gtk_container_set_border_width (GTK_CONTAINER (dialog), 5);
gtk_box_set_spacing (GTK_BOX (content_area), 2); /* 2 * 5 + 2 = 12 */
gtk_container_set_border_width (GTK_CONTAINER (action_area), 5);
gtk_container_set_border_width (GTK_CONTAINER (dialog), 5);
gtk_box_set_spacing (GTK_BOX (content_area), 2); /* 2 * 5 + 2 = 12 */
gtk_container_set_border_width (GTK_CONTAINER (action_area), 5);