Re: Detecting running application

[Chris B. Vetter]

On 5/11/06, Richard Frith-Macdonald <richard@tiptree.demon.co.uk> wrote:
[...]
> > I've just tried to use DO, but apparently this will introduce a racing
> > condition if two applications are started within just a few seconds,
> > eg. during log in.
> Not sure what you mean ... one (and only one) of the applications
> should be able to register with a particular name.  If that's not the
> case, then DO name serving is thoroughly broken ... so I suspect any
> problem is with the logic in your code.  If not, there is a bug we
> need to fix in the nameserver code.

I was experimenting by simply sending notifications back and forth
between bundle A and bundle B. That would introduce a racing
condition, as sending a message from A back to B might be delayed, so
B would finish the initialization even though A was already loaded.

Next, as suggested, I tried to use NSMessagePorts and
NSPortNameServer. However, -registerPort:forName: seems to completely
ignore the given name, instead looks like it always uses the
application's name to register the port. So A would register a port
with -bundlePath as name, but B isn't able to "see" that because
[[NSPortNameServer systemDefaultPortNameServer] portForName:
bundlePath] always returns nil.

> If the application is not yours, then obviously any solution in which
> you code a category to override -initWithPath: will not work since
> other applications won't contain the category.  In fact I don't think
> there is any possible *general purpose* solution unless it's built
> into the gnustep libraries, and adding such a thing there seems
> perverse because I can't immediately see what use it would be to
> people generally.

It's too special to be added to GNUstep. But the question remains why
I can launch any application twice and won't be notified that it's
already running -- as it used to be.

> That could be my failing ... I still don't see what you actually want
> to achieve and why.
> Probably a special case solution is fine ... but I don't know what
> special case we are looking at...

As an example, imagine a bundle that would scan a folder for
images/pictures and display each as your desktop background
successively.

Now it wouldn't make sense to load such a bundle more than once, would it?
Probably, you would have it loaded with the first application you start.

> I think I'm clear now that you only want one application to be able
> to load bundles , but is that one application per user, one per host,
> one per lan?

Per user, see above.

> Why is it important that only one application is able to load these
> bundles?
[...]

It's just one bundle and see above. Multiple instances just wouldn't
make sense in this example, plus they would consume a lot of memory
and generally bog down your box.

And no, I'm not working on this specific idea.

--
Chris