Why is the information displayed twice in TreeView when using CellRenderer in gtkmm

Question

Having the following code:

MyTreeView::MyTreeView(GtkTreeView* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
    : Gtk::TreeView(cobject)
{
    Glib::RefPtr< Gtk::TreeStore > treeModel;
    treeModel = Gtk::TreeStore::create(treeColumns);

    this->set_model(treeModel);

    Gtk::TreeModel::Row row = *(treeModel->append());
    row[treeColumns.id] = 1;
    row[treeColumns.name] = "one";

    Gtk::TreeModel::Row childrow = *(treeModel->append(row.children()));
    childrow[treeColumns.id] = 11;
    childrow[treeColumns.name] = "eleven";

    childrow = *(treeModel->append(row.children()));
    childrow[treeColumns.id] = 12;
    childrow[treeColumns.name] = "twelve";

    row = *(treeModel->append());
    row[treeColumns.id] = 2;
    row[treeColumns.name] = "two";


    row = *(treeModel->append());
    row[treeColumns.id] = 3;
    row[treeColumns.name] = "three";

    childrow = *(treeModel->append(row.children()));
    childrow[treeColumns.id] = 31;
    childrow[treeColumns.name] = "thirtyone";

    Gtk::TreeModel::Row subchild = *(treeModel->append(childrow.children()));
    subchild[treeColumns.id] = 311;
    subchild[treeColumns.name] = "three hundred eleven";

    Gtk::TreeViewColumn *view_column = Gtk::manage(new Gtk::TreeViewColumn("Name", treeColumns.name));
    Gtk::CellRendererText *cellRenderer = Gtk::manage(new Gtk::CellRendererText());

    view_column->pack_start(*cellRenderer, false);
    view_column->set_cell_data_func(*cellRenderer, sigc::mem_fun(*this, &MyTreeView::on_cell_data_name));
    this->append_column(*view_column);
}


void MyTreeView::on_cell_data_name(Gtk::CellRenderer* renderer, const Gtk::TreeModel::iterator& iter)
{
    //Get the value from the model and show it appropriately in the view:
    Gtk::TreeModel::Row row = *iter;
    int id = row[treeColumns.id];
    Glib::ustring name = row[treeColumns.name];

    Gtk::CellRendererText* text_renderer = dynamic_cast<Gtk::CellRendererText*>(renderer);

    if (id == 11)
    {
        text_renderer->property_weight().set_value(Pango::Weight::WEIGHT_HEAVY);
    }
    else
    {
        text_renderer->property_weight().set_value(Pango::Weight::WEIGHT_NORMAL);
    }

    if(text_renderer)
    {
        text_renderer->property_text() = name;
    }
}

I have the following:

So the data is duplicated in some sort of subcolumn or somesuch. Why does it happen? What can i do to only have the rendered text (with correct font).

I have managed to make an example without using Glade, the problem is still there:

treeview.cpp:

#include <gtkmm.h>

#include "MyWindow.hpp"
int main(int argc, char *argv[])
{
    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.spike.treeview");

    MyWindow window;    
    app->run(window);

    return 0;
}

MyWindow.hpp:

#include <gtkmm.h>

#include "MyTreeView.hpp"

class MyWindow : public Gtk::ApplicationWindow
{
public:
    MyWindow();
    virtual ~MyWindow();

protected:
    MyTreeView *treeView;
};

MyTreeView.hpp:

#include <gtkmm.h>

class MyTreeView : public Gtk::TreeView
{
public:
    MyTreeView();

    void on_cell_data_name(Gtk::CellRenderer* renderer, const Gtk::TreeModel::iterator& iter);

    class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(id); add(name); add(type); add(publicKey); add(privateKey); }

        Gtk::TreeModelColumn<int> id;
        Gtk::TreeModelColumn<Glib::ustring> name;
        Gtk::TreeModelColumn<char> type;
        Gtk::TreeModelColumn<Glib::ustring> publicKey;
        Gtk::TreeModelColumn<Glib::ustring> privateKey;
      } treeColumns;
};

MyWindow.cpp:

#include <iostream>

#include "MyWindow.hpp"

MyWindow::MyWindow()
{
    treeView = Gtk::manage(new MyTreeView());
    add(*treeView);
    show_all_children();
}

MyWindow::~MyWindow()
{}

MyTreeView.cpp:

#include <iostream>

#include "MyTreeView.hpp"

MyTreeView::MyTreeView()
{
    Glib::RefPtr< Gtk::TreeStore > treeModel;
    treeModel = Gtk::TreeStore::create(treeColumns);

    this->set_model(treeModel);

    Gtk::TreeModel::Row row = *(treeModel->append());
    row[treeColumns.id] = 1;
    row[treeColumns.name] = "one";

    Gtk::TreeModel::Row childrow = *(treeModel->append(row.children()));
    childrow[treeColumns.id] = 11;
    childrow[treeColumns.name] = "eleven";

    childrow = *(treeModel->append(row.children()));
    childrow[treeColumns.id] = 12;
    childrow[treeColumns.name] = "twelve";

    row = *(treeModel->append());
    row[treeColumns.id] = 2;
    row[treeColumns.name] = "two";


    row = *(treeModel->append());
    row[treeColumns.id] = 3;
    row[treeColumns.name] = "three";

    childrow = *(treeModel->append(row.children()));
    childrow[treeColumns.id] = 31;
    childrow[treeColumns.name] = "thirtyone";

    Gtk::TreeModel::Row subchild = *(treeModel->append(childrow.children()));
    subchild[treeColumns.id] = 311;
    subchild[treeColumns.name] = "three hundred eleven";

//  this->append_column_editable("Name (orig)", treeColumns.name);
//  this->append_column("Id", treeColumns.id);


    Gtk::TreeViewColumn *view_column = Gtk::manage(new Gtk::TreeViewColumn("Name", treeColumns.name));
    Gtk::CellRendererText *cellRenderer = Gtk::manage(new Gtk::CellRendererText());

    view_column->pack_start(*cellRenderer, false);
    view_column->set_cell_data_func(*cellRenderer, sigc::mem_fun(*this, &MyTreeView::on_cell_data_name));
    this->append_column(*view_column);
}


void MyTreeView::on_cell_data_name(Gtk::CellRenderer* renderer, const Gtk::TreeModel::iterator& iter)
{
    //Get the value from the model and show it appropriately in the view:
    Gtk::TreeModel::Row row = *iter;
    int id = row[treeColumns.id];
    Glib::ustring name = row[treeColumns.name];

    Gtk::CellRendererText* text_renderer = dynamic_cast<Gtk::CellRendererText*>(renderer);

    if (id == 11)
    {
        text_renderer->property_weight().set_value(Pango::Weight::WEIGHT_HEAVY);
    }
    else
    {
        text_renderer->property_weight().set_value(Pango::Weight::WEIGHT_NORMAL);
    }

    if(text_renderer)
    {
        text_renderer->property_text() = name;
    }
}

Answer 1

Because of this line:

Gtk::TreeViewColumn *view_column = Gtk::manage(new Gtk::TreeViewColumn("Name", treeColumns.name));

You've specified the TreeModel column instead of just the title, so it has added a default cell renderer with the default renderering of that data in that column. You need this instead:

Gtk::TreeViewColumn *view_column = Gtk::manage(new Gtk::TreeViewColumn("Name"));