[gtkmm-documentation] RadioButton section: Describe Gtk::RadioButton::join_group()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 622bca45dec1a42dd8aafcb8cb93d257c84500a3
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Sun Aug 7 17:00:30 2016 +0200

    RadioButton section: Describe Gtk::RadioButton::join_group()
    
    * docs/tutorial/C/index-in.docbook: RadioButton section: Describe join_group().
    * examples/book/buttons/radiobutton/radiobuttons.cc:
    * examples/book/keyboard_events/simple/examplewindow.cc: Use join_group().
    Bug #769374

 docs/tutorial/C/index-in.docbook                   |   44 ++++++++-----------
 examples/book/buttons/radiobutton/radiobuttons.cc  |    7 +--
 .../book/keyboard_events/simple/examplewindow.cc   |    3 +-
 3 files changed, 22 insertions(+), 32 deletions(-)
---
diff --git a/docs/tutorial/C/index-in.docbook b/docs/tutorial/C/index-in.docbook
index bd0b6f6..9488c56 100644
--- a/docs/tutorial/C/index-in.docbook
+++ b/docs/tutorial/C/index-in.docbook
@@ -907,36 +907,34 @@ put three radio buttons in it:
 <programlisting>class RadioButtons : public Gtk::Window
 {
 public:
-    RadioButtons();
+  RadioButtons();
 
 protected:
-    Gtk::RadioButton m_rb1, m_rb2, m_rb3;
+  Gtk::RadioButton m_rb1, m_rb2, m_rb3;
 };
 
 RadioButtons::RadioButtons()
-  : m_rb1("button1"),
-    m_rb2("button2"),
-    m_rb3("button3")
+: m_rb1("button1"),
+  m_rb2("button2"),
+  m_rb3("button3")
 {
-    Gtk::RadioButton::Group group = m_rb1.get_group();
-    m_rb2.set_group(group);
-    m_rb3.set_group(group);
+  m_rb2.join_group(m_rb1);
+  m_rb3.join_group(m_rb1);
 }</programlisting>
 <para>
 We told &gtkmm; to put all three <classname>RadioButton</classname>s in the
-same group by obtaining the group with <methodname>get_group()</methodname> and using
-<methodname>set_group()</methodname> to tell the other
-<classname>RadioButton</classname>s to share that group.
+same group by using <methodname>join_group()</methodname> to tell the other
+<classname>RadioButton</classname>s to share group with the first
+<classname>RadioButton</classname>.
 </para>
 
 <para>
-Note that you can't just do
+Note that you can't do
 <programlisting>m_rb2.set_group(m_rb1.get_group()); //doesn't work</programlisting>
-because the group is modified by <methodname>set_group()</methodname> and therefore
-non-const.
+because <methodname>get_group()</methodname> returns a <classname>RadioButton::Group</classname>
+which is modified by <methodname>set_group()</methodname> and therefore is non-const.
 </para>
 
-
 <para>
 The second way to set up radio buttons is to make a group first, and
 then add radio buttons to it. Here's an example:
@@ -944,25 +942,21 @@ then add radio buttons to it. Here's an example:
 <programlisting>class RadioButtons : public Gtk::Window
 {
 public:
-    RadioButtons();
+  RadioButtons();
 };
 
 RadioButtons::RadioButtons()
 {
-    Gtk::RadioButton::Group group;
-    Gtk::RadioButton *m_rb1 = Gtk::manage(
-      new Gtk::RadioButton(group,"button1"));
-    Gtk::RadioButton *m_rb2 = manage(
-      new Gtk::RadioButton(group,"button2"));
-      Gtk::RadioButton *m_rb3 = manage(
-        new Gtk::RadioButton(group,"button3"));
+  Gtk::RadioButton::Group group;
+  Gtk::RadioButton* m_rb1 = Gtk::manage(new Gtk::RadioButton(group, "button1"));
+  Gtk::RadioButton* m_rb2 = Gtk::manage(new Gtk::RadioButton(group, "button2"));
+  Gtk::RadioButton* m_rb3 = Gtk::manage(new Gtk::RadioButton(group, "button3"));
 }</programlisting>
 
 <para>
 We made a new group by simply declaring a variable, <literal>group</literal>,
 of type <classname>Gtk::RadioButton::Group</classname>. Then we made three radio
-buttons, using a constructor to make each of them part of
-<literal>group</literal>.
+buttons, using a constructor to make each of them part of <literal>group</literal>.
 </para>
 </sect2>
 
diff --git a/examples/book/buttons/radiobutton/radiobuttons.cc 
b/examples/book/buttons/radiobutton/radiobuttons.cc
index ed4b14b..227d998 100644
--- a/examples/book/buttons/radiobutton/radiobuttons.cc
+++ b/examples/book/buttons/radiobutton/radiobuttons.cc
@@ -1,5 +1,3 @@
-//$Id: radiobuttons.cc 836 2007-05-09 03:02:38Z jjongsma $ -*- c++ -*-
-
 /* gtkmm example Copyright (C) 2002 gtkmm development team
  *
  * This program is free software; you can redistribute it and/or modify
@@ -33,9 +31,8 @@ RadioButtons::RadioButtons() :
   set_border_width(0);
 
   // Put radio buttons 2 and 3 in the same group as 1:
-  Gtk::RadioButton::Group group = m_RadioButton1.get_group();
-  m_RadioButton2.set_group(group);
-  m_RadioButton3.set_group(group);
+  m_RadioButton2.join_group(m_RadioButton1);
+  m_RadioButton3.join_group(m_RadioButton1);
 
   // Add outer box to the window (because the window
   // can only contain a single widget)
diff --git a/examples/book/keyboard_events/simple/examplewindow.cc 
b/examples/book/keyboard_events/simple/examplewindow.cc
index 6e0a23e..c8528ee 100644
--- a/examples/book/keyboard_events/simple/examplewindow.cc
+++ b/examples/book/keyboard_events/simple/examplewindow.cc
@@ -26,8 +26,7 @@ ExampleWindow::ExampleWindow()
   m_first.set_label("First");
   m_second.set_label("Second");
 
-  Gtk::RadioButton::Group group = m_first.get_group();
-  m_second.set_group(group);
+  m_second.join_group(m_first);
   m_first.set_active();
 
   // Main Container: