Re: [gtk-list] Re: gtk_signal_connect_interp()

[Tim Janik <timj gimp org>]

On 10 Feb 1998, Owen Taylor wrote:

> 
> Marc Ewing <marc@redhat.com> writes:
> 
> > Owen Taylor <owt1@cornell.edu> writes:
> > > > if I need to have the
> > > > data portion of a signal handler freed or taken care of in some
> > > > way when the handler is removed, I need to do something like:
> > > > 
> > > >  gtk_signal_connect_interp(GTK_OBJECT(item), "expand",
> > > >                            expand_tree, s, g_free, FALSE);
> > > > 
> > > > (where the data, s, is the result of a g_strdup()).  Is this
> > > > correct?  Does gtk_signal_connect_interp() do more than that?
> > > > Is there some other way to accomplish what I need?
> > > 
> > > Hmmm. Right now, this won't work, because gtk_signal_connect_interp
> > > expects the function to be a special marshall function instead of an
> > > everyday garden-variety signal handler.  I discussed solutions to this
> > > problem with Marius a few months ago, but nothing came of it.
> > > 
> > > For now, the right thing to do is to free your data in the "destroy"
> > > callback (and if you gtk_signal_disconnect anywhere explicitly, also
> > > free it there).
> > 
> > Is there a "legal" way to obtain the data pointer for a signal
> > handler during the destroy so I don't have to keep a table of
> > those data pointers around anywhere?
> 
> The "poor man's" way of doing this would be to use the fact
> you can have multiple "destroy" handlers. So you could simply
> create a destroy handler for each other handler you set up.
> 
>   gtk_signal_connect (object, "clicked", my_function, my_data);
>   gtk_signal_connect (object, "destroy", g_free, my_data);

i guess the latter was meant to say
   gtk_signal_connect_object (object, "destroy", g_free, my_data);
you would g_free(object) otherwise.

 
> In general, this is not going to be very efficient, but if
> you are passing the _same_ data to all callbacks for a certain
> widget, (a common case), then it is pretty natural.
> 
> > It seems to me that this would be a generally useful (optional)
> > feature of signal handlers.  Often times I find myself wanting
> > to stick some data in the data bit, and then forget about it
> > forever.  Passing a function as an argument to gtk_signal_connect()
> > (or something variant) that can handle the data cleanup would
> > make this easy to program.
> 
> Agreed. Assuming nobody objects to my proposal too much, it will
> probably be in 0.99.4. 

already wrote the first objection/correction ;)

> 
> Regards,
>                                         Owen
> 

---
ciaoTJ