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BonoboObject

BonoboObject — Base object for wrapping Bonobo::Unknown derived objects. Implements Figure 2, “The Bonobo::Unknown interface”.

Synopsis

#define             BONOBO_OBJECT_TYPE
#define             BONOBO_OBJREF                       (o)
void                (*BonoboObjectPOAFn)                (PortableServer_Servant servant,
                                                         CORBA_Environment *ev);
                    BonoboObject;
                    BonoboObjectClass;
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,
                                                         CORBA_Environment *opt_ev);
Bonobo_Unknown      bonobo_object_query_remote          (Bonobo_Unknown unknown,
                                                         const char *repo_id,
                                                         CORBA_Environment *opt_ev);
Bonobo_Unknown      bonobo_object_corba_objref          (BonoboObject *object);
Bonobo_Unknown      bonobo_object_dup_ref               (Bonobo_Unknown object,
                                                         CORBA_Environment *opt_ev);
Bonobo_Unknown      bonobo_object_release_unref         (Bonobo_Unknown object,
                                                         CORBA_Environment *opt_ev);
gpointer            bonobo_object_ref                   (gpointer obj);
void                bonobo_object_idle_unref            (gpointer obj);
gpointer            bonobo_object_unref                 (gpointer obj);
void                bonobo_object_set_immortal          (BonoboObject *object,
                                                         gboolean immortal);
gpointer            bonobo_object_trace_refs            (gpointer obj,
                                                         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);
#define             BONOBO_OBJECT_CHECK                 (o,
                                                         c,
                                                         e)
gboolean            bonobo_unknown_ping                 (Bonobo_Unknown object,
                                                         CORBA_Environment *opt_ev);
void                bonobo_object_list_unref_all        (GList **list);
void                bonobo_object_slist_unref_all       (GSList **list);
BonoboObject *      bonobo_object                       (gpointer p);
#define             bonobo_object_fast                  (o)
#define             bonobo_object_from_servant          (s)
#define             bonobo_object_get_servant           (o)
PortableServer_POA  bonobo_object_get_poa               (BonoboObject *object);
GType               bonobo_type_unique                  (GType parent_type,
                                                         BonoboObjectPOAFn init_fn,
                                                         BonoboObjectPOAFn fini_fn,
                                                         int epv_struct_offset,
                                                         const GTypeInfo *info,
                                                         const gchar *type_name);
gboolean            bonobo_type_setup                   (GType type,
                                                         BonoboObjectPOAFn init_fn,
                                                         BonoboObjectPOAFn fini_fn,
                                                         int epv_struct_offset);
#define             BONOBO_TYPE_FUNC_FULL               (class_name,
                                                         corba_name,
                                                         parent,
                                                         prefix)
#define             BONOBO_TYPE_FUNC                    (class_name,
                                                         parent,
                                                         prefix)

Object Hierarchy

  GObject
   +----BonoboObject
         +----BonoboGenericFactory
         +----BonoboPersist
         +----BonoboMonikerExtender
         +----BonoboItemContainer
         +----BonoboStreamMem
         +----BonoboItemHandler
         +----BonoboListener
         +----BonoboMoniker

Properties

  "poa"                      gpointer              : Read / Write / Construct Only

Signals

  "destroy"                                        : Run Last
  "system-exception"                               : Run Last

Description

BonoboObject provides an easy to use way of writing CORBA servers. It drastically simplifies the issues of epv and vepv construction by automating these, and automatically instantiates a CORBA_Object on g_object_new. This removes clutter from construction time. For libbonobo-2.0, it strongly deprecates BonoboXObject.

Figure 2. The Bonobo::Unknown interface

The Bonobo::Unknown interface

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

BONOBO_OBJECT_TYPE

#define BONOBO_OBJECT_TYPE        BONOBO_TYPE_OBJECT /* deprecated, you should use BONOBO_TYPE_OBJECT */

Returns the GtkType for the BonoboObject object.

BONOBO_OBJREF()

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

This macro returns the CORBA object reference inside a BonoboObject.

o :

 a BonoboObject

BonoboObjectPOAFn ()

void                (*BonoboObjectPOAFn)                (PortableServer_Servant servant,
                                                         CORBA_Environment *ev);

Signature of POA initialization and finalization functions

servant :

 the object's servant

ev :

 CORBA environment

BonoboObject

typedef struct _BonoboObject BonoboObject;

Implements Bonobo::Unknown.

BonoboObjectClass

typedef struct {
	GObjectClass parent_class;

	/* signals. */
	void         (*destroy)          (BonoboObject *object);
	void         (*system_exception) (BonoboObject *object,
					  CORBA_Object  cobject,
					  CORBA_Environment *ev);

	BonoboObjectPOAFn          poa_init_fn;
	BonoboObjectPOAFn          poa_fini_fn;

	POA_Bonobo_Unknown__vepv       *vepv;

	/* The offset of this class' additional epv */
	int                             epv_struct_offset;

	PortableServer_ServantBase__epv base_epv;
	POA_Bonobo_Unknown__epv         epv;

	gpointer                        dummy[4];
} BonoboObjectClass;

BonoboObject's class.

bonobo_object_add_interface ()

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

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.

object :

 The BonoboObject to which an interface is going to be added.

newobj :

 The BonoboObject containing the new interface to be added.

bonobo_object_query_local_interface ()

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

object :

 A BonoboObject which is the aggregate of multiple objects.

repo_id :

 The id of the interface being queried.

Returns :

 A BonoboObject for the requested interface.

bonobo_object_query_interface ()

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

object :

 A BonoboObject to be queried for a given interface.

repo_id :

 The name of the interface to be queried.

opt_ev :

 optional exception environment

Returns :

 The CORBA interface named repo_id for object.

bonobo_object_query_remote ()

Bonobo_Unknown      bonobo_object_query_remote          (Bonobo_Unknown unknown,
                                                         const char *repo_id,
                                                         CORBA_Environment *opt_ev);

A helper wrapper for query interface

unknown :

 an unknown object ref ( or NIL )

repo_id :

 the interface to query for

opt_ev :

 an optional exception environment

Returns :

 the interface or CORBA_OBJECT_NIL

bonobo_object_corba_objref ()

Bonobo_Unknown      bonobo_object_corba_objref          (BonoboObject *object);

object :

 A BonoboObject whose CORBA object is requested.

Returns :

 The CORBA interface object for which object is a wrapper.

bonobo_object_dup_ref ()

Bonobo_Unknown      bonobo_object_dup_ref               (Bonobo_Unknown object,
                                                         CORBA_Environment *opt_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.

object :

 a Bonobo_Unknown corba object

opt_ev :

 an optional exception environment

Returns :

 duplicated & ref'd corba object reference.

bonobo_object_release_unref ()

Bonobo_Unknown      bonobo_object_release_unref         (Bonobo_Unknown object,
                                                         CORBA_Environment *opt_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.

object :

 a Bonobo_Unknown corba object

opt_ev :

 an optional exception environment

Returns :

 CORBA_OBJECT_NIL.

bonobo_object_ref ()

gpointer            bonobo_object_ref                   (gpointer obj);

Increments the reference count for the aggregate BonoboObject.

obj :

 A BonoboObject you want to ref-count

Returns :

 object

bonobo_object_idle_unref ()

void                bonobo_object_idle_unref            (gpointer obj);

obj :

bonobo_object_unref ()

gpointer            bonobo_object_unref                 (gpointer obj);

Decrements the reference count for the aggregate BonoboObject.

obj :

 A BonoboObject you want to unref.

Returns :

 NULL.

bonobo_object_set_immortal ()

void                bonobo_object_set_immortal          (BonoboObject *object,
                                                         gboolean immortal);

object :

immortal :

bonobo_object_trace_refs ()

gpointer            bonobo_object_trace_refs            (gpointer obj,
                                                         const char *fn,
                                                         int line,
                                                         gboolean ref);

obj :

fn :

line :

ref :

Returns :

bonobo_object_dump_interfaces ()

void                bonobo_object_dump_interfaces       (BonoboObject *object);

object :

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 GObjects 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.

object :

 The object on which we operate

corba_object :

ev :

 CORBA Environment to check

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.

o :

c :

e :

bonobo_unknown_ping ()

gboolean            bonobo_unknown_ping                 (Bonobo_Unknown object,
                                                         CORBA_Environment *opt_ev);

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.

object :

 a CORBA object reference of type Bonobo::Unknown

opt_ev :

 optional exception environment

Returns :

 TRUE if the Bonobo::Unknown object is alive.

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.

list :

 A list of BonoboObjects *s

bonobo_object_slist_unref_all ()

void                bonobo_object_slist_unref_all       (GSList **list);

list :

bonobo_object ()

BonoboObject *      bonobo_object                       (gpointer p);

This function can be passed a BonoboObject * or a PortableServer_Servant, and it will return a BonoboObject *.

p :

 a pointer to something

Returns :

 a BonoboObject or NULL on error.

bonobo_object_fast()

#define             bonobo_object_fast(o)

o :

bonobo_object_from_servant()

#define       bonobo_object_from_servant(s) ((BonoboObject *)(((guchar *) (s)) - BONOBO_OBJECT_HEADER_SIZE))

s :

Returns :

bonobo_object_get_servant()

#define       bonobo_object_get_servant(o)  ((PortableServer_Servant)((guchar *)(o) + BONOBO_OBJECT_HEADER_SIZE))

o :

Returns :

bonobo_object_get_poa ()

PortableServer_POA  bonobo_object_get_poa               (BonoboObject *object);

Gets the POA associated with this part of the BonoboObject aggregate it is possible to have different POAs per interface.

object :

 the object associated with an interface

Returns :

 the poa, never NIL.

bonobo_type_unique ()

GType               bonobo_type_unique                  (GType parent_type,
                                                         BonoboObjectPOAFn init_fn,
                                                         BonoboObjectPOAFn fini_fn,
                                                         int epv_struct_offset,
                                                         const GTypeInfo *info,
                                                         const gchar *type_name);

This function is the main entry point for deriving bonobo server interfaces.

parent_type :

 the parent GType

init_fn :

 a POA initialization function

fini_fn :

 a POA finialization function or NULL

epv_struct_offset :

 the offset into the struct that the epv commences at, or 0 if we are inheriting a plain GObject from a BonoboObject, adding no new CORBA interfaces

info :

 the standard GTypeInfo.

type_name :

 the name of the type being registered.

Returns :

 the constructed GType.

bonobo_type_setup ()

gboolean            bonobo_type_setup                   (GType type,
                                                         BonoboObjectPOAFn init_fn,
                                                         BonoboObjectPOAFn fini_fn,
                                                         int epv_struct_offset);

This function initializes a type derived from BonoboObject, such that when you instantiate a new object of this type with g_type_new the CORBA object will be correctly created and embedded.

type :

 The type to initialize

init_fn :

 the POA_init function for the CORBA interface or NULL

fini_fn :

 NULL or a custom POA free fn.

epv_struct_offset :

 the offset in the class structure where the epv is or 0

Returns :

 TRUE on success, FALSE on error.

BONOBO_TYPE_FUNC_FULL()

#define             BONOBO_TYPE_FUNC_FULL(class_name, corba_name, parent, prefix)

Macro that includes all the boilerplate code need to register a new BonoboObject-derived class. The programmer has to define two functions only: prefix_init and prefix_class_init. As a result of the macro expansion, a function named @prefix_get_type() is defined.

class_name :

 Name of the GObject class, LikeThis

corba_name :

 Name of the CORBA interface, with IDL-to-C mapping, Like_This

parent :

 GType of the parent class, LIKE_TYPE_THIS

prefix :

 prefix of the implementation functions

BONOBO_TYPE_FUNC()

#define             BONOBO_TYPE_FUNC(class_name, parent, prefix)

Like BONOBO_TYPE_FUNC, but doesn't set POA ini and fini functions.

class_name :

parent :

prefix :

Property Details

The "poa" property

  "poa"                      gpointer              : Read / Write / Construct Only

Pass this property during construction to specify a custom POA for a BonoboObject. Example: 

1
2
3
4
5
6
7
 
BonoboObject * my_bonobo_object_new (void)
{
    BonoboObject *object;
    object = g_object_new (MY_TYPE_BONOBO_OBJECT, "poa",
                   bonobo_poa_get_threaded (BONOBO_POA_ALL_AT_IDLE), NULL);
    return object;
}

Signal Details

The "destroy" signal

void                user_function                      (BonoboObject *bonoboobject,
                                                        gpointer      user_data)         : Run Last

Signal emitted when the last reference of a BonoboObject has been lost and the object is being destroyed / finalized / deactivated.

bonoboobject :

 the object which received the signal.

user_data :

 user data set when the signal handler was connected.

The "system-exception" signal

void                user_function                      (BonoboObject         *bonoboobject,
                                                        CorbaObject          *arg1,
                                                        BonoboCorbaException *arg2,
                                                        gpointer              user_data)         : Run Last

Signal emitted from bonobo_object_check_env if a system exception is identified.

bonoboobject :

 the BonoboObject which received the signal.

arg1 :

 the CORBA_Object contained in bonoboobject.

arg2 :

 the exception that has just occurred.

user_data :

 user data set when the signal handler was connected.

See Also

GObject

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