Sets iter to point to the first child of parent.
If parent has no children, FALSE is returned and iter is set to be invalid. parent will remain a valid node after this function has been called.
If parent is NULL returns the first node, equivalent to gtk_tree_model_get_iter_first (tree_model, iter);
the new [GtkTreeIter-struct|GtkTreeIter-struct] to be set to the child
the [GtkTreeIter-struct|GtkTreeIter-struct], or NULL
TRUE, if iter has been set to the first child
Sets iter to point to the first child of parent.
If parent has no children, FALSE is returned and iter is set to be invalid. parent will remain a valid node after this function has been called.
If parent is NULL returns the first node, equivalent to gtk_tree_model_get_iter_first (tree_model, iter);