Re: gnome-vfs API freeze items

[James Henstridge <james daa com au>]

On Sat, 1 Sep 2001, Maciej Stachowiak wrote:

> > This actually needs to happen to all libraries in GNOME.  I think it
> > would be good to have an API review to see if any API's are
> > inappropriate for LBs.
>
> Has it been done for libgnome* yet? Also, can you point me to
> information on how (and why) to do this?

Here is a little information on using GClosures for callbacks in a
library.

A GClosure wraps up the function, user data and destroy notify arguments
that would traditionally be used in a _full variant.  The function that
takes a closure as the callback should store the closure and contain code
like the following:
   if (G_CLOSURE_NEEDS_MARSHAL (closure))
     g_closure_set_marshal (closure, foo_marshal_BLAH__BLAH);

This sets the closure marshal function if one hasn't already been set.
This is required for closures that wrap C functions.  Your code should
call g_closure_ref() on the closure.  If your function usually takes
ownership of the closure, you should call g_closure_sink() as well.

When you don't need the closure anymore, call g_closure_unref() on it.

You can invoke the closure with the g_closure_invoke() function.  You need
to pass in an initialised GValue for the return_value argument, and an
array of initialised GValues (which have been filled as well) as
param_values.  You can leave the invocation_hint argument as NULL.
  GValue return_value = { 0 }
  GValue param_values[1] = { { 0 } };

  g_value_init(&return_value, G_TYPE_INT); /* for instance ... */
  g_value_init(&param_values[0], G_TYPE_OBJECT);
  g_value_set_object(&param_values[0], some_object);
  g_closure_invoke(closure, return_value, 1, param_values, NULL);
  g_value_unset(&param_values[0]);

  /* do something with the return_value */
  g_value_unset(&return_value);

James.

-- 
Email: james daa com au
WWW:   http://www.daa.com.au/~james/