Flutter Engine
FontLanguage.h
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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
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8  * http://www.apache.org/licenses/LICENSE-2.0
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10  * Unless required by applicable law or agreed to in writing, software
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13  * See the License for the specific language governing permissions and
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15  */
16 
17 #ifndef MINIKIN_FONT_LANGUAGE_H
18 #define MINIKIN_FONT_LANGUAGE_H
19 
20 #include <string>
21 #include <vector>
22 
23 #include <hb.h>
24 
25 namespace minikin {
26 
27 // Due to the limits in font fallback score calculation, we can't use anything
28 // more than 12 languages.
29 const size_t FONT_LANGUAGES_LIMIT = 12;
30 
31 // The language or region code is encoded to 15 bits.
32 const uint16_t INVALID_CODE = 0x7fff;
33 
34 class FontLanguages;
35 
36 // FontLanguage is a compact representation of a BCP 47 language tag. It
37 // does not capture all possible information, only what directly affects
38 // font rendering.
39 struct FontLanguage {
40  public:
41  enum EmojiStyle : uint8_t {
46  };
47  // Default constructor creates the unsupported language.
49  : mScript(0ul),
50  mLanguage(INVALID_CODE),
51  mRegion(INVALID_CODE),
52  mHbLanguage(HB_LANGUAGE_INVALID),
53  mSubScriptBits(0ul),
54  mEmojiStyle(EMSTYLE_EMPTY) {}
55 
56  // Parse from string
57  FontLanguage(const char* buf, size_t length);
58 
59  bool operator==(const FontLanguage other) const {
60  return !isUnsupported() && isEqualScript(other) &&
61  mLanguage == other.mLanguage && mRegion == other.mRegion &&
62  mEmojiStyle == other.mEmojiStyle;
63  }
64 
65  bool operator!=(const FontLanguage other) const { return !(*this == other); }
66 
67  bool isUnsupported() const { return mLanguage == INVALID_CODE; }
68  EmojiStyle getEmojiStyle() const { return mEmojiStyle; }
69  hb_language_t getHbLanguage() const { return mHbLanguage; }
70 
71  bool isEqualScript(const FontLanguage& other) const;
72 
73  // Returns true if this script supports the given script. For example, ja-Jpan
74  // supports Hira, ja-Hira doesn't support Jpan.
75  bool supportsHbScript(hb_script_t script) const;
76 
77  std::string getString() const;
78 
79  // Calculates a matching score. This score represents how well the input
80  // languages cover this language. The maximum score in the language list is
81  // returned. 0 = no match, 1 = script match, 2 = script and primary language
82  // match.
83  int calcScoreFor(const FontLanguages& supported) const;
84 
85  uint64_t getIdentifier() const {
86  return ((uint64_t)mLanguage << 49) | ((uint64_t)mScript << 17) |
87  ((uint64_t)mRegion << 2) | mEmojiStyle;
88  }
89 
90  private:
91  friend class FontLanguages; // for FontLanguages constructor
92 
93  // ISO 15924 compliant script code. The 4 chars script code are packed into a
94  // 32 bit integer.
95  uint32_t mScript;
96 
97  // ISO 639-1 or ISO 639-2 compliant language code.
98  // The two- or three-letter language code is packed into a 15 bit integer.
99  // mLanguage = 0 means the FontLanguage is unsupported.
100  uint16_t mLanguage;
101 
102  // ISO 3166-1 or UN M.49 compliant region code. The two-letter or three-digit
103  // region code is packed into a 15 bit integer.
104  uint16_t mRegion;
105 
106  // The language to be passed HarfBuzz shaper.
107  hb_language_t mHbLanguage;
108 
109  // For faster comparing, use 7 bits for specific scripts.
110  static const uint8_t kBopomofoFlag = 1u;
111  static const uint8_t kHanFlag = 1u << 1;
112  static const uint8_t kHangulFlag = 1u << 2;
113  static const uint8_t kHiraganaFlag = 1u << 3;
114  static const uint8_t kKatakanaFlag = 1u << 4;
115  static const uint8_t kSimplifiedChineseFlag = 1u << 5;
116  static const uint8_t kTraditionalChineseFlag = 1u << 6;
117  uint8_t mSubScriptBits;
118 
119  EmojiStyle mEmojiStyle;
120 
121  static uint8_t scriptToSubScriptBits(uint32_t script);
122 
123  static EmojiStyle resolveEmojiStyle(const char* buf,
124  size_t length,
125  uint32_t script);
126 
127  // Returns true if the provide subscript bits has the requested subscript
128  // bits. Note that this function returns false if the requested subscript bits
129  // are empty.
130  static bool supportsScript(uint8_t providedBits, uint8_t requestedBits);
131 };
132 
133 // An immutable list of languages.
135  public:
136  explicit FontLanguages(std::vector<FontLanguage>&& languages);
137  FontLanguages() : mUnionOfSubScriptBits(0), mIsAllTheSameLanguage(false) {}
138  FontLanguages(FontLanguages&&) = default;
139 
140  size_t size() const { return mLanguages.size(); }
141  bool empty() const { return mLanguages.empty(); }
142  const FontLanguage& operator[](size_t n) const { return mLanguages[n]; }
143 
144  private:
145  friend struct FontLanguage; // for calcScoreFor
146 
147  std::vector<FontLanguage> mLanguages;
148  uint8_t mUnionOfSubScriptBits;
149  bool mIsAllTheSameLanguage;
150 
151  uint8_t getUnionOfSubScriptBits() const { return mUnionOfSubScriptBits; }
152  bool isAllTheSameLanguage() const { return mIsAllTheSameLanguage; }
153 
154  // Do not copy and assign.
155  FontLanguages(const FontLanguages&) = delete;
156  void operator=(const FontLanguages&) = delete;
157 };
158 
159 } // namespace minikin
160 
161 #endif // MINIKIN_FONT_LANGUAGE_H
bool operator!=(const FontLanguage other) const
Definition: FontLanguage.h:65
uint64_t getIdentifier() const
Definition: FontLanguage.h:85
bool operator==(const FontLanguage other) const
Definition: FontLanguage.h:59
std::string getString() const
bool isUnsupported() const
Definition: FontLanguage.h:67
hb_language_t getHbLanguage() const
Definition: FontLanguage.h:69
size_t size() const
Definition: FontLanguage.h:140
const size_t FONT_LANGUAGES_LIMIT
Definition: FontLanguage.h:29
const FontLanguage & operator[](size_t n) const
Definition: FontLanguage.h:142
int calcScoreFor(const FontLanguages &supported) const
const uint16_t INVALID_CODE
Definition: FontLanguage.h:32
size_t length
EmojiStyle getEmojiStyle() const
Definition: FontLanguage.h:68
bool isEqualScript(const FontLanguage &other) const
friend class FontLanguages
Definition: FontLanguage.h:91
bool supportsHbScript(hb_script_t script) const