[racket] multiple instances of compiled for distribution software

Zelah Hutchinson

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May 19, 2013, 8:10:43 PM5/19/13

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I am curious as to whether it would be possible to run multiple instances of a compiled Racket program. If so, then how may I do this? When I try to run the program twice by double clicking in Mac OS, I still only get one running process. This seems like a very serious limitation. Is there a way around this?

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Matthew Flatt

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May 20, 2013, 8:47:55 AM5/20/13

to Zelah Hutchinson, us...@racket-lang.org

At Sun, 19 May 2013 16:10:43 -0800, Zelah Hutchinson wrote:
> I am curious as to whether it would be possible to run multiple
> instances of a compiled Racket program. If so, then how may I do
> this? When I try to run the program twice by double clicking in Mac
> OS, I still only get one running process. This seems like a very
> serious limitation. Is there a way around this?

Racket GUI programs on Mac OS X behave like other Mac OS X GUI
programs, which means that double-clicking the icon moves a previously
started instance to the front --- but also that you can start multiple
instances by using the command line.

Here's one way:

http://reviews.cnet.com/8301-13727_7-57564478-263/how-to-open-multiple-instances-of-an-application-in-os-x/

I don't know why there isn't a GUI way to do that in Mac OS X, but
below is a little Racket program that you can turn into an application
and use to launch a new instance of any Mac application.

----------------------------------------

#lang racket/gui

(define f (get-file
"Choose an Application"
#f
#f
#f
#f
'(packages)
'(("*.app" "Application"))))

(system* "/usr/bin/open"
"-n"
"-a"
f)

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Hendrik Boom

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May 20, 2013, 11:21:38 AM5/20/13

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On Sun, May 19, 2013 at 04:10:43PM -0800, Zelah Hutchinson wrote:
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> I am curious as to whether it would be possible to run multiple instances of a compiled Racket program. If so, then how may I do this? When I try to run the program twice by double clicking in Mac OS, I still only get one running process. This seems like a very serious limitation. Is there a way around this?<hr size="1px" noshade style="clear:both;margin-top:10px;height:1px;">
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>
Mentioned this to my son, who had an intel mac laptop on his lap, and he
said, Command-N.

And showed me a number of programs for which it worked, by typing
command-N when the program's first window had focus.

Including DrRacket.

-- hendrik

Justin R. Slepak

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May 20, 2013, 12:04:14 PM5/20/13

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Cmd-N typically just opens a new window in the current instance. Use cmd-tab or look in the Dock, and you'll see you still only have one instance of your program running. Explicitly invoking the executable inside the .app bundle will produce a separate instance -- you can see on cmd-tab that you have two instances running.

---
Justin Slepak
PhD student, Computer Science dept.

Zelah Hutchinson

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May 20, 2013, 8:48:50 PM5/20/13

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So I think I have a handle on how to run multiple instances of a compiled program under Mac OS. I should be able to catch the command-n keyboard input in my compiled application. But I run into a similar problem when I work in Windows OS. I compile my source code for distribution. When I double click the application icon for a second time, I still only get one instance of the program. This seems like unusual behavior under Windows. What should I do here to obtain multiple instances?

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Zelah Hutchinson

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May 21, 2013, 4:38:45 PM5/21/13

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So I think I have a handle on how to run multiple instances of a compiled program under Mac OS. I should be able to catch the command-n keyboard input in my compiled application. But I run into a similar problem when I work in Windows OS. I compile my source code for distribution. When I double click the application icon for a second time, I still only get one instance of the program. I would like to get a second instance by double clicking the application icon. What should I do?

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Zelah Hutchinson

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May 21, 2013, 5:05:50 PM5/21/13

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So I think I have a handle on how to run multiple instances of a compiled program under Mac OS. I should be able to catch the command-n keyboard input in my compiled application. But I run into a similar problem when I work in Windows OS. I compile my source code for distribution. When I double click the application icon for a second time, I still only get one instance of the program. I would like to get a second instance by double clicking the application icon. What should I do?

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Matthew Flatt

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May 22, 2013, 10:07:17 AM5/22/13

to Zelah Hutchinson, us...@racket-lang.org

At Mon, 20 May 2013 16:48:50 -0800, Zelah Hutchinson wrote:
> So I think I have a handle on how to run multiple instances of a
> compiled program under Mac OS. I should be able to catch the
> command-n keyboard input in my compiled application. But I run into a
> similar problem when I work in Windows OS. I compile my source code
> for distribution. When I double click the application icon for a
> second time, I still only get one instance of the program. This seems
> like unusual behavior under Windows. What should I do here to obtain
> multiple instances?

It does seem like it has become unusual behavior under Windows. I think
it was common back when we made that choice, but it's also possible
that I was confused back then.

Single-instance mode can be disabled in an executable, but I see that
the configuration is currently only available at the level of the
`create-embedding-executable' function. I'll add a more accessible
point of configuration.

Meanwhile, you could manually edit the binary to change its mode. The
string "yes, please check for another" is embedded in the generated
".exe" file. If you change that leading "y" to "n" (I know that sounds
crazy), then single-instance mode is disabled.

Below is a Racket program that will change an executable for you.

----------------------------------------

#lang racket/gui

(define exe-file (get-file))

(define-values (i o)
(open-input-output-file exe-file #:exists 'update))

(define m (regexp-match-positions
#rx#"yes, please check for another"
i))
(unless m
(error "not a single-instance Racket-generate GUI executable"))

(close-input-port i)

(file-position o (caar m))
(write-byte (char->integer #\n) o)

(close-output-port o)

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