The CellAreaBox renders cell renderers into a row or a column depending on its Orientation.
GtkCellAreaBox uses a notion of packing. Packing refers to adding cell renderers with reference to a particular position in a CellAreaBox. There are two reference positions: the start and the end of the box. When the CellAreaBox is oriented in the gtk_orientation_vertical orientation, the start is defined as the top of the box and the end is defined as the bottom. In the gtk_orientation_horizontal orientation start is defined as the left side and the end is defined as the right side.
Alignments of CellRenderers rendered in adjacent rows can be configured by configuring the CellAreaBox align child cell property with cell_set_property or by specifying the "align" argument to pack_start_full and pack_end_full.