GObject

typedef struct _GObject GObject;

All the fields in the GObject structure are private to the GObject implementation and should never be accessed directly.

GObjectClass

typedef struct {
  GTypeClass   g_type_class;

  /* overridable methods */
  GObject*   (*constructor)     (GType                  type,
                                 guint                  n_construct_properties,
                                 GObjectConstructParam *construct_properties);
  void       (*set_property)		(GObject        *object,
                                         guint           property_id,
                                         const GValue   *value,
                                         GParamSpec     *pspec);
  void       (*get_property)		(GObject        *object,
                                         guint           property_id,
                                         GValue         *value,
                                         GParamSpec     *pspec);
  void       (*dispose)			(GObject        *object);
  void       (*finalize)		(GObject        *object);
  
  /* seldomly overidden */
  void       (*dispatch_properties_changed) (GObject      *object,
					     guint	   n_pspecs,
					     GParamSpec  **pspecs);

  /* signals */
  void	     (*notify)			(GObject	*object,
					 GParamSpec	*pspec);
} GObjectClass;

The class structure for the GObject type.

GObjectConstructParam

typedef struct {
  GParamSpec *pspec;
  GValue     *value;
} GObjectConstructParam;

The GObjectConstructParam struct is an auxiliary structure used to hand GParamSpec/GValue pairs to the constructor of a GObjectClass.

GObjectGetPropertyFunc ()

void        (*GObjectGetPropertyFunc)       (GObject *object,
                                             guint property_id,
                                             GValue *value,
                                             GParamSpec *pspec);

The type of the get_property function of GObjectClass.

GObjectSetPropertyFunc ()

void        (*GObjectSetPropertyFunc)       (GObject *object,
                                             guint property_id,
                                             const GValue *value,
                                             GParamSpec *pspec);

The type of the set_property function of GObjectClass.

GObjectFinalizeFunc ()

void        (*GObjectFinalizeFunc)          (GObject *object);

The type of the finalize function of GObjectClass.

G_TYPE_IS_OBJECT()

#define G_TYPE_IS_OBJECT(type)      (G_TYPE_FUNDAMENTAL (type) == G_TYPE_OBJECT)

Returns a boolean value of FALSE or TRUE indicating whether the passed in type id is a G_TYPE_OBJECT or derived from it.

G_OBJECT()

#define G_OBJECT(object)            (G_TYPE_CHECK_INSTANCE_CAST ((object), G_TYPE_OBJECT, GObject))

Casts a GObject or derived pointer into a (GObject*) pointer. Depending on the current debugging level, this function may invoke certain runtime checks to identify invalid casts.

G_IS_OBJECT()

#define G_IS_OBJECT(object)         (G_TYPE_CHECK_INSTANCE_TYPE ((object), G_TYPE_OBJECT))

Checks whether a valid GTypeInstance pointer is of type G_TYPE_OBJECT.

G_OBJECT_CLASS()

#define G_OBJECT_CLASS(class)       (G_TYPE_CHECK_CLASS_CAST ((class), G_TYPE_OBJECT, GObjectClass))

Casts a derived GObjectClass structure into a GObjectClass structure.

G_IS_OBJECT_CLASS()

#define G_IS_OBJECT_CLASS(class)    (G_TYPE_CHECK_CLASS_TYPE ((class), G_TYPE_OBJECT))

Checks whether class "is a" valid GObjectClass structure of type G_TYPE_OBJECT or derived.

G_OBJECT_GET_CLASS()

#define G_OBJECT_GET_CLASS(object)  (G_TYPE_INSTANCE_GET_CLASS ((object), G_TYPE_OBJECT, GObjectClass))

Returns the class structure associated to a GObject instance.

G_OBJECT_TYPE()

#define G_OBJECT_TYPE(object)       (G_TYPE_FROM_INSTANCE (object))

Return the type id of an object.

G_OBJECT_TYPE_NAME()

#define G_OBJECT_TYPE_NAME(object)  (g_type_name (G_OBJECT_TYPE (object)))

Returns the name of an object's type.

G_OBJECT_CLASS_TYPE()

#define G_OBJECT_CLASS_TYPE(class)  (G_TYPE_FROM_CLASS (class))

Return the type id of a class structure.

G_OBJECT_CLASS_NAME()

#define G_OBJECT_CLASS_NAME(class)  (g_type_name (G_OBJECT_CLASS_TYPE (class)))

Return the name of a class structure's type.

g_object_class_install_property ()

void        g_object_class_install_property (GObjectClass *oclass,
                                             guint property_id,
                                             GParamSpec *pspec);

Installs a new property. This is usually done in the class initializer.

g_object_class_find_property ()

GParamSpec* g_object_class_find_property    (GObjectClass *oclass,
                                             const gchar *property_name);

Looks up the GParamSpec for a property of a class.

g_object_class_list_properties ()

GParamSpec** g_object_class_list_properties (GObjectClass *oclass,
                                             guint *n_properties);

Returns an array of GParamSpec* for all properties of a class.

g_object_class_override_property ()

void        g_object_class_override_property
                                            (GObjectClass *oclass,
                                             guint property_id,
                                             const gchar *name);

Registers property_id as referring to a property with the name name in a parent class or in an interface implemented by oclass. This allows this class to override a property implementation in a parent class or to provide the implementation of a property from an interface.

g_object_interface_install_property ()

void        g_object_interface_install_property
                                            (gpointer g_iface,
                                             GParamSpec *pspec);

Add a property to an interface; this is only useful for interfaces that are added to GObject-derived types. Adding a property to an interface forces all objects classes with that interface to have a compatible property. The compatible property could be a newly created GParamSpec, but normally g_object_class_override_property() will be used so that the object class only needs to provide an implementation and inherits the property description, default value, bounds, and so forth from the interface property.

This function is meant to be called from the interface's default vtable initialization function (the class_init member of GTypeInfo.) It must not be called after after class_init has been called for any object types implementing this interface.

Since 2.4

g_object_interface_find_property ()

GParamSpec* g_object_interface_find_property
                                            (gpointer g_iface,
                                             const gchar *property_name);

Find the GParamSpec with the given name for an interface. Generally, the interface vtable passed in as g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek().

Since 2.4

g_object_interface_list_properties ()

GParamSpec** g_object_interface_list_properties
                                            (gpointer g_iface,
                                             guint *n_properties_p);

Lists the properties of an interface.Generally, the interface vtable passed in as g_iface will be the default vtable from g_type_default_interface_ref(), or, if you know the interface has already been loaded, g_type_default_interface_peek().

Since 2.4

g_object_new ()

gpointer    g_object_new                    (GType object_type,
                                             const gchar *first_property_name,
                                             ...);

Creates a new instance of a GObject subtype and sets its properties.

Construction parameters (see G_PARAM_CONSTRUCT, G_PARAM_CONSTRUCT_ONLY) which are not explicitly specified are set to their default values.

g_object_newv ()

gpointer    g_object_newv                   (GType object_type,
                                             guint n_parameters,
                                             GParameter *parameters);

Creates a new instance of a GObject subtype and sets its properties.

Construction parameters (see G_PARAM_CONSTRUCT, G_PARAM_CONSTRUCT_ONLY) which are not explicitly specified are set to their default values.

GParameter

typedef struct {
  const gchar *name;
  GValue       value;
} GParameter;

The GParameter struct is an auxiliary structure used to hand parameter name/value pairs to g_object_newv().

g_object_ref ()

gpointer    g_object_ref                    (gpointer object);

Increases the reference count of object.

g_object_unref ()

void        g_object_unref                  (gpointer object);

Decreases the reference count if object. When its reference count drops to 0, the object is finalized (i.e. its memory is freed).

GWeakNotify ()

void        (*GWeakNotify)                  (gpointer data,
                                             GObject *where_the_object_was);

A GWeakNotify function can be added to an object as a callback that gets triggered when the object is finalized. Since the object is already being finalized when the GWeakNotify is called, there's not much you could do with the object, apart from e.g. using its adress as hash-index or the like.

g_object_weak_ref ()

void        g_object_weak_ref               (GObject *object,
                                             GWeakNotify notify,
                                             gpointer data);

Adds a weak reference callback to an object. Weak references are used for notification when an object is finalized. They are called "weak references" because they allow you to safely hold a pointer to an object without calling g_object_ref() (g_object_ref() adds a strong reference, that is, forces the object to stay alive).

g_object_weak_unref ()

void        g_object_weak_unref             (GObject *object,
                                             GWeakNotify notify,
                                             gpointer data);

Removes a weak reference callback to an object.

g_object_add_weak_pointer ()

void        g_object_add_weak_pointer       (GObject *object,
                                             gpointer *weak_pointer_location);

Adds a weak reference from weak_pointer to object to indicate that the pointer located at weak_pointer_location is only valid during the lifetime of object. When the object is finalized, weak_pointer will be set to NULL.

g_object_remove_weak_pointer ()

void        g_object_remove_weak_pointer    (GObject *object,
                                             gpointer *weak_pointer_location);

Removes a weak reference from object that was previously added using g_object_add_weak_pointer(). The weak_pointer_location has to match the one used with g_object_add_weak_pointer().

g_object_connect ()

gpointer    g_object_connect                (gpointer object,
                                             const gchar *signal_spec,
                                             ...);

A convenience function to connect multiple signals at once.

The signal specs expected by this function have the form "modifier::signal_name", where modifier can be one of the following:

  menu->toplevel = g_object_connect (g_object_new (GTK_TYPE_WINDOW,
						   "type", GTK_WINDOW_POPUP,
						   "child", menu,
						   NULL),
				     "signal::event", gtk_menu_window_event, menu,
				     "signal::size_request", gtk_menu_window_size_request, menu,
				     "signal::destroy", gtk_widget_destroyed, &menu->toplevel,
				     NULL);

g_object_disconnect ()

void        g_object_disconnect             (gpointer object,
                                             const gchar *signal_spec,
                                             ...);

A convenience function to disconnect multiple signals at once.

The signal specs expected by this function have the form "any_signal", which means to disconnect any signal with matching callback and data, or "any_signal::signal_name", which only disconnects the signal named "signal_name".

g_object_set ()

void        g_object_set                    (gpointer object,
                                             const gchar *first_property_name,
                                             ...);

Sets properties on an object.

g_object_get ()

void        g_object_get                    (gpointer object,
                                             const gchar *first_property_name,
                                             ...);

Gets properties of an object.

In general, a copy is made of the property contents and the caller is responsible for freeing the memory in the appropriate manner for the type, for instance by calling g_free() or g_object_unref().

 gint intval;
 gchar *strval;
 GObject *objval; 
 
 g_object_get (my_object,
               "intproperty", &intval,
               "strproperty", &strval,
               "objproperty", &objval,
               NULL);

 /* Do something with intval, strval, objval */
 
 g_free (strval);
 g_object_unref (objval);

g_object_notify ()

void        g_object_notify                 (GObject *object,
                                             const gchar *property_name);

Emits a "notify" signal for the property property_name on object.

g_object_freeze_notify ()

void        g_object_freeze_notify          (GObject *object);

Stops emission of "notify" signals on object. The signals are queued until g_object_thaw_notify() is called on object.

This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.

g_object_thaw_notify ()

void        g_object_thaw_notify            (GObject *object);

Reverts the effect of a previous call to g_object_freeze_notify(). This causes all queued "notify" signals on object to be emitted.

g_object_get_data ()

gpointer    g_object_get_data               (GObject *object,
                                             const gchar *key);

Gets a named field from the objects table of associations (see g_object_set_data()).

g_object_set_data ()

void        g_object_set_data               (GObject *object,
                                             const gchar *key,
                                             gpointer data);

Each object carries around a table of associations from strings to pointers. This function lets you set an association.

If the object already had an association with that name, the old association will be destroyed.

g_object_set_data_full ()

void        g_object_set_data_full          (GObject *object,
                                             const gchar *key,
                                             gpointer data,
                                             GDestroyNotify destroy);

Like g_object_set_data() except it adds notification for when the association is destroyed, either by setting it to a different value or when the object is destroyed.

g_object_steal_data ()

gpointer    g_object_steal_data             (GObject *object,
                                             const gchar *key);

Remove a specified datum from the object's data associations, without invoking the association's destroy handler.

g_object_get_qdata ()

gpointer    g_object_get_qdata              (GObject *object,
                                             GQuark quark);

This function gets back user data pointers stored via g_object_set_qdata().

g_object_set_qdata ()

void        g_object_set_qdata              (GObject *object,
                                             GQuark quark,
                                             gpointer data);

This sets an opaque, named pointer on an object. The name is specified through a GQuark (retrived e.g. via g_quark_from_static_string()), and the pointer can be gotten back from the object with g_object_get_qdata() until the object is finalized. Setting a previously set user data pointer, overrides (frees) the old pointer set, using NULL as pointer essentially removes the data stored.

g_object_set_qdata_full ()

void        g_object_set_qdata_full         (GObject *object,
                                             GQuark quark,
                                             gpointer data,
                                             GDestroyNotify destroy);

This function works like g_object_set_qdata(), but in addition, a void (*destroy) (gpointer) function may be specified which is called with data as argument when the object is finalized, or the data is being overwritten by a call to g_object_set_qdata() with the same quark.

g_object_steal_qdata ()

gpointer    g_object_steal_qdata            (GObject *object,
                                             GQuark quark);

This function gets back user data pointers stored via g_object_set_qdata() and removes the data from object without invoking it's destroy() function (if any was set). Usually, calling this function is only required to update user data pointers with a destroy notifier, for example:

void
object_add_to_user_list (GObject     *object,
                         const gchar *new_string)
{
  /* the quark, naming the object data */
  GQuark quark_string_list = g_quark_from_static_string ("my-string-list");
  /* retrive the old string list */
  GList *list = g_object_steal_qdata (object, quark_string_list);
  
  /* prepend new string */
  list = g_list_prepend (list, g_strdup (new_string));
  /* this changed 'list', so we need to set it again */
  g_object_set_qdata_full (object, quark_string_list, list, free_string_list);
}
static void
free_string_list (gpointer data)
{
  GList *node, *list = data;
  
  for (node = list; node; node = node->next)
    g_free (node->data);
  g_list_free (list);
}

Using g_object_get_qdata() in the above example, instead of g_object_steal_qdata() would have left the destroy function set, and thus the partial string list would have been freed upon g_object_set_qdata_full().

g_object_set_property ()

void        g_object_set_property           (GObject *object,
                                             const gchar *property_name,
                                             const GValue *value);

Sets a property on an object.

g_object_get_property ()

void        g_object_get_property           (GObject *object,
                                             const gchar *property_name,
                                             GValue *value);

Gets a property of an object.

In general, a copy is made of the property contents and the caller is responsible for freeing the memory by calling g_value_unset().

Note that g_object_get_property() is really intended for language bindings, g_object_get() is much more convenient for C programming.

g_object_new_valist ()

GObject*    g_object_new_valist             (GType object_type,
                                             const gchar *first_property_name,
                                             va_list var_args);

Creates a new instance of a GObject subtype and sets its properties.

Construction parameters (see G_PARAM_CONSTRUCT, G_PARAM_CONSTRUCT_ONLY) which are not explicitly specified are set to their default values.

g_object_set_valist ()

void        g_object_set_valist             (GObject *object,
                                             const gchar *first_property_name,
                                             va_list var_args);

Sets properties on an object.

g_object_get_valist ()

void        g_object_get_valist             (GObject *object,
                                             const gchar *first_property_name,
                                             va_list var_args);

Gets properties of an object.

In general, a copy is made of the property contents and the caller is responsible for freeing the memory in the appropriate manner for the type, for instance by calling g_free() or g_object_unref().

See g_object_get().

g_object_watch_closure ()

void        g_object_watch_closure          (GObject *object,
                                             GClosure *closure);

This function essentially limits the life time of the closure to the life time of the object. That is, when the object is finalized, the closure is invalidated by calling g_closure_invalidate() on it, in order to prevent invocations of the closure with a finalized (nonexisting) object. Also, g_object_ref() and g_object_unref() are added as marshal guards to the closure, to ensure that an extra reference count is held on object during invocation of the closure. Usually, this function will be called on closures that use this object as closure data.

g_object_run_dispose ()

void        g_object_run_dispose            (GObject *object);

Releases all references to other objects. This can be used to break reference cycles.

G_OBJECT_WARN_INVALID_PROPERTY_ID()

#define     G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, pspec)

This macros should be used to emit a standard warning about unexpected properties in set_property() and get_property() implementations.

The "notify" signal

void        user_function                  (GObject *gobject,
                                            GParamSpec *arg1,
                                            gpointer user_data);

The notify signal is emitted on an object when one of its properties has been changed. Note that getting this signal doesn't guarantee that the value of the property has actually changed, it may also be emitted when the setter for the property is called to reinstate the previous value.