Sets the value of one or more cells in the row referenced by @iter. The variable argument list should contain integer column numbers, each column number followed by the value to be set. The list is terminated by a -1. For example, to set column 0 with type %G_TYPE_STRING to "Foo", you would write <literal>gtk_tree_store_set (store, iter, 0, "Foo", -1)</literal>. The value will be referenced by the store if it is a %G_TYPE_OBJECT, and it will be copied if it is a %G_TYPE_STRING or %G_TYPE_BOXED.