Struct glib::Binding

#[repr(transparent)]
pub struct Binding { /* private fields */ }

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:

⚠️ The following code is in 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 [ObjectExt::set()][crate::prelude::ObjectExt::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:

⚠️ The following code is in 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:

⚠️ The following code is in 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 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 g_signal_stop_emission() or g_signal_handler_block().

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 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.

Binding is available since GObject 2.26

Properties

flags

Flags to be used to control the Binding

Readable | Writeable | Construct Only

source

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

Readable | Writeable | Construct Only

source-property

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

This should be in [canonical form][canonical-parameter-names] to get the best performance.

Readable | Writeable | Construct Only

target

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

Readable | Writeable | Construct Only

target-property

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

This should be in [canonical form][canonical-parameter-names] to get the best performance.

Readable | Writeable | Construct Only

Implements

ObjectExt

Implementations

impl Binding

pub fn flags(&self) -> BindingFlags

Retrieves the flags passed when constructing the Binding.

Returns

the BindingFlags used by the Binding

pub fn source_property(&self) -> GString

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

Returns

the name of the source property

pub fn target_property(&self) -> GString

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

Returns

the name of the target property

pub fn unbind(&self)

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 Binding instance after calling 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 ObjectExt::bind_property() and is owned by the binding.

impl Binding

pub fn source(&self) -> Option<Object>

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

pub fn target(&self) -> Option<Object>

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

Trait Implementations

impl Clone for Binding

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Binding

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Binding

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl HasParamSpec for Binding

type ParamSpec = ParamSpecObject

type SetValue = Binding

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, Binding>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for Binding

fn hash<H>(&self, state: &mut H)where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Binding

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl ParentClassIs for Binding

type Parent = Object

impl<OT: ObjectType> PartialEq<OT> for Binding

fn eq(&self, other: &OT) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for Binding

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for Binding

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for Binding

impl Send for Binding

impl Sync for Binding