Re: Introspection

[muppet <scott asofyet org>]

On Jan 10, 2005, at 11:12 PM, Maciej Katafiasz wrote:

> > ... In any case, there should
> >   probably be a way to find out the struct offsets, so that
> >   language bindings don't have to implement the struct layout
> >   calculations themselves.
>
> Bindings are supposed to use libffi anyway.

i didn't know i was *supposed* to have used libffi.  ;-)

> It's quite probable that they will have to do things like generating  
> thunks/marshallers for vmethods on the fly anyway, so that's an  
> already existing dependency, and I guess libffi is supposed to do  
> things like creating structs layout on demand, right?

libffi isn't a dependency for either gtk2-perl or (afaik) pygtk.

i would've pounced on libffi for things like binding variadic C  
functions, but the docs at  
http://sources.redhat.com/cgi-bin/cvsweb.cgi/libffi/README? 
rev=1.8&content-type=text/x-cvsweb-markup&cvsroot=libffi, as well as  
gcc-3.4.1/libffi/README say that libffi doesn't support them, so...



> > * Should documentation be included in the metadata ?
>
> YES! Everyone loves docstrings.

... so long as you have gobs of ram for the bloat they will add to the  
binary blob.


> > * Should type information for parametrized container types
> >   be provided on the gobject level, or should we do a simple
> >   ad-hoc description for such types ?
>
> How would such ad-hoc description work? Hardcoded knowledge about  
> GList,
> GHashTable, etc. into each binding?

I would think something like "GList of GObject" or "GHashTable string  
to integer" would be quite sufficient.  Generically, "GList of  
<typename>", "GSList of <typename>", "GHashTable <key typename> to  
<value typename>".

The bindings have to have *some* knowledge of what they're wrapping.   
For instance, Gtk2-Perl hides the existence of GList & GHashTable  
altogether, instead translating these into perl's native arrays and  
hashes.  This is actually harder than just giving back opaque handles  
to the caller, but makes the API easier to use in perl.  The bindings  
also have to have some knowledge of a GObject and a GBoxed.  It's  
having to know about *every* struct and *every* instance of a GList  
that introspection would help avoid.


--
That's it!  It's one thing for a ghost to scare my children, but it's  
another to play my theremin!
  - Homer Simpson