[Libguestfs] Libguestfs gobject bindings

[Daniel P. Berrange]

On Fri, Jan 13, 2012 at 12:50:30PM +0000, Richard W.M. Jones wrote:
> On Fri, Jan 13, 2012 at 12:28:50PM +0000, Daniel P. Berrange wrote:
> > GIO provides all the infrastructure you need to do this, via the
> > GSimpleAsyncResult object, and its g_simple_async_result_run_in_thread
> > method.
> 
> So it does; we could use that.  Might want to only offer this for
> functions that are truly long-running.  I doubt anyone will be happy
> with launching threads to handle guestfs_set_verbose et al.
> 
> We could flag long-running functions.  cf. 'Progress' flag in
> generator/generator_actions.ml -- which brings me on to the subject of
> if we need to do anything special for long-running functions that
> generate progress messages?

I'd be inclined to define a GObject interface GuestfsProgress *
with 3 virtual methods:

  void (*progress_start)(GuestfsProgress *prog);
  void (*progress_tick)(GuestfsProgress *prog, gfloat *percent);
  void (*progress_finish)(GuestfsProgress *prog);

Applications wishing to have progress info would create
an implementation of this interface.

Then, either GuestfsSession would want a global method like

   guestfs_session_set_progress(GuestfsSession *s, GuestfsProgress *prog);

Or, you could make each individual long running API, would
accept an optional GuestfsProgress *prog  parameter.

The latter is probably better if we consider that with
async methods, you might invoke several methods in a
row & want to handle progress separately for each on
their own.

> And second question: event API?  error handling in the GObject API
> (does GObject have any concept of exceptions)?

Events will want to be turned into GObject signals I presume.
At the C level every API that can fail has a GError ** argument.
This gets translated to whatever error mechanism a language
has, usually exceptions.

Daniel
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