Gtkmm columnview - cannot programatically activate

Question

Want to programatically activate a gtkmm columnview but when I set up the handler and then call the activate() member it does not invoke the handler. I have modified a simple example of the columnview class as per the gtkmm examples. The header file is below:

#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H

#include <gtkmm.h>

class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  ~ExampleWindow() override;

protected:
  // Signal handlers:
  void on_button_quit();
  void on_setup_label(const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign);
  void on_setup_progressbar(const Glib::RefPtr<Gtk::ListItem>& list_item);
  void on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item);
  void on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item);
  void on_bind_number(const Glib::RefPtr<Gtk::ListItem>& list_item);
  void on_bind_percentage(const Glib::RefPtr<Gtk::ListItem>& list_item);
  void on_columnview_activate(guint position);

  // A Gio::ListStore item.
  class ModelColumns : public Glib::Object
  {
  public:
    unsigned int m_col_id;
    Glib::ustring m_col_name;
    short m_col_number;
    int m_col_percentage;

    static Glib::RefPtr<ModelColumns> create(unsigned int col_id,
      const Glib::ustring& col_name, short col_number, int col_percentage)
    {
      return Glib::make_refptr_for_instance<ModelColumns>(
        new ModelColumns(col_id, col_name, col_number, col_percentage));
    }

  protected:
    ModelColumns(unsigned int col_id, const Glib::ustring& col_name,
      short col_number, int col_percentage)
    : m_col_id(col_id), m_col_name(col_name), m_col_number(col_number),
      m_col_percentage(col_percentage)
    {}
  }; // ModelColumns

  // Child widgets:
  Gtk::Box m_VBox;
  Gtk::ScrolledWindow m_ScrolledWindow;
  Gtk::ColumnView m_ColumnView;
  Gtk::Box m_ButtonBox;
  Gtk::Button m_Button_Quit;

  Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;
};

#endif //GTKMM_EXAMPLEWINDOW_H

The cpp file is below:

#include "examplewindow.h"

ExampleWindow::ExampleWindow()
: m_VBox(Gtk::Orientation::VERTICAL),
  m_Button_Quit("Quit")
{
  set_title("Gtk::ColumnView (Gio::ListStore) example");
  set_default_size(500, 250);

  m_VBox.set_margin(5);
  set_child(m_VBox);

  // Add the ColumnView, inside a ScrolledWindow, with the button underneath:
  m_ScrolledWindow.set_child(m_ColumnView);

  // Only show the scrollbars when they are necessary:
  m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
  m_ScrolledWindow.set_expand();

  m_VBox.append(m_ScrolledWindow);
  m_VBox.append(m_ButtonBox);

  m_ButtonBox.append(m_Button_Quit);
  m_ButtonBox.set_margin(5);
  m_Button_Quit.set_hexpand(true);
  m_Button_Quit.set_halign(Gtk::Align::END);
  m_Button_Quit.signal_clicked().connect(
    sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

  // Create the List model:
  m_ListStore = Gio::ListStore<ModelColumns>::create();
  m_ListStore->append(ModelColumns::create(1, "Billy Bob", 10, 15));
  m_ListStore->append(ModelColumns::create(2, "Joey Jojo", 20, 40));
  m_ListStore->append(ModelColumns::create(3, "Rob McRoberts", 30, 70));

  // Set list model and selection model.
  auto selection_model = Gtk::SingleSelection::create(m_ListStore);
  selection_model->set_autoselect(false);
  selection_model->set_can_unselect(true);
  m_ColumnView.set_model(selection_model);
  m_ColumnView.add_css_class("data-table"); // high density table

  // Make the columns reorderable.
  // This is not necessary, but it's nice to show the feature.
  m_ColumnView.set_reorderable(true);

  // Add the ColumnView's columns:

  // Id column
  auto factory = Gtk::SignalListItemFactory::create();
  factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
    &ExampleWindow::on_setup_label), Gtk::Align::END));
  factory->signal_bind().connect(
    sigc::mem_fun(*this, &ExampleWindow::on_bind_id));
  auto column = Gtk::ColumnViewColumn::create("ID", factory);
  m_ColumnView.append_column(column);

  // Name column
  factory = Gtk::SignalListItemFactory::create();
  factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
    &ExampleWindow::on_setup_label), Gtk::Align::START));
  factory->signal_bind().connect(
    sigc::mem_fun(*this, &ExampleWindow::on_bind_name));
  column = Gtk::ColumnViewColumn::create("Name", factory);
  m_ColumnView.append_column(column);

  // Number column
  factory = Gtk::SignalListItemFactory::create();
  factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
    &ExampleWindow::on_setup_label), Gtk::Align::END));
  factory->signal_bind().connect(
    sigc::mem_fun(*this, &ExampleWindow::on_bind_number));
  column = Gtk::ColumnViewColumn::create("Formatted number", factory);
  m_ColumnView.append_column(column);

  // Percentage column
  factory = Gtk::SignalListItemFactory::create();
  factory->signal_setup().connect(
    sigc::mem_fun(*this, &ExampleWindow::on_setup_progressbar));
  factory->signal_bind().connect(
    sigc::mem_fun(*this, &ExampleWindow::on_bind_percentage));
  column = Gtk::ColumnViewColumn::create("Some percentage", factory);
  m_ColumnView.append_column(column);

   m_ColumnView.signal_activate().connect(
     sigc::mem_fun(
        *this,
        &ExampleWindow::on_columnview_activate
     )
      );

   m_ColumnView.activate();
   printf("After columnview activate called.\n");
}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_button_quit()
{
  set_visible(false);
}

void ExampleWindow::on_columnview_activate(guint position)
{
   printf("Columnview activate routine called for row %d.\n", position);
}

void ExampleWindow::on_setup_label(
  const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign)
{
  list_item->set_child(*Gtk::make_managed<Gtk::Label>("", halign));
}

void ExampleWindow::on_setup_progressbar(
  const Glib::RefPtr<Gtk::ListItem>& list_item)
{
  auto progressbar = Gtk::make_managed<Gtk::ProgressBar>();
  progressbar->set_show_text(true);
  list_item->set_child(*progressbar);
}

void ExampleWindow::on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item)
{
  auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
  if (!col)
    return;
  auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
  if (!label)
    return;
  label->set_text(Glib::ustring::format(col->m_col_id));
}

void ExampleWindow::on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item)
{
  auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
  if (!col)
    return;
  auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
  if (!label)
    return;
  label->set_text(col->m_col_name);
}

void ExampleWindow::on_bind_number(const Glib::RefPtr<Gtk::ListItem>& list_item)
{
  auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
  if (!col)
    return;
  auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
  if (!label)
    return;
  // 10 digits, using leading zeroes.
  label->set_text(Glib::ustring::sprintf("%010d", col->m_col_number));
}

void ExampleWindow::on_bind_percentage(const Glib::RefPtr<Gtk::ListItem>& list_item)
{
  auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
  if (!col)
    return;
  auto progressbar = dynamic_cast<Gtk::ProgressBar*>(list_item->get_child());
  if (!progressbar)
    return;
  progressbar->set_fraction(col->m_col_percentage * 0.01);
}

If I double click on a row then the activate handler will be called, but not when I call activate() manually. I have been converting from gtkmm 4.8 to 4.10 and in the past could use a treeview but is now deprecated. Activating a treeview via code worked in the past.

1. Created simple example as per forum request.
2. Compiled and ran code and only works as discussed above.

Further information

3. Attempting to replace row_activated() call in deprecated TreeView class.

4. Converting from gtkmm 4.8 to 4.10.

5. Compiling with g++ and disabling deprecated classes and functions.