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<a name="sec-i18n-expecting-utf8"></a>Expecting UTF8</h2></div></div></div>
<p>
A properly internationalized application will not make assumptions about the
number of bytes in a character. That means that you shouldn't use pointer
arithmetic to step through the characters in a string, and it means you
shouldn't use <code class="classname">std::string</code> or standard C functions such
as <code class="function">strlen()</code> because they make the same assumption.
</p>
<p>
However, you probably already avoid bare char* arrays and pointer arithmetic by
using <code class="classname">std::string</code>, so you just need to start using
<code class="classname">Glib::ustring</code> instead. See the <a class="link" href="sec-basics-ustring.html" title="Glib::ustring">Basics</a> chapter about
<code class="classname">Glib::ustring</code>.
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<div class="titlepage"><div><div><h3 class="title">
<a name="i18n-ustring-iostreams"></a>Glib::ustring and std::iostreams</h3></div></div></div>
<p>
Unfortunately, the integration with the standard iostreams is not completely
foolproof. <span class="application">gtkmm</span> converts <code class="classname">Glib::ustring</code>s to a
locale-specific encoding (which usually is not UTF-8) if you output them to an
<code class="classname">ostream</code> with <code class="function">operator<<</code>.
Likewise, retrieving <code class="classname">Glib::ustring</code>s from
<code class="classname">istream</code> with <code class="function">operator>></code>
causes a conversion in the opposite direction. But this scheme breaks down if
you go through a <code class="classname">std::string</code>, e.g. by inputting text
from a stream to a <code class="classname">std::string</code> and then implicitly
converting it to a <code class="classname">Glib::ustring</code>. If the string
contained non-ASCII characters and the current locale is not UTF-8 encoded, the
result is a corrupted <code class="classname">Glib::ustring</code>. You can work around
this with a manual conversion. For instance, to retrieve the
<code class="classname">std::string</code> from a <code class="classname">ostringstream</code>:
</p>
<pre class="programlisting"><code class="code">std::locale::global(std::locale("")); // Set the global locale to the user's preferred locale.
// Usually unnecessary here, because Glib::init()
// or Gtk::Application::create() does it for you.
std::ostringstream output;
output << percentage << " % done";
label->set_text(Glib::locale_to_utf8(output.str()));</code></pre>
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