gtk_widget_size_request (GTK_WIDGET (tree_view), &requisition);
tree_view->priv->hadjustment->upper = MAX (tree_view->priv->hadjustment->upper, (gfloat)requisition.width);
gtk_widget_size_request (GTK_WIDGET (tree_view), &requisition);
tree_view->priv->hadjustment->upper = MAX (tree_view->priv->hadjustment->upper, (gfloat)requisition.width);