Add Graphics.loop_at_exit function

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13869 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

otherlibs/graph/graphics.ml

@@ -212,6 +212,18 @@ let read_key () =
 let key_pressed () =
   let e = wait_next_event [Poll] in e.keypressed
 
+let loop_at_exit events handler =
+  let events = List.filter (fun e -> e <> Poll) events in
+  at_exit (fun _ ->
+    try
+      while true do
+        let e = wait_next_event events in
+        handler e
+      done
+    with Exit -> close_graph ()
+       | e -> close_graph (); raise e
+  )
+
 (*** Sound *)
 
 external sound : int -> int -> unit = "caml_gr_sound"

otherlibs/graph/graphics.mli

@@ -303,6 +303,14 @@ external wait_next_event : event list -> status = "caml_gr_wait_event"
    are queued, and dequeued one by one when the [Key_pressed]
    event is specified. *)
 
+val loop_at_exit : event list -> (status -> unit) -> unit
+(** Loop before exiting the program, the list given as argument is the
+    list of handlers and the events on which these handlers are called.
+    To exit cleanly the loop, the handler should raise Exit. Any other
+    exception will be propagated outside of the loop.
+    @since 4.01
+*)
+
 (** {6 Mouse and keyboard polling} *)
 
 val mouse_pos : unit -> int * int