Derives the allocation of renderer inside area if area were to be renderered in cell_area.
the #GtkCellAreaContext used to hold sizes for area.
the #GtkWidget that area is rendering on
the #GtkCellRenderer to get the allocation for
the whole allocated area for area in widget for this row
where to store the allocation for renderer
Derives the allocation of renderer inside area if area were to be renderered in cell_area.