the #GKeyFile to retrieve the papersize from
the name ofthe group in the key file to read, or %NULL to read the first group
Return: a new #GtkPaperSize object with the restored paper size, or %NULL if an error occurred
GException on failure. ConstructionException GTK+ fails to create the object.
2.12
Reads a paper size from the group @group_name in the key file @key_file.