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<tr><th colspan="3" align="center">Marking strings for translation</th></tr>
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<th width="60%" align="center">Chapter 27. Internationalization and Localization</th>
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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-i18n-marking-strings"></a>Marking strings for translation</h2></div></div></div>
<p>
String literals should be typed in the source code in English, but
they should be surrounded by a call to the <code class="function">gettext()</code>
function. These strings will be extracted for translation and the
translations may be used at runtime instead of the original English
strings.
</p>
<p>
The <span class="application">GNU gettext</span> package allows you to mark
strings in source code, extract those strings for translation, and use
the translated strings in your application.
</p>
<p>
However, <span class="application">Glib</span> defines
<code class="function">gettext()</code>
support macros which are shorter wrappers in an easy-to-use form.
To use these macros, include <code class="literal"><glibmm/i18n.h></code>,
and then, for example, substitute:</p>
<pre class="programlisting"><code class="code">display_message("Getting ready for i18n.");</code></pre>
<p>with:</p>
<pre class="programlisting"><code class="code">display_message(_("Getting ready for i18n."));</code></pre>
<p>
For reference, it is possible to generate a file which contains all
strings which appear in your code, even if they are not marked for translation,
together with file name and line
number references. To generate such a file named
<code class="literal">my-strings</code>, execute the following command,
within the source code directory:
</p>
<pre class="programlisting"><code class="code">xgettext -a -o my-strings --omit-header *.cc *.h</code></pre>
<p>
Finally, to let your program use the translation for the current locale,
add this code to the beginning of your <code class="filename">main.cc</code> file, to initialize gettext.
</p>
<pre class="programlisting"><code class="code">bindtextdomain(GETTEXT_PACKAGE, PROGRAMNAME_LOCALEDIR);
bind_textdomain_codeset(GETTEXT_PACKAGE, "UTF-8");
textdomain(GETTEXT_PACKAGE);</code></pre>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-i18n-gettext"></a>How gettext works</h3></div></div></div>
<p>
The <span class="application">intltool-update</span> or
<span class="application">xgettext</span> script extracts the strings
and puts them in a <code class="filename">mypackage.pot</code> file.
The translators of your application create their translations by
first copying this <code class="filename">.pot</code> file to a
<code class="filename">localename.po</code> file. A locale identifies a
language and an encoding for that language, including date and numerical
formats. Later, when the text in your source code has changed, the
<span class="application">msgmerge</span> or <span class="application">intltool-update</span>
script is used to update the <code class="filename">localename.po</code> files from
the regenerated <code class="filename">.pot</code> file.
</p>
<p>
At install time, the <code class="filename">.po</code> files are converted to
a binary format (with the extension <code class="filename">.mo</code>) and
placed in a system-wide directory for locale files, for example
<code class="filename">/usr/share/locale/</code>.
</p>
<p>
When the application runs, the <span class="application">gettext</span>
library checks the system-wide directory to see if there is a
<code class="filename">.mo</code> file for the user's locale environment
(you can set the locale with, for instance, "export LANG=de_DE.UTF-8"
from a bash console). Later, when the program reaches a
<code class="literal">gettext</code> call, it looks for a translation of a
particular string. If none is found, the original string is used.
</p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-i18n-testing"></a>Testing and adding translations</h3></div></div></div>
<p>
To convince yourself that you've done well, you may wish to add a
translation for a new locale. In order to do that, go to the
<code class="filename">po</code> subdirectory of your project and
execute the following command:
</p>
<pre class="programlisting"><code class="code">intltool-update --pot</code></pre>
<p>
That will create a file named <code class="filename">programname.pot</code>.
Now copy that file to <code class="filename">languagecode.po</code>, such as
<code class="filename">de.po</code> or <code class="filename">hu.po</code>. Also add
that language code to <code class="literal">LINGUAS</code>. The
<code class="filename">.po</code> file contains a header and a list of English strings,
with space for the translated strings to be entered. Make sure you set the
encoding of the <code class="filename">.po</code> file (specified in the header, but
also as content) to <code class="literal">UTF-8</code>.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="icons/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top">
<p>
It's possible that certain strings will be marked as
<code class="literal">fuzzy</code> in the <code class="filename">.po</code> file.
These translations will not substitute the original string. To make
them appear, simply remove the <code class="literal">fuzzy</code> tag.
A <code class="literal">fuzzy</code> tag appears if a string content changed,
but the location is still the same.
</p>
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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-i18n-resources"></a>Resources</h3></div></div></div>
<p>
More information about what lies behind the internationalization and localization process
is presented and demonstrated in:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="ulink" href="https://wiki.gnome.org/TranslationProject/DevGuidelines" target="_top">
L10N Guidelines for Developers</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="http://bazaar.launchpad.net/~intltool/intltool/trunk/view/head:/README" target="_top">Intltool README</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="https://wiki.gnome.org/TranslationProject/GitHowTo" target="_top">How to use Git for GNOME translators</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="http://www.gnu.org/software/gettext/manual/gettext.html" target="_top">gettext manual</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="http://ftp.gnome.org/pub/GNOME/sources/gtkmm_hello/" target="_top"><code class="literal">gtkmm_hello</code> example package</a>
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="http://ftp.gnome.org/pub/GNOME/sources/gnomemm_hello/" target="_top"><code class="literal">gnomemm_hello</code> example package</a>
</p>
</li>
</ul></div>
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