[gtkmm-documentation] Update the PlacesSidebar example

[Kjell Ahlstedt <kjellahl src gnome org>]

commit f6a70a15be1227aef980e9cba4891d64cc2c9745
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Thu Jan 12 18:39:45 2017 +0100

    Update the PlacesSidebar example
    
    The signal_populate_popup() handlers now get a Container* and the container
    is not always a menu.

 examples/book/placessidebar/examplewindow.cc |   28 +++++++++++++++++++++----
 examples/book/placessidebar/examplewindow.h  |    2 +-
 2 files changed, 24 insertions(+), 6 deletions(-)
---
diff --git a/examples/book/placessidebar/examplewindow.cc b/examples/book/placessidebar/examplewindow.cc
index 8677c5e..a8d77c6 100644
--- a/examples/book/placessidebar/examplewindow.cc
+++ b/examples/book/placessidebar/examplewindow.cc
@@ -38,6 +38,7 @@ ExampleWindow::ExampleWindow()
   m_show_enter_location.signal_toggled().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_show_enter_location_toggled));
   m_show_enter_location.set_active(false);
 
+  m_places_sidebar.property_populate_all() = true;
   m_places_sidebar.signal_open_location().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_placessidebar_open_location));
   m_places_sidebar.signal_populate_popup().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_placessidebar_populate_popup));
   //m_places_sidebar.signal_drag_action_requested().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_placessidebar_drag_action_requested));
@@ -116,14 +117,31 @@ void ExampleWindow::on_placessidebar_open_location(const Glib::RefPtr<Gio::File>
   dialog.run();
 }
 
-void ExampleWindow::on_placessidebar_populate_popup(Gtk::Menu* menu, const Glib::RefPtr<Gio::File>& /* 
selected_item */, const Glib::RefPtr<Gio::Volume>& /* selected_volume */)
+void ExampleWindow::on_placessidebar_populate_popup(Gtk::Container* container, const 
Glib::RefPtr<Gio::File>& /* selected_item */, const Glib::RefPtr<Gio::Volume>& /* selected_volume */)
 {
-  auto properties_menu_item = new Gtk::MenuItem("Properties...");
+  if (auto menu = dynamic_cast<Gtk::Menu*>(container))
+  {
+    auto properties_menu_item = Gtk::manage(new Gtk::MenuItem("Properties..."));
+
+    properties_menu_item->signal_activate().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_menu_properties_activate));
+    properties_menu_item->show();
+
+    menu->attach(*properties_menu_item, 0, 1, 0, 1);
+  }
+  else if (auto box = dynamic_cast<Gtk::Box*>(container))
+  {
+    auto properties_button = Gtk::manage(new Gtk::ModelButton());
+    properties_button->property_text() = "Properties...";
 
-  properties_menu_item->signal_activate().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_menu_properties_activate));
-  properties_menu_item->show();
+    properties_button->signal_clicked().connect(sigc::mem_fun(*this, 
&ExampleWindow::on_menu_properties_activate));
+    properties_button->show();
 
-  menu->attach(*properties_menu_item, 0, 1, 0, 1);
+    box->pack_end(*properties_button);
+  }
+  else
+  {
+    std::cout << "on_placessidebar_populate_popup(): Unknown type of container." << std::endl;
+  }
 }
 
 void ExampleWindow::on_menu_properties_activate()
diff --git a/examples/book/placessidebar/examplewindow.h b/examples/book/placessidebar/examplewindow.h
index 88c1b22..f0d4db6 100644
--- a/examples/book/placessidebar/examplewindow.h
+++ b/examples/book/placessidebar/examplewindow.h
@@ -32,7 +32,7 @@ protected:
   void on_show_desktop_toggled();
   void on_show_enter_location_toggled();
   void on_placessidebar_open_location(const Glib::RefPtr<Gio::File>& location, Gtk::PlacesOpenFlags 
open_flags);
-  void on_placessidebar_populate_popup(Gtk::Menu* menu, const Glib::RefPtr<Gio::File>& selected_item, const 
Glib::RefPtr<Gio::Volume>& selected_volume);
+  void on_placessidebar_populate_popup(Gtk::Container* container, const Glib::RefPtr<Gio::File>& 
selected_item, const Glib::RefPtr<Gio::Volume>& selected_volume);
   int on_placessidebar_drag_action_requested(const Glib::RefPtr<Gdk::DragContext>& context, const 
Glib::RefPtr<Gio::File>& dest_file, const std::vector< Glib::RefPtr<Gio::File> >& source_file_list);
   void on_menu_properties_activate();