Re: GtkBuildable type resolver

On Jun 5, 2007, at 1:38 PM, Johan Dahlin wrote:

Tristan Van Berkom wrote:
On Mon, 2007-06-04 at 16:04 -0300, Johan Dahlin wrote:
One thing that might or might not be a can of worms is
language bindings. I wonder if someone more experienced
than myself in this realm could point out how we plan
to load widgets written in other languages from the GtkBuilder
perspective, namely how will we obtain the runtime GType of
the object from its name in the xml/glade file.

Python avoids this by registering all the types as soon as you load the bindings. However this is unfortunately memory wise and might be changed
in the future.

So, too, with Gtk2-Perl. This happens so that the mapping between perl package names and C GTypes exists in time for perl code to instantiate the correct type. (Perl developers don't use GTypes, they use package names, which are class names in Perl.) This means that "use"ing a module can trigger a series of gperl_register_type (gtype, package_name) calls; since you're passing in the GType, you will have registered the class already.

For all Perl-derived GObjects, the GType registration is handled by a single entry point, Glib::Type::register_object(). This usually happens at a user level from the Glib::Object::Subclass pragmatic module, which means that the registration happens as part of the parsing the Perl source.

There *is* a C function in the binding to fetch the GType corresponding to a perl package name: gperl_type_from_package(). So, given

     package CoolStuff::Window;
     use Gtk2;
     use Glib::Object::Subclass
         properties => [ ... ],
         signals => { ... },
         interfaces => [ ... ],

then this works:

    #include <gperl.h>

    gtype = gperl_type_from_package ("CoolStuff::Window");
    object = g_object_new (gtype, ...);

*provided* that the perl code defining package CoolStuff::Window has already been parsed and executed.

If you wanted to have an automatic lookup of whatever_get_type() functions, we'd have to add to the bindings functions which would ensure that the interpreter is loaded and that module has been parsed, and then ask for the gtype. My gut tells me that another solution exists, but i don't know what it is.

I hate to break it to you, but magic data pixies don't exist.
  -- Simon Cozens

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