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| 31 | </td>
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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Internationalization with Qt</h1>
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| 33 |
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| 34 |
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| 35 | <p> <!-- index internationalization --><a name="internationalization"></a><!-- index i18n --><a name="i18n"></a>
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| 36 | <p> The internationalization of an application is the process of making
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| 37 | the application usable by people in countries other than one's own.
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| 38 | <p> <!-- toc -->
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| 39 | <ul>
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| 40 | <li><a href="#1"> Step by Step
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| 41 | </a>
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| 42 | <ul>
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| 43 | <li><a href="#1-1"> Use QString for all User-visible Text
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| 44 | </a>
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| 45 | <li><a href="#1-2"> Use tr() for all Literal Text
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| 46 | </a>
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| 47 | <li><a href="#1-3"> Use QKeySequence() for Accelerator Values
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| 48 | </a>
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| 49 | <li><a href="#1-4"> Use QString::arg() for Dynamic Text
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| 50 | </a>
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| 51 | <li><a href="#1-5"> Produce Translations
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| 52 | </a>
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| 53 | <li><a href="#1-6"> Support for Encodings
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| 54 | </a>
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| 55 | <li><a href="#1-7"> Localize
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| 56 | </a>
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| 57 | </ul>
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| 58 | <li><a href="#2"> Dynamic Translation
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| 59 | </a>
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| 60 | <li><a href="#3"> System Support
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| 61 | </a>
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| 62 | <ul>
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| 63 | <li><a href="#3-1"> Unix/X11
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| 64 | </a>
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| 65 | <li><a href="#3-2"> Windows
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| 66 | </a>
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| 67 | </ul>
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| 68 | <li><a href="#4"> Note about Locales on X11
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| 69 | </a>
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| 70 | <li><a href="#5"> Relevant Qt Classes
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| 71 | </a>
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| 72 | </ul>
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| 73 | <!-- endtoc -->
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| 74 |
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| 75 | <p> In some cases internationalization is simple, for example, making a US
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| 76 | application accessible to Australian or British users may require
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| 77 | little more than a few spelling corrections. But to make a US
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| 78 | application usable by Japanese users, or a Korean application usable
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| 79 | by German users, will require that the software operate not only in
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| 80 | different languages, but use different input techniques, character
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| 81 | encodings and presentation conventions.
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| 82 | <p> Qt tries to make internationalization as painless as possible for
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| 83 | developers. All input widgets and text drawing methods in Qt offer
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| 84 | built-in support for all supported languages. The built-in font engine
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| 85 | is capable of correctly and attractively rendering text that contains
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| 86 | characters from a variety of different writing systems at the same
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| 87 | time.
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| 88 | <p> Qt supports most languages in use today, in particular:
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| 89 | <ul>
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| 90 | <li> All East Asian languages (Chinese, Japanese and Korean)
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| 91 | <li> All Western languages (using Latin script)
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| 92 | <li> Arabic
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| 93 | <li> Cyrillic languages (Russian)
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| 94 | <li> Greek
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| 95 | <li> Hebrew
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| 96 | <li> Thai and Lao
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| 97 | <li> All scripts in Unicode 3.2 that do not require special processing
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| 98 | </ul>
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| 99 | <p> On Windows NT/2000/XP and Unix/X11 with Xft (client side font support)
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| 100 | the following languages are also supported:
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| 101 | <ul>
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| 102 | <li> Bengali
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| 103 | <li> Devanagari
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| 104 | <li> Dhivehi (Thaana)
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| 105 | <li> Gujarati
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| 106 | <li> Gurmukhi
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| 107 | <li> Kannada
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| 108 | <li> Khmer
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| 109 | <li> Malayalam (X11 only)
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| 110 | <li> Myanmar (X11 only)
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| 111 | <li> Syriac
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| 112 | <li> Tamil
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| 113 | <li> Telugu
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| 114 | <li> Tibetan (X11 only)
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| 115 | </ul>
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| 116 | <p> Many of these writing systems exhibit special features:
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| 117 | <p> <ul>
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| 118 | <p> <li> <b>Special line breaking behavior.</b> Some of the Asian languages are
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| 119 | written without spaces between words. Line breaking can occur either
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| 120 | after every character (with exceptions) as in Chinese, Japanese and
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| 121 | Korean, or after logical word boundaries as in Thai.
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| 122 | <p> <li> <b>Bidirectional writing.</b> Arabic and Hebrew are written from right to
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| 123 | left, except for numbers and embedded English text which is written
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| 124 | left to right. The exact behavior is defined in the <a href="http://www.unicode.org/unicode/reports/tr9/">Unicode Technical Report
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| 125 | #9</a>.
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| 126 | <p> <li> <b>Non spacing or diacritical marks</b> (accents or umlauts in European
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| 127 | languages). Some languages such as Vietnamese make extensive use of
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| 128 | these marks and some characters can have more than one mark at the
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| 129 | same time to clarify pronunciation.
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| 130 | <p> <li> <b>Ligatures.</b> In special contexts, some pairs of characters get
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| 131 | replaced by a combined glyph forming a ligature. Common examples are
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| 132 | the fl and fi ligatures used in typesetting US and European books.
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| 133 | <p> </ul>
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| 134 | <p> Qt tries to take care of all the special features listed above. You
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| 135 | usually don't have to worry about these features so long as you use
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| 136 | Qt's input widgets (e.g. <a href="qlineedit.html">QLineEdit</a>, <a href="qtextedit.html">QTextEdit</a>, and derived classes)
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| 137 | and Qt's display widgets (e.g. <a href="qlabel.html">QLabel</a>).
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| 138 | <p> Support for these writing systems is transparent to the programmer
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| 139 | and completely encapsulated in Qt's text engine. This means that you
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| 140 | don't need to have any knowledge about the writing system used in a
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| 141 | particular language, except for the following small points:
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| 142 | <ul>
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| 143 | <p> <li> <a href="qpainter.html#drawText">QPainter::drawText</a>( int x, int y, const <a href="qstring.html">QString</a> &str ) will always
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| 144 | draw the string with it's left edge at the position specified with
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| 145 | the x, y parameters. This will usually give you left aligned strings.
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| 146 | Arabic and Hebrew application strings are usually right
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| 147 | aligned, so for these languages use the version of drawText() that
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| 148 | takes a <a href="qrect.html">QRect</a> since this will align in accordance with the language.
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| 149 | <p> <li> When you write your own text input controls, use <a href="qfontmetrics.html#charWidth">QFontMetrics::charWidth</a>() to determine the width of a character in a
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| 150 | string. In some languages (e.g. Arabic or languages from the Indian
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| 151 | subcontinent), the width and shape of a glyph changes depending on the
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| 152 | surrounding characters. Writing input controls usually requires a
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| 153 | certain knowledge of the scripts it is going to be used in. Usually
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| 154 | the easiest way is to subclass <a href="qlineedit.html">QLineEdit</a> or <a href="qtextedit.html">QTextEdit</a>.
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| 155 | <p> </ul>
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| 156 | <p> The following sections give some information on the status
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| 157 | of the internationalization (i18n) support in Qt.
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| 158 | <p> See also the <a href="linguist-manual.html">Qt Linguist</a> manual.
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| 159 | <p> <h2> Step by Step
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| 160 | </h2>
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| 161 | <a name="1"></a><p> Writing multi-platform international software with Qt is a gentle,
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| 162 | incremental process. Your software can become internationalized in
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| 163 | the following stages:
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| 164 | <p> <h3> Use <a href="qstring.html">QString</a> for all User-visible Text
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| 165 | </h3>
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| 166 | <a name="1-1"></a><p> Since QString uses the Unicode encoding internally, every
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| 167 | language in the world can be processed transparently using
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| 168 | familiar text processing operations. Also, since all Qt
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| 169 | functions that present text to the user take a QString as a
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| 170 | parameter, there is no char* to QString conversion overhead.
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| 171 | <p> Strings that are in "programmer space" (such as <a href="qobject.html">QObject</a> names
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| 172 | and file format texts) need not use QString; the traditional
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| 173 | char* or the <a href="qcstring.html">QCString</a> class will suffice.
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| 174 | <p> You're unlikely to notice that you are using Unicode;
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| 175 | QString, and <a href="qchar.html">QChar</a> are just like easier versions of the crude
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| 176 | const char* and char from traditional C.
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| 177 | <p> <h3> Use tr() for all Literal Text
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| 178 | </h3>
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| 179 | <a name="1-2"></a><p> Wherever your program uses <tt>"quoted text"</tt> for text that will
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| 180 | be presented to the user, ensure that it is processed by the <a href="qapplication.html#translate">QApplication::translate</a>() function. Essentially all that is necessary
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| 181 | to achieve this is to use <a href="qobject.html#tr">QObject::tr</a>(). For example, assuming the
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| 182 | <tt>LoginWidget</tt> is a subclass of QWidget:
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| 183 | <p> <pre>
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| 184 | LoginWidget::LoginWidget()
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| 185 | {
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| 186 | <a href="qlabel.html">QLabel</a> *label = new <a href="qlabel.html">QLabel</a>( tr("Password:"), this );
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| 187 | ...
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| 188 | }
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| 189 | </pre>
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| 190 |
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| 191 | <p> This accounts for 99% of the user-visible strings you're likely to
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| 192 | write.
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| 193 | <p> If the quoted text is not in a member function of a
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| 194 | <a href="qobject.html">QObject</a> subclass, use either the tr() function of an
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| 195 | appropriate class, or the <a href="qapplication.html#translate">QApplication::translate</a>() function
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| 196 | directly:
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| 197 | <p> <pre>
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| 198 | void some_global_function( LoginWidget *logwid )
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| 199 | {
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| 200 | <a href="qlabel.html">QLabel</a> *label = new <a href="qlabel.html">QLabel</a>(
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| 201 | LoginWidget::tr("Password:"), logwid );
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| 202 | }
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| 203 |
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| 204 | void same_global_function( LoginWidget *logwid )
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| 205 | {
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| 206 | <a href="qlabel.html">QLabel</a> *label = new <a href="qlabel.html">QLabel</a>(
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| 207 | qApp-><a href="qapplication.html#translate">translate</a>("LoginWidget", "Password:"),
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| 208 | logwid );
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| 209 | }
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| 210 | </pre>
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| 211 |
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| 212 | <p> If you need to have translatable text completely
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| 213 | outside a function, there are two macros to help: QT_TR_NOOP()
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| 214 | and QT_TRANSLATE_NOOP(). They merely mark the text for
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| 215 | extraction by the <em>lupdate</em> utility described below.
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| 216 | The macros expand to just the text (without the context).
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| 217 | <p> Example of QT_TR_NOOP():
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| 218 | <pre>
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| 219 | QString FriendlyConversation::greeting( int greet_type )
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| 220 | {
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| 221 | static const char* greeting_strings[] = {
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| 222 | QT_TR_NOOP( "Hello" ),
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| 223 | QT_TR_NOOP( "Goodbye" )
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| 224 | };
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| 225 | return tr( greeting_strings[greet_type] );
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| 226 | }
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| 227 | </pre>
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| 228 |
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| 229 | <p> Example of QT_TRANSLATE_NOOP():
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| 230 | <pre>
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| 231 | static const char* greeting_strings[] = {
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| 232 | QT_TRANSLATE_NOOP( "FriendlyConversation", "Hello" ),
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| 233 | QT_TRANSLATE_NOOP( "FriendlyConversation", "Goodbye" )
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| 234 | };
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| 235 |
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| 236 | QString FriendlyConversation::greeting( int greet_type )
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| 237 | {
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| 238 | return tr( greeting_strings[greet_type] );
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| 239 | }
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| 240 |
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| 241 | <a href="qstring.html">QString</a> global_greeting( int greet_type )
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| 242 | {
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| 243 | return qApp-><a href="qapplication.html#translate">translate</a>( "FriendlyConversation",
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| 244 | greeting_strings[greet_type] );
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| 245 | }
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| 246 | </pre>
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| 247 |
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| 248 | <p> If you disable the const char* to <a href="qstring.html">QString</a> automatic conversion
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| 249 | by compiling your software with the macro QT_NO_CAST_ASCII
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| 250 | defined, you'll be very likely to catch any strings you are
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| 251 | missing. See <a href="qstring.html#fromLatin1">QString::fromLatin1</a>() for more information.
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| 252 | Disabling the conversion can make programming a bit cumbersome.
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| 253 | <p> If your source language uses characters outside Latin-1, you
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| 254 | might find <a href="qobject.html#trUtf8">QObject::trUtf8</a>() more convenient than
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| 255 | <a href="qobject.html#tr">QObject::tr</a>(), as tr() depends on the
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| 256 | <a href="qapplication.html#defaultCodec">QApplication::defaultCodec</a>(), which makes it more fragile than
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| 257 | QObject::trUtf8().
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| 258 | <p> <h3> Use <a href="qkeysequence.html">QKeySequence</a>() for Accelerator Values
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| 259 | </h3>
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| 260 | <a name="1-3"></a><p> Accelerator values such as Ctrl+Q or Alt+F need to be
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| 261 | translated too. If you hardcode <tt>CTRL+Key_Q</tt> for "Quit" in
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| 262 | your application, translators won't be able to override
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| 263 | it. The correct idiom is
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| 264 | <p> <pre>
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| 265 | <a href="qpopupmenu.html">QPopupMenu</a> *file = new <a href="qpopupmenu.html">QPopupMenu</a>( this );
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| 266 | file-><a href="qmenudata.html#insertItem">insertItem</a>( tr("&Quit"), this, SLOT(quit()),
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| 267 | QKeySequence(tr("Ctrl+Q", "File|Quit")) );
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| 268 | </pre>
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| 269 |
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| 270 | <p> <h3> Use <a href="qstring.html#arg">QString::arg</a>() for Dynamic Text
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| 271 | </h3>
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| 272 | <a name="1-4"></a><p> The QString::arg() functions offer a simple means for substituting
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| 273 | arguments:
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| 274 | <pre>
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| 275 | void FileCopier::showProgress( int done, int total,
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| 276 | const <a href="qstring.html">QString</a>& current_file )
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| 277 | {
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| 278 | label.setText( tr("%1 of %2 files copied.\nCopying: %3")
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| 279 | .arg(done)
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| 280 | .arg(total)
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| 281 | .arg(current_file) );
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| 282 | }
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| 283 | </pre>
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| 284 |
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| 285 | <p> In some languages the order of arguments may need to change, and this
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| 286 | can easily be achieved by changing the order of the % arguments. For
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| 287 | example:
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| 288 | <pre>
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| 289 | <a href="qstring.html">QString</a> s1 = "%1 of %2 files copied. Copying: %3";
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| 290 | <a href="qstring.html">QString</a> s2 = "Kopierer nu %3. Av totalt %2 filer er %1 kopiert.";
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| 291 |
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| 292 | <a href="qapplication.html#qDebug">qDebug</a>( s1.<a href="qstring.html#arg">arg</a>(5).arg(10).arg("somefile.txt").ascii() );
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| 293 | <a href="qapplication.html#qDebug">qDebug</a>( s2.<a href="qstring.html#arg">arg</a>(5).arg(10).arg("somefile.txt").ascii() );
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| 294 | </pre>
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| 295 |
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| 296 | <p> produces the correct output in English and Norwegian:
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| 297 | <pre>
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| 298 | 5 of 10 files copied. Copying: somefile.txt
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| 299 | Kopierer nu somefile.txt. Av totalt 10 filer er 5 kopiert.
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| 300 | </pre>
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| 301 |
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| 302 | <p> <h3> Produce Translations
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| 303 | </h3>
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| 304 | <a name="1-5"></a><p> Once you are using tr() throughout an application, you can start
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| 305 | producing translations of the user-visible text in your program.
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| 306 | <p> <a href="linguist-manual.html">Qt Linguist</a>'s manual provides
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| 307 | further information about Qt's translation tools, <em>Qt Linguist</em>, <em>lupdate</em> and <em>lrelease</em>.
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| 308 | <p> Translation of a Qt application is a three-step process:
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| 309 | <p> <ol type=1>
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| 310 | <p> <li> Run <em>lupdate</em> to extract translatable text from the C++ source
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| 311 | code of the Qt application, resulting in a message file for
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| 312 | translators (a <tt>.ts</tt> file). The utility recognizes the tr() construct
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| 313 | and the QT_*_NOOP macros described above and produces <tt>.ts</tt> files
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| 314 | (usually one per language).
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| 315 | <p> <li> Provide translations for the source texts in the <tt>.ts</tt> file, using
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| 316 | <em>Qt Linguist</em>. Since <tt>.ts</tt> files are in XML format, you can also
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| 317 | edit them by hand.
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| 318 | <p> <li> Run <em>lrelease</em> to obtain a light-weight message file (a <tt>.qm</tt>
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| 319 | file) from the <tt>.ts</tt> file, suitable only for end use. Think of the <tt>.ts</tt> files as "source files", and <tt>.qm</tt> files as "object files". The
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| 320 | translator edits the <tt>.ts</tt> files, but the users of your application
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| 321 | only need the <tt>.qm</tt> files. Both kinds of files are platform and
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| 322 | locale independent.
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| 323 | <p> </ol>
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| 324 | <p> Typically, you will repeat these steps for every release of your
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| 325 | application. The <em>lupdate</em> utility does its best to reuse the
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| 326 | translations from previous releases.
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| 327 | <p> Before you run <em>lupdate</em>, you should prepare a project file. Here's
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| 328 | an example project file (<tt>.pro</tt> file):
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| 329 | <p> <pre>
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| 330 | HEADERS = funnydialog.h \
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| 331 | wackywidget.h
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| 332 | SOURCES = funnydialog.cpp \
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| 333 | main.cpp \
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| 334 | wackywidget.cpp
|
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| 335 | FORMS = fancybox.ui
|
|---|
| 336 | TRANSLATIONS = superapp_dk.ts \
|
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| 337 | superapp_fi.ts \
|
|---|
| 338 | superapp_no.ts \
|
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| 339 | superapp_se.ts
|
|---|
| 340 | </pre>
|
|---|
| 341 |
|
|---|
| 342 | <p> When you run <em>lupdate</em> or <em>lrelease</em>, you must give the name of the
|
|---|
| 343 | project file as a command-line argument.
|
|---|
| 344 | <p> In this example, four exotic languages are supported: Danish, Finnish,
|
|---|
| 345 | Norwegian and Swedish. If you use <a href="qmake-manual.html">qmake</a>, you usually don't need an extra project
|
|---|
| 346 | file for <em>lupdate</em>; your <tt>qmake</tt> project file will work fine once
|
|---|
| 347 | you add the <tt>TRANSLATIONS</tt> entry.
|
|---|
| 348 | <p> In your application, you must <a href="qtranslator.html#load">QTranslator::load</a>() the translation
|
|---|
| 349 | files appropriate for the user's language, and install them using <a href="qapplication.html#installTranslator">QApplication::installTranslator</a>().
|
|---|
| 350 | <p> If you have been using the old Qt tools (<tt>findtr</tt>, <tt>msg2qm</tt> and <tt>mergetr</tt>), you can use <em>qm2ts</em> to convert your old <tt>.qm</tt> files.
|
|---|
| 351 | <p> <em>linguist</em>, <em>lupdate</em> and <em>lrelease</em> are installed in the <tt>bin</tt>
|
|---|
| 352 | subdirectory of the base directory Qt is installed into. Click Help|Manual
|
|---|
| 353 | in <em>Qt Linguist</em> to access the user's manual; it contains a tutorial
|
|---|
| 354 | to get you started.
|
|---|
| 355 | <p> While these utilities offer a convenient way to create <tt>.qm</tt> files,
|
|---|
| 356 | any system that writes <tt>.qm</tt> files is sufficient. You could make an
|
|---|
| 357 | application that adds translations to a <a href="qtranslator.html">QTranslator</a> with
|
|---|
| 358 | <a href="qtranslator.html#insert">QTranslator::insert</a>() and then writes a <tt>.qm</tt> file with
|
|---|
| 359 | <a href="qtranslator.html#save">QTranslator::save</a>(). This way the translations can come from any
|
|---|
| 360 | source you choose.
|
|---|
| 361 | <p> <a name="qt-itself"></a>
|
|---|
| 362 | Qt itself contains over 400 strings that will also need to be
|
|---|
| 363 | translated into the languages that you are targeting. You will find
|
|---|
| 364 | translation files for French and German in <tt>$QTDIR/translations</tt> as
|
|---|
| 365 | well as a template for translating to other languages. (This directory
|
|---|
| 366 | also contains some additional unsupported translations which may be
|
|---|
| 367 | useful.)
|
|---|
| 368 | <p> Typically, your application's main() function will look like this:
|
|---|
| 369 | <pre>
|
|---|
| 370 | int main( int argc, char **argv )
|
|---|
| 371 | {
|
|---|
| 372 | <a href="qapplication.html">QApplication</a> app( argc, argv );
|
|---|
| 373 |
|
|---|
| 374 | // translation file for Qt
|
|---|
| 375 | <a href="qtranslator.html">QTranslator</a> qt( 0 );
|
|---|
| 376 | qt.<a href="qtranslator.html#load">load</a>( QString( "qt_" ) + QTextCodec::locale(), "." );
|
|---|
| 377 | app.<a href="qapplication.html#installTranslator">installTranslator</a>( &qt );
|
|---|
| 378 |
|
|---|
| 379 | // translation file for application strings
|
|---|
| 380 | <a href="qtranslator.html">QTranslator</a> myapp( 0 );
|
|---|
| 381 | myapp.<a href="qtranslator.html#load">load</a>( QString( "myapp_" ) + QTextCodec::locale(), "." );
|
|---|
| 382 | app.<a href="qapplication.html#installTranslator">installTranslator</a>( &myapp );
|
|---|
| 383 |
|
|---|
| 384 | ...
|
|---|
| 385 |
|
|---|
| 386 | return app.<a href="qapplication.html#exec">exec</a>();
|
|---|
| 387 | }
|
|---|
| 388 | </pre>
|
|---|
| 389 |
|
|---|
| 390 | <p> <h3> Support for Encodings
|
|---|
| 391 | </h3>
|
|---|
| 392 | <a name="1-6"></a><p> The <a href="qtextcodec.html">QTextCodec</a> class and the facilities in <a href="qtextstream.html">QTextStream</a> make it easy to
|
|---|
| 393 | support many input and output encodings for your users' data. When an
|
|---|
| 394 | application starts, the locale of the machine will determine the 8-bit
|
|---|
| 395 | encoding used when dealing with 8-bit data: such as for font
|
|---|
| 396 | selection, text display, 8-bit text I/O and character input.
|
|---|
| 397 | <p> The application may occasionally require encodings other than the
|
|---|
| 398 | default local 8-bit encoding. For example, an application in a
|
|---|
| 399 | Cyrillic KOI8-R locale (the de-facto standard locale in Russia) might
|
|---|
| 400 | need to output Cyrillic in the ISO 8859-5 encoding. Code for this
|
|---|
| 401 | would be:
|
|---|
| 402 | <p> <pre>
|
|---|
| 403 | <a href="qstring.html">QString</a> string = ...; // some Unicode text
|
|---|
| 404 |
|
|---|
| 405 | <a href="qtextcodec.html">QTextCodec</a>* codec = QTextCodec::<a href="qtextcodec.html#codecForName">codecForName</a>( "ISO 8859-5" );
|
|---|
| 406 | <a href="qcstring.html">QCString</a> encoded_string = codec-><a href="qtextcodec.html#fromUnicode">fromUnicode</a>( string );
|
|---|
| 407 |
|
|---|
| 408 | ...; // use encoded_string in 8-bit operations
|
|---|
| 409 | </pre>
|
|---|
| 410 |
|
|---|
| 411 | <p> For converting Unicode to local 8-bit encodings, a shortcut is
|
|---|
| 412 | available: the <a href="qstring.html#local8Bit">local8Bit</a>() method
|
|---|
| 413 | of <a href="qstring.html">QString</a> returns such 8-bit data. Another useful shortcut is the
|
|---|
| 414 | <a href="qstring.html#utf8">utf8</a>() method, which returns text in the
|
|---|
| 415 | 8-bit UTF-8 encoding: this perfectly preserves Unicode information
|
|---|
| 416 | while looking like plain US-ASCII if the text is wholly US-ASCII.
|
|---|
| 417 | <p> For converting the other way, there are the <a href="qstring.html#fromUtf8">QString::fromUtf8</a>() and
|
|---|
| 418 | <a href="qstring.html#fromLocal8Bit">QString::fromLocal8Bit</a>() convenience functions, or the general code,
|
|---|
| 419 | demonstrated by this conversion from ISO 8859-5 Cyrillic to Unicode
|
|---|
| 420 | conversion:
|
|---|
| 421 | <p> <pre>
|
|---|
| 422 | <a href="qcstring.html">QCString</a> encoded_string = ...; // Some ISO 8859-5 encoded text.
|
|---|
| 423 |
|
|---|
| 424 | <a href="qtextcodec.html">QTextCodec</a>* codec = QTextCodec::<a href="qtextcodec.html#codecForName">codecForName</a>("ISO 8859-5");
|
|---|
| 425 | <a href="qstring.html">QString</a> string = codec-><a href="qtextcodec.html#toUnicode">toUnicode</a>(encoded_string);
|
|---|
| 426 |
|
|---|
| 427 | ...; // Use string in all of Qt's QString operations.
|
|---|
| 428 | </pre>
|
|---|
| 429 |
|
|---|
| 430 | <p> Ideally Unicode I/O should be used as this maximizes the portability
|
|---|
| 431 | of documents between users around the world, but in reality it is
|
|---|
| 432 | useful to support all the appropriate encodings that your users will
|
|---|
| 433 | need to process existing documents. In general, Unicode (UTF-16 or
|
|---|
| 434 | UTF-8) is best for information transferred between arbitrary people,
|
|---|
| 435 | while within a language or national group, a local standard is often
|
|---|
| 436 | more appropriate. The most important encoding to support is the one
|
|---|
| 437 | returned by <a href="qtextcodec.html#codecForLocale">QTextCodec::codecForLocale</a>(), as this is the one the user
|
|---|
| 438 | is most likely to need for communicating with other people and
|
|---|
| 439 | applications (this is the codec used by local8Bit()).
|
|---|
| 440 | <p> Qt supports most of the more frequently used encodings natively. For a
|
|---|
| 441 | complete list of supported encodings see the <a href="qtextcodec.html">QTextCodec</a>
|
|---|
| 442 | documentation.
|
|---|
| 443 | <p> In some cases and for less frequently used encodings it may be
|
|---|
| 444 | necessary to write your own <a href="qtextcodec.html">QTextCodec</a> subclass. Depending on the
|
|---|
| 445 | urgency, it may be useful to contact Trolltech technical support or
|
|---|
| 446 | ask on the <tt>qt-interest</tt> mailing list to see if someone else is
|
|---|
| 447 | already working on supporting the encoding. A useful interim measure
|
|---|
| 448 | can be to use the <a href="qtextcodec.html#loadCharmapFile">QTextCodec::loadCharmapFile</a>() function to build a
|
|---|
| 449 | data-driven codec, although this approach has a memory and speed
|
|---|
| 450 | penalty, especially with dynamically loaded libraries. For details of
|
|---|
| 451 | writing your own QTextCodec, see the main QTextCodec class
|
|---|
| 452 | documentation.
|
|---|
| 453 | <p> <!-- index localization --><a name="localization"></a>
|
|---|
| 454 | <p> <h3> Localize
|
|---|
| 455 | </h3>
|
|---|
| 456 | <a name="1-7"></a><p> Localization is the process of adapting to local conventions, for
|
|---|
| 457 | example presenting dates and times using the locally preferred
|
|---|
| 458 | formats. Such localizations can be accomplished using appropriate tr()
|
|---|
| 459 | strings.
|
|---|
| 460 | <p> <pre>
|
|---|
| 461 | void Clock::setTime(const <a href="qtime.html">QTime</a>& t)
|
|---|
| 462 | {
|
|---|
| 463 | if ( tr("AMPM") == "AMPM" ) {
|
|---|
| 464 | // 12-hour clock
|
|---|
| 465 | } else {
|
|---|
| 466 | // 24-hour clock
|
|---|
| 467 | }
|
|---|
| 468 | }
|
|---|
| 469 | </pre>
|
|---|
| 470 |
|
|---|
| 471 | <p> In the example, for the US we would leave the translation of "AMPM" as
|
|---|
| 472 | it is and thereby use the 12-hour clock branch; but in Europe we would
|
|---|
| 473 | translate it as something else (anything else, e.g. "EU") and this
|
|---|
| 474 | will make the code use the 24-hour clock branch.
|
|---|
| 475 | <p> Localizing images is not recommended. Choose clear icons that are
|
|---|
| 476 | appropriate for all localities, rather than relying on local puns or
|
|---|
| 477 | stretched metaphors.
|
|---|
| 478 | <p> <h2> Dynamic Translation
|
|---|
| 479 | </h2>
|
|---|
| 480 | <a name="2"></a><p> Some applications, such as Qt Linguist, must be able to support changes
|
|---|
| 481 | to the user's language settings while they are still running. To make
|
|---|
| 482 | widgets aware of changes to the system language, implement a public
|
|---|
| 483 | slot called <tt>languageChange()</tt> in each widget that needs to be notified.
|
|---|
| 484 | In this slot, you should update the text displayed by widgets using the
|
|---|
| 485 | <a href="qobject.html#tr">QObject::tr</a>(){tr()} function in the usual way; for example:
|
|---|
| 486 | <p> <pre>
|
|---|
| 487 | void MyWidget::languageChange()
|
|---|
| 488 | {
|
|---|
| 489 | titleLabel->setText(tr("Document Title"));
|
|---|
| 490 | ...
|
|---|
| 491 | okPushButton->setText(tr("&OK"));
|
|---|
| 492 | }
|
|---|
| 493 | </pre>
|
|---|
| 494 |
|
|---|
| 495 | <p> The default event handler for <a href="qwidget.html">QWidget</a> subclasses responds to the
|
|---|
| 496 | <a href="qevent.html#Type-enum">LanguageChange</a> event, and will call this slot
|
|---|
| 497 | when necessary; other application components can also connect signals
|
|---|
| 498 | to this slot to force widgets to update themselves.
|
|---|
| 499 | <p> <h2> System Support
|
|---|
| 500 | </h2>
|
|---|
| 501 | <a name="3"></a><p> Some of the operating systems and windowing systems that Qt runs on
|
|---|
| 502 | only have limited support for Unicode. The level of support available
|
|---|
| 503 | in the underlying system has some influence on the support that Qt can
|
|---|
| 504 | provide on those platforms, although in general Qt applications need
|
|---|
| 505 | not be too concerned with platform-specific limitations.
|
|---|
| 506 | <p> <h3> Unix/X11
|
|---|
| 507 | </h3>
|
|---|
| 508 | <a name="3-1"></a><p> <ul>
|
|---|
| 509 | <li> Locale-oriented fonts and input methods. Qt hides these and
|
|---|
| 510 | provides Unicode input and output.
|
|---|
| 511 | <li> Filesystem conventions such as
|
|---|
| 512 | <a href="http://www.ietf.org/rfc/rfc2279.txt">UTF-8</a>
|
|---|
| 513 | are under development
|
|---|
| 514 | in some Unix variants. All Qt file functions allow Unicode,
|
|---|
| 515 | but convert filenames to the local 8-bit encoding, as
|
|---|
| 516 | this is the Unix convention
|
|---|
| 517 | (see <a href="qfile.html#setEncodingFunction">QFile::setEncodingFunction</a>()
|
|---|
| 518 | to explore alternative encodings).
|
|---|
| 519 | <li> File I/O defaults to the local 8-bit encoding,
|
|---|
| 520 | with Unicode options in <a href="qtextstream.html">QTextStream</a>.
|
|---|
| 521 | </ul>
|
|---|
| 522 | <p> <h3> Windows
|
|---|
| 523 | </h3>
|
|---|
| 524 | <a name="3-2"></a><p> <ul>
|
|---|
| 525 | <li> Qt provides full Unicode support, including input methods, fonts,
|
|---|
| 526 | clipboard, drag-and-drop and file names.
|
|---|
| 527 | <li> File I/O defaults to Latin-1, with Unicode options in QTextStream.
|
|---|
| 528 | Note that some Windows programs do not understand big-endian
|
|---|
| 529 | Unicode text files even though that is the order prescribed by
|
|---|
| 530 | the Unicode Standard in the absence of higher-level protocols.
|
|---|
| 531 | <li> Unlike programs written with MFC or plain winlib, Qt programs
|
|---|
| 532 | are portable between Windows 95/98 and Windows NT.
|
|---|
| 533 | <em>You do not need different binaries to support Unicode.</em>
|
|---|
| 534 | </ul>
|
|---|
| 535 | <p> <h2> Note about Locales on X11
|
|---|
| 536 | </h2>
|
|---|
| 537 | <a name="4"></a><p> Many Unix distributions contain only partial support for some locales.
|
|---|
| 538 | For example, if you have a <tt>/usr/share/locale/ja_JP.EUC</tt> directory,
|
|---|
| 539 | this does not necessarily mean you can display Japanese text; you also
|
|---|
| 540 | need JIS encoded fonts (or Unicode fonts), and the <tt>/usr/share/locale/ja_JP.EUC</tt> directory needs to be complete. For best
|
|---|
| 541 | results, use complete locales from your system vendor.
|
|---|
| 542 | <p> <h2> Relevant Qt Classes
|
|---|
| 543 | </h2>
|
|---|
| 544 | <a name="5"></a><p> These classes are relevant to internationalizing Qt applications.
|
|---|
| 545 |
|
|---|
| 546 | <p><table width="100%">
|
|---|
| 547 | <tr bgcolor=#f0f0f0><td><b><a href="qbig5codec.html">QBig5Codec</a></b><td>Conversion to and from the Big5 encoding
|
|---|
| 548 | <tr bgcolor=#f0f0f0><td><b><a href="qeucjpcodec.html">QEucJpCodec</a></b><td>Conversion to and from EUC-JP character sets
|
|---|
| 549 | <tr bgcolor=#f0f0f0><td><b><a href="qeuckrcodec.html">QEucKrCodec</a></b><td>Conversion to and from EUC-KR character sets
|
|---|
| 550 | <tr bgcolor=#f0f0f0><td><b><a href="qgb18030codec.html">QGb18030Codec</a></b><td>Conversion to and from the Chinese GB18030/GBK/GB2312 encoding
|
|---|
| 551 | <tr bgcolor=#f0f0f0><td><b><a href="qgb2312codec.html">QGb2312Codec</a></b><td>Conversion to and from the Chinese GB2312 encoding
|
|---|
| 552 | <tr bgcolor=#f0f0f0><td><b><a href="qgbkcodec.html">QGbkCodec</a></b><td>Conversion to and from the Chinese GBK encoding
|
|---|
| 553 | <tr bgcolor=#f0f0f0><td><b><a href="qhebrewcodec.html">QHebrewCodec</a></b><td>Conversion to and from visually ordered Hebrew
|
|---|
| 554 | <tr bgcolor=#f0f0f0><td><b><a href="qjiscodec.html">QJisCodec</a></b><td>Conversion to and from JIS character sets
|
|---|
| 555 | <tr bgcolor=#f0f0f0><td><b><a href="qsjiscodec.html">QSjisCodec</a></b><td>Conversion to and from Shift-JIS
|
|---|
| 556 | <tr bgcolor=#f0f0f0><td><b><a href="qtextcodec.html">QTextCodec</a></b><td>Conversion between text encodings
|
|---|
| 557 | <tr bgcolor=#f0f0f0><td><b><a href="qtextdecoder.html">QTextDecoder</a></b><td>State-based decoder
|
|---|
| 558 | <tr bgcolor=#f0f0f0><td><b><a href="qtextencoder.html">QTextEncoder</a></b><td>State-based encoder
|
|---|
| 559 | <tr bgcolor=#f0f0f0><td><b><a href="qtranslator.html">QTranslator</a></b><td>Internationalization support for text output
|
|---|
| 560 | <tr bgcolor=#f0f0f0><td><b><a href="qtranslatormessage.html">QTranslatorMessage</a></b><td>Translator message and its properties
|
|---|
| 561 | <tr bgcolor=#f0f0f0><td><b><a href="qtsciicodec.html">QTsciiCodec</a></b><td>Conversion to and from the Tamil TSCII encoding
|
|---|
| 562 | </table>
|
|---|
| 563 | <!-- eof -->
|
|---|
| 564 | <p><address><hr><div align=center>
|
|---|
| 565 | <table width=100% cellspacing=0 border=0><tr>
|
|---|
| 566 | <td>Copyright © 2007
|
|---|
| 567 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
|
|---|
| 568 | <td align=right><div align=right>Qt 3.3.8</div>
|
|---|
| 569 | </table></div></address></body>
|
|---|
| 570 | </html>
|
|---|
