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GObject Reference Manual | |
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#include <glib-object.h>
GObject;
GObjectClass;
GObjectConstructParam;
void (*GObjectGetPropertyFunc) (GObject *object,
guint property_id,
GValue *value,
GParamSpec *pspec);
void (*GObjectSetPropertyFunc) (GObject *object,
guint property_id,
const GValue *value,
GParamSpec *pspec);
void (*GObjectFinalizeFunc) (GObject *object);
#define G_TYPE_IS_OBJECT (type)
#define G_OBJECT (object)
#define G_IS_OBJECT (object)
#define G_OBJECT_CLASS (class)
#define G_IS_OBJECT_CLASS (class)
#define G_OBJECT_GET_CLASS (object)
#define G_OBJECT_TYPE (object)
#define G_OBJECT_TYPE_NAME (object)
#define G_OBJECT_CLASS_TYPE (class)
#define G_OBJECT_CLASS_NAME (class)
void g_object_class_install_property (GObjectClass *oclass,
guint property_id,
GParamSpec *pspec);
GParamSpec* g_object_class_find_property (GObjectClass *oclass,
const gchar *property_name);
GParamSpec** g_object_class_list_properties (GObjectClass *oclass,
guint *n_properties);
void g_object_class_override_property (GObjectClass *oclass,
guint property_id,
const gchar *name);
void g_object_interface_install_property (gpointer g_iface,
GParamSpec *pspec);
GParamSpec* g_object_interface_find_property (gpointer g_iface,
const gchar *property_name);
GParamSpec** g_object_interface_list_properties (gpointer g_iface,
guint *n_properties_p);
gpointer g_object_new (GType object_type,
const gchar *first_property_name,
...);
gpointer g_object_newv (GType object_type,
guint n_parameters,
GParameter *parameters);
GParameter;
gpointer g_object_ref (gpointer object);
void g_object_unref (gpointer object);
gpointer g_object_ref_sink (gpointer object);
typedef GInitiallyUnowned;
typedef GInitiallyUnownedClass;
#define G_TYPE_INITIALLY_UNOWNED
gboolean g_object_is_floating (gpointer object);
void g_object_force_floating (GObject *object);
void (*GWeakNotify) (gpointer data,
GObject *where_the_object_was);
void g_object_weak_ref (GObject *object,
GWeakNotify notify,
gpointer data);
void g_object_weak_unref (GObject *object,
GWeakNotify notify,
gpointer data);
void g_object_add_weak_pointer (GObject *object,
gpointer *weak_pointer_location);
void g_object_remove_weak_pointer (GObject *object,
gpointer *weak_pointer_location);
void (*GToggleNotify) (gpointer data,
GObject *object,
gboolean is_last_ref);
void g_object_add_toggle_ref (GObject *object,
GToggleNotify notify,
gpointer data);
void g_object_remove_toggle_ref (GObject *object,
GToggleNotify notify,
gpointer data);
gpointer g_object_connect (gpointer object,
const gchar *signal_spec,
...);
void g_object_disconnect (gpointer object,
const gchar *signal_spec,
...);
void g_object_set (gpointer object,
const gchar *first_property_name,
...);
void g_object_get (gpointer object,
const gchar *first_property_name,
...);
void g_object_notify (GObject *object,
const gchar *property_name);
void g_object_freeze_notify (GObject *object);
void g_object_thaw_notify (GObject *object);
gpointer g_object_get_data (GObject *object,
const gchar *key);
void g_object_set_data (GObject *object,
const gchar *key,
gpointer data);
void g_object_set_data_full (GObject *object,
const gchar *key,
gpointer data,
GDestroyNotify destroy);
gpointer g_object_steal_data (GObject *object,
const gchar *key);
gpointer g_object_get_qdata (GObject *object,
GQuark quark);
void g_object_set_qdata (GObject *object,
GQuark quark,
gpointer data);
void g_object_set_qdata_full (GObject *object,
GQuark quark,
gpointer data,
GDestroyNotify destroy);
gpointer g_object_steal_qdata (GObject *object,
GQuark quark);
void g_object_set_property (GObject *object,
const gchar *property_name,
const GValue *value);
void g_object_get_property (GObject *object,
const gchar *property_name,
GValue *value);
GObject* g_object_new_valist (GType object_type,
const gchar *first_property_name,
va_list var_args);
void g_object_set_valist (GObject *object,
const gchar *first_property_name,
va_list var_args);
void g_object_get_valist (GObject *object,
const gchar *first_property_name,
va_list var_args);
void g_object_watch_closure (GObject *object,
GClosure *closure);
void g_object_run_dispose (GObject *object);
#define G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec)
GObject is the fundamental type providing the common attributes and methods for all object types in GTK+, Pango and other libraries based on GObject. The GObject class provides methods for object construction and destruction, property access methods, and signal support. Signals are described in detail in Signals(3).
GInitiallyUnowned is derived from GObject. The only difference between the two is that the initial reference of a GInitiallyUnowned is flagged as a floating reference. This means that it is not specifically claimed to be "owned" by any code portion. The main motivation for providing floating references is C convenience. In particular, it allows code to be written as:
container = create_container(); container_add_child (container, create_child());
If container_add_child()g_object_ref_sink() the
passed in child, no reference of the newly created child is leaked.
Without floating references, container_add_child()g_object_ref() the new child, so to implement this code without
reference leaks, it would have to be written as:
Child *child; container = create_container(); child = create_child(); container_add_child (container, child); g_object_unref (child);
The floating reference can be converted into
an ordinary reference by calling g_object_ref_sink().
For already sunken objects (objects that don't have a floating reference
anymore), g_object_ref_sink() is equivalent to g_object_ref() and returns
a new reference.
Since floating references are useful almost exclusively for C convenience,
language bindings that provide automated reference and memory ownership
maintenance (such as smart pointers or garbage collection) therefore don't
need to expose floating references in their API.
Some object implementations may need to save an objects floating state across certain code portions (an example is GtkMenu), to achive this, the following sequence can be used:
// save floating state gboolean was_floating = g_object_is_floating (object); g_object_ref_sink (object); // protected code portion ...; // restore floating state if (was_floating) g_object_force_floating (object); g_obejct_unref (object); // release previously acquired reference
GObject is the fundamental type providing the common attributes and methods for all object types in GTK+, Pango and other libraries based on GObject. The GObject class provides methods for object construction and destruction, property access methods, and signal support. Signals are described in detail in Signals(3).
GInitiallyUnowned is derived from GObject. The only difference between the two is that the initial reference of a GInitiallyUnowned is flagged as a floating reference. This means that it is not specifically claimed to be "owned" by any code portion. The main motivation for providing floating references is C convenience. In particular, it allows code to be written as:
If container_add_child()g_object_ref_sink() the
passed in child, no reference of the newly created child is leaked.
Without floating references, container_add_child()g_object_ref() the new child, so to implement this code without
reference leaks, it would have to be written as:
Example 2.
Child *child; container = create_container(); child = create_child(); container_add_child (container, child); g_object_unref (child);
The floating reference can be converted into
an ordinary reference by calling g_object_ref_sink().
For already sunken objects (objects that don't have a floating reference
anymore), g_object_ref_sink() is equivalent to g_object_ref() and returns
a new reference.
Since floating references are useful almost exclusively for C convenience,
language bindings that provide automated reference and memory ownership
maintenance (such as smart pointers or garbage collection) therefore don't
need to expose floating references in their API.
Some object implementations may need to save an objects floating state across certain code portions (an example is GtkMenu), to achive this, the following sequence can be used:
Example 3.
/* save floating state */
gboolean was_floating = g_object_is_floating (object);
g_object_ref_sink (object);
/* protected code portion */
...;
/* restore floating state */
if (was_floating)
g_object_force_floating (object);
g_obejct_unref (object); /* release previously acquired reference */
typedef struct _GObject GObject;
All the fields in the GObject structure are private to the GObject implementation and should never be accessed directly.
All the fields in the GObject structure are private to the GObject implementation and should never be accessed directly.
typedef struct {
GTypeClass g_type_class;
/* seldomly overidden */
GObject* (*constructor) (GType type,
guint n_construct_properties,
GObjectConstructParam *construct_properties);
/* overridable methods */
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);
/* called when done constructing */
void (*constructed) (GObject *object);
} GObjectClass;
The class structure for the GObject type.
Example 4. Implementing singletons using a constructor
static MySingleton *the_singleton = NULL;
static GObject*
my_singleton_constructor (GType type,
guint n_construct_params,
GObjectConstructParam *construct_params)
{
GObject *object;
if (!the_singleton)
{
object = G_OBJECT_CLASS (parent_class)->constructor (type,
n_construct_params,
construct_params);
the_singleton = MY_SINGLETON (object);
}
else
object = g_object_ref (G_OBJECT (the_singleton));
return object;
}
The class structure for the GObject type.
Example 5. Implementing singletons using a constructor
static MySingleton *the_singleton = NULL;
static GObject*
my_singleton_constructor (GType type,
guint n_construct_params,
GObjectConstructParam *construct_params)
{
GObject *object;
if (!the_singleton)
{
object = G_OBJECT_CLASS (parent_class)->constructor (type,
n_construct_params,
construct_params);
the_singleton = MY_SINGLETON (object);
}
else
object = g_object_ref (G_OBJECT (the_singleton));
return object;
}
GTypeClass g_type_class; |
the parent class |
constructor () |
the constructor function is called by g_object_new() to
complete the object initialization after all the construction properties are
set. The first thing a constructor implementation must do is chain up to the
constructor of the parent class. Overriding constructor should be rarely
needed, e.g. to handle construct properties, or to implement singletons.
|
set_property () |
the generic setter for all properties of this type. Should be
overridden for every type with properties. Implementations of set_property
don't need to emit property change notification explicitly, this is handled
by the type system.
|
get_property () |
the generic getter for all properties of this type. Should be overridden for every type with properties. |
dispose () |
the dispose function is supposed to drop all references to other
objects, but keep the instance otherwise intact, so that client method
invocations still work. It may be run multiple times (due to reference
loops). Before returning, dispose should chain up to the dispose method
of the parent class.
|
finalize () |
instance finalization function, should finish the finalization of
the instance begun in dispose and chain up to the finalize method of the
parent class.
|
dispatch_properties_changed () |
emits property change notification for a bunch
of properties. Overriding dispatch_properties_changed should be rarely
needed.
|
notify () |
the class closure for the notify signal |
constructed () |
the constructed function is called by g_object_new() as the
final step of the object creation process. At the point of the call, all
construction properties have been set on the object. The purpose of this
call is to allow for object initialisation steps that can only be performed
after construction properties have been set. constructed implementors
should chain up to the constructed call of their parent class to allow it
to complete its initialisation.
|
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.
The GObjectConstructParam struct is an auxiliary
structure used to hand GParamSpec/GValue pairs to the constructor of
a GObjectClass.
GParamSpec *pspec; |
the GParamSpec of the construct parameter |
GValue *value; |
the value to set the parameter to |
void (*GObjectGetPropertyFunc) (GObject *object, guint property_id, GValue *value, GParamSpec *pspec);
The type of the get_property function of GObjectClass.
The type of the get_property function of GObjectClass.
object : |
a GObject |
property_id : |
the numeric id under which the property was registered with
g_object_class_install_property().
|
value : |
a GValue to return the property value in |
pspec : |
the GParamSpec describing the property |
void (*GObjectSetPropertyFunc) (GObject *object, guint property_id, const GValue *value, GParamSpec *pspec);
The type of the set_property function of GObjectClass.
The type of the set_property function of GObjectClass.
object : |
a GObject |
property_id : |
the numeric id under which the property was registered with
g_object_class_install_property().
|
value : |
the new value for the property |
pspec : |
the GParamSpec describing the property |
void (*GObjectFinalizeFunc) (GObject *object);
The type of the finalize function of GObjectClass.
The type of the finalize function of GObjectClass.
object : |
the GObject being finalized |
#define G_TYPE_IS_OBJECT(type) (G_TYPE_FUNDAMENTAL (type) == G_TYPE_OBJECT)
Check if the passed in type id is a G_TYPE_OBJECT or derived from it.
Returns a boolean value of FALSE or TRUE indicating whether
the passed in type id is a G_TYPE_OBJECT or derived from it.
type : |
Type id to check |
| Returns : | FALSE or TRUE, indicating whether type is a G_TYPE_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.
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.
object : |
Object which is subject to casting. |
#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.
Checks whether a valid GTypeInstance pointer is of type G_TYPE_OBJECT.
object : |
Instance to check for being a G_TYPE_OBJECT.
|
#define G_OBJECT_CLASS(class) (G_TYPE_CHECK_CLASS_CAST ((class), G_TYPE_OBJECT, GObjectClass))
Casts a derived GObjectClass structure into a GObjectClass structure.
Casts a derived GObjectClass structure into a GObjectClass structure.
class : |
a valid GObjectClass |
#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.
Checks whether class "is a" valid GObjectClass structure of type
G_TYPE_OBJECT or derived.
class : |
a GObjectClass |
#define G_OBJECT_GET_CLASS(object) (G_TYPE_INSTANCE_GET_CLASS ((object), G_TYPE_OBJECT, GObjectClass))
Get the class structure associated to a GObject instance.
Returns the class structure associated to a GObject instance.
object : |
a GObject instance. |
#define G_OBJECT_TYPE(object) (G_TYPE_FROM_INSTANCE (object))
Get the type id of an object.
Return the type id of an object.
object : |
Object to return the type id for. |
| Returns : | Type id of object.
|
#define G_OBJECT_TYPE_NAME(object) (g_type_name (G_OBJECT_TYPE (object)))
Get the name of an object's type.
Returns the name of an object's type.
object : |
Object to return the type name for. |
| Returns : | Type name of object. The string is owned by the type system and
should not be freed.
|
#define G_OBJECT_CLASS_TYPE(class) (G_TYPE_FROM_CLASS (class))
Get the type id of a class structure.
Return the type id of a class structure.
class : |
a valid GObjectClass |
| Returns : | Type id of class.
|
#define G_OBJECT_CLASS_NAME(class) (g_type_name (G_OBJECT_CLASS_TYPE (class)))
Return the name of a class structure's type.
Return the name of a class structure's type.
class : |
a valid GObjectClass |
| Returns : | Type name of class. The string is owned by the type system and
should not be freed.
|
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.
Installs a new property. This is usually done in the class initializer.
oclass : |
a GObjectClass |
property_id : |
the id for the new property |
pspec : |
the GParamSpec for the new property |
GParamSpec* g_object_class_find_property (GObjectClass *oclass, const gchar *property_name);
Looks up the GParamSpec for a property of a class.
Looks up the GParamSpec for a property of a class.
oclass : |
a GObjectClass |
property_name : |
the name of the property to look up |
| Returns : | the GParamSpec for the property, or NULL if the class
doesn't have a property of that name
|
GParamSpec** g_object_class_list_properties (GObjectClass *oclass, guint *n_properties);
Get an array of GParamSpec* for all properties of a class.
Returns an array of GParamSpec* for all properties of a class.
oclass : |
a GObjectClass |
n_properties : |
return location for the length of the returned array |
| Returns : | an array of GParamSpec* which should be freed after use |
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_class_find_property() or
g_object_class_list_properties() will return the overridden
property. However, in one case, the construct_properties argument of
the constructor virtual function, the GParamSpecOverride is passed
instead, so that the param_id field of the GParamSpec will be
correct. For virtually all uses, this makes no difference. If you
need to get the overridden property, you can call
g_param_spec_get_redirect_target().
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.
Internally, overriding is implemented by creating a property of type
GParamSpecOverride; generally operations that query the properties of
the object class, such as g_object_class_find_property() or
g_object_class_list_properties() will return the overridden
property. However, in one case, the construct_properties argument of
the constructor virtual function, the GParamSpecOverride is passed
instead, so that the param_id field of the GParamSpec will be
correct. For virtually all uses, this makes no difference. If you
need to get the overridden property, you can call
g_param_spec_get_redirect_target().
oclass : |
a GObjectClass |
property_id : |
the new property ID |
name : |
the name of a property registered in a parent class or in an interface of this class. |
Since 2.4
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.
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.
g_iface : |
any interface vtable for the interface, or the default vtable for the interface. |
pspec : |
the GParamSpec for the new property |
Since 2.4
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().
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().
g_iface : |
any interface vtable for the interface, or the default vtable for the interface |
property_name : |
name of a property to lookup. |
| Returns : | the GParamSpec for the property of the interface with the
name property_name, or NULL if no such property exists.
|
Since 2.4
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().
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().
g_iface : |
any interface vtable for the interface, or the default vtable for the interface |
n_properties_p : |
location to store number of properties returned. |
| Returns : | a pointer to an array of pointers to GParamSpec
structures. The paramspecs are owned by GLib, but the
array should be freed with g_free() when you are done with
it.
|
Since 2.4
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.
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.
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.
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.
object_type : |
the type id of the GObject subtype to instantiate |
n_parameters : |
the length of the parameters array
|
parameters : |
an array of GParameter |
| Returns : | a new instance of object_type
|
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().
The GParameter struct is an auxiliary structure used
to hand parameter name/value pairs to g_object_newv().
gpointer g_object_ref (gpointer object);
Increases the reference count of object.
Increases the reference count of object.
object : |
a GObject |
| Returns : | the same object
|
void g_object_unref (gpointer object);
Decreases the reference count of object. When its reference count
drops to 0, the object is finalized (i.e. its memory is freed).
Decreases the reference count of object.
When its reference count drops to 0, the object is finalized
(i.e. its memory is freed).
object : |
a GObject |
gpointer g_object_ref_sink (gpointer object);
Increase the reference count of object, and possibly remove the
floating reference, if object
has a floating reference.
In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.
Increase the reference count of object, and possibly remove the
floating reference, if object
has a floating reference.
In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.
object : |
a GObject |
| Returns : | object
|
Since 2.10
typedef struct _GObject GInitiallyUnowned;
All the fields in the GInitiallyUnowned structure are private to the GInitiallyUnowned implementation and should never be accessed directly.
All the fields in the GInitiallyUnowned structure are private to the GInitiallyUnowned implementation and should never be accessed directly.
typedef struct _GObjectClass GInitiallyUnownedClass;
The class structure for the GInitiallyUnowned type.
The class structure for the GInitiallyUnowned type.
#define G_TYPE_INITIALLY_UNOWNED (g_initially_unowned_get_type())
The type for GInitiallyUnowned.
The type for GInitiallyUnowned.
gboolean g_object_is_floating (gpointer object);
Checks wether object has a floating
reference.
Checks wether object has a floating
reference.
Since 2.10
void g_object_force_floating (GObject *object);
This function is intended for GObject implementations to re-enforce a
floating object reference.
Doing this is seldomly required, all
GInitiallyUnowneds are created with a floating reference which
usually just needs to be sunken by calling g_object_ref_sink().
This function is intended for GObject implementations to re-enforce a
floating object reference.
Doing this is seldomly required, all
GInitiallyUnowneds are created with a floating reference which
usually just needs to be sunken by calling g_object_ref_sink().
object : |
a GObject |
Since 2.10
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.
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.
data : |
data that was provided when the weak reference was established |
where_the_object_was : |
the object being finalized |
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).
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 : |
GObject to reference weakly |
notify : |
callback to invoke before the object is freed |
data : |
extra data to pass to notify |
void g_object_weak_unref (GObject *object, GWeakNotify notify, gpointer data);
Removes a weak reference callback to an object.
Removes a weak reference callback to an object.
object : |
GObject to remove a weak reference from |
notify : |
callback to search for |
data : |
data to search for |
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.
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.
object : |
The object that should be weak referenced. |
weak_pointer_location : |
The memory address of a 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().
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().
object : |
The object that is weak referenced. |
weak_pointer_location : |
The memory address of a pointer. |
void (*GToggleNotify) (gpointer data, GObject *object, gboolean is_last_ref);
A callback function used for notification when the state
of a toggle reference changes. See g_object_add_toggle_ref().
A callback function used for notification when the state
of a toggle reference changes. See g_object_add_toggle_ref().
data : |
Callback data passed to g_object_add_toggle_ref()
|
object : |
The object on which g_object_add_toggle_ref() was called.
|
is_last_ref : |
TRUE if the toggle reference is now the
last reference to the object. FALSE if the toggle
reference was the last reference and there are now other
references.
|
void g_object_add_toggle_ref (GObject *object, GToggleNotify notify, gpointer data);
Increases the reference count of the object by one and sets a callback to be called when all other references to the object are dropped, or when this is already the last reference to the object and another reference is established.
This functionality is intended for binding object to a proxy
object managed by another memory manager. This is done with two
paired references: the strong reference added by
g_object_add_toggle_ref() and a reverse reference to the proxy
object which is either a strong reference or weak reference.
The setup is that when there are no other references to object,
only a weak reference is held in the reverse direction from object
to the proxy object, but when there are other references held to
object, a strong reference is held. The notify callback is called
when the reference from object to the proxy object should be
toggled from strong to weak (is_last_ref
true) or weak to strong (is_last_ref false).
Since a (normal) reference must be held to the object before
calling g_object_toggle_ref(), the initial state of the reverse
link is always strong.
Multiple toggle references may be added to the same gobject, however if there are multiple toggle references to an object, none of them will ever be notified until all but one are removed. For this reason, you should only ever use a toggle reference if there is important state in the proxy object.
Increases the reference count of the object by one and sets a callback to be called when all other references to the object are dropped, or when this is already the last reference to the object and another reference is established.
This functionality is intended for binding object to a proxy
object managed by another memory manager. This is done with two
paired references: the strong reference added by
g_object_add_toggle_ref() and a reverse reference to the proxy
object which is either a strong reference or weak reference.
The setup is that when there are no other references to object,
only a weak reference is held in the reverse direction from object
to the proxy object, but when there are other references held to
object, a strong reference is held. The notify callback is called
when the reference from object to the proxy object should be
toggled from strong to weak (is_last_ref
true) or weak to strong (is_last_ref false).
Since a (normal) reference must be held to the object before
calling g_object_toggle_ref(), the initial state of the reverse
link is always strong.
Multiple toggle references may be added to the same gobject, however if there are multiple toggle references to an object, none of them will ever be notified until all but one are removed. For this reason, you should only ever use a toggle reference if there is important state in the proxy object.
object : |
a GObject |
notify : |
a function to call when this reference is the last reference to the object, or is no longer the last reference. |
data : |
data to pass to notify
|
Since 2.8
void g_object_remove_toggle_ref (GObject *object, GToggleNotify notify, gpointer data);
Removes a reference added with g_object_add_toggle_ref(). The
reference count of the object is decreased by one.
Removes a reference added with g_object_add_toggle_ref(). The
reference count of the object is decreased by one.
object : |
a GObject |
notify : |
a function to call when this reference is the last reference to the object, or is no longer the last reference. |
data : |
data to pass to notify
|
Since 2.8
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:
| signal |
equivalent to |
| object_signal, object-signal |
equivalent to |
| swapped_signal, swapped-signal |
equivalent to |
| swapped_object_signal, swapped-object-signal |
equivalent to |
| signal_after, signal-after |
equivalent to |
| object_signal_after, object-signal-after |
equivalent to |
| swapped_signal_after, swapped-signal-after |
equivalent to |
| swapped_object_signal_after, swapped-object-signal-after |
equivalent to |
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);
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:
| signal |
equivalent to |
| object_signal, object-signal |
equivalent to |
| swapped_signal, swapped-signal |
equivalent to |
| swapped_object_signal, swapped-object-signal |
equivalent to |
| signal_after, signal-after |
equivalent to |
| object_signal_after, object-signal-after |
equivalent to |
| swapped_signal_after, swapped-signal-after |
equivalent to |
| swapped_object_signal_after, swapped-object-signal-after |
equivalent to |
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);
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".
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".
void g_object_set (gpointer object, const gchar *first_property_name, ...);
Sets properties on an object.
Sets properties on an object.
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().
Example 6. Using g_object_get()
g_object_get() to get the contents
of three properties - one of type G_TYPE_INT,
one of type G_TYPE_STRING, and one of type ""
gint intval;
gchar *strval;
GObject *objval;
g_object_get (my_object,
"int-property", &intval,
"str-property", &strval,
"obj-property", &objval,
NULL);
// Do something with intval, strval, objval
g_free (strval);
g_object_unref (objval);
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().
Example 7. Using g_object_get()
An example of using g_object_get() to get the contents
of three properties - one of type G_TYPE_INT,
one of type G_TYPE_STRING, and one of type ""
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);
void g_object_notify (GObject *object, const gchar *property_name);
Emits a "notify" signal for the property property_name on object.
Emits a "notify" signal for the property property_name on object.
object : |
a GObject |
property_name : |
the name of a property installed on the class of object.
|
void g_object_freeze_notify (GObject *object);
Increases the freeze count on object. If the freeze count is
non-zero, the emission of "notify" signals on object is
stopped. The signals are queued until the freeze count is decreased
to zero.
This is necessary for accessors that modify multiple properties to prevent premature notification while the object is still being modified.
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.
object : |
a GObject |
void g_object_thaw_notify (GObject *object);
Reverts the effect of a previous call to
g_object_freeze_notify(). The freeze count is decreased on object
and when it reaches zero, all queued "notify" signals are emitted.
It is an error to call this function when the freeze count is zero.
Reverts the effect of a previous call to g_object_freeze_notify().
This causes all queued "notify" signals on object to be emitted.
object : |
a GObject |
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()).
Gets a named field from the objects table of associations (see 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.
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 : |
GObject containing the associations. |
key : |
name of the key |
data : |
data to associate with that key |
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.
Note that the destroy callback is not called if data is NULL.
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.
Note that the destroy callback is not called if data is NULL.
object : |
GObject containing the associations |
key : |
name of the key |
data : |
data to associate with that key |
destroy : |
function to call when the association is destroyed |
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.
Remove a specified datum from the object's data associations, without invoking the association's destroy handler.
gpointer g_object_get_qdata (GObject *object, GQuark quark);
This function gets back user data pointers stored via
g_object_set_qdata().
This function gets back user data pointers stored via
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.
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.
object : |
The GObject to set store a user data pointer |
quark : |
A GQuark, naming the user data pointer |
data : |
An opaque user data pointer |
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.
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.
object : |
The GObject to set store a user data pointer |
quark : |
A GQuark, naming the user data pointer |
data : |
An opaque user data pointer |
destroy : |
Function to invoke with data as argument, when data
needs to be freed
|
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().
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().
void g_object_set_property (GObject *object, const gchar *property_name, const GValue *value);
Sets a property on an object.
Sets a property on an object.
object : |
a GObject |
property_name : |
the name of the property to set |
value : |
the value |
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.
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.
object : |
a GObject |
property_name : |
the name of the property to get |
value : |
return location for the property value |
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.
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.
void g_object_set_valist (GObject *object, const gchar *first_property_name, va_list var_args);
Sets properties on an object.
Sets properties on an object.
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().
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().
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.
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.
object : |
GObject restricting lifetime of closure
|
closure : |
GClosure to watch |
void g_object_run_dispose (GObject *object);
Releases all references to other objects. This can be used to break reference cycles.
This functions should only be called from object system implementations.
Releases all references to other objects. This can be used to break reference cycles.
This functions should only be called from object system implementations.
object : |
a GObject |
#define G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, pspec)
This macro should be used to emit a standard warning about unexpected
properties in set_property() and get_property() implementations.
This macro should be used to emit a standard warning about unexpected
properties in set_property() and get_property() implementations.
object : |
the GObject on which set_property() or get_property() was called
|
property_id : |
the numeric id of the property |
pspec : |
the GParamSpec of the property |
"notify" signalvoid user_function (GObject *pspec, GParamSpec *gobject, gpointer user_data) : Run First / No Recursion / Has Details / Action / No Hooks
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.
This signal is typically used to obtain change notification for a
single property, by specifying the property name as a detail in the
g_signal_connect() call, like this:
g_signal_connect (text_view->buffer, "notify::paste-target-list",
G_CALLBACK (gtk_text_view_target_list_notify),
text_view)
It is important to note that you must use canonical parameter names as detail strings for the notify signal.
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.
This signal is typically used to obtain change notification for a
single property, by specifying the property name as a detail in the
g_signal_connect() call, like this:
g_signal_connect (text_view->buffer, "notify::paste-target-list",
G_CALLBACK (gtk_text_view_target_list_notify),
text_view)
It is important to note that you must use canonical parameter names as detail strings for the notify signal.
pspec : |
the GParamSpec of the property which changed |
gobject : |
the object which received the signal. |
user_data : |
user data set when the signal handler was connected. |