Re: signals versus vfuncs

[Tim Janik <timj gtk org>]

On Fri, 9 Jan 2004, muppet wrote:

>
> Christof Petig said:
> > Iterators usually contain pointers to internal data structures, Paths
> > are just an ordinal representation of a (potential) node position.
> > Prepare to accept zero'd iterators (I sometimes get some from
> > GtkTreeView after changing between models).

[...]

> is there any way at all to get notification when an iter is no longer in use?
> perhaps there's something simple i'm missing...

there's no way to know when an iterator is being freed or copied since
they are pure value objects. but that's not a real problem, because
an iterator basically "refers to a certain state of a model", rather than
maintains its own state (which would require notification/hooks).

if you implement your own model and need to deal with life-time issues
and iterators, you basically do:

setup_model() {
  model->stamp = 1;
  model->glue_object = new_glue_object();
}

modify_model() {
  model->stamp++; /* "invalidates" all iterators with old stamp */
  destroy_glue_object (model->glue_object);
  model->glue_object = new_glue_object();
}

fill_iter() {
  iter->stamp = model->stamp;
  iter->data1 = model->glue_object; /* valid as long as stamp is valid */
  iter->data2 = ...;                /* valid as long as data1 is valid */
}

use_iter() {
  g_return_if_fail (iter->stamp == model->stamp);
  /* since iter->stamp is valid, iter->data1 is also valid */
  use_glue_object (iter->data1, iter->data2);
}

>
> --
> muppet <scott at asofyet dot org>

---
ciaoTJ