hbox widgets with different heights

[Ignacio Nodal <inodal teleline es>]

Hi again,

I'm packing a label, a scale and a button in a hbox. If I resize the
widget the label and the button should remain of the same size and the
scale should be expanded. So I used:
[...]
    _box = gtk_hbox_new(FALSE, 0);

    _label = gtk_label_new("Integer:");
    gtk_box_pack_start(GTK_BOX(_box), _label, FALSE, FALSE, 5);

    _adj = gtk_adjustment_new(val_default,val_min,val_max,0.1,1.0,1.0);
    _scale = gtk_hscale_new(GTK_ADJUSTMENT(_adj));
    gtk_range_set_update_policy
(GTK_RANGE(_scale),GTK_UPDATE_CONTINUOUS);
    gtk_scale_set_digits (GTK_SCALE(_scale),0);
    gtk_scale_set_value_pos (GTK_SCALE(_scale), GTK_POS_TOP);
    gtk_scale_set_draw_value (GTK_SCALE(_scale), TRUE);
    gtk_box_pack_start(GTK_BOX(_box),_scale, TRUE, TRUE, 0);

    _button = gtk_button_new_with_label("[-]");
    gtk_box_pack_start(GTK_BOX(_box),_button, FALSE, FALSE, 5);
[...]
That works fine.. the problem is I don't like the height of the button,
I would like it a little smaller, so I tried : 
	gtk_widget_set_usize(GTK_WIDGET(_button),20,5);
..but the button widget didn't care at all.. 

Is there any way to make a widget in a hbox smaller in height than the
other widgets??

Thanks in advance,
	Ignacio Nodal