#include <qxcbeventqueue.h>

Inheritance diagram for QXcbEventQueue:

Collaboration diagram for QXcbEventQueue:

Public Types
enum	{ PoolSize = 100 }

enum	PeekOption { PeekDefault = 0 , PeekFromCachedIndex = 1 , PeekRetainMatch = 2 , PeekConsumeMatch = 3 , PeekConsumeMatchAndContinue = 4 }

using	PeekerCallback = bool ()(xcb_generic_event_t event, void *peekerData)

Public Types inherited from QThread
enum	Priority { IdlePriority , LowestPriority , LowPriority , NormalPriority , HighPriority , HighestPriority , TimeCriticalPriority , InheritPriority }

enum class	QualityOfService { Auto , High , Eco }

Public Member Functions
	QXcbEventQueue (QXcbConnection *connection)

	~QXcbEventQueue ()

void	run () override

bool	isEmpty () const

xcb_generic_event_t *	takeFirst (QEventLoop::ProcessEventsFlags flags)

xcb_generic_event_t *	takeFirst ()

void	flushBufferedEvents ()

void	wakeUpDispatcher ()

template<typename Peeker>
xcb_generic_event_t *	peek (Peeker &&peeker)

template<typename Peeker>
xcb_generic_event_t *	peek (PeekOption config, Peeker &&peeker)

qint32	generatePeekerId ()

bool	removePeekerId (qint32 peekerId)

bool	peekEventQueue (PeekerCallback peeker, void *peekerData=nullptr, PeekOptions option=PeekDefault, qint32 peekerId=-1)

const QXcbEventNode *	flushedTail () const

void	waitForNewEvents (const QXcbEventNode *sinceFlushedTail, unsigned long time=(std::numeric_limits< unsigned long >::max)())

Public Member Functions inherited from QThread
	QThread (QObject *parent=nullptr)

	~QThread ()

void	setPriority (Priority priority)

Priority	priority () const

bool	isFinished () const

bool	isRunning () const

void	requestInterruption ()

bool	isInterruptionRequested () const

void	setStackSize (uint stackSize)

uint	stackSize () const

QAbstractEventDispatcher *	eventDispatcher () const

void	setEventDispatcher (QAbstractEventDispatcher *eventDispatcher)

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

int	loopLevel () const

bool	isCurrentThread () const noexcept

void	setServiceLevel (QualityOfService serviceLevel)

QualityOfService	serviceLevel () const

bool	wait (QDeadlineTimer deadline=QDeadlineTimer(QDeadlineTimer::Forever))

bool	wait (unsigned long time)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. time is the time to wait in milliseconds.

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	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`.

Additional Inherited Members
Public Slots inherited from QThread
void	start (Priority=InheritPriority)

void	terminate ()

void	exit (int retcode=0)

void	quit ()

Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

Signals inherited from QThread
void	started (QPrivateSignal)

void	finished (QPrivateSignal)

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 QThread
static Qt::HANDLE	currentThreadId () noexcept Q_DECL_PURE_FUNCTION

static QThread *	currentThread ()

static bool	isMainThread () noexcept

static int	idealThreadCount () noexcept

static void	yieldCurrentThread ()

template<typename Function, typename... Args>
static QThread *	create (Function &&f, Args &&... args)

static void	sleep (unsigned long)

static void	msleep (unsigned long)

static void	usleep (unsigned long)

static void	sleep (std::chrono::nanoseconds nsec)

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 Member Functions inherited from QThread
int	exec ()

	QThread (QThreadPrivate &dd, QObject *parent=nullptr)

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)

Static Protected Member Functions inherited from QThread
static void	setTerminationEnabled (bool enabled=true)

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

Lock-free event passing:

The lock-free solution uses a singly-linked list to pass events from the reader thread to the main thread. An atomic operation is used to sync the tail node of the list between threads. The reader thread takes special care when accessing the tail node. It does not dequeue the last node and does not access (read or write) the tail node's 'next' member. This lets the reader add more items at the same time as the main thread is dequeuing nodes from the head. A custom linked list implementation is used, because std::list does not have any thread-safety guarantees. The custom list is lightweight - no reference counting, back links, etc.

Memory management:

In a normally functioning application, XCB plugin won't buffer more than few batches of events, couple events per batch. Instead of constantly calling new / delete, we can create a pool of nodes that we reuse. The main thread uses an atomic operation to sync how many nodes have been restored (available for reuse). If at some point a user application will block the main thread for a long time, we might run out of nodes in the pool. Then we create nodes on a heap. These will be automatically "garbage collected" out of the linked list, once the main thread stops blocking.

Definition at line 32 of file qxcbeventqueue.h.

Member Typedef Documentation

◆ PeekerCallback

using QXcbEventQueue::PeekerCallback = bool (*)(xcb_generic_event_t *event, void *peekerData)

Definition at line 84 of file qxcbeventqueue.h.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

Enumerator
PoolSize

Definition at line 39 of file qxcbeventqueue.h.

◆ PeekOption

enum QXcbEventQueue::PeekOption

Enumerator
PeekDefault
PeekFromCachedIndex
PeekRetainMatch
PeekConsumeMatch
PeekConsumeMatchAndContinue

Definition at line 41 of file qxcbeventqueue.h.

Constructor & Destructor Documentation

◆ QXcbEventQueue()

QXcbEventQueue::QXcbEventQueue ( QXcbConnection * connection )

Definition at line 45 of file qxcbeventqueue.cpp.

References dispatcherOwnerDestructing.

◆ ~QXcbEventQueue()

QXcbEventQueue::~QXcbEventQueue ( )

Definition at line 65 of file qxcbeventqueue.cpp.

References flushBufferedEvents().

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Member Function Documentation

◆ flushBufferedEvents()

void QXcbEventQueue::flushBufferedEvents ( )

Definition at line 145 of file qxcbeventqueue.cpp.

Referenced by ~QXcbEventQueue(), peek(), peekEventQueue(), and waitForNewEvents().

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◆ flushedTail()

const QXcbEventNode * QXcbEventQueue::flushedTail ( ) const

inline

Definition at line 88 of file qxcbeventqueue.h.

◆ generatePeekerId()

qint32 QXcbEventQueue::generatePeekerId ( )

Definition at line 224 of file qxcbeventqueue.cpp.

◆ isEmpty()

bool QXcbEventQueue::isEmpty ( ) const

inline

Definition at line 65 of file qxcbeventqueue.h.

Referenced by peek(), peekEventQueue(), and takeFirst().

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◆ peek() [1/2]

template<typename Peeker>

xcb_generic_event_t * QXcbEventQueue::peek ( Peeker && peeker )

inline

Definition at line 75 of file qxcbeventqueue.h.

References PeekConsumeMatch.

◆ peek() [2/2]

template<typename Peeker>

xcb_generic_event_t * QXcbEventQueue::peek	(	PeekOption	config,
		Peeker &&	peeker )

inline

Definition at line 125 of file qxcbeventqueue.h.

References flushBufferedEvents(), isEmpty(), PeekConsumeMatch, and PeekConsumeMatchAndContinue.

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◆ peekEventQueue()

bool QXcbEventQueue::peekEventQueue	(	PeekerCallback	peeker,
		void *	peekerData = nullptr,
		PeekOptions	option = PeekDefault,
		qint32	peekerId = -1 )

Definition at line 246 of file qxcbeventqueue.cpp.

References flushBufferedEvents(), isEmpty(), and PeekFromCachedIndex.

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◆ removePeekerId()

bool QXcbEventQueue::removePeekerId ( qint32 peekerId )

Definition at line 231 of file qxcbeventqueue.cpp.

◆ run()

void QXcbEventQueue::run ( void )

overridevirtual

Reimplemented from QThread.

Definition at line 176 of file qxcbeventqueue.cpp.

References wakeUpDispatcher().

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◆ takeFirst() [1/2]

xcb_generic_event_t * QXcbEventQueue::takeFirst ( )

Definition at line 111 of file qxcbeventqueue.cpp.

References isEmpty().

Referenced by takeFirst().

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◆ takeFirst() [2/2]

xcb_generic_event_t * QXcbEventQueue::takeFirst ( QEventLoop::ProcessEventsFlags flags )

Definition at line 82 of file qxcbeventqueue.cpp.

References takeFirst().

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◆ waitForNewEvents()

void QXcbEventQueue::waitForNewEvents	(	const QXcbEventNode *	sinceFlushedTail,
		unsigned long	time = (std::numeric_limits<unsigned long>::max)() )

Definition at line 319 of file qxcbeventqueue.cpp.

References flushBufferedEvents().

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◆ wakeUpDispatcher()

void QXcbEventQueue::wakeUpDispatcher ( )

Definition at line 213 of file qxcbeventqueue.cpp.

Referenced by run().

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The documentation for this class was generated from the following files:

qtbase/src/plugins/platforms/xcb/qxcbeventqueue.h (91f9ba2993a2652bcb349ce639aff67b5bfc8938)
qtbase/src/plugins/platforms/xcb/qxcbeventqueue.cpp (3d72e8829fb9ebcd3b1179b54ad4053de05368ff)

Public Types

Public Member Functions

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ PeekerCallback

Member Enumeration Documentation

◆ anonymous enum

◆ PeekOption

Constructor & Destructor Documentation

◆ QXcbEventQueue()

◆ ~QXcbEventQueue()

Member Function Documentation

◆ flushBufferedEvents()

◆ flushedTail()

◆ generatePeekerId()

◆ isEmpty()

◆ peek() [1/2]

◆ peek() [2/2]

◆ peekEventQueue()

◆ removePeekerId()

◆ run()

◆ takeFirst() [1/2]

◆ takeFirst() [2/2]

◆ waitForNewEvents()

◆ wakeUpDispatcher()