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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html> <head> <title> Internationalization </title> <meta name="GENERATOR" content= "Modular DocBook HTML Stylesheet Version 1.45"> <link rel="HOME" title="GTK+ / Gnome Application Development" href="ggad.html"> <link rel="UP" title="Gnome Application Basics" href= "cha-startup.html"> <link rel="PREVIOUS" title="Gnome Application Basics" href= "cha-startup.html"> <link rel="NEXT" title="Argument Parsing with popt" href= "z77.html"> </head> <body bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink= "#840084" alink="#0000FF"> <div class="NAVHEADER"> <table width="100%" border="0" bgcolor="#ffffff" cellpadding= "1" cellspacing="0"> <tr> <th colspan="4" align="center"> <font color="#000000" size="2">GTK+ / Gnome Application Development</font> </th> </tr> <tr> <td width="25%" bgcolor="#ffffff" align="left"> <a href="cha-startup.html"><font color="#0000ff" size= "2"><b><<< Previous</b></font></a> </td> <td width="25%" colspan="2" bgcolor="#ffffff" align= "center"> <font color="#0000ff" size="2"><b><a href="ggad.html"> <font color="#0000ff" size="2"><b> Home</b></font></a></b></font> </td> <td width="25%" bgcolor="#ffffff" align="right"> <a href="z77.html"><font color="#0000ff" size="2"><b> Next >>></b></font></a> </td> </tr> </table> </div> <div class="SECT1"> <h1 class="SECT1"> <a name="SEC-I18N">Internationalization</a> </h1> <p> All user-visible strings in a Gnome application should be marked for translation. Translation is achieved using the GNU <tt class="APPLICATION">gettext</tt> facility. <tt class="APPLICATION">gettext</tt> is simply a message catalog; it stores key-value pairs, where the key is the string hard-coded into the program, and the value is a translated string (if appropriate) or simply the key (if there's no translation, or the key is already in the correct language). </p> <p> As a programmer, it's not your responsibility to provide translations. However, you must make sure strings are marked for translation---so that <tt class="APPLICATION"> gettext</tt>'s scripts can extract a list of strings to be translated---and you must call a special function on each string when the catalog lookup should take place. </p> <div class="FIGURE"> <a name="ML-I18N"></a> <div class="FUNCSYNOPSIS"> <a name="ML-I18N.SYNOPSIS"></a> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="FUNCSYNOPSISINFO">#include <libgnome/gnome-i18n.h></pre> </td> </tr> </table> <p> <code><code class="FUNCDEF"><tt class="FUNCTION"> _</tt></code>(<tt class= "PARAMETER"><i>string</i></tt>);</code> </p> <p> <code><code class="FUNCDEF"><tt class="FUNCTION"> N_</tt></code>(<tt class= "PARAMETER"><i>string</i></tt>);</code> </p> </div> <p> <b>Figure 2. Translation Macros</b> </p> </div> <p> Gnome makes this easy, by defining two macros shown in <a href="sec-i18n.html#ML-I18N">Figure 2</a>. The macro <tt class="FUNCTION">_()</tt> both marks the string for translation and performs the message-catalog lookup. You should use it in any context C permits a function call. The <tt class="FUNCTION">N_()</tt> macro is a no-op, but marks the string for translation. You can use it when C does not permit a function call; for example in static array initializers. If you mark a string for translation with <tt class="FUNCTION">N_()</tt>, you must eventually call <tt class="FUNCTION">_()</tt> on it to actually perform the lookup. </p> <p> Here's a simple example: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> #include <gnome.h>static char* a[] = { N_("Translate Me"), N_("Me Too")};int main(int argc, char** argv){ bindtextdomain(PACKAGE, GNOMELOCALEDIR); textdomain(PACKAGE); printf(_("Translated String\n")); printf(_(a[0])); printf(_(a[1])); return 0;} </pre> </td> </tr> </table> <p> Notice that the string literals <span class="STRUCTNAME"> "Translate Me"</span> and <span class="STRUCTNAME">"Me Too"</span> are marked so that <tt class="APPLICATION"> gettext</tt> can find them and produce a list of strings to be translated. Translators will use this list to create the actual translations. Later, <tt class="FUNCTION">_()</tt> includes a function call to perform the tranlation lookup on each member of the array. Since a function call is allowed when the string literal <span class="STRUCTNAME"> "Translated String"</span> is introduced, everything can happen in a single step. </p> <p> At the beginning of your program, you have to call <tt class="FUNCTION">bindtextdomain()</tt> and <tt class= "FUNCTION">textdomain()</tt> as shown in the above example. In the above code, <tt class="FUNCTION">PACKAGE</tt> is a string representing the package the program is found in, typically defined in <tt class="FILENAME">config.h</tt> (see <a href="cha-source.html">the chapter called <i> Creating Your Source Tree</i></a>). You must arrange to define <tt class="FUNCTION">GNOMELOCALEDIR</tt>, typically in your <tt class="FILENAME">Makefile.am</tt> (<tt class= "APPLICATION">$(prefix)/share/locale</tt>, or <tt class= "APPLICATION">$(datadir)/locale</tt>, is the standard value). Translations are stored in <tt class="FUNCTION"> GNOMELOCALEDIR</tt>. </p> <p> When marking strings for translation, you must make sure your strings are translatable. Avoid constructing a string at runtime via concatenation. For example, do not do this: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gchar* message = g_strconcat(_("There is an error on device "), device, NULL); </pre> </td> </tr> </table> <p> The problem is that in some languages it may be correct to put the name of the device first (or in the middle). If you use <tt class="FUNCTION">g_snprintf()</tt> or <tt class= "FUNCTION">g_strdup_printf()</tt> instead of concatenation, the translator can change the word order. Here's the right way to do it: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gchar* message = g_strdup_printf(_("There is an error on device %s"), device); </pre> </td> </tr> </table> <p> Now the translator can move <span class="STRUCTNAME"> %s</span> as needed. </p> <p> Complicated syntax-on-the-fly should be avoided whenever possible. For example, translating this is a major problem: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> printf(_("There %s %d dog%s\n"), n_dogs > 1 ? _("were") : _("was"), n_dogs, n_dogs > 1 ? _("s") : ""); </pre> </td> </tr> </table> <p> It is better to move the conditional out of the <tt class= "FUNCTION">printf()</tt>: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> if (n_dogs > 0) printf(_("There were %d dogs\n"), n_dogs); else printf(_("There was 1 dog\n")); </pre> </td> </tr> </table> <p> However, as the <tt class="APPLICATION">gettext</tt> manual points out, even this will not always work; some languages will distinguish more categories than "exactly one" and "more than one" (that is, they might have a word form for "exactly two" in addition to English's singular and plural forms). That manual suggests that a lookup table indexed by the number you plan to use might work in some cases: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> static const char* ndogs_phrases[] = { N_("There were no dogs.\n"), N_("There was one dog.\n"), N_("There were two dogs.\n"), N_("There were three dogs.\n")}; </pre> </td> </tr> </table> <p> As you can see, this rapidly becomes unpleasant to deal with. Avoid it if you can. The <tt class="APPLICATION"> gettext</tt> documentation has more examples, if you find yourself in a hairy situation. </p> <p> Internationalization must also be considered when parsing or displaying certain kinds of data, including dates and decimal numbers. In general, the C library provides sufficient facilities to deal with this; use <tt class= "FUNCTION">strftime()</tt>, <tt class="FUNCTION"> strcoll()</tt>, and so on to handle these cases; a good C or POSIX book will explain them. The glib <span class= "STRUCTNAME">GDate</span> facility handles dates using <tt class="FUNCTION">strftime()</tt> internally. </p> <p> One common mistake to avoid: don't use locale-dependent functions when reading and writing files. For example, <tt class="FUNCTION">printf()</tt> and <tt class="FUNCTION"> scanf()</tt> adjust their decimal number format for the locale, so you can't use this format in files. Users in Europe won't be able to read files created in the United States. </p> </div> <div class="NAVFOOTER"> <br> <br> <table width="100%" border="0" bgcolor="#ffffff" cellpadding= "1" cellspacing="0"> <tr> <td width="25%" bgcolor="#ffffff" align="left"> <a href="cha-startup.html"><font color="#0000ff" size= "2"><b><<< Previous</b></font></a> </td> <td width="25%" colspan="2" bgcolor="#ffffff" align= "center"> <font color="#0000ff" size="2"><b><a href="ggad.html"> <font color="#0000ff" size="2"><b> Home</b></font></a></b></font> </td> <td width="25%" bgcolor="#ffffff" align="right"> <a href="z77.html"><font color="#0000ff" size="2"><b> Next >>></b></font></a> </td> </tr> <tr> <td colspan="2" align="left"> <font color="#000000" size="2"><b>Gnome Application Basics</b></font> </td> <td colspan="2" align="right"> <font color="#000000" size="2"><b>Argument Parsing with <tt class="APPLICATION">popt</tt></b></font> </td> </tr> </table> </div> </body></html>⌨️ 快捷键说明
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