ScriptUtils.java revision 292deb632cbab232334190e68d29184094d6d51b 
1/*
2 * Copyright (C) 2012 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
17package com.android.inputmethod.latin.utils;
18
19import java.util.Locale;
20import java.util.TreeMap;
21
22/**
23 * A class to help with handling different writing scripts.
24 */
25public class ScriptUtils {
26    // Used for hardware keyboards
27    public static final int SCRIPT_UNKNOWN = -1;
28    // TODO: should we use ISO 15924 identifiers instead?
29    public static final int SCRIPT_LATIN = 0;
30    public static final int SCRIPT_CYRILLIC = 1;
31    public static final int SCRIPT_GREEK = 2;
32    public static final int SCRIPT_ARABIC = 3;
33    public static final int SCRIPT_HEBREW = 4;
34    public static final TreeMap<String, Integer> mLanguageToScript;
35    static {
36        // List of the supported languages and their associated script. We won't check
37        // words written in another script than the selected script, because we know we
38        // don't have those in our dictionary so we will underline everything and we
39        // will never have any suggestions, so it makes no sense checking them, and this
40        // is done in {@link #shouldFilterOut}. Also, the script is used to choose which
41        // proximity to pass to the dictionary descent algorithm.
42        // IMPORTANT: this only contains languages - do not write countries in there.
43        // Only the language is searched from the map.
44        mLanguageToScript = new TreeMap<>();
45        mLanguageToScript.put("cs", SCRIPT_LATIN);
46        mLanguageToScript.put("da", SCRIPT_LATIN);
47        mLanguageToScript.put("de", SCRIPT_LATIN);
48        mLanguageToScript.put("el", SCRIPT_GREEK);
49        mLanguageToScript.put("en", SCRIPT_LATIN);
50        mLanguageToScript.put("es", SCRIPT_LATIN);
51        mLanguageToScript.put("fi", SCRIPT_LATIN);
52        mLanguageToScript.put("fr", SCRIPT_LATIN);
53        mLanguageToScript.put("hr", SCRIPT_LATIN);
54        mLanguageToScript.put("it", SCRIPT_LATIN);
55        mLanguageToScript.put("lt", SCRIPT_LATIN);
56        mLanguageToScript.put("lv", SCRIPT_LATIN);
57        mLanguageToScript.put("nb", SCRIPT_LATIN);
58        mLanguageToScript.put("nl", SCRIPT_LATIN);
59        mLanguageToScript.put("pt", SCRIPT_LATIN);
60        mLanguageToScript.put("sl", SCRIPT_LATIN);
61        mLanguageToScript.put("ru", SCRIPT_CYRILLIC);
62    }
63    /*
64     * Returns whether the code point is a letter that makes sense for the specified
65     * locale for this spell checker.
66     * The dictionaries supported by Latin IME are described in res/xml/spellchecker.xml
67     * and is limited to EFIGS languages and Russian.
68     * Hence at the moment this explicitly tests for Cyrillic characters or Latin characters
69     * as appropriate, and explicitly excludes CJK, Arabic and Hebrew characters.
70     */
71    public static boolean isLetterPartOfScript(final int codePoint, final int scriptId) {
72        switch (scriptId) {
73        case SCRIPT_LATIN:
74            // Our supported latin script dictionaries (EFIGS) at the moment only include
75            // characters in the C0, C1, Latin Extended A and B, IPA extensions unicode
76            // blocks. As it happens, those are back-to-back in the code range 0x40 to 0x2AF,
77            // so the below is a very efficient way to test for it. As for the 0-0x3F, it's
78            // excluded from isLetter anyway.
79            return codePoint <= 0x2AF && Character.isLetter(codePoint);
80        case SCRIPT_CYRILLIC:
81            // All Cyrillic characters are in the 400~52F block. There are some in the upper
82            // Unicode range, but they are archaic characters that are not used in modern
83            // Russian and are not used by our dictionary.
84            return codePoint >= 0x400 && codePoint <= 0x52F && Character.isLetter(codePoint);
85        case SCRIPT_GREEK:
86            // Greek letters are either in the 370~3FF range (Greek & Coptic), or in the
87            // 1F00~1FFF range (Greek extended). Our dictionary contains both sort of characters.
88            // Our dictionary also contains a few words with 0xF2; it would be best to check
89            // if that's correct, but a web search does return results for these words so
90            // they are probably okay.
91            return (codePoint >= 0x370 && codePoint <= 0x3FF)
92                    || (codePoint >= 0x1F00 && codePoint <= 0x1FFF)
93                    || codePoint == 0xF2;
94        case SCRIPT_ARABIC:
95            // Arabic letters can be in any of the following blocks:
96            // Arabic U+0600..U+06FF
97            // Arabic Supplement U+0750..U+077F
98            // Arabic Extended-A U+08A0..U+08FF
99            // Arabic Presentation Forms-A U+FB50..U+FDFF
100            // Arabic Presentation Forms-B U+FE70..U+FEFF
101            return (codePoint >= 0x600 && codePoint <= 0x6FF)
102                    || (codePoint >= 0x750 && codePoint <= 0x77F)
103                    || (codePoint >= 0x8A0 && codePoint <= 0x8FF)
104                    || (codePoint >= 0xFB50 && codePoint <= 0xFDFF)
105                    || (codePoint >= 0xFE70 && codePoint <= 0xFEFF);
106        case SCRIPT_HEBREW:
107            // Hebrew letters are in the Hebrew unicode block, which spans from U+0590 to U+05FF,
108            // or in the Alphabetic Presentation Forms block, U+FB00..U+FB4F, but only in the
109            // Hebrew part of that block, which is U+FB1D..U+FB4F.
110            return (codePoint >= 0x590 && codePoint <= 0x5FF
111                    || codePoint >= 0xFB1D && codePoint <= 0xFB4F);
112        case SCRIPT_UNKNOWN:
113            return true;
114        default:
115            // Should never come here
116            throw new RuntimeException("Impossible value of script: " + scriptId);
117        }
118    }
119
120    public static int getScriptFromLocale(final Locale locale) {
121        final Integer script = mLanguageToScript.get(locale.getLanguage());
122        if (null == script) {
123            throw new RuntimeException("We have been called with an unsupported language: \""
124                    + locale.getLanguage() + "\". Framework bug?");
125        }
126        return script;
127    }
128}
129