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.
TabStops(const int32_t * stops,size_t nStops,int32_t tabWidth)56     TabStops(const int32_t* stops, size_t nStops, int32_t tabWidth)
57             : mStops(stops), mStopsSize(nStops), mTabWidth(tabWidth) {}
58 
nextTab(float widthSoFar)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:
~LineWidth()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 
reverseLineBreakResult109     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