Since we set the size request of the label, the later measure()
call would return at least the size we set, making the size only ever
grow.
highest_value = gtk_adjustment_get_upper (adjustment);
old_text = g_strdup (gtk_label_get_label (GTK_LABEL (priv->value_widget)));
+ gtk_widget_set_size_request (priv->value_widget, -1, -1);
text = gtk_scale_format_value (scale, lowest_value);
gtk_label_set_label (GTK_LABEL (priv->value_widget), text);