app: improve doc of gtk_application_get_window_by_id()

https://bugzilla.gnome.org/show_bug.cgi?id=764846

diff --git a/gtk/gtkapplication.c b/gtk/gtkapplication.c
index df6795aab98646e9b0624306f5e4f27e496c54e0..48a4a891cbd491436832578d1ed95f6065d7fcc7 100644 (file)
--- a/gtk/gtkapplication.c
+++ b/gtk/gtkapplication.c
@@ -1159,6 +1159,9 @@ gtk_application_get_windows (GtkApplication *application)
  *
  * Returns the #GtkApplicationWindow with the given ID.
  *
+ * The ID of a #GtkApplicationWindow can be retrieved with
+ * gtk_application_window_get_id().
+ *
  * Returns: (nullable) (transfer none): the window with ID @id, or
  *   %NULL if there is no window with this ID
  *