// Add import column
Gtk::CellRendererToggle * import_render = Gtk::manage(new Gtk::CellRendererToggle());
import_render->signal_toggled().connect (sigc::mem_fun(*this, &SessionMetadataSetImportable::selection_changed));
viewcol = Gtk::manage(new Gtk::TreeView::Column (_("Import"), *import_render));
viewcol->add_attribute (import_render->property_active(), tree_cols.import);
tree_view.append_column (*viewcol);
// Add import column
Gtk::CellRendererToggle * import_render = Gtk::manage(new Gtk::CellRendererToggle());
import_render->signal_toggled().connect (sigc::mem_fun(*this, &SessionMetadataSetImportable::selection_changed));
viewcol = Gtk::manage(new Gtk::TreeView::Column (_("Import"), *import_render));
viewcol->add_attribute (import_render->property_active(), tree_cols.import);
tree_view.append_column (*viewcol);