Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cornell!uw-beaver!uw-june!fred.cs.washington.edu!wjs
From: wjs@fred.cs.washington.edu (William Shipley)
Newsgroups: comp.sys.next
Subject: Re: Can an App launch itself?
Message-ID: <12194@june.cs.washington.edu>
Date: 8 Jun 90 13:19:00 GMT
References: <11277@sdcc6.ucsd.edu>
Sender: news@cs.washington.edu
Reply-To: wjs@fred.cs.washington.edu (William Shipley)
Distribution: usa
Organization: University of Washington Computer Science
Lines: 40
Summary: Yes mostly.

In article <11277@sdcc6.ucsd.edu> cs171faj@sdcc8.ucsd.edu writes:
>Let's say you have an app running; can you make a certain 
>button create another copy of the app that has the same
>functionality as the original (i.e. looks the same, with
>all buttons and things functioning)?
>
>jeff beck 

If all you want is a brand-new, pristine copy of your app running, you
ought to be able to do a system("open myApp") or some such.  (You could
fork and exec, if you wish).  There's a global variable or function that
will give you the path in which your app resides, if you don't expect it
to be in the normal places.

However, if you want your variables to be inherited, it's a little trickier.
The Application class isn't re-entrant, that is, you can't have more than
one instance of the Application class in any given process.  This is a Major
Bummer, because it means you can't create a bunch of cthreads, all with 
different Application objects.  What would be the advantage to this, you
ask?  Well, you could change NXHost for each Application object, so that
a single process could support multiple windows on multiple NeXTs.

This would be totally keen for multi-player game design, but there are myriad
other applications, including courseware.

One fix is that you CAN do is many normal forks (which mark memory for the
child as copy-on-write, meaning they are memory efficient) BEFORE you ever
create any Application object.  (This involves rewriting the IB-provided 
main.m so that you fork before you do the NXApp = [Application new];).
Each process can then have its own Application object running.  "What do
you win?" you are asking.  If, before you fork, you mark some pages as
SHARED, then you can have shared memory between the Applications, which is
sometimes more convienient than messaging.

This all sounds complicated and hypothetical, but I've actually tried it,
and I'll send anyone (ugly) code on request.

-william "please NeXT make your classes re-entrant" shipley

ObSilliness:  THE Jeff Beck?  No kidding.  How's the band?