gi-gobject-2.0.23: GObject bindings
Copyright Will Thompson Iñaki García Etxebarria and Jonas Platte LGPL-2.1 Iñaki García Etxebarria None Haskell2010

GI.GObject.Objects.Binding

Description

Binding is the representation of a binding between a property on a Object instance (or source) and another property on another Object instance (or target). Whenever the source property changes, the same value is applied to the target property; for instance, the following binding:

C code

 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 g_object_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 Object instances, so that if either property changes, the other is updated as well, for instance:

C code

 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 code

 g_object_bind_property_full (adjustment1, "value",
G_BINDING_BIDIRECTIONAL,
celsius_to_fahrenheit,
fahrenheit_to_celsius,
NULL, NULL);

will keep the "value" property of the two adjustments in sync; the celsiusToFahrenheit 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 fahrenheitToCelsius 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 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 notify signal only if the value has effectively been changed. A binding is implemented using the notify signal, so it is susceptible to all the various ways of blocking a signal emission, like signalStopEmission or signalHandlerBlock.

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

Bindings for languages with garbage collection can use bindingUnbind 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.

Binding is available since GObject 2.26

Since: 2.26

Synopsis

Exported types

newtype Binding Source #

Memory-managed wrapper type.

Constructors

 Binding (ManagedPtr Binding)

Instances

Instances details
 Source # Instance detailsDefined in GI.GObject.Objects.Binding Methods(==) :: Binding -> Binding -> Bool #(/=) :: Binding -> Binding -> Bool # Source # Convert Binding to and from GValue with toGValue and fromGValue. Instance detailsDefined in GI.GObject.Objects.Binding Methods Source # Instance detailsDefined in GI.GObject.Objects.Binding Methods Source # Instance detailsDefined in GI.GObject.Objects.Binding Methods Source # Instance detailsDefined in GI.GObject.Objects.Binding Source # Instance detailsDefined in GI.GObject.Objects.Binding Source # Instance detailsDefined in GI.GObject.Objects.Binding type ParentTypes Binding = '[Object]

class (GObject o, IsDescendantOf Binding o) => IsBinding o Source #

Type class for types which can be safely cast to Binding, for instance with toBinding.

Instances

Instances details
 Source # Instance detailsDefined in GI.GObject.Objects.Binding

toBinding :: (MonadIO m, IsBinding o) => o -> m Binding Source #

Cast to Binding, for types for which this is known to be safe. For general casts, use castTo.

Methods

getFlags

Arguments

 :: (HasCallStack, MonadIO m, IsBinding a) => a binding: a Binding -> m [BindingFlags] Returns: the BindingFlags used by the Binding

Retrieves the flags passed when constructing the Binding.

Since: 2.26

getSource

Arguments

 :: (HasCallStack, MonadIO m, IsBinding a) => a binding: a Binding -> m Object Returns: the source Object

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

Since: 2.26

getSourceProperty

Arguments

 :: (HasCallStack, MonadIO m, IsBinding a) => a binding: a Binding -> m Text Returns: the name of the source property

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

Since: 2.26

getTarget

Arguments

 :: (HasCallStack, MonadIO m, IsBinding a) => a binding: a Binding -> m Object Returns: the target Object

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

Since: 2.26

getTargetProperty

Arguments

 :: (HasCallStack, MonadIO m, IsBinding a) => a binding: a Binding -> m Text Returns: the name of the target property

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

Since: 2.26

unbind

Arguments

 :: (HasCallStack, MonadIO m, IsBinding a) => a binding: a Binding -> m ()

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

This function will release the reference that is being held on the binding instance; if you want to hold on to the Binding instance after calling bindingUnbind, you will need to hold a reference to it.

Since: 2.38

Properties

flags

Flags to be used to control the Binding

Since: 2.26

constructBindingFlags :: (IsBinding o, MonadIO m) => [BindingFlags] -> m (GValueConstruct o) Source #

Construct a GValueConstruct with valid value for the “flags” property. This is rarely needed directly, but it is used by new.

getBindingFlags :: (MonadIO m, IsBinding o) => o -> m [BindingFlags] Source #

Get the value of the “flags” property. When overloading is enabled, this is equivalent to

get binding #flags


source

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

Since: 2.26

constructBindingSource :: (IsBinding o, MonadIO m, IsObject a) => a -> m (GValueConstruct o) Source #

Construct a GValueConstruct with valid value for the “source” property. This is rarely needed directly, but it is used by new.

getBindingSource :: (MonadIO m, IsBinding o) => o -> m Object Source #

Get the value of the “source” property. When overloading is enabled, this is equivalent to

get binding #source


sourceProperty

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

Since: 2.26

constructBindingSourceProperty :: (IsBinding o, MonadIO m) => Text -> m (GValueConstruct o) Source #

Construct a GValueConstruct with valid value for the “source-property” property. This is rarely needed directly, but it is used by new.

getBindingSourceProperty :: (MonadIO m, IsBinding o) => o -> m Text Source #

Get the value of the “source-property” property. When overloading is enabled, this is equivalent to

get binding #sourceProperty


target

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

Since: 2.26

constructBindingTarget :: (IsBinding o, MonadIO m, IsObject a) => a -> m (GValueConstruct o) Source #

Construct a GValueConstruct with valid value for the “target” property. This is rarely needed directly, but it is used by new.

getBindingTarget :: (MonadIO m, IsBinding o) => o -> m Object Source #

Get the value of the “target” property. When overloading is enabled, this is equivalent to

get binding #target


targetProperty

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

Construct a GValueConstruct with valid value for the “target-property” property. This is rarely needed directly, but it is used by new.
Get the value of the “target-property” property. When overloading is enabled, this is equivalent to
get binding #targetProperty