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| 1 | +/* |
| 2 | + * Copyright (C) 2015 The Android Open Source Project |
| 3 | + * |
| 4 | + * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | + * you may not use this file except in compliance with the License. |
| 6 | + * You may obtain a copy of the License at |
| 7 | + * |
| 8 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | + * |
| 10 | + * Unless required by applicable law or agreed to in writing, software |
| 11 | + * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | + * See the License for the specific language governing permissions and |
| 14 | + * limitations under the License. |
| 15 | + */ |
| 16 | + |
| 17 | +/** |
| 18 | + * A module for breaking paragraphs into lines, supporting high quality |
| 19 | + * hyphenation and justification. |
| 20 | + */ |
| 21 | + |
| 22 | +#ifndef MINIKIN_LINE_BREAKER_H |
| 23 | +#define MINIKIN_LINE_BREAKER_H |
| 24 | + |
| 25 | +#include "unicode/brkiter.h" |
| 26 | +#include "unicode/locid.h" |
| 27 | +#include <cmath> |
| 28 | +#include <vector> |
| 29 | + |
| 30 | +namespace android { |
| 31 | + |
| 32 | +enum BreakStrategy { |
| 33 | + kBreakStrategy_Greedy = 0, |
| 34 | + kBreakStrategy_HighQuality = 1, |
| 35 | + kBreakStrategy_Balanced = 2 |
| 36 | +}; |
| 37 | + |
| 38 | +// TODO: want to generalize to be able to handle array of line widths |
| 39 | +class LineWidths { |
| 40 | + public: |
| 41 | + void setWidths(float firstWidth, int firstWidthLineCount, float restWidth) { |
| 42 | + mFirstWidth = firstWidth; |
| 43 | + mFirstWidthLineCount = firstWidthLineCount; |
| 44 | + mRestWidth = restWidth; |
| 45 | + } |
| 46 | + float getLineWidth(int line) const { |
| 47 | + return (line < mFirstWidthLineCount) ? mFirstWidth : mRestWidth; |
| 48 | + } |
| 49 | + private: |
| 50 | + float mFirstWidth; |
| 51 | + int mFirstWidthLineCount; |
| 52 | + float mRestWidth; |
| 53 | +}; |
| 54 | + |
| 55 | +class TabStops { |
| 56 | + public: |
| 57 | + void set(const int* stops, size_t nStops, int tabWidth) { |
| 58 | + if (stops != nullptr) { |
| 59 | + mStops.assign(stops, stops + nStops); |
| 60 | + } else { |
| 61 | + mStops.clear(); |
| 62 | + } |
| 63 | + mTabWidth = tabWidth; |
| 64 | + } |
| 65 | + float nextTab(float widthSoFar) const { |
| 66 | + for (size_t i = 0; i < mStops.size(); i++) { |
| 67 | + if (mStops[i] > widthSoFar) { |
| 68 | + return mStops[i]; |
| 69 | + } |
| 70 | + } |
| 71 | + return floor(widthSoFar / mTabWidth + 1) * mTabWidth; |
| 72 | + } |
| 73 | + private: |
| 74 | + std::vector<int> mStops; |
| 75 | + int mTabWidth; |
| 76 | +}; |
| 77 | + |
| 78 | +class LineBreaker { |
| 79 | + public: |
| 80 | + ~LineBreaker() { |
| 81 | + utext_close(&mUText); |
| 82 | + delete mBreakIterator; |
| 83 | + } |
| 84 | + |
| 85 | + // Note: Locale persists across multiple invocations (it is not cleaned up by finish()), |
| 86 | + // explicitly to avoid the cost of creating ICU BreakIterator objects. It should always |
| 87 | + // be set on the first invocation, but callers are encouraged not to call again unless |
| 88 | + // locale has actually changed. |
| 89 | + // That logic could be here but it's better for performance that it's upstream because of |
| 90 | + // the cost of constructing and comparing the ICU Locale object. |
| 91 | + void setLocale(const icu::Locale& locale) { |
| 92 | + delete mBreakIterator; |
| 93 | + UErrorCode status = U_ZERO_ERROR; |
| 94 | + mBreakIterator = icu::BreakIterator::createLineInstance(locale, status); |
| 95 | + // TODO: check status |
| 96 | + // TODO: load hyphenator from locale |
| 97 | + } |
| 98 | + |
| 99 | + void resize(size_t size) { |
| 100 | + mTextBuf.resize(size); |
| 101 | + mCharWidths.resize(size); |
| 102 | + } |
| 103 | + |
| 104 | + size_t size() const { |
| 105 | + return mTextBuf.size(); |
| 106 | + } |
| 107 | + |
| 108 | + uint16_t* buffer() { |
| 109 | + return mTextBuf.data(); |
| 110 | + } |
| 111 | + |
| 112 | + float* charWidths() { |
| 113 | + return mCharWidths.data(); |
| 114 | + } |
| 115 | + |
| 116 | + // set text to current contents of buffer |
| 117 | + void setText(); |
| 118 | + |
| 119 | + void setLineWidths(float firstWidth, int firstWidthLineCount, float restWidth); |
| 120 | + |
| 121 | + void setTabStops(const int* stops, size_t nStops, int tabWidth) { |
| 122 | + mTabStops.set(stops, nStops, tabWidth); |
| 123 | + } |
| 124 | + |
| 125 | + BreakStrategy getStrategy() const { return mStrategy; } |
| 126 | + |
| 127 | + void setStrategy(BreakStrategy strategy) { mStrategy = strategy; } |
| 128 | + |
| 129 | + // TODO: this class is actually fairly close to being general and not tied to using |
| 130 | + // Minikin to do the shaping of the strings. The main thing that would need to be changed |
| 131 | + // is having some kind of callback (or virtual class, or maybe even template), which could |
| 132 | + // easily be instantiated with Minikin's Layout. Future work for when needed. |
| 133 | + float addStyleRun(const MinikinPaint* paint, const FontCollection* typeface, |
| 134 | + FontStyle style, size_t start, size_t end, bool isRtl); |
| 135 | + |
| 136 | + void addReplacement(size_t start, size_t end, float width); |
| 137 | + |
| 138 | + size_t computeBreaks(); |
| 139 | + |
| 140 | + const int* getBreaks() const { |
| 141 | + return mBreaks.data(); |
| 142 | + } |
| 143 | + |
| 144 | + const float* getWidths() const { |
| 145 | + return mWidths.data(); |
| 146 | + } |
| 147 | + |
| 148 | + const uint8_t* getFlags() const { |
| 149 | + return mFlags.data(); |
| 150 | + } |
| 151 | + |
| 152 | + void finish(); |
| 153 | + |
| 154 | + private: |
| 155 | + // ParaWidth is used to hold cumulative width from beginning of paragraph. Note that for |
| 156 | + // very large paragraphs, accuracy could degrade using only 32-bit float. Note however |
| 157 | + // that float is used extensively on the Java side for this. This is a typedef so that |
| 158 | + // we can easily change it based on performance/accuracy tradeoff. |
| 159 | + typedef double ParaWidth; |
| 160 | + |
| 161 | + // A single candidate break |
| 162 | + struct Candidate { |
| 163 | + size_t offset; // offset to text buffer, in code units |
| 164 | + size_t prev; // index to previous break |
| 165 | + ParaWidth preBreak; |
| 166 | + ParaWidth postBreak; |
| 167 | + float penalty; // penalty of this break (for example, hyphen penalty) |
| 168 | + float score; // best score found for this break |
| 169 | + }; |
| 170 | + |
| 171 | + float currentLineWidth() const; |
| 172 | + |
| 173 | + void addWordBreak(size_t offset, ParaWidth preBreak, ParaWidth postBreak, float penalty); |
| 174 | + |
| 175 | + void addCandidate(Candidate cand); |
| 176 | + |
| 177 | + void computeBreaksGreedy(); |
| 178 | + |
| 179 | + void computeBreaksOpt(); |
| 180 | + |
| 181 | + icu::BreakIterator* mBreakIterator = nullptr; |
| 182 | + UText mUText = UTEXT_INITIALIZER; |
| 183 | + std::vector<uint16_t>mTextBuf; |
| 184 | + std::vector<float>mCharWidths; |
| 185 | + |
| 186 | + // layout parameters |
| 187 | + BreakStrategy mStrategy = kBreakStrategy_Greedy; |
| 188 | + LineWidths mLineWidths; |
| 189 | + TabStops mTabStops; |
| 190 | + |
| 191 | + // result of line breaking |
| 192 | + std::vector<int> mBreaks; |
| 193 | + std::vector<float> mWidths; |
| 194 | + std::vector<uint8_t> mFlags; |
| 195 | + |
| 196 | + ParaWidth mWidth = 0; |
| 197 | + std::vector<Candidate> mCandidates; |
| 198 | + |
| 199 | + // the following are state for greedy breaker (updated while adding style runs) |
| 200 | + size_t mLastBreak; |
| 201 | + size_t mBestBreak; |
| 202 | + float mBestScore; |
| 203 | + ParaWidth mPreBreak; // prebreak of last break |
| 204 | + int mFirstTabIndex; |
| 205 | +}; |
| 206 | + |
| 207 | +} // namespace android |
| 208 | + |
| 209 | +#endif // MINIKIN_LINE_BREAKER_H |
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