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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 <deque>
     26 #include <vector>
     27 
     28 #include "minikin/FontCollection.h"
     29 #include "minikin/Layout.h"
     30 #include "minikin/Macros.h"
     31 #include "minikin/MeasuredText.h"
     32 #include "minikin/MinikinFont.h"
     33 #include "minikin/Range.h"
     34 #include "minikin/U16StringPiece.h"
     35 
     36 namespace minikin {
     37 
     38 enum class BreakStrategy : uint8_t {
     39     Greedy = 0,
     40     HighQuality = 1,
     41     Balanced = 2,
     42 };
     43 
     44 enum class HyphenationFrequency : uint8_t {
     45     None = 0,
     46     Normal = 1,
     47     Full = 2,
     48 };
     49 
     50 class Hyphenator;
     51 class WordBreaker;
     52 
     53 class TabStops {
     54 public:
     55     // Caller must free stops. stops can be nullprt.
     56     TabStops(const int32_t* stops, size_t nStops, int32_t tabWidth)
     57             : mStops(stops), mStopsSize(nStops), mTabWidth(tabWidth) {}
     58 
     59     float nextTab(float widthSoFar) const {
     60         for (size_t i = 0; i < mStopsSize; i++) {
     61             if (mStops[i] > widthSoFar) {
     62                 return mStops[i];
     63             }
     64         }
     65         return floor(widthSoFar / mTabWidth + 1) * mTabWidth;
     66     }
     67 
     68 private:
     69     const int32_t* mStops;
     70     size_t mStopsSize;
     71     int32_t mTabWidth;
     72 };
     73 
     74 // Implement this for the additional information during line breaking.
     75 // The functions in this class's interface may be called several times. The implementation
     76 // must return the same value for the same input.
     77 class LineWidth {
     78 public:
     79     virtual ~LineWidth() {}
     80 
     81     // Called to find out the width for the line. This must not return negative values.
     82     virtual float getAt(size_t lineNo) const = 0;
     83 
     84     // Called to find out the minimum line width. This mut not return negative values.
     85     virtual float getMin() const = 0;
     86 
     87     // Called to find out the available left-side padding for the line.
     88     virtual float getLeftPaddingAt(size_t lineNo) const = 0;
     89 
     90     // Called to find out the available right-side padding for the line.
     91     virtual float getRightPaddingAt(size_t lineNo) const = 0;
     92 };
     93 
     94 struct LineBreakResult {
     95 public:
     96     LineBreakResult() = default;
     97 
     98     // Following five vectors have the same length.
     99     // TODO: Introduce individual line info struct if copy cost in JNI is negligible.
    100     std::vector<int> breakPoints;
    101     std::vector<float> widths;
    102     std::vector<float> ascents;
    103     std::vector<float> descents;
    104     std::vector<int> flags;
    105 
    106     LineBreakResult(LineBreakResult&&) = default;
    107     LineBreakResult& operator=(LineBreakResult&&) = default;
    108 
    109     void reverse() {
    110         std::reverse(breakPoints.begin(), breakPoints.end());
    111         std::reverse(widths.begin(), widths.end());
    112         std::reverse(ascents.begin(), ascents.end());
    113         std::reverse(descents.begin(), descents.end());
    114         std::reverse(flags.begin(), flags.end());
    115     }
    116 
    117 private:
    118     MINIKIN_PREVENT_COPY_AND_ASSIGN(LineBreakResult);
    119 };
    120 
    121 LineBreakResult breakIntoLines(const U16StringPiece& textBuffer, BreakStrategy strategy,
    122                                HyphenationFrequency frequency, bool justified,
    123                                const MeasuredText& measuredText, const LineWidth& lineWidth,
    124                                const TabStops& tabStops);
    125 
    126 }  // namespace minikin
    127 
    128 #endif  // MINIKIN_LINE_BREAKER_H
    129