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GtkObject

GtkObject — The base class of the GTK+ type hierarchy

Synopsis


#include <gtk/gtk.h>


            GtkObject;
#define     GTK_OBJECT_TYPE                 (object)
#define     GTK_OBJECT_TYPE_NAME            (object)
enum        GtkObjectFlags;
#define     GTK_OBJECT_FLAGS                (obj)
#define     GTK_OBJECT_FLOATING             (obj)
enum        GtkArgFlags;
GtkObject*  gtk_object_new                  (GtkType type,
                                             const gchar *first_property_name,
                                             ...);
void        gtk_object_sink                 (GtkObject *object);
GtkObject*  gtk_object_ref                  (GtkObject *object);
void        gtk_object_unref                (GtkObject *object);
void        gtk_object_weakref              (GtkObject *object,
                                             GtkDestroyNotify notify,
                                             gpointer data);
void        gtk_object_weakunref            (GtkObject *object,
                                             GtkDestroyNotify notify,
                                             gpointer data);
void        gtk_object_destroy              (GtkObject *object);
void        gtk_object_get                  (GtkObject *object,
                                             const gchar *first_property_name,
                                             ...);
void        gtk_object_set                  (GtkObject *object,
                                             const gchar *first_property_name,
                                             ...);
void        gtk_object_set_data             (GtkObject *object,
                                             const gchar *key,
                                             gpointer data);
void        gtk_object_set_data_full        (GtkObject *object,
                                             const gchar *key,
                                             gpointer data,
                                             GtkDestroyNotify destroy);
void        gtk_object_remove_data          (GtkObject *object,
                                             const gchar *key);
gpointer    gtk_object_get_data             (GtkObject *object,
                                             const gchar *key);
void        gtk_object_remove_no_notify     (GtkObject *object,
                                             const gchar *key);
void        gtk_object_set_user_data        (GtkObject *object,
                                             gpointer data);
gpointer    gtk_object_get_user_data        (GtkObject *object);
void        gtk_object_add_arg_type         (const gchar *arg_name,
                                             GtkType arg_type,
                                             guint arg_flags,
                                             guint arg_id);
void        gtk_object_set_data_by_id       (GtkObject *object,
                                             GQuark data_id,
                                             gpointer data);
void        gtk_object_set_data_by_id_full  (GtkObject *object,
                                             GQuark data_id,
                                             gpointer data,
                                             GtkDestroyNotify destroy);
gpointer    gtk_object_get_data_by_id       (GtkObject *object,
                                             GQuark data_id);
void        gtk_object_remove_data_by_id    (GtkObject *object,
                                             GQuark data_id);
void        gtk_object_remove_no_notify_by_id
                                            (GtkObject *object,
                                             GQuark key_id);
#define     gtk_object_data_try_key
#define     gtk_object_data_force_id


Object Hierarchy


  GObject
   +----GtkObject
         +----GtkWidget
         +----GtkAdjustment
         +----GtkCellRenderer
         +----GtkFileFilter
         +----GtkItemFactory
         +----GtkTooltips
         +----GtkTreeViewColumn

Properties


  "user-data"            gpointer              : Read / Write

Signal Prototypes


"destroy"   void        user_function      (GtkObject *object,
                                            gpointer user_data);

Description

Description

GtkObject is the base class for all widgets, and for a few non-widget objects such as GtkAdjustment. GtkObject predates GObject; non-widgets that derive from GtkObject rather than GObject do so for backward compatibility reasons.

The most interesting difference between GtkObject and GObject is the "floating" reference count. A GObject is created with a reference count of 1, owned by the creator of the GObject. (The owner of a reference is the code section that has the right to call g_object_unref() in order to remove that reference.) A GtkObject is created with a reference count of 1 also, but it isn't owned by anyone; calling g_object_unref() on the newly-created GtkObject is incorrect. Instead, the initial reference count of a GtkObject is "floating". The floating reference can be removed by anyone at any time, by calling gtk_object_sink(). gtk_object_sink() does nothing if an object is already sunk (has no floating reference).

When you add a widget to its parent container, the parent container will do this:

  g_object_ref (G_OBJECT (child_widget));
  gtk_object_sink (GTK_OBJECT (child_widget));

This means that the container now owns a reference to the child widget (since it called g_object_ref()), and the child widget has no floating reference.

The purpose of the floating reference is to keep the child widget alive until you add it to a parent container:

   button = gtk_button_new ();
   /* button has one floating reference to keep it alive */
   gtk_container_add (GTK_CONTAINER (container), button);
   /* button has one non-floating reference owned by the container */

GtkWindow is a special case, because GTK+ itself will ref/sink it on creation. That is, after calling gtk_window_new(), the GtkWindow will have one reference which is owned by GTK+, and no floating references.

One more factor comes into play: the "destroy" signal, emitted by the gtk_object_destroy() method. The "destroy" signal asks all code owning a reference to an object to release said reference. So, for example, if you call gtk_object_destroy() on a GtkWindow, GTK+ will release the reference count that it owns; if you call gtk_object_destroy() on a GtkButton, then the button will be removed from its parent container and the parent container will release its reference to the button. Because these references are released, calling gtk_object_destroy() should result in freeing all memory associated with an object, unless some buggy code fails to release its references in response to the "destroy" signal. Freeing memory (referred to as finalization only happens if the reference count reaches zero.

Some simple rules for handling GtkObject:

  • Never call g_object_unref() unless you have previously called g_object_ref(), even if you created the GtkObject. (Note: this is not true for GObject; for GObject, the creator of the object owns a reference.)

  • Call gtk_object_destroy() to get rid of most objects in most cases. In particular, widgets are almost always destroyed in this way.

  • Because of the floating reference count, you don't need to worry about reference counting for widgets and toplevel windows, unless you explicitly call g_object_ref() yourself.

Details

GtkObject

typedef struct _GtkObject GtkObject;

The object itself. You should never use these members directly - use the accessing macros instead.


GTK_OBJECT_TYPE()

#define GTK_OBJECT_TYPE(object)		  (G_TYPE_FROM_INSTANCE (object))

Gets the type of an object.

object :a GtkObject.

GTK_OBJECT_TYPE_NAME()

#define GTK_OBJECT_TYPE_NAME(object)	  (g_type_name (GTK_OBJECT_TYPE (object)))

Gets the name of an objects type.

object :a GtkObject.

enum GtkObjectFlags

typedef enum
{
  GTK_IN_DESTRUCTION	= 1 << 0, /* Used internally during dispose */
  GTK_FLOATING		= 1 << 1,
  GTK_RESERVED_1	= 1 << 2,
  GTK_RESERVED_2	= 1 << 3
} GtkObjectFlags;

Tells about the state of the object.

GTK_IN_DESTRUCTIONthe object is currently being destroyed. This is used internally by GTK+ to prevent reinvokations during destruction.
GTK_FLOATINGthe object is orphaned. Objects that take strong hold of an object may gtk_object_sink() it, after obtaining their own references, if they believe they are nearly primary ownership of the object. GTK_CONNECTED: signals are connected to this object.
GTK_RESERVED_1reserved for future use
GTK_RESERVED_2reserved for future use

GTK_OBJECT_FLAGS()

#define GTK_OBJECT_FLAGS(obj)		  (GTK_OBJECT (obj)->flags)

Gets the GtkObjectFlags for an object without directly accessing its members.

obj :the object whose flags are returned.

GTK_OBJECT_FLOATING()

#define GTK_OBJECT_FLOATING(obj)	  ((GTK_OBJECT_FLAGS (obj) & GTK_FLOATING) != 0)

Evaluates to TRUE if the object still has its floating reference count. See the overview documentation for GtkObject.

obj :the object to examine.

enum GtkArgFlags

typedef enum
{
  GTK_ARG_READABLE	 = G_PARAM_READABLE,
  GTK_ARG_WRITABLE	 = G_PARAM_WRITABLE,
  GTK_ARG_CONSTRUCT	 = G_PARAM_CONSTRUCT,
  GTK_ARG_CONSTRUCT_ONLY = G_PARAM_CONSTRUCT_ONLY,
  GTK_ARG_CHILD_ARG	 = 1 << 4
} GtkArgFlags;

Warning

GtkArgFlags is deprecated and should not be used in newly-written code.

Possible flags indicating how an argument should be treated. Deprecated in favor of GParamSpec features.

GTK_ARG_READABLEthe argument is readable. (i.e. can be queried)
GTK_ARG_WRITABLEthe argument is writable. (i.e. settable)
GTK_ARG_CONSTRUCTthe argument needs construction.
GTK_ARG_CONSTRUCT_ONLYthe argument needs construction (and will be set once during object creation), but is otherwise cannot be set. Hence this flag is not allowed with GTK_ARG_WRITABLE, and is redundant with GTK_ARG_CONSTRUCT.
GTK_ARG_CHILD_ARGan argument type that applies to (and may be different for) each child. Used by GtkContainer.

gtk_object_new ()

GtkObject*  gtk_object_new                  (GtkType type,
                                             const gchar *first_property_name,
                                             ...);

Warning

gtk_object_new is deprecated and should not be used in newly-written code. Use g_object_new() instead.

Constructs an object given its arguments, enumerated in the call to the function.

type :the type identifying this object. Returned by gtk_type_unique() (although for a properly-written object it should be accessible through a GTK_TYPE_FOO macro.)
first_property_name :name of the first property to set when constructing the object.
... :the first argument's value, followed by any number of name/argument-value pairs, terminated with NULL.
Returns :the new GtkObject.

gtk_object_sink ()

void        gtk_object_sink                 (GtkObject *object);

Removes the floating reference from a GtkObject, if it exists; otherwise does nothing. See the GtkObject overview documentation at the top of the page.

object :the object to sink.

gtk_object_ref ()

GtkObject*  gtk_object_ref                  (GtkObject *object);

Warning

gtk_object_ref is deprecated and should not be used in newly-written code. Use g_object_ref() instead.

Increases the reference count of the object.

object :the object to reference.
Returns :object.

gtk_object_unref ()

void        gtk_object_unref                (GtkObject *object);

Warning

gtk_object_unref is deprecated and should not be used in newly-written code. Use g_object_unref() instead.

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

object :the object to dereference.

gtk_object_weakref ()

void        gtk_object_weakref              (GtkObject *object,
                                             GtkDestroyNotify notify,
                                             gpointer data);

Warning

gtk_object_weakref is deprecated and should not be used in newly-written code. Use g_object_weak_ref() instead.

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).

object :object to weakly reference.
notify :callback to invoke before the object is freed.
data :extra data to pass to notify.

gtk_object_weakunref ()

void        gtk_object_weakunref            (GtkObject *object,
                                             GtkDestroyNotify notify,
                                             gpointer data);

Warning

gtk_object_weakunref is deprecated and should not be used in newly-written code. Use g_object_weak_unref() instead.

Removes a weak reference callback to an object.

object :object stop weakly referencing.
notify :callback to search for.
data :data to search for.

gtk_object_destroy ()

void        gtk_object_destroy              (GtkObject *object);

Emits the "destroy" signal notifying all reference holders that they should release the GtkObject. See the overview documentation at the top of the page for more details.

The memory for the object itself won't be deleted until its reference count actually drops to 0; gtk_object_destroy() merely asks reference holders to release their references, it does not free the object.

object :the object to destroy.

gtk_object_get ()

void        gtk_object_get                  (GtkObject *object,
                                             const gchar *first_property_name,
                                             ...);

Warning

gtk_object_get is deprecated and should not be used in newly-written code. Use g_object_get() instead.

Gets properties of an object.

object :a GtkObject.
first_property_name :name of first property to get the value for.
... :NULL-terminated list of name-return location pairs.

gtk_object_set ()

void        gtk_object_set                  (GtkObject *object,
                                             const gchar *first_property_name,
                                             ...);

Warning

gtk_object_set is deprecated and should not be used in newly-written code. Use g_object_set() instead.

Sets properties on an object.

void set_box_properties (GtkBox* box)
{
  gtk_object_set (GTK_OBJECT (box), "homogeneous", TRUE,
                                    "spacing", 8,
				    NULL);
}

object :a GtkObject.
first_property_name :name of the first property to set
... :the value of the first argument, followed optionally by more name/value pairs, followed by NULL.

gtk_object_set_data ()

void        gtk_object_set_data             (GtkObject *object,
                                             const gchar *key,
                                             gpointer data);

Warning

gtk_object_set_data is deprecated and should not be used in newly-written code. Use g_object_set_data() instead.

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.

object :object containing the associations.
key :name of the key.
data :data to associate with that key.

gtk_object_set_data_full ()

void        gtk_object_set_data_full        (GtkObject *object,
                                             const gchar *key,
                                             gpointer data,
                                             GtkDestroyNotify destroy);

Warning

gtk_object_set_data_full is deprecated and should not be used in newly-written code. Use g_object_set_data_full() instead.

Like gtk_object_set_data() except it adds notification for when the association is destroyed, either by gtk_object_remove_data() or when the object is destroyed.

object :object containing the associations.
key :name of the key.
data :data to associate with that key.
destroy :function to call when the association is destroyed.

gtk_object_remove_data ()

void        gtk_object_remove_data          (GtkObject *object,
                                             const gchar *key);

Warning

gtk_object_remove_data is deprecated and should not be used in newly-written code. Use g_object_set_data() to set the object data to NULL instead.

Removes a specified datum from the object's data associations (the object_data). Subsequent calls to gtk_object_get_data() will return NULL.

If you specified a destroy handler with gtk_object_set_data_full(), it will be invoked.

object :the object maintaining the association.
key :name of the key for that association.

gtk_object_get_data ()

gpointer    gtk_object_get_data             (GtkObject *object,
                                             const gchar *key);

Warning

gtk_object_get_data is deprecated and should not be used in newly-written code. Use g_object_get_data() instead.

Get a named field from the object's table of associations (the object_data).

object :the object maintaining the associations.
key :name of the key for that association.
Returns :the data if found, or NULL if no such data exists.

gtk_object_remove_no_notify ()

void        gtk_object_remove_no_notify     (GtkObject *object,
                                             const gchar *key);

Warning

gtk_object_remove_no_notify is deprecated and should not be used in newly-written code. Use g_object_steal_data() instead.

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

Just like gtk_object_remove_data() except that any destroy handler will be ignored. Therefore this only affects data set using gtk_object_set_data_full().

object :the object maintaining the association.
key :name of the key for that association.

gtk_object_set_user_data ()

void        gtk_object_set_user_data        (GtkObject *object,
                                             gpointer data);

Warning

gtk_object_set_user_data is deprecated and should not be used in newly-written code. Use g_object_set_data() instead.

For convenience, every object offers a generic user data pointer. This function sets it.

object :the object whose user data should be set.
data :the new value for the user data.

gtk_object_get_user_data ()

gpointer    gtk_object_get_user_data        (GtkObject *object);

Warning

gtk_object_get_user_data is deprecated and should not be used in newly-written code. Use g_object_get_data() instead.

Get the object's user data pointer.

This is intended to be a pointer for your convenience in writing applications.

object :the object.
Returns :the user data field for object.

gtk_object_add_arg_type ()

void        gtk_object_add_arg_type         (const gchar *arg_name,
                                             GtkType arg_type,
                                             guint arg_flags,
                                             guint arg_id);

Warning

gtk_object_add_arg_type is deprecated and should not be used in newly-written code.

Deprecated in favor of the GObject property system including GParamSpec. Add a new type of argument to an object class. Usually this is called when registering a new type of object.

arg_name :fully qualify object name, for example GtkObject::user_data.
arg_type :type of the argument.
arg_flags :bitwise-OR of the GtkArgFlags enum. (Whether the argument is settable or gettable, whether it is set when the object is constructed.)
arg_id :an internal number, passed in from here to the "set_arg" and "get_arg" handlers of the object.

gtk_object_set_data_by_id ()

void        gtk_object_set_data_by_id       (GtkObject *object,
                                             GQuark data_id,
                                             gpointer data);

Warning

gtk_object_set_data_by_id is deprecated and should not be used in newly-written code. Use g_object_set_qdata() instead.

Just like gtk_object_set_data() except that it takes a GQuark instead of a string, so it is slightly faster.

Use gtk_object_data_try_key() and gtk_object_data_force_id() to get an id from a string.

object :object containing the associations.
data_id :quark of the key.
data :data to associate with that key.

gtk_object_set_data_by_id_full ()

void        gtk_object_set_data_by_id_full  (GtkObject *object,
                                             GQuark data_id,
                                             gpointer data,
                                             GtkDestroyNotify destroy);

Warning

gtk_object_set_data_by_id_full is deprecated and should not be used in newly-written code. Use g_object_set_qdata_full() instead.

Just like gtk_object_set_data_full() except that it takes a GQuark instead of a string, so it is slightly faster.

Use gtk_object_data_try_key() and gtk_object_data_force_id() to get an id from a string.

object :object containing the associations.
data_id :quark of the key.
data :data to associate with that key.
destroy :function to call when the association is destroyed.

gtk_object_get_data_by_id ()

gpointer    gtk_object_get_data_by_id       (GtkObject *object,
                                             GQuark data_id);

Warning

gtk_object_get_data_by_id is deprecated and should not be used in newly-written code. Use g_object_get_qdata() instead.

Just like gtk_object_get_data() except that it takes a GQuark instead of a string, so it is slightly faster.

Use gtk_object_data_try_key() and gtk_object_data_force_id() to get an id from a string.

object :object containing the associations.
data_id :quark of the key.
Returns :the data if found, or NULL if no such data exists.

gtk_object_remove_data_by_id ()

void        gtk_object_remove_data_by_id    (GtkObject *object,
                                             GQuark data_id);

Warning

gtk_object_remove_data_by_id is deprecated and should not be used in newly-written code. Use g_object_set_qdata() with data of NULL instead.

Just like gtk_object_remove_data() except that it takes a GQuark instead of a string, so it is slightly faster.

Remove a specified datum from the object's data associations. Subsequent calls to gtk_object_get_data() will return NULL.

Use gtk_object_data_try_key() and gtk_object_data_force_id() to get an id from a string.

object :object containing the associations.
data_id :quark of the key.

gtk_object_remove_no_notify_by_id ()

void        gtk_object_remove_no_notify_by_id
                                            (GtkObject *object,
                                             GQuark key_id);

Warning

gtk_object_remove_no_notify_by_id is deprecated and should not be used in newly-written code. Use g_object_steal_qdata() instead.

Just like gtk_object_remove_no_notify() except that it takes a GQuark instead of a string, so it is slightly faster.

Use gtk_object_data_try_key() and gtk_object_data_force_id() to get an id from a string.

object :object containing the associations.
key_id :quark of the key.

gtk_object_data_try_key

#define	gtk_object_data_try_key	    g_quark_try_string

Warning

gtk_object_data_try_key is deprecated and should not be used in newly-written code.

Useless deprecated macro. Ignore it.


gtk_object_data_force_id

#define	gtk_object_data_force_id    g_quark_from_string

Warning

gtk_object_data_force_id is deprecated and should not be used in newly-written code.

Useless deprecated macro. Ignore it.

Properties

The "user-data" property

  "user-data"            gpointer              : Read / Write

Anonymous User Data Pointer.

Signals

The "destroy" signal

void        user_function                  (GtkObject *object,
                                            gpointer user_data);

Signals that all holders of a reference to the GtkObject should release the reference that they hold. May result in finalization of the object if all references are released.

object :the object which received the signal.
user_data :user data set when the signal handler was connected.

See Also

GObject