Re: Graceful termination again

[Enrico Sersale]

On 2006-01-23 15:05:41 +0200 Richard Frith-Macdonald <address@hidden> wrote:

> On 23 Jan 2006, at 08:50, Roman Belenov wrote:
>
> > I hacked a bit trying to implement logoff with graceful application
> > termination on GNUstep and got some questions:
> >
> > 1) How to get a list of all running GNUstep applications ?
> > launchedApplications seems to return only the list of apps launched  from the
> > current one. For now I just use a list of message ports obtained by examining
> > corresponding subdirectory and treat everythying as a proxy for application.
>
> Well, the way workspace operations generally *should* work as I  understand 
> it, is that they should contact the workspace manager  application and ask it 
> to do the job for them.  There is partial  support for this in the 
> NSWorkspace class, but it has never been  completed.  Basically, the idea is 
> that the local NSWorkspace  instance should first try to ask the workspace 
> manager application to  do jobs, and if no application is found, it should do 
> the best it  can.  In the case of launched tasks, this means that every 
> application keeps track of any tasks it sees being launched, but  since there 
> is no workspace application launching all tasks, there is  no central 
> repository of all the information.
> So, what you should ideally be doing is fixing that ...
> Problem is that it was never completed because to make it useful  there needs 
> to be a workspace manager application and when I wrote it  no such 
> application existed.  Then later  Enrico wrote GWorkspace  without much 
> attention to integration with the NSWorkspace class, and  we never got 
> together to make it all work.

I've always thought that the NSWorkspace class *implies* the existence of a Workspace 
application; it is sufficient to read some method declarations to understand this. (and, 
probably, it implies also the fact that the Workspace application coincides with the 
"window manager"...).
For this reason, I have had already proposed an "integration" of GWorkspace 
with the NSWorkspace class five or six years ago but my app was just at its beginning 
(and very buggy) and I received a big NO from the GNUstep mainteners :-)
After some years the _workspaceApplication method has been added to NSWorkspace 
with GWorkspace as default but, in the meantime, GWorkspace had gone its way 
without (mea culpa) too much attention for the NSWorkspace class; only some of 
the methods that NSWorkspace could use have been implemented; for example: 
-selectFile:inFileViewerRootedAtPath: exists but _launchApplication:arguments: 
doesn't.
That being said, I can implement in GWorkspace all we want, if we think that 
this is the right way, but I'd want to propose something else. Perhaps some of 
the older gnusteppers remember this:

"The Zen of no UI
  Why don't we just write a GNU-DO based WorkspaceMaster which could perform all the 
necessary tasks like copying files, killing apps, checking for removable media etc. 
pp. and then just use the NSWorkspace class plus some new notifications to handle 
the workspace task?"

In other words: I want to re-propose a "workspace" daemon that implements all 
the NSWorkspace methods that imply distributed information, leaving all the other things 
to the normal NSWorkspace instance.
With this solution, the need of the _workspaceApplication method would remain, 
but only for those (one or two) methods that require user interaction for 
confirmation or in case of error as -performFileOperation:::::. The daemon 
could anyway have a default implementation that, or does nothing, or perform 
the operation without asking the user.

Moreover, I think that it can be written very easily copying from the gdnc and 
GWorkspace sources.

> > 2) What is the correct way to check the result of sending terminate to
> > application (from another one) ? Experiments show that if  application 
> > actually
> > terminates, I get an exception caused by connection timeout.
>
> Yes .. you expect the connection to go away when the app terminates.   I 
> don't think there is any realistic way you can be absolutely sure  an app has 
> completely gone away (though you could try registering a  port using the name 
> of the task ... if it works then the app has  gone ... if it fails either the 
> app is still running or another app  with the same name has started).  It's 
> probably best to just assume  that loss of the connection to the app means 
> that it has died.
> Of course, in the case of the workspace manager application (which  should 
> generally have launched the app and be responsible for  shutting it down 
> too), you have an NSTask object corresponding to the  launched application, 
> so you can check the NSTask instance to see if  the application is still 
> running after it has been told to terminate.
>
>
>
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