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enum { COLUMN_FOO, N_COLUMNS};…gdouble foo = 123.45;GtkTreeIter iter;/* create the store */GtkListStore *liststore = gtk_list_store_new (N_COLUMNS, G_TYPE_STRING);gtk_list_store_append (liststore, &iter);gtk_list_store_set (liststore, &iter, COLUMN_FOO, g_strdup_printf ("%.2f", foo));/* configure combo */GtkWidget *combo = gtk_combo_box_new_with_model (GTK_TREE_MODEL (liststore));GtkCellRenderer *renderer = gtk_cell_renderer_text_new ();gtk_cell_layout_pack_start (GTK_CELL_LAYOUT (combo), renderer, TRUE);gtk_cell_layout_add_attributes (GTK_CELL_LAYOUT (combo), renderer, "text", COLUMN_FOO);/* should be enought */gtk_widget_show_all (combo);