Re: Force Quit for GNUstep

[Richard Frith-Macdonald]

On 7 Jul 2006, at 01:23, Fred Kiefer wrote:

> Andreas Höschler schrieb:
> > on the Mac we have this Force Quit panel to kill applications that no
> > longer respond to events. Does something equivalent exist for  
> > GNUstep?
> > We developers use a terminal session and kill but that's no suitable
> > appproach for our mums and dads or possibly customers.
>
> There is a specific X protocol (_NET_WM_PING) that is supposed to  
> handle
> this case and would allow the window manager to determine that a
> specific applications is currently no longer responding. I always  
> wanted
> to implement this for GNUstep, but never did get around to it.

That would be a very useful feature for window manager interaction  
and playing nicely with X applications, but I'm not sure it's what  
the original question was about.

Is the problem to determine whether an application is still  
responding, or is the problem to shut down an application, or is it a  
combination of both (to shut down the application if, and only if, it  
is not responding)?

To see if an application is responding, you can attempt to make a DO  
connection to it.
To shut down a responding application ... you tell it to shut down  
over the DO connection.
For these first two, the code in http://svn.gna.org/viewcvs/gnustep/ 
libs/gui/trunk/Tools/gclose.m (and gcloseall.m) provides an  
implementation/example.
To close down a process which is not responding, you have to send it  
a signal (TERM, and QUIT if TERM does not work) ... don't know what  
you do on windows though.

I think the equivalent of the MacOS-X 'force quit' panel would be a  
small gnustep application which would use the NSWorkspace class to  
determine what apps are running, and display them in a list.  When  
the panel is made visible (and at intervals while visible), it would  
try to make a DO connection to each app it lists ... if a DO  
connection cannot be established in a reasonable time, the  
corresponding entry in the list would be flagged as 'not  
responding'.  The user would be able to select any application and  
click a button to terminate it.  If the application is responding,  
the termination would be a clean, orderly shutdown via a DO request,  
if not, it would be done using the signal() system call (or windows  
equivalent).  Once shut down, the application would be removed from  
the list.

Presumably implementing support for _NET_WM_PING would allow you to  
write something similar as a pure X application, but without the  
option of termintating applications cleanly, just shutting them down  
via signal()

This makes me think ... we should probably (if we don't already) have  
the X backend trap SIGTERM and try to do a clean shutdown if an app  
receives it.