount;
   for (size_t i = start; i < end; i++) {
     uint16_t c = mTextBuf[i];
     // libtxt: Tab handling was removed here.
     if (isWordSpace(c))
       mSpaceCount += 1;
     mWidth += mCharWidths[i];
     if (!isLineEndSpace(c)) {
       postBreak = mWidth;
       postSpaceCount = mSpaceCount;
       afterWord = i + 1;
     }
     if (i + 1 == current) {
       size_t wordStart = mWordBreaker.wordStart();
       size_t wordEnd = mWordBreaker.wordEnd();
       if (paint != nullptr && mHyphenator != nullptr &&
           mHyphenationFrequency != kHyphenationFrequency_None &&
           wordStart >= start && wordEnd > wordStart &&
           wordEnd - wordStart <= LONGEST_HYPHENATED_WORD) {
         mHyphenator->hyphenate(&mHyphBuf, &mTextBuf[wordStart],
                                wordEnd - wordStart, mLocale);
 #if VERBOSE_DEBUG
         std::string hyphenatedString;
         for (size_t j = wordStart; j < wordEnd; j++) {
           if (mHyphBuf[j - wordStart] ==
               HyphenationType::BREAK_AND_INSERT_HYPHEN) {
             hyphenatedString.push_back('-');
           }
           // Note: only works with ASCII, should do UTF-8 conversion here
           hyphenatedString.push_back(buffer()[j]);
         }
         ALOGD("hyphenated string: %s", hyphenatedString.c_str());
 #endif

         // measure hyphenated substrings
         for (size_t j = wordStart; j < wordEnd; j++) {
           HyphenationType hyph = mHyphBuf[j - wordStart];
           if (hyph != HyphenationType::DONT_BREAK) {
             paint->hyphenEdit = HyphenEdit::editForThisLine(hyph);
             const float firstPartWidth = Layout::measureText(
                 mTextBuf.data(), lastBreak, j - lastBreak, mTextBuf.size(),
                 isRtl, style, *paint, typeface, nullptr);
             ParaWidth hyphPostBreak = lastBreakWidth + firstPartWidth;

             paint->hyphenEdit = HyphenEdit::editForNextLine(hyph);
             const float secondPartWidth = Layout::measureText(
                 mTextBuf.data(), j, afterWord - j, mTextBuf.size(), isRtl,
                 style, *paint, typeface, nullptr);
             ParaWidth hyphPreBreak = postBreak - secondPartWidth;

             addWordBreak(j, hyphPreBreak, hyphPostBreak, postSpaceCount,
                          postSpaceCount, hyphenPenalty, hyph);

             paint->hyphenEdit = HyphenEdit::NO_EDIT;
           }
         }
       }

       // Skip break for zero-width characters inside replacement span
       if (paint != nullptr || current == end || mCharWidths[current] > 0) {
         float penalty = hyphenPenalty * mWordBreaker.breakBadness();
         addWordBreak(current, mWidth, postBreak, mSpaceCount, postSpaceCount,
                      penalty, HyphenationType::DONT_BREAK);
       }
       lastBreak = current;
       lastBreakWidth = mWidth;
       current = (size_t)mWordBreaker.next();
     }
   }

   return width;
 }

 // add a word break (possibly for a hyphenated fragment), and add desperate
 // breaks if needed (ie when word exceeds current line width)
 void LineBreaker::addWordBreak(size_t offset,
                                ParaWidth preBreak,
                                ParaWidth postBreak,
                                size_t preSpaceCount,
                                size_t postSpaceCount,
                                float penalty,
                                HyphenationType hyph) {
   Candidate cand;
   ParaWidth width = mCandidates.back().preBreak;
   // libtxt: add a fudge factor to this comparison.  The currentLineWidth passed
   // by the framework is based on maxIntrinsicWidth/Layout::measureText
   // calculations that may not precisely match the postBreak width.
   if (postBreak - width > currentLineWidth() + 0.00001) {
     // Add desperate breaks.
     // Note: these breaks are based on the shaping of the (non-broken) original
     // text; they are imprecise especially in the presence of kerning,
     // ligatures, and Arabic shaping.
     size_t i = mCandidates.back().offset;
     width += mCharWidths[i++];
     for (; i < offset; i++) {
       float w = mCharWidths[i];
       if (w > 0) {
         cand.offset = i;
         cand.preBreak = width;
         cand.postBreak = width;
         // postSpaceCount doesn't include trailing spaces
         cand.preSpaceCount = postSpaceCount;
         cand.postSpaceCount = postSpaceCount;
         cand.penalty = SCORE_DESPERATE;
         cand.hyphenType = HyphenationType::BREAK_AND_DONT_INSERT_HYPHEN;
 #if VERBOSE_DEBUG
         ALOGD("desperate cand: %zd %g:%g", mCandidates.size(), cand.postBreak,
               cand.preBreak);
 #endif
         addCandidate(cand);
         width += w;
       }
     }
   }

   cand.offset = offset;
   cand.preBreak = preBreak;
   cand.postBreak = postBreak;
   cand.penalty = penalty;
   cand.preSpaceCount = preSpaceCount;
   cand.postSpaceCount = postSpaceCount;
   cand.hyphenType = hyph;
 #if VERBOSE_DEBUG
   ALOGD("cand: %zd %g:%g", mCandidates.size(), cand.postBreak, cand.preBreak);
 #endif
   addCandidate(cand);
 }

 // Helper method for addCandidate()
 void LineBreaker::pushGreedyBreak() {
   const Candidate& bestCandidate = mCandidates[mBestBreak];
   pushBreak(
       bestCandidate.offset, bestCandidate.postBreak - mPreBreak,
       mLastHyphenation | HyphenEdit::editForThisLine(bestCandidate.hyphenType));
   mBestScore = SCORE_INFTY;
 #if VERBOSE_DEBUG
   ALOGD("break: %d %g", mBreaks.back(), mWidths.back());
 #endif
   mLastBreak = mBestBreak;
   mPreBreak = bestCandidate.preBreak;
   mLastHyphenation = HyphenEdit::editForNextLine(bestCandidate.hyphenType);
 }

 // TODO performance: could avoid populating mCandidates if greedy only
 void LineBreaker::addCandidate(Candidate cand) {
   const size_t candIndex = mCandidates.size();
   mCandidates.push_back(cand);

   // mLastBreak is the index of the last line break we decided to do in
   // mCandidates, and mPreBreak is its preBreak value. mBestBreak is the index
   // of the best line breaking candidate we have found since then, and
   // mBestScore is its penalty.
   if (cand.postBreak - mPreBreak > currentLineWidth()) {
     // This break would create an overfull line, pick the best break and break
     // there (greedy)
     if (mBestBreak == mLastBreak) {
       // No good break has been found since last break. Break here.
       mBestBreak = candIndex;
     }
     pushGreedyBreak();
   }

   while (mLastBreak != candIndex &&
          cand.postBreak - mPreBreak > currentLineWidth()) {
     // We should rarely come here. But if we are here, we have broken the line,
     // but the remaining part still doesn't fit. We now need to break at the
     // second best place after the last break, but we have not kept that
     // information, so we need to go back and find it.
     //
     // In some really rare cases, postBreak - preBreak of a candidate itself may
     // be over the current line width. We protect ourselves against an infinite
     // loop in that case by checking that we have not broken the line at this
     // candidate already.
     for (size_t i = mLastBreak + 1; i < candIndex; i++) {
       const float penalty = mCandidates[i].penalty;
       if (penalty <= mBestScore) {
         mBestBreak = i;
         mBestScore = penalty;
       }
     }
     if (mBestBreak == mLastBreak) {
       // We didn't find anything good. Break here.
       mBestBreak = candIndex;
     }
     pushGreedyBreak();
   }

   if (cand.penalty <= mBestScore) {
     mBestBreak = candIndex;
     mBestScore = cand.penalty;
   }
 }

 void LineBreaker::pushBreak(int offset, float width, uint8_t hyphenEdit) {
   mBreaks.push_back(offset);
   mWidths.push_back(width);
   int flags = (mFirstTabIndex < mBreaks.back()) << kTab_Shift;
   flags |= hyphenEdit;
   mFlags.push_back(flags);
   mFirstTabIndex = INT_MAX;
 }

 // libtxt: Add ability to set custom char widths. This allows manual definition
 // of the widths of arbitrary glyphs. To linebreak properly, call addStyleRun
 // with nullptr as the paint property, which will lead it to assume the width
 // has already been calculated. Used for properly breaking inline widgets.
 void LineBreaker::setCustomCharWidth(size_t offset, float width) {
   mCharWidths[offset] = (width);
 }

 void LineBreaker::addReplacement(size_t start, size_t end, float width) {
   mCharWidths[start] = width;
   std::fill(&mCharWidths[start + 1], &mCharWidths[end], 0.0f);
   addStyleRun(nullptr, nullptr, FontStyle(), start, end, false);
 }

 // Get the width of a space. May return 0 if there are no spaces.
 // Note: if there are multiple different widths for spaces (for example, because
 // of mixing of fonts), it's only guaranteed to pick one.
 float LineBreaker::getSpaceWidth() const {
   for (size_t i = 0; i < mTextBuf.size(); i++) {
     if (isWordSpace(mTextBuf[i])) {
       return mCharWidths[i];
     }
   }
   return 0.0f;
 }

 float LineBreaker::currentLineWidth() const {
   return mLineWidths.getLineWidth(mBreaks.size());
 }

 void LineBreaker::computeBreaksGreedy() {
   // All breaks but the last have been added in addCandidate already.
   size_t nCand = mCandidates.size();
   if (nCand > 0 && (nCand == 1 || mLastBreak != nCand - 1)) {
     pushBreak(mCandidates[nCand - 1].offset,
               mCandidates[nCand - 1].postBreak - mPreBreak, mLastHyphenation);
     // don't need to update mBestScore, because we're done
 #if VERBOSE_DEBUG
     ALOGD("final break: %d %g", mBreaks.back(), mWidths.back());
 #endif
   }
 }

 // Follow "prev" links in mCandidates array, and copy to result arrays.
 void LineBreaker::finishBreaksOptimal() {
   // clear existing greedy break result
   mBreaks.clear();
   mWidths.clear();
   mFlags.clear();
   size_t nCand = mCandidates.size();
   size_t prev;
   for (size_t i = nCand - 1; i > 0; i = prev) {
     prev = mCandidates[i].prev;
     mBreaks.push_back(mCandidates[i].offset);
     mWidths.push_back(mCandidates[i].postBreak - mCandidates[prev].preBreak);
     int flags = HyphenEdit::editForThisLine(mCandidates[i].hyphenType);
     if (prev > 0) {
       flags |= HyphenEdit::editForNextLine(mCandidates[prev].hyphenType);
     }
     mFlags.push_back(flags);
   }
   std::reverse(mBreaks.begin(), mBreaks.end());
   std::reverse(mWidths.begin(), mWidths.end());
   std::reverse(mFlags.begin(), mFlags.end());
 }

 void LineBreaker::computeBreaksOptimal(bool isRectangle) {
   size_t active = 0;
   size_t nCand = mCandidates.size();
   float width = mLineWidths.getLineWidth(0);
   float shortLineFactor = mJustified ? 0.75f : 0.5f;
   float maxShrink = mJustified ? SHRINKABILITY * getSpaceWidth() : 0.0f;

   // "i" iterates through candidates for the end of the line.
   for (size_t i = 1; i < nCand; i++) {
     bool atEnd = i == nCand - 1;
     float best = SCORE_INFTY;
     size_t bestPrev = 0;
     size_t lineNumberLast = 0;

     if (!isRectangle) {
       size_t lineNumberLast = mCandidates[active].lineNumber;
       width = mLineWidths.getLineWidth(lineNumberLast);
     }
     ParaWidth leftEdge = mCandidates[i].postBreak - width;
     float bestHope = 0;

     // "j" iterates through candidates for the beginning of the line.
     for (size_t j = active; j < i; j++) {
       if (!isRectangle) {
         size_t lineNumber = mCandidates[j].lineNumber;
         if (lineNumber != lineNumberLast) {
           float widthNew = mLineWidths.getLineWidth(lineNumber);
           if (widthNew != width) {
             leftEdge = mCandidates[i].postBreak - width;
             bestHope = 0;
             width = widthNew;
           }
           lineNumberLast = lineNumber;
         }
       }
       float jScore = mCandidates[j].score;
       if (jScore + bestHope >= best)
         continue;
       float delta = mCandidates[j].preBreak - leftEdge;

       // compute width score for line

       // Note: the "bestHope" optimization makes the assumption that, when delta
       // is non-negative, widthScore will increase monotonically as successive
       // candidate breaks are considered.
       float widthScore = 0.0f;
       float additionalPenalty = 0.0f;
       if ((atEnd || !mJustified) && delta < 0) {
         widthScore = SCORE_OVERFULL;
       } else if (atEnd && mStrategy != kBreakStrategy_Balanced) {
         // increase penalty for hyphen on last line
         additionalPenalty =
             LAST_LINE_PENALTY_MULTIPLIER * mCandidates[j].penalty;
         // Penalize very short (< 1 - shortLineFactor of total width) lines.
         float underfill = delta - shortLineFactor * width;
         widthScore = underfill > 0 ? underfill * underfill : 0;
       } else {
         widthScore = delta * delta;
         if (delta < 0) {
           if (-delta < maxShrink * (mCandidates[i].postSpaceCount -
                                     mCandidates[j].preSpaceCount)) {
             widthScore *= SHRINK_PENALTY_MULTIPLIER;
           } else {
             widthScore = SCORE_OVERFULL;
           }
         }
       }

       if (delta < 0) {
         active = j + 1;
       } else {
         bestHope = widthScore;
       }

       float score = jScore + widthScore + additionalPenalty;
       if (score <= best) {
         best = score;
         bestPrev = j;
       }
     }
     mCandidates[i].score = best + mCandidates[i].penalty + mLinePenalty;
     mCandidates[i].prev = bestPrev;
     mCandidates[i].lineNumber = mCandidates[bestPrev].lineNumber + 1;
 #if VERBOSE_DEBUG
     ALOGD("break %zd: score=%g, prev=%zd", i, mCandidates[i].score,
           mCandidates[i].prev);
 #endif
   }
   finishBreaksOptimal();
 }

 size_t LineBreaker::computeBreaks() {
   if (mStrategy == kBreakStrategy_Greedy) {
     computeBreaksGreedy();
   } else {
     computeBreaksOptimal(mLineWidths.isConstant());
   }
   return mBreaks.size();
 }

 void LineBreaker::finish() {
   mWordBreaker.finish();
   mWidth = 0;
   mLineWidths.clear();
   mCandidates.clear();
   mBreaks.clear();
   mWidths.clear();
   mFlags.clear();
   if (mTextBuf.size() > MAX_TEXT_BUF_RETAIN) {
     mTextBuf.clear();
     mTextBuf.shrink_to_fit();
     mCharWidths.clear();
     mCharWidths.shrink_to_fit();
     mHyphBuf.clear();
     mHyphBuf.shrink_to_fit();
     mCandidates.shrink_to_fit();
     mBreaks.shrink_to_fit();
     mWidths.shrink_to_fit();
     mFlags.shrink_to_fit();
   }
   mStrategy = kBreakStrategy_Greedy;
   mHyphenationFrequency = kHyphenationFrequency_Normal;
   mLinePenalty = 0.0f;
   mJustified = false;
 }

 }  // namespace minikin
	/*
	* Copyright (C) 2015 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 0

	#define LOG_TAG "Minikin"

	#include <algorithm>
	#include <limits>

	#include <log/log.h>

	#include <minikin/Layout.h>
	#include <minikin/LineBreaker.h>
	#include <utils/WindowsUtils.h>
	#include "LayoutUtils.h"

	using std::vector;

	namespace minikin {

	// Large scores in a hierarchy; we prefer desperate breaks to an overfull line.
	// All these constants are larger than any reasonable actual width score.
	const float SCORE_INFTY = std::numeric_limits<float>::max();
	const float SCORE_OVERFULL = 1e12f;
	const float SCORE_DESPERATE = 1e10f;

	// Multiplier for hyphen penalty on last line.
	const float LAST_LINE_PENALTY_MULTIPLIER = 4.0f;
	// Penalty assigned to each line break (to try to minimize number of lines)
	// TODO: when we implement full justification (so spaces can shrink and
	// stretch), this is probably not the most appropriate method.
	const float LINE_PENALTY_MULTIPLIER = 2.0f;

	// Penalty assigned to shrinking the whitepsace.
	const float SHRINK_PENALTY_MULTIPLIER = 4.0f;

	// Very long words trigger O(n^2) behavior in hyphenation, so we disable
	// hyphenation for unreasonably long words. This is somewhat of a heuristic
	// because extremely long words are possible in some languages. This does mean
	// that very long real words can get broken by desperate breaks, with no
	// hyphens.
	const size_t LONGEST_HYPHENATED_WORD = 45;

	// When the text buffer is within this limit, capacity of vectors is retained at
	// finish(), to avoid allocation.
	const size_t MAX_TEXT_BUF_RETAIN = 32678;

	// Maximum amount that spaces can shrink, in justified text.
	const float SHRINKABILITY = 1.0 / 3.0;

	void LineBreaker::setLocale(const icu::Locale& locale, Hyphenator* hyphenator) {
	mWordBreaker.setLocale(locale);
	mLocale = locale;
	mHyphenator = hyphenator;
	}

	void LineBreaker::setText() {
	mWordBreaker.setText(mTextBuf.data(), mTextBuf.size());

	// handle initial break here because addStyleRun may never be called
	mWordBreaker.next();
	mCandidates.clear();
	Candidate cand = {0, 0, 0.0, 0.0, 0.0,
	0.0, 0, 0, 0, HyphenationType::DONT_BREAK};
	mCandidates.push_back(cand);

	// reset greedy breaker state
	mBreaks.clear();
	mWidths.clear();
	mFlags.clear();
	mLastBreak = 0;
	mBestBreak = 0;
	mBestScore = SCORE_INFTY;
	mPreBreak = 0;
	mLastHyphenation = HyphenEdit::NO_EDIT;
	mFirstTabIndex = INT_MAX;
	mSpaceCount = 0;
	}

	void LineBreaker::setLineWidths(float firstWidth,
	int firstWidthLineCount,
	float restWidth) {
	mLineWidths.setWidths(firstWidth, firstWidthLineCount, restWidth);
	}

	void LineBreaker::setIndents(const std::vector<float>& indents) {
	mLineWidths.setIndents(indents);
	}

	// This function determines whether a character is a space that disappears at
	// end of line. It is the Unicode set:
	// [[:General_Category=Space_Separator:]-[:Line_Break=Glue:]], plus '\n'. Note:
	// all such characters are in the BMP, so it's ok to use code units for this.
	bool isLineEndSpace(uint16_t c) {
	return c == '\n' \|\| c == ' ' \|\| c == 0x1680 \|\|
	(0x2000 <= c && c <= 0x200A && c != 0x2007) \|\| c == 0x205F \|\|
	c == 0x3000;
	}

	// Ordinarily, this method measures the text in the range given. However, when
	// paint is nullptr, it assumes the widths have already been calculated and
	// stored in the width buffer. This method finds the candidate word breaks
	// (using the ICU break iterator) and sends them to addCandidate.
	float LineBreaker::addStyleRun(MinikinPaint* paint,
	const std::shared_ptr<FontCollection>& typeface,
	FontStyle style,
	size_t start,
	size_t end,
	bool isRtl) {
	float width = 0.0f;

	float hyphenPenalty = 0.0;
	if (paint != nullptr) {
	width = Layout::measureText(mTextBuf.data(), start, end - start,
	mTextBuf.size(), isRtl, style, *paint, typeface,
	mCharWidths.data() + start);

	// a heuristic that seems to perform well
	hyphenPenalty =
	0.5 * paint->size * paint->scaleX * mLineWidths.getLineWidth(0);
	if (mHyphenationFrequency == kHyphenationFrequency_Normal) {
	hyphenPenalty *=
	4.0; // TODO: Replace with a better value after some testing
	}

	if (mJustified) {
	// Make hyphenation more aggressive for fully justified text (so that
	// "normal" in justified mode is the same as "full" in ragged-right).
	hyphenPenalty *= 0.25;
	} else {
	// Line penalty is zero for justified text.
	mLinePenalty =
	std::max(mLinePenalty, hyphenPenalty * LINE_PENALTY_MULTIPLIER);
	}
	}

	size_t current = (size_t)mWordBreaker.current();
	size_t afterWord = start;
	size_t lastBreak = start;
	ParaWidth lastBreakWidth = mWidth;
	ParaWidth postBreak = mWidth;
	size_t postSpaceCount = mSpaceCount;
	for (size_t i = start; i < end; i++) {
	uint16_t c = mTextBuf[i];
	// libtxt: Tab handling was removed here.
	if (isWordSpace(c))
	mSpaceCount += 1;
	mWidth += mCharWidths[i];
	if (!isLineEndSpace(c)) {
	postBreak = mWidth;
	postSpaceCount = mSpaceCount;
	afterWord = i + 1;
	}
	if (i + 1 == current) {
	size_t wordStart = mWordBreaker.wordStart();
	size_t wordEnd = mWordBreaker.wordEnd();
	if (paint != nullptr && mHyphenator != nullptr &&
	mHyphenationFrequency != kHyphenationFrequency_None &&
	wordStart >= start && wordEnd > wordStart &&
	wordEnd - wordStart <= LONGEST_HYPHENATED_WORD) {
	mHyphenator->hyphenate(&mHyphBuf, &mTextBuf[wordStart],
	wordEnd - wordStart, mLocale);
	#if VERBOSE_DEBUG
	std::string hyphenatedString;
	for (size_t j = wordStart; j < wordEnd; j++) {
	if (mHyphBuf[j - wordStart] ==
	HyphenationType::BREAK_AND_INSERT_HYPHEN) {
	hyphenatedString.push_back('-');
	}
	// Note: only works with ASCII, should do UTF-8 conversion here
	hyphenatedString.push_back(buffer()[j]);
	}
	ALOGD("hyphenated string: %s", hyphenatedString.c_str());
	#endif

	// measure hyphenated substrings
	for (size_t j = wordStart; j < wordEnd; j++) {
	HyphenationType hyph = mHyphBuf[j - wordStart];
	if (hyph != HyphenationType::DONT_BREAK) {
	paint->hyphenEdit = HyphenEdit::editForThisLine(hyph);
	const float firstPartWidth = Layout::measureText(
	mTextBuf.data(), lastBreak, j - lastBreak, mTextBuf.size(),
	isRtl, style, *paint, typeface, nullptr);
	ParaWidth hyphPostBreak = lastBreakWidth + firstPartWidth;

	paint->hyphenEdit = HyphenEdit::editForNextLine(hyph);
	const float secondPartWidth = Layout::measureText(
	mTextBuf.data(), j, afterWord - j, mTextBuf.size(), isRtl,
	style, *paint, typeface, nullptr);
	ParaWidth hyphPreBreak = postBreak - secondPartWidth;

	addWordBreak(j, hyphPreBreak, hyphPostBreak, postSpaceCount,
	postSpaceCount, hyphenPenalty, hyph);

	paint->hyphenEdit = HyphenEdit::NO_EDIT;
	}
	}
	}

	// Skip break for zero-width characters inside replacement span
	if (paint != nullptr \|\| current == end \|\| mCharWidths[current] > 0) {
	float penalty = hyphenPenalty * mWordBreaker.breakBadness();
	addWordBreak(current, mWidth, postBreak, mSpaceCount, postSpaceCount,
	penalty, HyphenationType::DONT_BREAK);
	}
	lastBreak = current;
	lastBreakWidth = mWidth;
	current = (size_t)mWordBreaker.next();
	}
	}

	return width;
	}

	// add a word break (possibly for a hyphenated fragment), and add desperate
	// breaks if needed (ie when word exceeds current line width)
	void LineBreaker::addWordBreak(size_t offset,
	ParaWidth preBreak,
	ParaWidth postBreak,
	size_t preSpaceCount,
	size_t postSpaceCount,
	float penalty,
	HyphenationType hyph) {
	Candidate cand;
	ParaWidth width = mCandidates.back().preBreak;
	// libtxt: add a fudge factor to this comparison. The currentLineWidth passed
	// by the framework is based on maxIntrinsicWidth/Layout::measureText
	// calculations that may not precisely match the postBreak width.
	if (postBreak - width > currentLineWidth() + 0.00001) {
	// Add desperate breaks.
	// Note: these breaks are based on the shaping of the (non-broken) original
	// text; they are imprecise especially in the presence of kerning,
	// ligatures, and Arabic shaping.
	size_t i = mCandidates.back().offset;
	width += mCharWidths[i++];
	for (; i < offset; i++) {
	float w = mCharWidths[i];
	if (w > 0) {
	cand.offset = i;
	cand.preBreak = width;
	cand.postBreak = width;
	// postSpaceCount doesn't include trailing spaces
	cand.preSpaceCount = postSpaceCount;
	cand.postSpaceCount = postSpaceCount;
	cand.penalty = SCORE_DESPERATE;
	cand.hyphenType = HyphenationType::BREAK_AND_DONT_INSERT_HYPHEN;
	#if VERBOSE_DEBUG
	ALOGD("desperate cand: %zd %g:%g", mCandidates.size(), cand.postBreak,
	cand.preBreak);
	#endif
	addCandidate(cand);
	width += w;
	}
	}
	}

	cand.offset = offset;
	cand.preBreak = preBreak;
	cand.postBreak = postBreak;
	cand.penalty = penalty;
	cand.preSpaceCount = preSpaceCount;
	cand.postSpaceCount = postSpaceCount;
	cand.hyphenType = hyph;
	#if VERBOSE_DEBUG
	ALOGD("cand: %zd %g:%g", mCandidates.size(), cand.postBreak, cand.preBreak);
	#endif
	addCandidate(cand);
	}

	// Helper method for addCandidate()
	void LineBreaker::pushGreedyBreak() {
	const Candidate& bestCandidate = mCandidates[mBestBreak];
	pushBreak(
	bestCandidate.offset, bestCandidate.postBreak - mPreBreak,
	mLastHyphenation \| HyphenEdit::editForThisLine(bestCandidate.hyphenType));
	mBestScore = SCORE_INFTY;
	#if VERBOSE_DEBUG
	ALOGD("break: %d %g", mBreaks.back(), mWidths.back());
	#endif
	mLastBreak = mBestBreak;
	mPreBreak = bestCandidate.preBreak;
	mLastHyphenation = HyphenEdit::editForNextLine(bestCandidate.hyphenType);
	}

	// TODO performance: could avoid populating mCandidates if greedy only
	void LineBreaker::addCandidate(Candidate cand) {
	const size_t candIndex = mCandidates.size();
	mCandidates.push_back(cand);

	// mLastBreak is the index of the last line break we decided to do in
	// mCandidates, and mPreBreak is its preBreak value. mBestBreak is the index
	// of the best line breaking candidate we have found since then, and
	// mBestScore is its penalty.
	if (cand.postBreak - mPreBreak > currentLineWidth()) {
	// This break would create an overfull line, pick the best break and break
	// there (greedy)
	if (mBestBreak == mLastBreak) {
	// No good break has been found since last break. Break here.
	mBestBreak = candIndex;
	}
	pushGreedyBreak();
	}

	while (mLastBreak != candIndex &&
	cand.postBreak - mPreBreak > currentLineWidth()) {
	// We should rarely come here. But if we are here, we have broken the line,
	// but the remaining part still doesn't fit. We now need to break at the
	// second best place after the last break, but we have not kept that
	// information, so we need to go back and find it.
	//
	// In some really rare cases, postBreak - preBreak of a candidate itself may
	// be over the current line width. We protect ourselves against an infinite
	// loop in that case by checking that we have not broken the line at this
	// candidate already.
	for (size_t i = mLastBreak + 1; i < candIndex; i++) {
	const float penalty = mCandidates[i].penalty;
	if (penalty <= mBestScore) {
	mBestBreak = i;
	mBestScore = penalty;
	}
	}
	if (mBestBreak == mLastBreak) {
	// We didn't find anything good. Break here.
	mBestBreak = candIndex;
	}
	pushGreedyBreak();
	}

	if (cand.penalty <= mBestScore) {
	mBestBreak = candIndex;
	mBestScore = cand.penalty;
	}
	}

	void LineBreaker::pushBreak(int offset, float width, uint8_t hyphenEdit) {
	mBreaks.push_back(offset);
	mWidths.push_back(width);
	int flags = (mFirstTabIndex < mBreaks.back()) << kTab_Shift;
	flags \|= hyphenEdit;
	mFlags.push_back(flags);
	mFirstTabIndex = INT_MAX;
	}

	// libtxt: Add ability to set custom char widths. This allows manual definition
	// of the widths of arbitrary glyphs. To linebreak properly, call addStyleRun
	// with nullptr as the paint property, which will lead it to assume the width
	// has already been calculated. Used for properly breaking inline widgets.
	void LineBreaker::setCustomCharWidth(size_t offset, float width) {
	mCharWidths[offset] = (width);
	}

	void LineBreaker::addReplacement(size_t start, size_t end, float width) {
	mCharWidths[start] = width;
	std::fill(&mCharWidths[start + 1], &mCharWidths[end], 0.0f);
	addStyleRun(nullptr, nullptr, FontStyle(), start, end, false);
	}

	// Get the width of a space. May return 0 if there are no spaces.
	// Note: if there are multiple different widths for spaces (for example, because
	// of mixing of fonts), it's only guaranteed to pick one.
	float LineBreaker::getSpaceWidth() const {
	for (size_t i = 0; i < mTextBuf.size(); i++) {
	if (isWordSpace(mTextBuf[i])) {
	return mCharWidths[i];
	}
	}
	return 0.0f;
	}

	float LineBreaker::currentLineWidth() const {
	return mLineWidths.getLineWidth(mBreaks.size());
	}

	void LineBreaker::computeBreaksGreedy() {
	// All breaks but the last have been added in addCandidate already.
	size_t nCand = mCandidates.size();
	if (nCand > 0 && (nCand == 1 \|\| mLastBreak != nCand - 1)) {
	pushBreak(mCandidates[nCand - 1].offset,
	mCandidates[nCand - 1].postBreak - mPreBreak, mLastHyphenation);
	// don't need to update mBestScore, because we're done
	#if VERBOSE_DEBUG
	ALOGD("final break: %d %g", mBreaks.back(), mWidths.back());
	#endif
	}
	}

	// Follow "prev" links in mCandidates array, and copy to result arrays.
	void LineBreaker::finishBreaksOptimal() {
	// clear existing greedy break result
	mBreaks.clear();
	mWidths.clear();
	mFlags.clear();
	size_t nCand = mCandidates.size();
	size_t prev;
	for (size_t i = nCand - 1; i > 0; i = prev) {
	prev = mCandidates[i].prev;
	mBreaks.push_back(mCandidates[i].offset);
	mWidths.push_back(mCandidates[i].postBreak - mCandidates[prev].preBreak);
	int flags = HyphenEdit::editForThisLine(mCandidates[i].hyphenType);
	if (prev > 0) {
	flags \|= HyphenEdit::editForNextLine(mCandidates[prev].hyphenType);
	}
	mFlags.push_back(flags);
	}
	std::reverse(mBreaks.begin(), mBreaks.end());
	std::reverse(mWidths.begin(), mWidths.end());
	std::reverse(mFlags.begin(), mFlags.end());
	}

	void LineBreaker::computeBreaksOptimal(bool isRectangle) {
	size_t active = 0;
	size_t nCand = mCandidates.size();
	float width = mLineWidths.getLineWidth(0);
	float shortLineFactor = mJustified ? 0.75f : 0.5f;
	float maxShrink = mJustified ? SHRINKABILITY * getSpaceWidth() : 0.0f;

	// "i" iterates through candidates for the end of the line.
	for (size_t i = 1; i < nCand; i++) {
	bool atEnd = i == nCand - 1;
	float best = SCORE_INFTY;
	size_t bestPrev = 0;
	size_t lineNumberLast = 0;

	if (!isRectangle) {
	size_t lineNumberLast = mCandidates[active].lineNumber;
	width = mLineWidths.getLineWidth(lineNumberLast);
	}
	ParaWidth leftEdge = mCandidates[i].postBreak - width;
	float bestHope = 0;

	// "j" iterates through candidates for the beginning of the line.
	for (size_t j = active; j < i; j++) {
	if (!isRectangle) {
	size_t lineNumber = mCandidates[j].lineNumber;
	if (lineNumber != lineNumberLast) {
	float widthNew = mLineWidths.getLineWidth(lineNumber);
	if (widthNew != width) {
	leftEdge = mCandidates[i].postBreak - width;
	bestHope = 0;
	width = widthNew;
	}
	lineNumberLast = lineNumber;
	}
	}
	float jScore = mCandidates[j].score;
	if (jScore + bestHope >= best)
	continue;
	float delta = mCandidates[j].preBreak - leftEdge;

	// compute width score for line

	// Note: the "bestHope" optimization makes the assumption that, when delta
	// is non-negative, widthScore will increase monotonically as successive
	// candidate breaks are considered.
	float widthScore = 0.0f;
	float additionalPenalty = 0.0f;
	if ((atEnd \|\| !mJustified) && delta < 0) {
	widthScore = SCORE_OVERFULL;
	} else if (atEnd && mStrategy != kBreakStrategy_Balanced) {
	// increase penalty for hyphen on last line
	additionalPenalty =
	LAST_LINE_PENALTY_MULTIPLIER * mCandidates[j].penalty;
	// Penalize very short (< 1 - shortLineFactor of total width) lines.
	float underfill = delta - shortLineFactor * width;
	widthScore = underfill > 0 ? underfill * underfill : 0;
	} else {
	widthScore = delta * delta;
	if (delta < 0) {
	if (-delta < maxShrink * (mCandidates[i].postSpaceCount -
	mCandidates[j].preSpaceCount)) {
	widthScore *= SHRINK_PENALTY_MULTIPLIER;
	} else {
	widthScore = SCORE_OVERFULL;
	}
	}
	}

	if (delta < 0) {
	active = j + 1;
	} else {
	bestHope = widthScore;
	}

	float score = jScore + widthScore + additionalPenalty;
	if (score <= best) {
	best = score;
	bestPrev = j;
	}
	}
	mCandidates[i].score = best + mCandidates[i].penalty + mLinePenalty;
	mCandidates[i].prev = bestPrev;
	mCandidates[i].lineNumber = mCandidates[bestPrev].lineNumber + 1;
	#if VERBOSE_DEBUG
	ALOGD("break %zd: score=%g, prev=%zd", i, mCandidates[i].score,
	mCandidates[i].prev);
	#endif
	}
	finishBreaksOptimal();
	}

	size_t LineBreaker::computeBreaks() {
	if (mStrategy == kBreakStrategy_Greedy) {
	computeBreaksGreedy();
	} else {
	computeBreaksOptimal(mLineWidths.isConstant());
	}
	return mBreaks.size();
	}

	void LineBreaker::finish() {
	mWordBreaker.finish();
	mWidth = 0;
	mLineWidths.clear();
	mCandidates.clear();
	mBreaks.clear();
	mWidths.clear();
	mFlags.clear();
	if (mTextBuf.size() > MAX_TEXT_BUF_RETAIN) {
	mTextBuf.clear();
	mTextBuf.shrink_to_fit();
	mCharWidths.clear();
	mCharWidths.shrink_to_fit();
	mHyphBuf.clear();
	mHyphBuf.shrink_to_fit();
	mCandidates.shrink_to_fit();
	mBreaks.shrink_to_fit();
	mWidths.shrink_to_fit();
	mFlags.shrink_to_fit();
	}
	mStrategy = kBreakStrategy_Greedy;
	mHyphenationFrequency = kHyphenationFrequency_Normal;
	mLinePenalty = 0.0f;
	mJustified = false;
	}

	} // namespace minikin