[Jprogramming] Soft-stopping of a long loop

[Oleg Kobchenko]

Still for completeness, you may want to look at
  http://www.jsoftware.com/jwiki/Guides/Windows_Progress_Dialog

The fexist test is the easiest, though it is easier to
delete existing file to stop rather than to create.

Think about "a button on the same form [as long-running code]".
The code does not run on the form. So the form with progress 
and cancel button can be in a separate instance to overcome
the single-threadedness.

See also "wdstatus" in 
  http://www.jsoftware.com/help/user/script_winlib.htm

Maybe we need a command with simplicity of "wdstatus" interface
and implemented as wdstatus box with cancel button in a
remote J instance controlled with jsss/jssc.

Regarding repetative repaints such as plot in a loop:
If you re-read http://www.jsoftware.com/help/user/message_pump.htm
there is 5-second clause. Which means that you may need
wd'msgs' and/or wd'setinvalid' and/or glpaint, otherwise
the repaint will not happen and the screen will turn blank.


--- David Porter <aaadjp at comcast.net> wrote:

> Thanks to all for the suggestions.  For my purpose, that is, the purpose 
> of the end-user, anything short of a button on the same form would be 
> too "disconnected" to  be really useful.  However, these are all great 
> ideas for MY use while developing the code. 
> 
> It is a truly wonderful thing to be able to sit at the same table with 
> all this talent!
> 
> Thanks again,
> Dave
> 
> Eric Iverson wrote:
> > As several members have pointed out J is single threaded (in 
> > particular the J GUI and Engine run in the same single thread). The 
> > suggestions of semaphore and mapped files are perhaps more complicated 
> > than what you required.
> >
> > At the start of you run delete a known file (e.g., 
> > ~temp\interrup_run). And then test for the existance of that file at 
> > appropriate points in the running application (e.g., at the top of the 
> > main loop). If the file exists you can then do whatever you want 
> > within the application (e.g., use wd'mb ....' to put up a message 
> > asking what the user wants to do).
> >
> > ----- Original Message ----- From: "David Porter" <aaadjp at comcast.net>
> > To: "J programming list" <programming at jsoftware.com>
> > Sent: Tuesday, January 15, 2008 8:52 AM
> > Subject: [Jprogramming] Soft-stopping of a long loop
> >
> >
> >> I have a loop that processes around a hundred files.  Once started, 
> >> it must continue or, you must stop it using one of several ugly 
> >> methods from the operating system.
> >>
> >> I put in the break. control word that looks at a variable  to enable 
> >> a way to break out of the loop.  I thought setting that variable with 
> >> a button on the form would be a good idea, but all I get when I try 
> >> this while the loop is running is the Windows "boink" .  Is there a 
> >> good, or any, way to set this variable while the loop is running?
> >>
> >> Dave Porter



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