BonoboObject

Object Hierarchy

  GtkObject
   +----BonoboObject

Signal Prototypes

"query-interface"
            void        user_function      (BonoboObject *bonoboobject,
                                            gpointer arg1,
                                            gpointer arg2,
                                            gpointer user_data);
"system-exception"
            void        user_function      (BonoboObject *bonoboobject,
                                            gpointer arg1,
                                            gpointer arg2,
                                            gpointer user_data);

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); }; };

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(); }

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

typedef struct {
	POA_Bonobo_Unknown servant_placeholder;
	gpointer           bonobo_object;
} BonoboObjectServant;

typedef struct {
	GtkObject            base;

	Bonobo_Unknown       corba_objref;
	gpointer             servant;
	BonoboObjectPrivate *priv;
} BonoboObject;

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;

BonoboObject* bonobo_object_construct       (BonoboObject *object,
                                             CORBA_Object corba_object);

BonoboObject* bonobo_object_new_from_servant
                                            (void *servant);

BonoboObject* bonobo_object_from_servant    (PortableServer_Servant servant);

void        bonobo_object_bind_to_servant   (BonoboObject *object,
                                             void *servant);

PortableServer_Servant bonobo_object_get_servant
                                            (BonoboObject *object);

POA_Bonobo_Unknown__epv* bonobo_object_get_epv
                                            (void);

Bonobo_Unknown bonobo_object_activate_servant
                                            (BonoboObject *object,
                                             void *servant);

Bonobo_Unknown bonobo_object_activate_servant_full
                                            (BonoboObject *object,
                                             void *servant,
                                             gpointer shlib_id);

void        bonobo_object_add_interface     (BonoboObject *object,
                                             BonoboObject *newobj);

BonoboObject* bonobo_object_query_local_interface
                                            (BonoboObject *object,
                                             const char *repo_id);

Bonobo_Unknown bonobo_object_query_interface
                                            (BonoboObject *object,
                                             const char *repo_id);

Bonobo_Unknown bonobo_object_corba_objref   (BonoboObject *object);

Bonobo_Unknown bonobo_object_dup_ref        (Bonobo_Unknown object,
                                             CORBA_Environment *ev);

void        bonobo_object_release_unref     (Bonobo_Unknown object,
                                             CORBA_Environment *ev);

void        bonobo_object_ref               (BonoboObject *object);

void        bonobo_object_unref             (BonoboObject *object);

void        bonobo_object_idle_unref        (BonoboObject *object);

void        bonobo_object_init              (void);

void        bonobo_object_trace_refs        (BonoboObject *object,
                                             const char *fn,
                                             int line,
                                             gboolean ref);

void        bonobo_object_dump_interfaces   (BonoboObject *object);

void        bonobo_object_check_env         (BonoboObject *object,
                                             CORBA_Object corba_object,
                                             CORBA_Environment *ev);

void        bonobo_object_list_unref_all    (GList **list);

void        bonobo_object_slist_unref_all   (GSList **list);

#define BONOBO_OBJREF(o)          (bonobo_object_corba_objref(BONOBO_OBJECT(o)))

#define     BONOBO_OBJECT_CHECK(o,c,e)

gboolean    bonobo_unknown_ping             (Bonobo_Unknown object);

Signals

void        user_function                  (BonoboObject *bonoboobject,
                                            gpointer arg1,
                                            gpointer arg2,
                                            gpointer user_data);

void        user_function                  (BonoboObject *bonoboobject,
                                            gpointer arg1,
                                            gpointer arg2,
                                            gpointer user_data);

See Also

GtkObject