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Document that QProperty::subscribe might get executed deferred 

With the introduction of grouped property changes, notification
calls in bindable properties might be immediate or deferred,
depending on the context. This patch documents that one must not
rely on immediate execution of functions given to subscribe()
and onValueChanged().

Change-Id: I26ec4dbbff17a44ab62037ba1da9ce34c77da972
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
bb10
Andreas Buhr 2021-02-15 15:21:18 +01:00
parent 425ff34aa1
commit f9e543b8a3
1 changed files with 13 additions and 6 deletions
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19
src/corelib/kernel/qproperty.cpp
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@ -944,6 +944,7 @@ QString QPropertyBindingError::description() const
Installs \a f as a change handler. Whenever the underlying property changes, \a f will be called, as
long as the returned \c QPropertyChangeHandler and the property are kept alive.
On each value change, the handler is either called immediately, or deferred, depending on the context.
\sa onValueChanged(), subscribe()
*/
@ -1267,7 +1268,8 @@ QString QPropertyBindingError::description() const
\fn template <typename T> template <typename Functor> QPropertyChangeHandler<T, Functor> QProperty<T>::onValueChanged(Functor f)
Registers the given functor \a f as a callback that shall be called whenever
the value of the property changes.
the value of the property changes. On each value change, the handler
is either called immediately, or deferred, depending on the context.
The callback \a f is expected to be a type that has a plain call operator () without any
parameters. This means that you can provide a C++ lambda expression, an std::function
@ -1281,7 +1283,8 @@ QString QPropertyBindingError::description() const
\fn template <typename T> template <typename Functor> QPropertyChangeHandler<T, Functor> QProperty<T>::subscribe(Functor f)
Subscribes the given functor \a f as a callback that is called immediately and whenever
the value of the property changes in the future.
the value of the property changes in the future. On each value change, the handler
is either called immediately, or deferred, depending on the context.
The callback \a f is expected to be a type that has a plain call operator () without any
parameters. This means that you can provide a C++ lambda expression, an std::function
@ -1682,7 +1685,8 @@ QString QPropertyBindingError::description() const
\fn template <typename Class, typename T, auto offset, auto Callback> template <typename Functor> QPropertyChangeHandler<T, Functor> QObjectBindableProperty<Class, T, offset, Callback>::onValueChanged(Functor f)
Registers the given functor \a f as a callback that shall be called whenever
the value of the property changes.
the value of the property changes. On each value change, the handler
is either called immediately, or deferred, depending on the context.
The callback \a f is expected to be a type that has a plain call operator () without any
parameters. This means that you can provide a C++ lambda expression, an std::function
@ -1696,7 +1700,8 @@ QString QPropertyBindingError::description() const
\fn template <typename Class, typename T, auto offset, auto Callback> template <typename Functor> QPropertyChangeHandler<T, Functor> QObjectBindableProperty<Class, T, offset, Callback>::subscribe(Functor f)
Subscribes the given functor \a f as a callback that is called immediately and whenever
the value of the property changes in the future.
the value of the property changes in the future. On each value change, the handler
is either called immediately, or deferred, depending on the context.
The callback \a f is expected to be a type that has a plain call operator () without any
parameters. This means that you can provide a C++ lambda expression, an std::function
@ -1897,7 +1902,8 @@ QString QPropertyBindingError::description() const
\fn template <typename T> template <typename Functor> QPropertyChangeHandler<T, Functor> QPropertyAlias<T>::onValueChanged(Functor f)
Registers the given functor \a f as a callback that shall be called whenever
the value of the aliased property changes.
the value of the aliased property changes. On each value change, the handler
is either called immediately, or deferred, depending on the context.
The callback \a f is expected to be a type that has a plain call operator () without any
parameters. This means that you can provide a C++ lambda expression, an std::function
@ -1911,7 +1917,8 @@ QString QPropertyBindingError::description() const
\fn template <typename T> template <typename Functor> QPropertyChangeHandler<T, Functor> QPropertyAlias<T>::subscribe(Functor f)
Subscribes the given functor \a f as a callback that is called immediately and whenever
the value of the aliased property changes in the future.
the value of the aliased property changes in the future. On each value change, the handler
is either called immediately, or deferred, depending on the context.
The callback \a f is expected to be a type that has a plain call operator () without any
parameters. This means that you can provide a C++ lambda expression, an std::function