The QQuickAttachedPropertyPropagator class provides a way to propagate attached properties. More...

#include <qquickattachedpropertypropagator.h>

Inheritance diagram for QQuickAttachedPropertyPropagator:

Collaboration diagram for QQuickAttachedPropertyPropagator:

Public Member Functions
	QQuickAttachedPropertyPropagator (QObject *parent=nullptr)
	Constructs a QQuickAttachedPropertyPropagator with the given parent.

	~QQuickAttachedPropertyPropagator ()
	Destroys the QQuickAttachedPropertyPropagator.

QList< QQuickAttachedPropertyPropagator * >	attachedChildren () const
	This function returns the attached children of this attached object.

QQuickAttachedPropertyPropagator *	attachedParent () const
	This function returns the attached parent of this attached object.

Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)
	Constructs an object with parent object parent.

virtual	~QObject ()
	Destroys the object, deleting all its child objects.

virtual bool	event (QEvent *event)
	This virtual function receives events to an object and should return true if the event e was recognized and processed.

virtual bool	eventFilter (QObject watched, QEvent event)
	Filters events if this object has been installed as an event filter for the watched object.

QString	objectName () const

Q_WEAK_OVERLOAD void	setObjectName (const QString &name)
	Sets the object's name to name.

void	setObjectName (QAnyStringView name)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QBindable< QString >	bindableObjectName ()

bool	isWidgetType () const
	Returns `true` if the object is a widget; otherwise returns `false`.

bool	isWindowType () const
	Returns `true` if the object is a window; otherwise returns `false`.

bool	isQuickItemType () const
	Returns `true` if the object is a QQuickItem; otherwise returns `false`.

bool	signalsBlocked () const noexcept
	Returns `true` if signals are blocked; otherwise returns `false`.

bool	blockSignals (bool b) noexcept
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it).

QThread *	thread () const
	Returns the thread in which the object lives.

bool	moveToThread (QThread *thread QT6_DECL_NEW_OVERLOAD_TAIL)
	Changes the thread affinity for this object and its children and returns `true` on success.

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
	This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.

int	startTimer (std::chrono::nanoseconds time, Qt::TimerType timerType=Qt::CoarseTimer)

void	killTimer (int id)
	Kills the timer with timer identifier, id.

void	killTimer (Qt::TimerId id)

template<typename T >
T	findChild (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.

template<typename T >
QList< T >	findChildren (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects.

template<typename T >
T	findChild (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

template<typename T >
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

const QObjectList &	children () const
	Returns a list of child objects.

void	setParent (QObject *parent)
	Makes the object a child of parent.

void	installEventFilter (QObject *filterObj)
	Installs an event filter filterObj on this object.

void	removeEventFilter (QObject *obj)
	Removes an event filter object obj from this object.

QMetaObject::Connection	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const

bool	disconnect (const char signal=nullptr, const QObject receiver=nullptr, const char *member=nullptr) const

bool	disconnect (const QObject receiver, const char member=nullptr) const

void	dumpObjectTree () const
	Dumps a tree of children to the debug output.

void	dumpObjectInfo () const
	Dumps information about signal connections, etc.

bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value.

bool	setProperty (const char *name, QVariant &&value)

QVariant	property (const char *name) const
	Returns the value of the object's name property.

QList< QByteArray >	dynamicPropertyNames () const

QBindingStorage *	bindingStorage ()

const QBindingStorage *	bindingStorage () const

QObject *	parent () const
	Returns a pointer to the parent object.

bool	inherits (const char *classname) const
	Returns `true` if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns `false`.

Protected Member Functions
void	initialize ()
	Finds and sets the attached parent for this attached object, and then does the same for its children.

virtual void	attachedParentChange (QQuickAttachedPropertyPropagator newParent, QQuickAttachedPropertyPropagator oldParent)
	This function is called whenever the attached parent of this QQuickAttachedPropertyPropagator changes from oldParent to newParent.

Protected Member Functions inherited from QObject
QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns \nullptr.

int	senderSignalIndex () const

int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal.

bool	isSignalConnected (const QMetaMethod &signal) const

virtual void	timerEvent (QTimerEvent *event)
	This event handler can be reimplemented in a subclass to receive timer events for the object.

virtual void	childEvent (QChildEvent *event)
	This event handler can be reimplemented in a subclass to receive child events.

virtual void	customEvent (QEvent *event)
	This event handler can be reimplemented in a subclass to receive custom events.

virtual void	connectNotify (const QMetaMethod &signal)

virtual void	disconnectNotify (const QMetaMethod &signal)

	QObject (QObjectPrivate &dd, QObject *parent=nullptr)

Friends
Q_QUICKCONTROLS2_EXPORT QDebug	operator<< (QDebug debug, const QQuickAttachedPropertyPropagator *propagator)

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

Signals inherited from QObject
void	destroyed (QObject *=nullptr)
	This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.

void	objectNameChanged (const QString &objectName, QPrivateSignal)
	This signal is emitted after the object's name has been changed.

Static Public Member Functions inherited from QObject
static QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	\threadsafe

static QMetaObject::Connection	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)

template<typename Func1 , typename Func2 >
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)

static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	\threadsafe

static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)

static bool	disconnect (const QMetaObject::Connection &)
	Disconnect a connection.

template<typename Func1 , typename Func2 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object receiver, Func2 slot)

template<typename Func1 >
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject receiver, void **zero)

Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Properties inherited from QObject
QString	objectName
	the name of this object

Related Symbols inherited from QObject
template< class T > T	qobject_cast (const QObject *object)
	Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.

template< typename T > T	qFindChildqFindChildren (const QObject *obj, const QString &name)()

template< typename T > QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()

	QObjectList
	\macro Q_CLASSINFO(Name, Value)

Detailed Description

The QQuickAttachedPropertyPropagator class provides a way to propagate attached properties.

\inmodule QtQuickControls2

Since: 6.5

In QML, it is possible to \l {Attached Properties and Attached Signal Handlers}{attach properties and signal handlers} to objects. \l {Providing Attached Properties} goes into more detail about how to expose your own C++ attached types.

QQuickAttachedPropertyPropagator provides an API to propagate attached properties from a parent object to its children, similar to \l {Control::}{font} and \l {Item::}{palette} propagation. It supports propagation through \l {Item}{items}, \l {Popup}{popups}, and \l {Window}{windows}.

If propagation of properties is not important, consider using a \l {QML_SINGLETON}{C++} or \l {Contents of a Module Definition qmldir File}{QML} singleton instead, as it is better suited for that use case, and is more efficient in that it only requires one QObject.

To use QQuickAttachedPropertyPropagator: \list

Derive from it
Call \l initialize() in the constructor
Define set/inherit/propagate/reset functions for each property as needed
Reimplement \l attachedParentChange() to handle property inheritance
Implement a static qmlAttachedProperties function and declare the type as an attached QML type with \l QML_ELEMENT and \l QML_ATTACHED, as detailed in \l {Providing Attached Properties} \endlist

For an example that demonstrates this in depth, see \l {Qt Quick Controls - Attached Style Properties Example}.

See also: {Styling Qt Quick Controls}

Definition at line 14 of file qquickattachedpropertypropagator.h.

Constructor & Destructor Documentation

◆ QQuickAttachedPropertyPropagator()

QQuickAttachedPropertyPropagator::QQuickAttachedPropertyPropagator ( QObject * parent = nullptr )

explicit

Constructs a QQuickAttachedPropertyPropagator with the given parent.

The parent will be used to find this object's \l {attachedParent()}{attached parent}.

Derived classes should call \l initialize() in their constructor.

Definition at line 378 of file qquickattachedpropertypropagator.cpp.

References d, and QObject::parent().

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◆ ~QQuickAttachedPropertyPropagator()

QQuickAttachedPropertyPropagator::~QQuickAttachedPropertyPropagator ( )

Destroys the QQuickAttachedPropertyPropagator.

Definition at line 388 of file qquickattachedpropertypropagator.cpp.

References d, and QObject::parent().

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Member Function Documentation

◆ attachedChildren()

QList< QQuickAttachedPropertyPropagator * > QQuickAttachedPropertyPropagator::attachedChildren ( ) const

This function returns the attached children of this attached object.

The attached children are used when propagating property values:

\quotefromfile ../../examples/quickcontrols/attachedstyleproperties/MyStyle/mystyle.cpp \skipto MyStyle::propagateTheme \printuntil } \printuntil }

Definition at line 405 of file qquickattachedpropertypropagator.cpp.

References d.

Referenced by initialize(), QQuickMaterialStyle::propagateAccent(), QQuickUniversalStyle::propagateAccent(), QQuickMaterialStyle::propagateBackground(), QQuickUniversalStyle::propagateBackground(), QQuickMaterialStyle::propagateForeground(), QQuickUniversalStyle::propagateForeground(), QQuickImagineStyle::propagatePath(), QQuickMaterialStyle::propagatePrimary(), QQuickMaterialStyle::propagateTheme(), and QQuickUniversalStyle::propagateTheme().

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◆ attachedParent()

QQuickAttachedPropertyPropagator * QQuickAttachedPropertyPropagator::attachedParent ( ) const

This function returns the attached parent of this attached object.

The attached parent is used when inheriting property values:

\quotefromfile ../../examples/quickcontrols/attachedstyleproperties/MyStyle/mystyle.cpp \skipto MyStyle::resetTheme \printuntil }

Definition at line 420 of file qquickattachedpropertypropagator.cpp.

References d.

Referenced by initialize(), QQuickMaterialStyle::resetAccent(), QQuickUniversalStyle::resetAccent(), QQuickMaterialStyle::resetBackground(), QQuickUniversalStyle::resetBackground(), QQuickMaterialStyle::resetForeground(), QQuickUniversalStyle::resetForeground(), QQuickImagineStyle::resetPath(), QQuickMaterialStyle::resetPrimary(), QQuickMaterialStyle::resetTheme(), and QQuickUniversalStyle::resetTheme().

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◆ attachedParentChange()

void QQuickAttachedPropertyPropagator::attachedParentChange	(	QQuickAttachedPropertyPropagator *	newParent,
		QQuickAttachedPropertyPropagator *	oldParent )

protectedvirtual

This function is called whenever the attached parent of this QQuickAttachedPropertyPropagator changes from oldParent to newParent.

Subclasses should reimplement this function to inherit attached properties from newParent.

\quotefromfile ../../examples/quickcontrols/attachedstyleproperties/MyStyle/mystyle.cpp \skipto attachedParentChange \printuntil } \printuntil }

Reimplemented in QQuickImagineStyle, QQuickMaterialStyle, and QQuickUniversalStyle.

Definition at line 472 of file qquickattachedpropertypropagator.cpp.

References Q_UNUSED.

◆ initialize()

void QQuickAttachedPropertyPropagator::initialize ( )

protected

Finds and sets the attached parent for this attached object, and then does the same for its children.

This must be called upon construction of the attached object in order for propagation to work.

It can be useful to read global/default values before calling this function. For example, before calling initialize(), the \l {Imagine Style}{Imagine} style checks a static "globalsInitialized" flag to see if it should read default values from \l QSettings. The values from that file form the basis for any attached property values that have not been explicitly set.

\quotefromfile ../../examples/quickcontrols/attachedstyleproperties/MyStyle/mystyle.cpp \skipto MyStyle::MyStyle \printuntil }

Definition at line 442 of file qquickattachedpropertypropagator.cpp.

References attachedChildren(), attachedParent(), child, d, findAttachedChildren(), findAttachedParent(), QQuickAttachedPropertyPropagatorPrivate::get(), metaObject(), QObject::parent(), qCDebug, and QList< T >::size().