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<div class="sect1" title="Asynchronous operations">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-async-printing-ops"></a>Asynchronous operations</h2></div></div></div>
<p>
By default, <code class="methodname">PrintOperation::run()</code> returns when a print
operation is completed. If you need to run a non-blocking print operation,
call <code class="methodname">PrintOperation::set_allow_async()</code>. Note that <code class="methodname">set_allow_async()</code> is not supported
on all platforms, however the <code class="literal">done</code> signal will still be emitted.
</p>
<p>
<code class="methodname">run()</code> may return
<code class="literal">PRINT_OPERATION_RESULT_IN_PROGRESS</code>. To track status
and handle the result or error you need to implement signal handlers for
the <code class="literal">done</code> and <code class="literal">status_changed</code> signals:
</p>
<p>For instance,
</p>
<pre class="programlisting">
// in class ExampleWindow's method...
Glib::RefPtr<PrintOperation> op = PrintOperation::create();
// ...set up op...
op->signal_done().connect(sigc::bind(sigc::mem_fun(*this, &ExampleWindow::on_printoperation_done), op));
// run the op
</pre>
<p>
</p>
<p>Second, check for an error and connect to the <code class="literal">status_changed</code> signal. For instance:
</p>
<pre class="programlisting">
void ExampleWindow::on_printoperation_done(Gtk::PrintOperationResult result, const Glib::RefPtr<PrintOperation>& op)
{
if (result == Gtk::PRINT_OPERATION_RESULT_ERROR)
//notify user
else if (result == Gtk::PRINT_OPERATION_RESULT_APPLY)
//Update PrintSettings with the ones used in this PrintOperation
if (! op->is_finished())
op->signal_status_changed().connect(sigc::bind(sigc::mem_fun(*this, &ExampleWindow::on_printoperation_status_changed), op));
}
</pre>
<p>
</p>
<p>Finally, check the status. For instance,
</p>
<pre class="programlisting">
void ExampleWindow::on_printoperation_status_changed(const Glib::RefPtr<PrintFormOperation>& op)
{
if (op->is_finished())
//the print job is finished
else
//get the status with get_status() or get_status_string()
//update UI
}
</pre>
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