Re: gobject introspection

[Havoc Pennington <hp redhat com>]

Hi,

Michael Lawrence wrote:
> I am wondering what is happening with GObject introspection. It seems 
> that it has been in the works for some time now but that development has 
> stalled.

Rob Taylor started working on it again, see 
http://bugzilla.gnome.org/show_bug.cgi?id=363228

> 1) What are the overall goals of the project? From what I gather the 
> goals are twofold:
>   a) To define a common representation (GIDL) for GObject-based API's. 
> Binding generators can then be ported to use a standard format rather 
> than the current assortment of defs files, GAPI, etc.
>   b) To support run-time introspection by accessing a binary blob of 
> metadata.

Combining a) and b) I would say part of the goal is run-time binding 
generation, i.e. right now most of the bindings involve a couple megs of 
static function stubs, ideally this could be replaced with perhaps a 
couple hundred K of generic code that built binding objects on demand 
(much as e.g. dbus-python works)

> 2) How is the GIDL/metadata generated? The Vala project has some scripts 
> that generate GIDL from header files. This is obviously a difficult 
> task, because things like memory management, in/out parameters, etc 
> cannot be automatically derived from header files. Thus, human 
> annotation is necessary.

My preference is this pipeline:
 - Scan headers (or code in other language) and generate a base IDL
   file (or in-memory parse tree)
 - Allow "magic comments" in the headers to modify the IDL that would
   otherwise have been created. Similar to gtk-doc comments.
 - Allow a "merge file," a lookaside IDL file that overrides or adds to
   the scanned IDL - similar to magic comments but not in the C code
   itself
 - Output (or keep in-memory parse tree, as appropriate) the resulting
   IDL
 - Output a binary type lib containing the same information

A pipeline should also be possible where you write the IDL file first 
and then a C header is generated. This is useful when the IDL file is 
part of a spec or shared between multiple apps.

Havoc