Waiting for both keyword and timer events with OCamlSDL (SDL2) - timer

Question

I need to be able to wait for two types of events in the app using OCamlSDL:
User key presses
Timer events with fixed-time interval
I can see in the tutorial how to wait for events in a loop. My idea was to set up a timer using SDL_AddTimer and feed via it custom USER events which will be processed in the same loop as the keyboard events. However I do not see OCAML binding for SDL_AddTimer SDL function. How can I implement something like this?

Answer 1

The solution I found involves running separate POSIX thread which uses Sldevent.add to send user-defined events which are then processed in the main event processing loop with keyboard events. Here is a code except which starts the thread:
...
and timer_cb () = Sdlevent.add [USER 0] in
let timer_thread = Thread.create timer_loop (timer_flag, timer_cb) in
loop state; (* runs main program logic *)
timer_flag := true;
Thread.join timer_thread
Timer function (executed in separate thread):
let rec timer_loop (flag, callback) =
if !flag then
Thread.exit
else
(Thread.delay 0.5;
callback ();
(timer_loop (flag, callback)))
Event handling loop except:
let rec loop state =
match wait_event () with
| KEYDOWN {keysym=KEY_LEFT} ->
(* process left arrow key press here *)
loop state
| USER 0 ->
(* Process ticks here *)
loop state
| KEYDOWN {keysym=KEY_ESCAPE} ->
(* ESC to exit the app *)
()
| _ ->
loop state