Description
BonoboObject is the base object in Bonobo for wrapping CORBA servers
as Gtk+ objects. HOWEVER, since it's use is complicated, it is left
in bonobo for the benefit of Nautilus' binary compatibility. It is
strongly recommended that BonoboXObject be used for all new CORBA
server implementations.
Again if you are looking to implement a CORBA interface you want to
see BonoboXObject.
The Bonobo::Unknown interface (wrapped by
BonoboObject) is the foundation for the component system: it provides
life cycle management for objects as well as service discovery.
The Bonobo interfaces are all based on the
Bonobo::Unknown interface. This
interface is very simple and provides two basic services:
object lifetime management and object
functionality-discovery. This interface only contains three
methods, here it is:
module Bonobo {
interface Unknown {
void void ref();
void void unref();
Object query_interface (in string repoid);
};
};
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The ref() and unref()
methods are used to control the lifetime of an object. The
query_interface method is used to discover
optional functionality provided by the object implementation.
The lifetime management is based on reference counting: when a
component is initially launched, it starts life with a reference
count of one. This reference is held by the component invoker.
Each time a reference is kept to this object (say, you store a
copy of the object in an array), the reference count is
incremented. Every time a reference goes out of scope, the
reference count needs to be decremented. When the reference
count reaches zero, the component knows that there are no
outstanding references to it, and it is safe to shutdown. At
this point, the component shuts down.
It is possible to ask an object which implements the
Bonobo::Unknown interface if it supports
other CORBA interfaces. For example, it would be possible to
ask an object whether it supports the
"IDL:Bonobo/EmbeddablePrint:1.0" interface to find out if it is
possible to print its contents. If the return value from
invoking the query_interface method on the
interface is CORBA_OBJECT_NIL, then we know that the requested interface
is not supported. Otherwise, we can invoke
IDL:Bonobo/EmbeddablePrint:1.0 methods on the returned CORBA
Object.
Clients of the query_interface method use
it to discover dynamically if a component supports a given
interface. Sometimes the client code would require a specific
interface to exist, but many times it is possible to operate in
a "downgraded" mode. You should design your code to be able to
cope with the lack of interfaces in objects. This will allow
your program to deal with more components, and this also allows
components to work in more situations.
For example, a help browser can load an HTML renderer component and
ask this component which sort of features are supported by it:
stop_animations (BrowserHTML html)
{
BrowserControl control
control = html->query_interface ("IDL:Browser/Control:1.0");
if (control)
control->stop_animations();
}
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The return value of the query_interface invocation contains a
reference to a CORBA object that is derived from the
Bonobo::Unknown interface or
CORBA_OBJECT_NIL if the interface is not supported by the
object. And this interface would have been already
ref()ed before it was returned. It is up
to the caller to call unref() when they are
done using the interface.
BonoboObject implements the Bonobo::Unknown interface and exports the
implementations of the methods in this class to simplify creating
new objects that inherit from Bonobo::Unknown. This base object
provides default implementations for the ref, unref and
query_interface methods.
Other implementations reuse this implementation by listing on their
VEPV tables the bonobo_object_epv entry point vector.
The Bonobo::Unknown interface is inspired
by the Microsoft COM IUnknown interface
but it has been translated into the CORBA world.
Details
BonoboObjectServant
typedef struct {
POA_Bonobo_Unknown servant_placeholder;
gpointer bonobo_object;
} BonoboObjectServant; |
This structure defines the type for BonoboObject-based CORBA servants.
BonoboObject provides a mapping from the servant to the BonoboObject
by using the bonobo_object field in the structure. Typically in the
C CORBA binding, per-servant information is piggy-backed to the POA
servant. With the BonoboObject setup per-servant information is
typically attached to the BonoboObject (by using the regular
inheritance mechanism of Gtk+). Going from a
PortableServer_Servant to the actual BonoboObject is accomplished
using the bonobo_object_from_servant() routine.
If you decide not to use this scheme for fetching your per-servant
information, but still want to inherit from a BonoboObject object,
just make sure that the second field of your servant is a gpointer.
BonoboObject
typedef struct {
GtkObject base;
Bonobo_Unknown corba_objref;
gpointer servant;
BonoboObjectPrivate *priv;
} BonoboObject; |
BonoboObjectClass
typedef struct {
GtkObjectClass parent_class;
/*
* signals.
*/
void (*query_interface) (BonoboObject *object, const char *repo_id, CORBA_Object *retval);
void (*system_exception)(BonoboObject *object, CORBA_Object cobject, CORBA_Environment *ev);
gpointer expansion;
} BonoboObjectClass; |
bonobo_object_construct ()
Initializes the provided BonoboObject object. This method is
usually invoked from the construct method for other Gtk-based CORBA
wrappers that derive from the Bonobo::Unknown interface
bonobo_object_new_from_servant ()
BonoboObject* bonobo_object_new_from_servant
(void *servant); |
bonobo_object_from_servant ()
BonoboObject* bonobo_object_from_servant (PortableServer_Servant servant); |
CORBA method implementations receive a parameter of type
PortableServer_Servant which is a pointer to the servant that was
used to create this specific CORBA object instance.
This routine allows the user to get the BonoboObject (ie, Gtk
object wrapper) from the servant. This BonoboObject is the Gtk
object wrapper associated with the CORBA object instance whose
method is being invoked.
bonobo_object_get_servant ()
PortableServer_Servant bonobo_object_get_servant
(BonoboObject *object); |
bonobo_object_get_epv ()
POA_Bonobo_Unknown__epv* bonobo_object_get_epv
(void); |
bonobo_object_activate_servant ()
Bonobo_Unknown bonobo_object_activate_servant
(BonoboObject *object,
void *servant); |
bonobo_object_activate_servant_full ()
Bonobo_Unknown bonobo_object_activate_servant_full
(BonoboObject *object,
void *servant,
gpointer shlib_id); |
This routine activates the servant which is wrapped inside the
object on the bonobo_poa (which is the default POA).
bonobo_object_add_interface ()
Adds the interfaces supported by newobj to the list of interfaces
for object. This function adds the interfaces supported by
newobj to the list of interfaces support by object. It should never
be used when the object has been exposed to the world. This is a firm
part of the contract.
bonobo_object_query_local_interface ()
bonobo_object_query_interface ()
Bonobo_Unknown bonobo_object_query_interface
(BonoboObject *object,
const char *repo_id); |
bonobo_object_corba_objref ()
Bonobo_Unknown bonobo_object_corba_objref (BonoboObject *object); |
bonobo_object_dup_ref ()
Bonobo_Unknown bonobo_object_dup_ref (Bonobo_Unknown object,
CORBA_Environment *ev); |
This function returns a duplicated CORBA Object reference;
it also bumps the ref count on the object. This is ideal to
use in any method returning a Bonobo_Object in a CORBA impl.
If object is CORBA_OBJECT_NIL it is returned unaffected.
bonobo_object_release_unref ()
void bonobo_object_release_unref (Bonobo_Unknown object,
CORBA_Environment *ev); |
This function releases a CORBA Object reference;
it also decrements the ref count on the bonobo object.
This is the converse of bonobo_object_dup_ref. We
tolerate object == CORBA_OBJECT_NIL silently.
bonobo_object_ref ()
Increments the reference count for the aggregate BonoboObject.
bonobo_object_unref ()
Decrements the reference count for the aggregate BonoboObject.
bonobo_object_idle_unref ()
bonobo_object_init ()
void bonobo_object_init (void); |
bonobo_object_trace_refs ()
void bonobo_object_trace_refs (BonoboObject *object,
const char *fn,
int line,
gboolean ref); |
bonobo_object_dump_interfaces ()
bonobo_object_check_env ()
void bonobo_object_check_env (BonoboObject *object,
CORBA_Object corba_object,
CORBA_Environment *ev); |
This routine verifies the ev environment for any fatal system
exceptions. If a system exception occurs, the object raises a
"system_exception" signal. The idea is that GtkObjects which are
used to wrap a CORBA interface can use this function to notify
the user if a fatal exception has occurred, causing the object
to become defunct.
bonobo_object_list_unref_all ()
void bonobo_object_list_unref_all (GList **list); |
This routine unrefs all valid objects in
the list and then removes them from list if
they have not already been so removed.
bonobo_object_slist_unref_all ()
void bonobo_object_slist_unref_all (GSList **list); |
BONOBO_OBJREF()
#define BONOBO_OBJREF(o) (bonobo_object_corba_objref(BONOBO_OBJECT(o))) |
BONOBO_OBJECT_CHECK()
#define BONOBO_OBJECT_CHECK(o,c,e) |
Checks if the exception in e needs to be signaled. If so, then
the proper exception signal is generated on the BonoboObject object
o for the CORBA reference c.
bonobo_unknown_ping ()
gboolean bonobo_unknown_ping (Bonobo_Unknown object); |
Pings the object object using the ref/unref methods from Bonobo::Unknown.
You can use this one to see if a remote object has gone away.