[racket] XNextEvent blocking 'read' in other thread?

Thank you all very much for your answers, they are very helpful.

AFAICT, after some light testing, Jon's code does what I want, but Kevin's
one is still blocking.
Also, both versions seem to suffer a heavy cost of a few seconds of
initialization compared to the basic XNextEvent version.

Laurent


On Wed, Nov 7, 2012 at 7:24 PM, Jon Rafkind <rafkind at cs.utah.edu> wrote:

>  Here is some goofy code from my barely-started window manager
>
>  (define (run)
>     (define (make-root-node)
>       (send (new RootNode (window x-root))
>             add-windows
>             (get-all-windows)))
>     (printf "Welcome to smokey\n")
>     (XSetInputFocus x-display None 0 0)
>     (let ((events (make-channel)))
>       ;; (run-events-thread events)
>       (start-x11-event-thread x-display events)
>       (let server-loop ((root (make-root-node)))
>         (sync (handle-evt events (lambda (event)
>                                    ;; (printf "Event ~a\n" event)
>                                    (server-loop
>                                      (send root handle-event event))))))))
>
>
> On 11/07/2012 11:13 AM, Kevin Tew wrote:
>
> yeah I'm putting it in a subdirectory.
>
> I'm also trying to get XConnectionNumber to work first.
>
> Kevin
>
> On 11/07/2012 11:09 AM, Jon Rafkind wrote:
>
> xlambda :p
>
> would you like to commit it to the repo?
>
> On 11/07/2012 10:23 AM, Kevin Tew wrote:
>
> I've attached my in-progress port of xmonad to x11-racket.
>
> Kevin
>
> On 11/07/2012 10:16 AM, Kevin Tew wrote:
>
> Racket threads are green or user threads, they are not scheduled by the
> operating system.
> Blocking on a socket in XNextEvent blocks the entire Racket VM.
>
>
> You need to use XConnectionNumber to get the X socket file descriptor
> number and then create a port that you can sync on with Racket's sync
> functionality.
>
> I'm not sure how you would create the port using the ffi.
>
> See
> http://fixunix.com/xwindows/91558-xconnectionnumber-select.html.
>
> Kevin
>
> On 11/07/2012 09:58 AM, Laurent wrote:
>
> Hi,
>
> I don't know if this issue is due to me, Racket, Xlib FFI or Xlib in
> itself, but I'm struggling with it. Hopefully someone knows.
>
> In a multi-threaded application using Jon's Xlib FFI (
> https://github.com/kazzmir/x11-racket ), I'm using one thread for
> processing X events with XNextEvent, which is a blocking call (apparently
> on a socket).
> I have another thread that listens to a tcp port, and does not need to do
> any X call.
>
> The problem is that the second thread blocks on 'read' even if there is
> something in the queue to read, unless some X event unblocks XNextEvent, in
> which case both threads run, until there is no X event left (and XNextEvent
> blocks again).
>
> I have called XInitThreads prior to any other X call to enable threads
> (and the return values says it's ok).
>
> Any idea anyone?
>
> Thanks,
> Laurent
>
>
>
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