Glib::Binding Class Reference

Bind two object properties. More...

`#include <glibmm/binding.h>`

Inheritance diagram for Glib::Binding:
[legend]

## Public Types

using | SlotTransform = sigc::slot< bool, const GValue*, GValue* >
| For instance, bool on_transform_to(const GValue* from_value, GValue* to_value);. More...
Public Types inherited from Glib::Object
using | DestroyNotify = void(*)(gpointer data)
Public Types inherited from sigc::trackable
typedef internal::func_destroy_notify | func_destroy_notify

## Public Member Functions

| Binding (Binding&& src) noexcept
Binding& | operator= (Binding&& src) noexcept
| ~Binding () noexcept override
GBinding* | gobj ()
| Provides access to the underlying C GObject. More...
const GBinding* | gobj () const
| Provides access to the underlying C GObject. More...
GBinding* | gobj_copy ()
| Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs. More...
Glib::RefPtr< Glib::ObjectBase > | get_source ()
| Retrieves the Object instance used as the source of the binding. More...
Glib::RefPtr< const Glib::ObjectBase > | get_source () const
| Retrieves the Object instance used as the source of the binding. More...
Glib::ustring | get_source_property () const
| Retrieves the name of the property of Binding::property_source() used as the source of the binding. More...
Glib::RefPtr< Glib::ObjectBase > | get_target ()
| Retrieves the Object instance used as the target of the binding. More...
Glib::RefPtr< const Glib::ObjectBase > | get_target () const
| Retrieves the Object instance used as the target of the binding. More...
Glib::ustring | get_target_property () const
| Retrieves the name of the property of Binding::property_target() used as the target of the binding. More...
BindingFlags | get_flags () const
| Retrieves the flags passed when constructing the Binding. More...
void | unbind ()
| Explicitly releases the binding between the source and the target property expressed by this Binding instance. More...
Glib::PropertyProxy_ReadOnly< Glib::BindingFlags > | property_flags () const
| Flags to be used to control the Binding. More...
Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Glib::ObjectBase > > | property_source () const
| The Object that should be used as the source of the binding. More...
Glib::PropertyProxy_ReadOnly< Glib::ustring > | property_source_property () const
| The name of the property of Binding::property_source() that should be used as the source of the binding. More...
Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Glib::ObjectBase > > | property_target () const
| The Object that should be used as the target of the binding. More...
Glib::PropertyProxy_ReadOnly< Glib::ustring > | property_target_property () const
| The name of the property of Binding::property_target() that should be used as the target of the binding. More...
Public Member Functions inherited from Glib::Object
| Object (const Object&)=delete
Object& | operator= (const Object&)=delete
| Object (Object&& src) noexcept
Object& | operator= (Object&& src) noexcept
void* | get_data (const QueryQuark& key)
void | set_data (const Quark& key, void* data)
void | set_data (const Quark& key, void* data, DestroyNotify notify)
void | remove_data (const QueryQuark& quark)
void* | steal_data (const QueryQuark& quark)
Public Member Functions inherited from Glib::ObjectBase
| ObjectBase (const ObjectBase&)=delete
ObjectBase& | operator= (const ObjectBase&)=delete
void | set_property_value (const Glib::ustring& property_name, const Glib::ValueBase& value)
| You probably want to use a specific property_*() accessor method instead. More...
void | get_property_value (const Glib::ustring& property_name, Glib::ValueBase& value) const
| You probably want to use a specific property_*() accessor method instead. More...
template<class PropertyType >
void | set_property (const Glib::ustring& property_name, const PropertyType& value)
| You probably want to use a specific property_*() accessor method instead. More...
template<class PropertyType >
void | get_property (const Glib::ustring& property_name, PropertyType& value) const
| You probably want to use a specific property_*() accessor method instead. More...
void | connect_property_changed (const Glib::ustring& property_name, const sigc::slot< void >& slot)
| You can use the signal_changed() signal of the property proxy instead. More...
void | connect_property_changed (const Glib::ustring& property_name, sigc::slot< void >&& slot)
| You can use the signal_changed() signal of the property proxy instead. More...
sigc::connection | connect_property_changed_with_return (const Glib::ustring& property_name, const sigc::slot< void >& slot)
| You can use the signal_changed() signal of the property proxy instead. More...
sigc::connection | connect_property_changed_with_return (const Glib::ustring& property_name, sigc::slot< void >&& slot)
| You can use the signal_changed() signal of the property proxy instead. More...
void | freeze_notify ()
| Increases the freeze count on object. More...
void | thaw_notify ()
| Reverts the effect of a previous call to freeze_notify(). More...
virtual void | reference () const
| Increment the reference count for this object. More...
virtual void | unreference () const
| Decrement the reference count for this object. More...
GObject* | gobj ()
| Provides access to the underlying C GObject. More...
const GObject* | gobj () const
| Provides access to the underlying C GObject. More...
GObject* | gobj_copy () const
| Give a ref-ed copy to someone. Use for direct struct access. More...
Public Member Functions inherited from sigc::trackable
| trackable () noexcept
| trackable (const trackable &src) noexcept
| trackable (trackable &&src)
| ~trackable ()
void | add_destroy_notify_callback (void *data, func_destroy_notify func) const
void | notify_callbacks ()
trackable & | operator= (const trackable &src)
trackable & | operator= (trackable &&src)
void | remove_destroy_notify_callback (void *data) const

## Static Public Member Functions

static GType | get_type ()
| Get the GType for this class, for use with the underlying GObject type system. More...
static Glib::RefPtr< Binding > | bind_property_value (const PropertyProxy_Base& source_property, const PropertyProxy_Base& target_property, BindingFlags flags=BINDING_DEFAULT, const SlotTransform& transform_to=SlotTransform(), const SlotTransform& transform_from=SlotTransform())
| Creates a binding between source_property and target_property, allowing you to set the transformation functions to be used by the binding. More...
static Glib::RefPtr< Binding > | bind_property (const PropertyProxy_Base& source_property, const PropertyProxy_Base& target_property, BindingFlags flags=BINDING_DEFAULT)
| Creates a binding between source_property and target_property. More...
template<typename T_source , typename T_target , typename T_functor_to >
static Glib::RefPtr< Binding > | bind_property (const PropertyProxy< T_source >& source_property, const PropertyProxy< T_target >& target_property, BindingFlags flags, const T_functor_to& transform_to)
| Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding. More...
template<typename T_source , typename T_target , typename T_functor_to >
static Glib::RefPtr< Binding > | bind_property (const PropertyProxy< T_source >& source_property, const PropertyProxy_WriteOnly< T_target >& target_property, BindingFlags flags, const T_functor_to& transform_to)
| Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding. More...
template<typename T_source , typename T_target , typename T_functor_to >
static Glib::RefPtr< Binding > | bind_property (const PropertyProxy_ReadOnly< T_source >& source_property, const PropertyProxy< T_target >& target_property, BindingFlags flags, const T_functor_to& transform_to)
| Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding. More...
template<typename T_source , typename T_target , typename T_functor_to >
static Glib::RefPtr< Binding > | bind_property (const PropertyProxy_ReadOnly< T_source >& source_property, const PropertyProxy_WriteOnly< T_target >& target_property, BindingFlags flags, const T_functor_to& transform_to)
| Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding. More...
template<typename T_source , typename T_target , typename T_functor_to , typename T_functor_from >
static Glib::RefPtr< Binding > | bind_property (const PropertyProxy< T_source >& source_property, const PropertyProxy< T_target >& target_property, BindingFlags flags, const T_functor_to& transform_to, const T_functor_from& transform_from)
| Creates a binding between source_property and target_property, allowing you to set the transformation functions to be used by the binding. More...

## Related Functions

(Note that these are not member functions.)
Glib::RefPtr< Glib::Binding > | wrap (GBinding* object, bool take_copy=false)
| A Glib::wrap() method for this object. More...
Related Functions inherited from Glib::Object
Glib::RefPtr< Glib::Object > | wrap (GObject* object, bool take_copy=false)

## Additional Inherited Members

Protected Member Functions inherited from Glib::Object
| Object ()
| Object (const Glib::ConstructParams& construct_params)
| Object (GObject* castitem)
| ~Object () noexcept override
Protected Member Functions inherited from Glib::ObjectBase
| ObjectBase ()
| This default constructor is called implicitly from the constructor of user-derived classes, even if, for instance, Gtk::Button calls a different ObjectBase constructor. More...
| ObjectBase (const char* custom_type_name)
| A derived constructor always overrides this choice. More...
| ObjectBase (const std::type_info& custom_type_info)
| This constructor is a special feature to allow creation of derived types on the fly, without having to use g_object_new() manually. More...
| ObjectBase (ObjectBase&& src) noexcept
ObjectBase& | operator= (ObjectBase&& src) noexcept
virtual | ~ObjectBase () noexcept=0
void | initialize (GObject* castitem)
void | initialize_move (GObject* castitem, Glib::ObjectBase* previous_wrapper)

## Detailed Description

Bind two object properties.

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

Glib::Binding::bind_property(object1->property_a(), object2->property_b());

will cause property_b() of object2 to be updated every time the value of property_a() of object1 changes.

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

Glib::Binding::bind_property(object1->property_a(), object2->property_b(),
Glib::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:

bool celsius_to_fahrenheit(const double& celsius, double& fahrenheit);
bool fahrenheit_to_celsius(const double& fahrenheit, double& celsius);
Glib::Binding::bind_property(adjustment1->property_value(),
adjustment2->property_value(), Glib::BINDING_BIDIRECTIONAL,
sigc::ptr_fun(celsius_to_fahrenheit), sigc::ptr_fun(fahrenheit_to_celsius));

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

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

Note that Glib::Binding does not resolve cycles by itself; a cycle like

object1->property_A() -> object2->property_B()
object2->property_B() -> object3->property_C()
object3->property_C() -> object1->property_A()

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 Glib::SignalProxyNormal::emission_stop() or g_signal_handler_block().

A binding will be severed, and the resources it allocates freed, whenever either one of the Glib::ObjectBase instances it refers to is deleted, when unbind() is called, or when the Glib::Binding instance loses its last reference.

Since glibmm 2.44:

## Member Typedef Documentation

using Glib::Binding::SlotTransform = sigc::slot<bool, const GValue*, GValue*>

For instance,
bool on_transform_to(const GValue* from_value, GValue* to_value);.

Returns
  `true` if the transformation was successful, and `false` otherwise.

## Constructor & Destructor Documentation

Glib::Binding::Binding | ( | Binding&& | src | ) |

noexcept

Glib::Binding::~Binding | ( |  | ) |

override noexcept

## Member Function Documentation

static Glib::RefPtr<Binding> Glib::Binding::bind_property | ( | const PropertyProxy_Base& | source_property,
|  | const PropertyProxy_Base& | target_property,
|  | BindingFlags | flags = `BINDING_DEFAULT`
| ) |  |

inline static

Creates a binding between source_property and target_property.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

See also
  bind_property_value()

Since glibmm 2.44:

template <typename T_source , typename T_target , typename T_functor_to >

static Glib::RefPtr<Binding> Glib::Binding::bind_property | ( | const PropertyProxy< T_source >& | source_property,
|  | const PropertyProxy< T_target >& | target_property,
|  | BindingFlags | flags,
|  | const T_functor_to & | transform_to
| ) |  |

inline static

Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.
  transform_to | The transformation function from the source to the target, or an empty slot to use the default.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

Template Parameters

  T_source | Type of the source property. Must be a type that can be stored in a Glib::Value<T_source> object.
  T_target | Type of the target property. Must be a type that can be stored in a Glib::Value<T_target> object.
  T_functor_to | Type of functor that translates from the source to the target. Must be convertible to sigc::slot<bool, const T_source&, T_target&>.

See also
  bind_property_value()

Since glibmm 2.44:

template <typename T_source , typename T_target , typename T_functor_to >

static Glib::RefPtr<Binding> Glib::Binding::bind_property | ( | const PropertyProxy< T_source >& | source_property,
|  | const PropertyProxy_WriteOnly< T_target >& | target_property,
|  | BindingFlags | flags,
|  | const T_functor_to & | transform_to
| ) |  |

inline static

Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.
  transform_to | The transformation function from the source to the target, or an empty slot to use the default.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

Template Parameters

  T_source | Type of the source property. Must be a type that can be stored in a Glib::Value<T_source> object.
  T_target | Type of the target property. Must be a type that can be stored in a Glib::Value<T_target> object.
  T_functor_to | Type of functor that translates from the source to the target. Must be convertible to sigc::slot<bool, const T_source&, T_target&>.

See also
  bind_property_value()

Since glibmm 2.44:

template <typename T_source , typename T_target , typename T_functor_to >

static Glib::RefPtr<Binding> Glib::Binding::bind_property | ( | const PropertyProxy_ReadOnly< T_source >& | source_property,
|  | const PropertyProxy< T_target >& | target_property,
|  | BindingFlags | flags,
|  | const T_functor_to & | transform_to
| ) |  |

inline static

Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.
  transform_to | The transformation function from the source to the target, or an empty slot to use the default.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

Template Parameters

  T_source | Type of the source property. Must be a type that can be stored in a Glib::Value<T_source> object.
  T_target | Type of the target property. Must be a type that can be stored in a Glib::Value<T_target> object.
  T_functor_to | Type of functor that translates from the source to the target. Must be convertible to sigc::slot<bool, const T_source&, T_target&>.

See also
  bind_property_value()

Since glibmm 2.44:

template <typename T_source , typename T_target , typename T_functor_to >

static Glib::RefPtr<Binding> Glib::Binding::bind_property | ( | const PropertyProxy_ReadOnly< T_source >& | source_property,
|  | const PropertyProxy_WriteOnly< T_target >& | target_property,
|  | BindingFlags | flags,
|  | const T_functor_to & | transform_to
| ) |  |

inline static

Creates a binding between source_property and target_property, allowing you to set a transformation function to be used by the binding.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.
  transform_to | The transformation function from the source to the target, or an empty slot to use the default.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

Template Parameters

  T_source | Type of the source property. Must be a type that can be stored in a Glib::Value<T_source> object.
  T_target | Type of the target property. Must be a type that can be stored in a Glib::Value<T_target> object.
  T_functor_to | Type of functor that translates from the source to the target. Must be convertible to sigc::slot<bool, const T_source&, T_target&>.

See also
  bind_property_value()

Since glibmm 2.44:

template <typename T_source , typename T_target , typename T_functor_to , typename T_functor_from >

static Glib::RefPtr<Binding> Glib::Binding::bind_property | ( | const PropertyProxy< T_source >& | source_property,
|  | const PropertyProxy< T_target >& | target_property,
|  | BindingFlags | flags,
|  | const T_functor_to & | transform_to,
|  | const T_functor_from & | transform_from
| ) |  |

inline static

Creates a binding between source_property and target_property, allowing you to set the transformation functions to be used by the binding.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.
  transform_to | The transformation function from the source to the target, or an empty slot to use the default.
  transform_from | The transformation function from the target to the source, or an empty slot to use the default.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

Template Parameters

  T_source | Type of the source property. Must be a type that can be stored in a Glib::Value<T_source> object.
  T_target | Type of the target property. Must be a type that can be stored in a Glib::Value<T_target> object.
  T_functor_to | Type of functor that translates from the source to the target. Must be convertible to sigc::slot<bool, const T_source&, T_target&>.
  T_functor_from | Type of functor that translates from the target to the source. Must be convertible to sigc::slot<bool, const T_target&, T_source&>.

See also
  bind_property_value()

Since glibmm 2.44:

static Glib::RefPtr<Binding> Glib::Binding::bind_property_value | ( | const PropertyProxy_Base& | source_property,
|  | const PropertyProxy_Base& | target_property,
|  | BindingFlags | flags = `BINDING_DEFAULT`,
|  | const SlotTransform& | transform_to = `SlotTransform()`,
|  | const SlotTransform& | transform_from = `SlotTransform()`
| ) |  |

static

Creates a binding between source_property and target_property, allowing you to set the transformation functions to be used by the binding.

If flags contains Glib::BINDING_BIDIRECTIONAL then the binding will be mutual: if target_property changes then the source_property will be updated as well. The transform_from function is only used in case of bidirectional bindings, otherwise it will be ignored.

The binding will automatically be removed when either the source or the target instance is deleted. To remove the binding without affecting the source and the target you can call unbind() on the returned Binding instance.

A Glib::ObjectBase instance can have multiple bindings.

If you supply transformation functions, it is usually easier to use one of the bind_property() overloads, to avoid the use of GValue in the transformation functions.

Parameters

  source_property | The source property to bind.
  target_property | The target property to bind.
  flags | Flags to pass to Binding.
  transform_to | The transformation function from the source to the target, or an empty slot to use the default.
  transform_from | The transformation function from the target to the source, or an empty slot to use the default.

Returns
  The Binding instance representing the binding between the two Glib::ObjectBase instances, or `nullptr` in case of error.

Since glibmm 2.44:

BindingFlags Glib::Binding::get_flags | ( |  | ) | const

Retrieves the flags passed when constructing the Binding.

Since glibmm 2.44:

Returns
  The BindingFlags used by the Binding.

Glib::RefPtr<Glib::ObjectBase> Glib::Binding::get_source | ( |  | ) |

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

Since glibmm 2.44:

Returns
  The source Object.

Glib::RefPtr<const Glib::ObjectBase> Glib::Binding::get_source | ( |  | ) | const

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

Since glibmm 2.44:

Returns
  The source Object.

Glib::ustring Glib::Binding::get_source_property | ( |  | ) | const

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

Since glibmm 2.44:

Returns
  The name of the source property.

Glib::RefPtr<Glib::ObjectBase> Glib::Binding::get_target | ( |  | ) |

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

Since glibmm 2.44:

Returns
  The target Object.

Glib::RefPtr<const Glib::ObjectBase> Glib::Binding::get_target | ( |  | ) | const

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

Since glibmm 2.44:

Returns
  The target Object.

Glib::ustring Glib::Binding::get_target_property | ( |  | ) | const

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

Since glibmm 2.44:

Returns
  The name of the target property.

static GType Glib::Binding::get_type | ( |  | ) |

static

Get the GType for this class, for use with the underlying GObject type system.

GBinding* Glib::Binding::gobj | ( |  | ) |

inline

Provides access to the underlying C GObject.

const GBinding* Glib::Binding::gobj | ( |  | ) | const

inline

Provides access to the underlying C GObject.

GBinding* Glib::Binding::gobj_copy | ( |  | ) |

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

Binding& Glib::Binding::operator= | ( | Binding&& | src | ) |

noexcept

Glib::PropertyProxy_ReadOnly< Glib::BindingFlags > Glib::Binding::property_flags | ( |  | ) | const

Flags to be used to control the Binding.

Since glibmm 2.44:

Default value: BINDING_DEFAULT

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

Glib::PropertyProxy_ReadOnly< Glib::RefPtr<Glib::ObjectBase> > Glib::Binding::property_source | ( |  | ) | const

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

Since glibmm 2.44:

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

Glib::PropertyProxy_ReadOnly< Glib::ustring > Glib::Binding::property_source_property | ( |  | ) | const

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

Since glibmm 2.44:

Default value: ""

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

Glib::PropertyProxy_ReadOnly< Glib::RefPtr<Glib::ObjectBase> > Glib::Binding::property_target | ( |  | ) | const

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

Since glibmm 2.44:

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

Glib::PropertyProxy_ReadOnly< Glib::ustring > Glib::Binding::property_target_property | ( |  | ) | const

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

Since glibmm 2.44:

Default value: ""

Returns
  A PropertyProxy_ReadOnly that allows you to get the value of the property, or receive notification when the value of the property changes.

void Glib::Binding::unbind | ( |  | ) |

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

The binding is also released if either the source object or the target object is deleted, or this Binding instance loses its last reference, i.e. there is no more Glib::RefPtr that holds a pointer to it.

Since glibmm 2.44:

## Friends And Related Function Documentation

Glib::RefPtr< Glib::Binding > wrap | ( | GBinding * | object,
|  | bool | take_copy = `false`
| ) |  |

related

A Glib::wrap() method for this object.

Parameters

  object | The C instance.
  take_copy | False if the result should take ownership of the C instance. True if it should take a new copy or ref.

Returns
  A C++ instance that wraps this C instance.