[Caml-list] Threads, graphics and timeouts ; functor for multiple windows

[Berke Durak <durak@liafa.jussieu.fr>]

Hello everyone,

Last year I was writing some Tetris® clone in Ocaml using the graphics
library... I had to patch the graphics library to include a Timeout
event, because it wouldn't work with threads.

I've tried again yesterday with 3.07.

Basically, whatever I do I get "interrupted system call select" errors.

Today, the graphics library still doesn't work with threads.  I have
tried both bytecode scheduling and pthreads.

I would like to make programs that work as follows :
  while true do
    let t = compute_timeout () in
    match wait_for_keypress_or_timeout t with
    | Timeout -> do_something
    | Keypress k -> do_something else
  done

I've tried with threads, using a "ticker" thread that communicated with
the main thread via events.  It didn't work because there is no timeout
event ; and even if the timer thread sends a signal every second, I
get the "interrupted system call select" error (particularly when the
system load increases).

I then used a Unix pipe with timed_read.  Same problem.

Is there a way to write a (graphical) Tetris with Ocaml with the
Graphics library ?

I'd like to make a few wild suggestions :

  - In the Event module :
    - Add a timeout event
    - Provide a mechanism for aborting events
    - Or add a timed wait function
  - In the Graphics library :
    - Fix the issues with threads
    - Include a timeout event (see my patch at
      http://www.liafa.jussieu.fr/~durak/)

Another suggestion to provide for multiple windows in graphics :
  module type WINDOW_ID =
    sig
      val id : int
    end

  module Builder(W:WINDOW_ID) : GRAPHICS_MODULE

Ie to have multiple windows (say two) you'd just have to make :
  let G1 = Graphics.Builder(struct let id = 1 end) in
  let G2 = Graphics.Builder(struct let id = 2 end) in
  G1.open_window " 100x30";
  G2.open_window " 100x50";
  G1.moveto 0 0; G1.draw_string "this is window 1";
  G2.moveto 0 0; G2.draw_string "this is window 1"
-- 
Berke Durak

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