GObject.Binding

Subclasses:

None

Methods

Inherited:

GObject.Object (37)

Structs:

GObject.ObjectClass (5)

	dup_source ()
	dup_target ()
	get_flags ()
	get_source ()
	get_source_property ()
	get_target ()
	get_target_property ()
	unbind ()

Virtual Methods

Inherited:

GObject.Object (7)

Properties

Name	Type	Flags	Short Description
flags	GObject.BindingFlags	r/w/co
source	GObject.Object	r/w/co
source-property	str	r/w/co
target	GObject.Object	r/w/co
target-property	str	r/w/co

Signals

Inherited:

GObject.Object (1)

Fields

Inherited:

GObject.Object (1)

Class Details

class GObject.Binding(**kwargs)

Bases:

GObject.Object

Abstract:

No

GObject instance (or source) and another property on another GObject instance (or target).

Whenever the source property changes, the same value is applied to the target property; for instance, the following binding:

``c

g_object_bind_property (object1, “property-a”,

object2, “property-b”, G_BINDING_DEFAULT);

``

will cause the property named “property-b” of object2 to be updated every time [method`GObject`.set] or the specific accessor changes the value of the property “property-a” of object1.

It is possible to create a bidirectional binding between two properties of two GObject instances, so that if either property changes, the other is updated as well, for instance:

``c

g_object_bind_property (object1, “property-a”,

object2, “property-b”, G_BINDING_BIDIRECTIONAL);

``

will keep the two properties in sync.

It is also possible to set a custom transformation function (in both directions, in case of a bidirectional binding) to apply a custom transformation from the source value to the target value before applying it; for instance, the following binding:

``c

g_object_bind_property_full (adjustment1, “value”,

adjustment2, “value”, G_BINDING_BIDIRECTIONAL, celsius_to_fahrenheit, fahrenheit_to_celsius, NULL, NULL);

``

will keep the “value” property of the two adjustments in sync; the celsius_to_fahrenheit function will be called whenever the “value” property of adjustment1 changes and will transform the current value of the property before applying it to the “value” property of adjustment2.

Vice versa, the fahrenheit_to_celsius function will be called whenever the “value” property of adjustment2 changes, and will transform the current value of the property before applying it to the “value” property of adjustment1.

Note that GObject.Binding does not resolve cycles by itself; a cycle like

``

object1:propertyA -> object2:propertyB object2:propertyB -> object3:propertyC object3:propertyC -> object1:propertyA

``

might lead to an infinite loop. The loop, in this particular case, can be avoided if the objects emit the GObject::notify signal only if the value has effectively been changed. A binding is implemented using the GObject::notify signal, so it is susceptible to all the various ways of blocking a signal emission, like [func`GObject`.signal_stop_emission] or [func`GObject`.signal_handler_block].

A binding will be severed, and the resources it allocates freed, whenever either one of the GObject instances it refers to are finalized, or when the GObject.Binding instance loses its last reference.

Bindings for languages with garbage collection can use [method`GObject`.Binding.unbind] to explicitly release a binding between the source and target properties, instead of relying on the last reference on the binding, source, and target instances to drop.

New in version 2.26.

dup_source()

Returns:

the source GObject.Object, or None if the source does not exist any more.

Return type:

GObject.Object or None

Retrieves the GObject.Object instance used as the source of the binding.

A GObject.Binding can outlive the source GObject.Object as the binding does not hold a strong reference to the source. If the source is destroyed before the binding then this function will return None.

New in version 2.68.

dup_target()

Returns:

the target GObject.Object, or None if the target does not exist any more.

Return type:

GObject.Object or None

Retrieves the GObject.Object instance used as the target of the binding.

A GObject.Binding can outlive the target GObject.Object as the binding does not hold a strong reference to the target. If the target is destroyed before the binding then this function will return None.

New in version 2.68.

get_flags()

Returns:

the GObject.BindingFlags used by the GObject.Binding

Return type:

GObject.BindingFlags

Retrieves the flags passed when constructing the GObject.Binding.

New in version 2.26.

get_source()

Returns:

the source GObject.Object, or None if the source does not exist any more.

Return type:

GObject.Object or None

Retrieves the GObject.Object instance used as the source of the binding.

A GObject.Binding can outlive the source GObject.Object as the binding does not hold a strong reference to the source. If the source is destroyed before the binding then this function will return None.

Use GObject.Binding.dup_source() if the source or binding are used from different threads as otherwise the pointer returned from this function might become invalid if the source is finalized from another thread in the meantime.

New in version 2.26.

Deprecated since version 2.68: Use GObject.Binding.dup_source() for a safer version of this function.

get_source_property()

Returns:

the name of the source property

Return type:

str

Retrieves the name of the property of GObject.Binding :source used as the source of the binding.

New in version 2.26.

get_target()

Returns:

the target GObject.Object, or None if the target does not exist any more.

Return type:

GObject.Object or None

Retrieves the GObject.Object instance used as the target of the binding.

A GObject.Binding can outlive the target GObject.Object as the binding does not hold a strong reference to the target. If the target is destroyed before the binding then this function will return None.

Use GObject.Binding.dup_target() if the target or binding are used from different threads as otherwise the pointer returned from this function might become invalid if the target is finalized from another thread in the meantime.

New in version 2.26.

Deprecated since version 2.68: Use GObject.Binding.dup_target() for a safer version of this function.

get_target_property()

Returns:

the name of the target property

Return type:

str

Retrieves the name of the property of GObject.Binding :target used as the target of the binding.

New in version 2.26.

unbind()

Explicitly releases the binding between the source and the target property expressed by self.

This function will release the reference that is being held on the self instance if the binding is still bound; if you want to hold on to the GObject.Binding instance after calling GObject.Binding.unbind(), you will need to hold a reference to it.

Note however that this function does not take ownership of self, it only unrefs the reference that was initially created by GObject.Object.bind_property() and is owned by the binding.

New in version 2.38.

Property Details

GObject.Binding.props.flags

Name:

flags

Type:

GObject.BindingFlags

Default Value:

GObject.BindingFlags.DEFAULT

Flags:

READABLE, WRITABLE, CONSTRUCT_ONLY

Flags to be used to control the GObject.Binding

New in version 2.26.

GObject.Binding.props.source

Name:

source

Type:

GObject.Object

Default Value:

None

Flags:

READABLE, WRITABLE, CONSTRUCT_ONLY

The GObject.Object that should be used as the source of the binding

New in version 2.26.

GObject.Binding.props.source_property

Name:

source-property

Type:

str

Default Value:

None

Flags:

READABLE, WRITABLE, CONSTRUCT_ONLY

The name of the property of GObject.Binding :source that should be used as the source of the binding.

This should be in canonical form to get the best performance.

New in version 2.26.

GObject.Binding.props.target

Name:

target

Type:

GObject.Object

Default Value:

None

Flags:

READABLE, WRITABLE, CONSTRUCT_ONLY

The GObject.Object that should be used as the target of the binding

New in version 2.26.

GObject.Binding.props.target_property

Name:

target-property

Type:

str

Default Value:

None

Flags:

READABLE, WRITABLE, CONSTRUCT_ONLY

The name of the property of GObject.Binding :target that should be used as the target of the binding.

This should be in canonical form to get the best performance.

New in version 2.26.