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 #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 android {
26 
27 // Due to the limits in font fallback score calculation, we can't use anything more than 17
28 // languages.
29 const size_t FONT_LANGUAGES_LIMIT = 17;
30 class FontLanguages;
31 
32 // FontLanguage is a compact representation of a BCP 47 language tag. It
33 // does not capture all possible information, only what directly affects
34 // font rendering.
35 struct FontLanguage {
36 public:
37     // Default constructor creates the unsupported language.
FontLanguageFontLanguage38     FontLanguage() : mScript(0ul), mLanguage(0ul), mSubScriptBits(0ul) {}
39 
40     // Parse from string
41     FontLanguage(const char* buf, size_t length);
42 
43     bool operator==(const FontLanguage other) const {
44         return !isUnsupported() && isEqualScript(other) && mLanguage == other.mLanguage;
45     }
46 
47     bool operator!=(const FontLanguage other) const {
48         return !(*this == other);
49     }
50 
isUnsupportedFontLanguage51     bool isUnsupported() const { return mLanguage == 0ul; }
hasEmojiFlagFontLanguage52     bool hasEmojiFlag() const { return mSubScriptBits & kEmojiFlag; }
53 
54     bool isEqualScript(const FontLanguage& other) const;
55 
56     // Returns true if this script supports the given script. For example, ja-Jpan supports Hira,
57     // ja-Hira doesn't support Jpan.
58     bool supportsHbScript(hb_script_t script) const;
59 
60     std::string getString() const;
61 
62     // Calculates a matching score. This score represents how well the input languages cover this
63     // language. The maximum score in the language list is returned.
64     // 0 = no match, 1 = script match, 2 = script and primary language match.
65     int calcScoreFor(const FontLanguages& supported) const;
66 
getIdentifierFontLanguage67     uint64_t getIdentifier() const { return (uint64_t)mScript << 32 | (uint64_t)mLanguage; }
68 
69 private:
70     friend class FontLanguages;  // for FontLanguages constructor
71 
72     // ISO 15924 compliant script code. The 4 chars script code are packed into a 32 bit integer.
73     uint32_t mScript;
74 
75     // ISO 639-1 or ISO 639-2 compliant language code.
76     // The two or three letter language code is packed into 32 bit integer.
77     // mLanguage = 0 means the FontLanguage is unsupported.
78     uint32_t mLanguage;
79 
80     // For faster comparing, use 8 bits for specific scripts.
81     static const uint8_t kBopomofoFlag = 1u;
82     static const uint8_t kEmojiFlag = 1u << 1;
83     static const uint8_t kHanFlag = 1u << 2;
84     static const uint8_t kHangulFlag = 1u << 3;
85     static const uint8_t kHiraganaFlag = 1u << 4;
86     static const uint8_t kKatakanaFlag = 1u << 5;
87     static const uint8_t kSimplifiedChineseFlag = 1u << 6;
88     static const uint8_t kTraditionalChineseFlag = 1u << 7;
89     uint8_t mSubScriptBits;
90 
91     static uint8_t scriptToSubScriptBits(uint32_t script);
92 
93     // Returns true if the provide subscript bits has the requested subscript bits.
94     // Note that this function returns false if the requested subscript bits are empty.
95     static bool supportsScript(uint8_t providedBits, uint8_t requestedBits);
96 };
97 
98 // An immutable list of languages.
99 class FontLanguages {
100 public:
101     FontLanguages(std::vector<FontLanguage>&& languages);
FontLanguages()102     FontLanguages() : mUnionOfSubScriptBits(0), mIsAllTheSameLanguage(false) {}
103     FontLanguages(FontLanguages&&) = default;
104 
size()105     size_t size() const { return mLanguages.size(); }
empty()106     bool empty() const { return mLanguages.empty(); }
107     const FontLanguage& operator[] (size_t n) const { return mLanguages[n]; }
108 
109 private:
110     friend struct FontLanguage;  // for calcScoreFor
111 
112     std::vector<FontLanguage> mLanguages;
113     uint8_t mUnionOfSubScriptBits;
114     bool mIsAllTheSameLanguage;
115 
getUnionOfSubScriptBits()116     uint8_t getUnionOfSubScriptBits() const { return mUnionOfSubScriptBits; }
isAllTheSameLanguage()117     bool isAllTheSameLanguage() const { return mIsAllTheSameLanguage; }
118 
119     // Do not copy and assign.
120     FontLanguages(const FontLanguages&) = delete;
121     void operator=(const FontLanguages&) = delete;
122 };
123 
124 }  // namespace android
125 
126 #endif  // MINIKIN_FONT_LANGUAGE_H
127