GTop CORBA ideas (was Re: GNOME CVS: gnome-utils martin)

[Martin Baulig <martin home-of-linux org>]

Elliot Lee <sopwith@redhat.com> writes:

> I think I am going to have to write a "when not to use CORBA" paper :-)

Well, I wanted to export the inner working of GTop through CORBA - my main
idea was to have some GTop_Applets that can be used as a GTopWidget
(subclassed from GtkWidget) like this:

	gtop_widget_corba_init ("gtop-client", &argc, argv);

	app = gnome_app_new ("test", "Hello World CORBAified");
	gtk_widget_realize (app);

	vbox = gtk_vbox_new (FALSE, 0);

	widget = gtop_widget_new ("/GTop/MemUsage", 0);
	gtk_box_pack_start (GTK_BOX (vbox), widget, FALSE, TRUE, 0);

	gnome_app_set_contents (GNOME_APP (app), vbox);

	gtk_widget_show (widget);
	gtk_widget_show (app);

To allow more than one program to use this widgets, I'm using a `gtop' CORBA
object that registers itself with the GNOME naming service:

        interface gtop {
                /* Request unique ID for applet with given name and subtype.
                 * Creates a new ID if `add_id' is true. */
                long request_gtop_applet_id (in string name, in long subtype,
                                             in short add_id);
                /* Called from the applet once it's ready. */
                void register_gtop_applet (in long id, in gtop_applet applet);
                /* Ask the server to start a new applet. */
                void start_new_gtop_applet (in long id, in long xid);
        };

When an applet is started it creates a new `gtop_applet' CORBA object:

        interface gtop_applet {
                void start_new_gtop_applet (in long id, in long xid);
        };

and registers itself with the `gtop' object (this is the code of an
example applet):

	gtop_applet_corba_init ("gtop-memusage", &argc, argv);

	id = GNOME_gtop_request_gtop_applet_id
		(gtop, "/GTop/MemUsage", 0, TRUE, &ev);

	GNOME_gtop_register_gtop_applet (gtop, id, gtop_applet, &ev);

	gtk_main ()

When the user creates a GTopWidget, gtop_widget_real_realize () looks up
the applet and finally tells the `gtop' object to start a new applet:

	id = GNOME_gtop_request_gtop_applet_id
		(gtop, "/GTop/MemUsage", 0, FALSE, &ev);

	xid = GDK_WINDOW_XWINDOW (GTK_WIDGET (widget)->window);

	GNOME_gtop_start_new_gtop_applet (gtop, id, xid, &ev);

The implementation of `start_new_gtop_applet' in the `gtop' object will use
a GHashTable to look up the `gtop_applet' object from the id and then pass the
request to this object.

Finally, the `start_new_gtop_applet' implementation in the `gtop_applet' object
will use `gtop_applet_new ()' (subclassed from GtkPlug) to create a new applet
and plug it to the given xid.

                                      * * *

Well, I just started with my CORBA exeriments, but there is already some working
code in GTop (tag: GNOME_CORBA_BRANCH) - there's a servant for the `gtop' object
(only works with a single applet at the moment), a very simple `hello world'
applet and a sample client - all in the `test' directory.

Martin

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