[tepl] utils: improve doc of list_box_get_row_at_index_with_filter()

[Sébastien Wilmet <swilmet src gnome org>]

commit c19a38174aefffc3192301448d5c34cdd313c458
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Nov 4 22:12:00 2020 +0100

    utils: improve doc of list_box_get_row_at_index_with_filter()

 tepl/tepl-utils.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/tepl/tepl-utils.c b/tepl/tepl-utils.c
index 3a949da..935219f 100644
--- a/tepl/tepl-utils.c
+++ b/tepl/tepl-utils.c
@@ -901,13 +901,17 @@ tepl_utils_list_box_scroll_to_selected_row (GtkListBox *list_box)
 /**
  * tepl_utils_list_box_get_row_at_index_with_filter:
  * @list_box: a #GtkListBox.
- * @index: the index of the row.
+ * @index: the index of the row, starting at 0. The index is among the filtered
+ *   rows only.
  * @filter_func: (scope call): non-%NULL callback function.
  * @user_data: user data passed to @filter_func.
  *
  * This function has the same semantics as gtk_list_box_get_row_at_index(), but
  * it takes into account only the rows for which @filter_func returns %TRUE.
  *
+ * As an example, if @index is 0, it returns the first #GtkListBoxRow for which
+ * @filter_func returns %TRUE.
+ *
  * Returns: (transfer none) (nullable): the child #GtkListBoxRow or %NULL.
  * Since: 5.2
  */