[racket] Plot: plot-new-window never happens?

That's extremely helpful, thank you.

Deren

On Tue, Apr 17, 2012 at 12:48 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> All GUI activity like window drawing happens only in the main thread of
> an eventspace. Your program also starts out in the main thread. So,
> yes, drawing has to wait until your loop completes.
>
> One solution is to put your loop in a separate thread. The example
> below creates a thread and passes it to `yield' to wait until the
> thread is done. The `yield' function is special in that it lets other
> GUI activity happen while it waits:
>
>  #lang at-exp racket
>  (require plot
>          racket/gui/base)
>  (plot-new-window? #t)
>  (yield
>  (thread
>   (lambda ()
>     (let loop ()
>       (let ((dummy (read)))
>         (if (and (number? dummy) (zero? dummy))
>             (void)
>             (begin
>               (plot (function (λ(x) (* x x)) -2 2))
>               (loop))))))))
>
> Although the above should work, it's not really a good idea to perform
> GUI actions outside of the main thread. So, here's an improved version
> that uses `queue-callback' to send the `plot' call back to the main
> thread:
>
>  #lang at-exp racket
>  (require plot
>          racket/gui/base)
>  (plot-new-window? #t)
>  (yield
>  (thread
>   (lambda ()
>     (let loop ()
>       (let ((dummy (read)))
>         (if (and (number? dummy) (zero? dummy))
>             (void)
>             (begin
>               ;; queue a callback instead of `plot' directly:
>               (queue-callback
>                (lambda ()
>                  (plot (function (λ(x) (* x x)) -2 2))))
>               (loop))))))))
>
> For more information, see
>
>  http://docs.racket-lang.org/gui/windowing-overview.html#(part._eventspaceinfo)
>
>
> At Tue, 17 Apr 2012 10:40:55 -0400, Deren Dohoda wrote:
>> I was messing around with a spline utility last night and was using
>> the plot-new-window? setting to get a plot. The goal was to share an
>> exe with a coworker who doesn't have Racket. Just a command-line app
>> but to get the plot to display I needed a window and this seemed
>> awesome. The problem is I couldn't get the plot to display when the
>> thread was in a procedure. The window would appear but it was like the
>> plot backend wasn't free to draw to it. Here's a way to reproduce it
>> on v5.2:
>>
>> #lang at-exp racket
>> (require plot)
>> (plot-new-window? #t)
>> (let loop ()
>>   (let ((dummy (read)))
>>     (if (and (number? dummy) (zero? dummy))
>>         (void)
>>         (begin
>>           (plot (function (λ(x) (* x x)) -2 2))
>>           (loop)))))
>>
>> So long as you are looping, new windows will appear without plot
>> contents. When you finally quit (here by entering the number zero) all
>> the plots are drawn in those windows. Any help? Did I do something
>> horribly dumb?
>>
>> Thanks,
>> Deren
>>
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