The area a cell in the column will be allocated, or null
location to return x offset of a cell relative to cell_area, or null
location to return y offset of a cell relative to cell_area, or null
location to return width needed to render a cell, or null
location to return height needed to render a cell, or null
Obtains the width and height needed to render the column. This is used primarily by the #GtkTreeView.