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Groups > comp.sys.acorn.programmer > #895

Re: TaskWindow -txt &xxxxxxxx

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On 18/10/2011 14:23, Erik G wrote:
> This surprised me a bit. What PRM 3-326 says about the *TaskWindow
> command is:
>
> "If -txt and -task are not used, then [a server, eg Edit, is started to
> show the output in a window]".
>
> I read this as: if either -txt or -task is used, no window is opened.

That's correct, with neither of the parameters it means use the default 
taskwindow handler application (starting it if necessary), and as such 
can be issued by either a program or the user at the command line.

If the parameters are supplied it means that a program wants to to start 
a taskwindow task and handle the output itself. Hence no window is 
automatically opened, and the Ego is sent round to allow the program to 
identify the started task.

> The table above shows that -task is the controlling parameter, which
> determines if a server is used to show a window. The -txt parameter is
> optional. Using -txt without -task has no effect (since no Ego message
> is sent, which is the only place the value of the -txt parameter is used).

I can't see the point of that right now, although there might be one.

> So when can a calling program leave out the -txt parameter? My theory is
> that it is possible to do so if the calling task is absolutely certain
> that the Taskwindow_Ego message it gets is about that one specific child
> it has just issued the *TaskWindow command for. Basically it should not
> issue another *TaskWindow command before it has received an Ego message
> for the previous one.

I concur. I've always used both looks like bad practice not to.

> Personally I would advise to always use the -txt parameter. If only to
> save the bother of putting it in afterwards when it turns out the
> program needs to handle more than one child at the same time after all.

Agreed.

> New question: what should an application do if the value in a
> TaskWindow_Ego message it receives does not match any value it knows about?

In general you should ignore any broadcast message which contains 
handles you don't recognise. If it's sent specifically to your task you 
may decide to take further action.

> I think the calling application should send a TaskWindow_Morite message
> to the child (who's handle in R1+4 of Ego message) in an attempt to kill
> off the rogue child. And maybe show an error message to the user.

You could do that, I'm not sure it's an error case worth handling, as it 
most likely you've supplied the wrong handle to yourself and will notice 
that bug very quickly, and somewhat less likely that the TaskWindow 
module has gone berserk.

> If the Ego message came from a genuine TaskWindow task, then the problem
> is due to an internal error in the calling application, and the Morite
> message will ensure no child lingers around.

It's sometimes worth leaving the orphan task window task in the task 
manager list, as then the bug is more obviously that you aren't picking 
up the Ego, rather than killing it and not being sure that the task was 
ever started.

> If the Ego message came from some damned fool program sending or
> broadcasting silly messages, then the Morite message will do no harm.

Maybe!

---druck

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TaskWindow -txt &xxxxxxxx Dave Higton <davehigton@dsl.pipex.com> - 2011-09-27 21:41 +0100
  Re: TaskWindow -txt &xxxxxxxx Martin Wuerthner <spamtrap@mw-software.com> - 2011-09-27 23:08 +0200
    Re: TaskWindow -txt &xxxxxxxx Dave Higton <davehigton@dsl.pipex.com> - 2011-09-27 22:33 +0100
    Re: TaskWindow -txt &xxxxxxxx "Ste (news)" <steve@revi11.plus.com> - 2011-09-28 15:27 +0100
      Re: TaskWindow -txt &xxxxxxxx Martin Wuerthner <spamtrap@mw-software.com> - 2011-09-28 17:16 +0200
        Re: TaskWindow -txt &xxxxxxxx "Ste (news)" <steve@revi11.plus.com> - 2011-09-28 19:52 +0100
          Re: TaskWindow -txt &xxxxxxxx Erik G <erikg@noname.invalid> - 2011-09-30 06:02 +0200
        Re: TaskWindow -txt &xxxxxxxx druck <news@druck.org.uk> - 2011-10-02 16:13 +0100
          Re: TaskWindow -txt &xxxxxxxx Erik G <erikg@noname.invalid> - 2011-10-13 11:23 +0200
            Re: TaskWindow -txt &xxxxxxxx Alex Macfarlane Smith <nospam@archifishal.co.uk> - 2011-10-13 21:08 +0100
            Re: TaskWindow -txt &xxxxxxxx druck <news@druck.org.uk> - 2011-10-15 12:13 +0100
              Re: TaskWindow -txt &xxxxxxxx Erik G <erikg@noname.invalid> - 2011-10-18 16:25 +0200
                Re: TaskWindow -txt &xxxxxxxx Martin Wuerthner <spamtrap@mw-software.com> - 2011-10-19 10:45 +0200
    Re: TaskWindow -txt &xxxxxxxx Erik G <erikg@noname.invalid> - 2011-09-30 05:47 +0200
      Re: TaskWindow -txt &xxxxxxxx Dave Higton <davehigton@dsl.pipex.com> - 2011-09-30 22:38 +0100
        Re: TaskWindow -txt &xxxxxxxx Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-01 05:49 +0200
          Re: TaskWindow -txt &xxxxxxxx Martin Wuerthner <spamtrap@mw-software.com> - 2011-10-01 13:19 +0200
        Re: TaskWindow -txt &xxxxxxxx Dave Higton <davehigton@dsl.pipex.com> - 2011-10-01 20:20 +0100
          Re: TaskWindow -txt &xxxxxxxx Steve Fryatt <news@stevefryatt.org.uk> - 2011-10-01 20:51 +0100
            Re: TaskWindow -txt &xxxxxxxx Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-01 22:46 +0200
              Re: TaskWindow -txt &xxxxxxxx Steve Fryatt <news@stevefryatt.org.uk> - 2011-10-01 22:07 +0100
              Re: TaskWindow -txt &xxxxxxxx Steve Fryatt <news@stevefryatt.org.uk> - 2011-10-01 22:04 +0100
              Re: TaskWindow -txt &xxxxxxxx Dave Higton <davehigton@dsl.pipex.com> - 2011-10-01 22:45 +0100
            Re: TaskWindow -txt &xxxxxxxx Dave Higton <davehigton@dsl.pipex.com> - 2011-10-01 22:44 +0100
          Re: TaskWindow -txt &xxxxxxxx Erik G <erikg@noname.invalid> - 2011-10-18 15:23 +0200
            Re: TaskWindow -txt &xxxxxxxx Erik G <erikg@noname.invalid> - 2011-10-18 15:55 +0200
            Re: TaskWindow -txt &xxxxxxxx druck <news@druck.org.uk> - 2011-10-19 20:27 +0100
  Re: TaskWindow -txt &xxxxxxxx Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-14 07:53 +0200
    Re: TaskWindow -txt &xxxxxxxx Gavin Wraith <gavin@wra1th.plus.com> - 2011-10-14 11:43 +0100
      Re: TaskWindow -txt &xxxxxxxx Martin Wuerthner <spamtrap@mw-software.com> - 2011-10-14 13:26 +0200
        Re: TaskWindow -txt &xxxxxxxx Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-10-15 20:37 +0200
    Re: TaskWindow -txt &xxxxxxxx druck <news@druck.freeuk.com> - 2011-10-16 18:26 +0100
      Re: TaskWindow -txt &xxxxxxxx Stewart Brodie <stewart.brodie@ntlworld.com> - 2011-10-16 23:28 +0100
        Re: TaskWindow -txt &xxxxxxxx druck <news@druck.org.uk> - 2011-10-19 20:30 +0100

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