[gtkmm-documentation] Builder chapter: Describe additional parameters to get_widget_derived()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 1045d515a99b061fd3bb9ed44e62c8677d4db908
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Fri Jan 29 12:50:13 2016 +0100

    Builder chapter: Describe additional parameters to get_widget_derived()
    
    Bug #134161

 docs/tutorial/C/index-in.docbook |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)
---
diff --git a/docs/tutorial/C/index-in.docbook b/docs/tutorial/C/index-in.docbook
index 3b30315..63c1a29 100644
--- a/docs/tutorial/C/index-in.docbook
+++ b/docs/tutorial/C/index-in.docbook
@@ -6650,6 +6650,26 @@ DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr&lt;Gtk:
 </programlisting>
 </para>
 
+<para>
+Starting with &gtkmm; 3.19.7, it's possible to pass additional arguments from
+<methodname>get_widget_derived()</methodname> to the constructor of the derived
+widget. For instance, this call to <methodname>get_widget_derived()</methodname>
+<programlisting>
+<![CDATA[DerivedDialog* pDialog = nullptr;
+builder->get_widget_derived("DialogBasic", pDialog, true);]]>
+</programlisting>
+can invoke this constructor
+<programlisting>
+<![CDATA[DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder, 
bool warning)
+: Gtk::Dialog(cobject),
+  m_builder(builder),
+  m_pButton(nullptr)
+{
+  // ....
+}]]>
+</programlisting>
+</para>
+
 <sect2 id="builder-example-accessing">
 <title>Example</title>
 <para>