Struct gio::Cancellable

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pub struct Cancellable { /* private fields */ }
Expand description

GCancellable allows operations to be cancelled.

GCancellable is a thread-safe operation cancellation stack used throughout GIO to allow for cancellation of synchronous and asynchronous operations.

§Signals

§cancelled

Emitted when the operation has been cancelled.

Can be used by implementations of cancellable operations. If the operation is cancelled from another thread, the signal will be emitted in the thread that cancelled the operation, not the thread that is running the operation.

Note that disconnecting from this signal (or any signal) in a multi-threaded program is prone to race conditions. For instance it is possible that a signal handler may be invoked even after a call to g_signal_handler_disconnect() for that handler has already returned.

There is also a problem when cancellation happens right before connecting to the signal. If this happens the signal will unexpectedly not be emitted, and checking before connecting to the signal leaves a race condition where this is still happening.

In order to make it safe and easy to connect handlers there are two helper functions: g_cancellable_connect() and g_cancellable_disconnect() which protect against problems like this.

An example of how to us this:

⚠️ The following code is in C ⚠️

    // Make sure we don't do unnecessary work if already cancelled
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      return;

    // Set up all the data needed to be able to handle cancellation
    // of the operation
    my_data = my_data_new (...);

    id = 0;
    if (cancellable)
      id = g_cancellable_connect (cancellable,
                      G_CALLBACK (cancelled_handler)
                      data, NULL);

    // cancellable operation here...

    g_cancellable_disconnect (cancellable, id);

    // cancelled_handler is never called after this, it is now safe
    // to free the data
    my_data_free (my_data);

Note that the cancelled signal is emitted in the thread that the user cancelled from, which may be the main thread. So, the cancellable signal should not do something that can block.

§Implements

CancellableExt, [trait@glib::ObjectExt], CancellableExtManual

GLib type: GObject with reference counted clone semantics.

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impl Cancellable

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pub const NONE: Option<&'static Cancellable> = None

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pub fn new() -> Cancellable

Creates a new #GCancellable object.

Applications that want to start one or more operations that should be cancellable should create a #GCancellable and pass it to the operations.

One #GCancellable can be used in multiple consecutive operations or in multiple concurrent operations.

§Returns

a #GCancellable.

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pub fn current() -> Option<Cancellable>

Gets the top cancellable from the stack.

§Returns

a #GCancellable from the top of the stack, or None if the stack is empty.

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impl Clone for Cancellable

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fn clone(&self) -> Self

Makes a clone of this shared reference.

This increments the strong reference count of the object. Dropping the object will decrement it again.

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

Performs copy-assignment from source. Read more
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impl Debug for Cancellable

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

Formats the value using the given formatter. Read more
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impl Default for Cancellable

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fn default() -> Self

Returns the “default value” for a type. Read more
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impl HasParamSpec for Cancellable

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type ParamSpec = ParamSpecObject

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type SetValue = Cancellable

Preferred value to be used as setter for the associated ParamSpec.
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type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, Cancellable>

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fn param_spec_builder() -> Self::BuilderFn

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impl Hash for Cancellable

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

Hashes the memory address of this object.

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

Feeds a slice of this type into the given Hasher. Read more
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impl Ord for Cancellable

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

Comparison for two GObjects.

Compares the memory addresses of the provided objects.

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

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl ParentClassIs for Cancellable

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

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

Equality for two GObjects.

Two GObjects are equal if their memory addresses are equal.

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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.
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impl<OT: ObjectType> PartialOrd<OT> for Cancellable

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

Partial comparison for two GObjects.

Compares the memory addresses of the provided objects.

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

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

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

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fn static_type() -> Type

Returns the type identifier of Self.
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impl Eq for Cancellable

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impl Send for Cancellable

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impl Sync for Cancellable

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<O> CancellableExt for O
where O: IsA<Cancellable>,

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fn cancel(&self)

Will set @self to cancelled, and will emit the #GCancellable::cancelled signal. (However, see the warning about race conditions in the documentation for that signal if you are planning to connect to it.) Read more
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fn fd(&self) -> i32

Gets the file descriptor for a cancellable job. This can be used to implement cancellable operations on Unix systems. The returned fd will turn readable when @self is cancelled. Read more
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fn is_cancelled(&self) -> bool

Checks if a cancellable job has been cancelled. Read more
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fn pop_current(&self)

Pops @self off the cancellable stack (verifying that @self is on the top of the stack).
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fn push_current(&self)

Pushes @self onto the cancellable stack. The current cancellable can then be received using g_cancellable_get_current(). Read more
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fn release_fd(&self)

Releases a resources previously allocated by g_cancellable_get_fd() or g_cancellable_make_pollfd(). Read more
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impl<O> CancellableExtManual for O
where O: IsA<Cancellable>,

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fn connect_cancelled<F: FnOnce(&Self) + Send + 'static>( &self, callback: F, ) -> Option<CancelledHandlerId>

Convenience function to connect to the signal::Cancellable::cancelled signal. Also handles the race condition that may happen if the cancellable is cancelled right before connecting. If the operation is cancelled from another thread, callback will be called in the thread that cancelled the operation, not the thread that is running the operation. This may be the main thread, so the callback should not do something that can block. Read more
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fn connect_cancelled_local<F: FnOnce(&Self) + 'static>( &self, callback: F, ) -> Option<CancelledHandlerId>

Local variant of Self::connect_cancelled.
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fn disconnect_cancelled(&self, id: CancelledHandlerId)

Disconnects a handler from a cancellable instance. Additionally, in the event that a signal handler is currently running, this call will block until the handler has finished. Calling this function from a callback registered with Self::connect_cancelled will therefore result in a deadlock. Read more
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fn future(&self) -> Pin<Box<dyn Future<Output = ()> + Send + Sync + 'static>>

Returns a Future that completes when the cancellable becomes cancelled. Completes immediately if the cancellable is already cancelled.
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fn set_error_if_cancelled(&self) -> Result<(), Error>

Set an error if the cancellable is already cancelled. If the @self is cancelled, sets the error to notify that the operation was cancelled. Read more
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impl<T> Cast for T
where T: ObjectType,

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fn upcast<T>(self) -> T
where T: ObjectType, Self: IsA<T>,

Upcasts an object to a superclass or interface T. Read more
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fn upcast_ref<T>(&self) -> &T
where T: ObjectType, Self: IsA<T>,

Upcasts an object to a reference of its superclass or interface T. Read more
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fn downcast<T>(self) -> Result<T, Self>
where T: ObjectType, Self: MayDowncastTo<T>,

Tries to downcast to a subclass or interface implementor T. Read more
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fn downcast_ref<T>(&self) -> Option<&T>
where T: ObjectType, Self: MayDowncastTo<T>,

Tries to downcast to a reference of its subclass or interface implementor T. Read more
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fn dynamic_cast<T>(self) -> Result<T, Self>
where T: ObjectType,

Tries to cast to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while upcast will do many checks at compile-time already. downcast will perform the same checks at runtime as dynamic_cast, but will also ensure some amount of compile-time safety. Read more
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fn dynamic_cast_ref<T>(&self) -> Option<&T>
where T: ObjectType,

Tries to cast to reference to an object of type T. This handles upcasting, downcasting and casting between interface and interface implementors. All checks are performed at runtime, while downcast and upcast will do many checks at compile-time already. Read more
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unsafe fn unsafe_cast<T>(self) -> T
where T: ObjectType,

Casts to T unconditionally. Read more
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unsafe fn unsafe_cast_ref<T>(&self) -> &T
where T: ObjectType,

Casts to &T unconditionally. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GList> for T

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GPtrArray> for T

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for T

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GList> for T

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GPtrArray> for T

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impl<T> FromGlibContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GList> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GPtrArray> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *const GSList> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GList> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GPtrArray> for T

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impl<T> FromGlibPtrArrayContainerAsVec<<T as GlibPtrDefault>::GlibType, *mut GSList> for T

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoClosureReturnValue for T
where T: Into<Value>,

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impl<U> IsSubclassableExt for U

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impl<T> ObjectExt for T
where T: ObjectType,

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fn is<U>(&self) -> bool
where U: StaticType,

Returns true if the object is an instance of (can be cast to) T.
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fn type_(&self) -> Type

Returns the type of the object.
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fn object_class(&self) -> &Class<Object>

Returns the ObjectClass of the object. Read more
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fn class(&self) -> &Class<T>
where T: IsClass,

Returns the class of the object.
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fn class_of<U>(&self) -> Option<&Class<U>>
where U: IsClass,

Returns the class of the object in the given type T. Read more
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fn interface<U>(&self) -> Option<InterfaceRef<'_, U>>
where U: IsInterface,

Returns the interface T of the object. Read more
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fn set_property(&self, property_name: &str, value: impl Into<Value>)

Sets the property property_name of the object to value value. Read more
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fn set_property_from_value(&self, property_name: &str, value: &Value)

Sets the property property_name of the object to value value. Read more
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fn set_properties(&self, property_values: &[(&str, &dyn ToValue)])

Sets multiple properties of the object at once. Read more
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fn set_properties_from_value(&self, property_values: &[(&str, Value)])

Sets multiple properties of the object at once. Read more
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fn property<V>(&self, property_name: &str) -> V
where V: for<'b> FromValue<'b> + 'static,

Gets the property property_name of the object and cast it to the type V. Read more
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fn property_value(&self, property_name: &str) -> Value

Gets the property property_name of the object. Read more
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fn has_property(&self, property_name: &str, type_: Option<Type>) -> bool

Check if the object has a property property_name of the given type_. Read more
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fn property_type(&self, property_name: &str) -> Option<Type>

Get the type of the property property_name of this object. Read more
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fn find_property(&self, property_name: &str) -> Option<ParamSpec>

Get the ParamSpec of the property property_name of this object.
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fn list_properties(&self) -> PtrSlice<ParamSpec>

Return all ParamSpec of the properties of this object.
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fn freeze_notify(&self) -> PropertyNotificationFreezeGuard

Freeze all property notifications until the return guard object is dropped. Read more
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unsafe fn set_qdata<QD>(&self, key: Quark, value: QD)
where QD: 'static,

Set arbitrary data on this object with the given key. Read more
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unsafe fn qdata<QD>(&self, key: Quark) -> Option<NonNull<QD>>
where QD: 'static,

Return previously set arbitrary data of this object with the given key. Read more
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unsafe fn steal_qdata<QD>(&self, key: Quark) -> Option<QD>
where QD: 'static,

Retrieve previously set arbitrary data of this object with the given key. Read more
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unsafe fn set_data<QD>(&self, key: &str, value: QD)
where QD: 'static,

Set arbitrary data on this object with the given key. Read more
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unsafe fn data<QD>(&self, key: &str) -> Option<NonNull<QD>>
where QD: 'static,

Return previously set arbitrary data of this object with the given key. Read more
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unsafe fn steal_data<QD>(&self, key: &str) -> Option<QD>
where QD: 'static,

Retrieve previously set arbitrary data of this object with the given key. Read more
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fn block_signal(&self, handler_id: &SignalHandlerId)

Block a given signal handler. Read more
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fn unblock_signal(&self, handler_id: &SignalHandlerId)

Unblock a given signal handler.
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fn stop_signal_emission(&self, signal_id: SignalId, detail: Option<Quark>)

Stop emission of the currently emitted signal.
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fn stop_signal_emission_by_name(&self, signal_name: &str)

Stop emission of the currently emitted signal by the (possibly detailed) signal name.
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fn connect<F>( &self, signal_name: &str, after: bool, callback: F, ) -> SignalHandlerId
where F: Fn(&[Value]) -> Option<Value> + Send + Sync + 'static,

Connect to the signal signal_name on this object. Read more
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fn connect_id<F>( &self, signal_id: SignalId, details: Option<Quark>, after: bool, callback: F, ) -> SignalHandlerId
where F: Fn(&[Value]) -> Option<Value> + Send + Sync + 'static,

Connect to the signal signal_id on this object. Read more
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fn connect_local<F>( &self, signal_name: &str, after: bool, callback: F, ) -> SignalHandlerId
where F: Fn(&[Value]) -> Option<Value> + 'static,

Connect to the signal signal_name on this object. Read more
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fn connect_local_id<F>( &self, signal_id: SignalId, details: Option<Quark>, after: bool, callback: F, ) -> SignalHandlerId
where F: Fn(&[Value]) -> Option<Value> + 'static,

Connect to the signal signal_id on this object. Read more
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unsafe fn connect_unsafe<F>( &self, signal_name: &str, after: bool, callback: F, ) -> SignalHandlerId
where F: Fn(&[Value]) -> Option<Value>,

Connect to the signal signal_name on this object. Read more
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unsafe fn connect_unsafe_id<F>( &self, signal_id: SignalId, details: Option<Quark>, after: bool, callback: F, ) -> SignalHandlerId
where F: Fn(&[Value]) -> Option<Value>,

Connect to the signal signal_id on this object. Read more
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fn connect_closure( &self, signal_name: &str, after: bool, closure: RustClosure, ) -> SignalHandlerId

Connect a closure to the signal signal_name on this object. Read more
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fn connect_closure_id( &self, signal_id: SignalId, details: Option<Quark>, after: bool, closure: RustClosure, ) -> SignalHandlerId

Connect a closure to the signal signal_id on this object. Read more
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fn watch_closure(&self, closure: &impl AsRef<Closure>)

Limits the lifetime of closure to the lifetime of the object. When the object’s reference count drops to zero, the closure will be invalidated. An invalidated closure will ignore any calls to invoke_with_values, or invoke when using Rust closures.
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fn emit<R>(&self, signal_id: SignalId, args: &[&dyn ToValue]) -> R

Emit signal by signal id. Read more
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fn emit_with_values(&self, signal_id: SignalId, args: &[Value]) -> Option<Value>

Same as Self::emit but takes Value for the arguments.
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fn emit_by_name<R>(&self, signal_name: &str, args: &[&dyn ToValue]) -> R

Emit signal by its name. Read more
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fn emit_by_name_with_values( &self, signal_name: &str, args: &[Value], ) -> Option<Value>

Emit signal by its name. Read more
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fn emit_by_name_with_details<R>( &self, signal_name: &str, details: Quark, args: &[&dyn ToValue], ) -> R

Emit signal by its name with details. Read more
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fn emit_by_name_with_details_and_values( &self, signal_name: &str, details: Quark, args: &[Value], ) -> Option<Value>

Emit signal by its name with details. Read more
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fn emit_with_details<R>( &self, signal_id: SignalId, details: Quark, args: &[&dyn ToValue], ) -> R

Emit signal by signal id with details. Read more
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fn emit_with_details_and_values( &self, signal_id: SignalId, details: Quark, args: &[Value], ) -> Option<Value>

Emit signal by signal id with details. Read more
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fn disconnect(&self, handler_id: SignalHandlerId)

Disconnect a previously connected signal handler.
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fn connect_notify<F>(&self, name: Option<&str>, f: F) -> SignalHandlerId
where F: Fn(&T, &ParamSpec) + Send + Sync + 'static,

Connect to the notify signal of the object. Read more
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fn connect_notify_local<F>(&self, name: Option<&str>, f: F) -> SignalHandlerId
where F: Fn(&T, &ParamSpec) + 'static,

Connect to the notify signal of the object. Read more
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unsafe fn connect_notify_unsafe<F>( &self, name: Option<&str>, f: F, ) -> SignalHandlerId
where F: Fn(&T, &ParamSpec),

Connect to the notify signal of the object. Read more
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fn notify(&self, property_name: &str)

Notify that the given property has changed its value. Read more
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fn notify_by_pspec(&self, pspec: &ParamSpec)

Notify that the given property has changed its value. Read more
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fn downgrade(&self) -> WeakRef<T>

Downgrade this object to a weak reference.
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fn add_weak_ref_notify<F>(&self, f: F) -> WeakRefNotify<T>
where F: FnOnce() + Send + 'static,

Add a callback to be notified when the Object is disposed.
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fn add_weak_ref_notify_local<F>(&self, f: F) -> WeakRefNotify<T>
where F: FnOnce() + 'static,

Add a callback to be notified when the Object is disposed. Read more
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fn bind_property<'a, 'f, 't, O>( &'a self, source_property: &'a str, target: &'a O, target_property: &'a str, ) -> BindingBuilder<'a, 'f, 't>
where O: ObjectType,

Bind property source_property on this object to the target_property on the target object. Read more
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fn ref_count(&self) -> u32

Returns the strong reference count of this object.
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unsafe fn run_dispose(&self)

Runs the dispose mechanism of the object. Read more
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impl<T> Property for T
where T: HasParamSpec,

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type Value = T

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impl<T> PropertyGet for T
where T: HasParamSpec,

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type Value = T

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fn get<R, F>(&self, f: F) -> R
where F: Fn(&<T as PropertyGet>::Value) -> R,

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impl<T> StaticTypeExt for T
where T: StaticType,

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fn ensure_type()

Ensures that the type has been registered with the type system.
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T> ToSendValue for T
where T: Send + ToValue + ?Sized,

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fn to_send_value(&self) -> SendValue

Returns a SendValue clone of self.
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impl<T> TransparentType for T

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T> TryFromClosureReturnValue for T
where T: for<'a> FromValue<'a> + StaticType + 'static,

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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<'a, T, C, E> FromValueOptional<'a> for T
where T: FromValue<'a, Checker = C>, C: ValueTypeChecker<Error = ValueTypeMismatchOrNoneError<E>>, E: Error + Send + 'static,

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impl<Super, Sub> MayDowncastTo<Sub> for Super
where Super: IsA<Super>, Sub: IsA<Super>,