QAbstractEventDispatcher

The QAbstractEventDispatcher class provides an interface to manage Qt’s event queue. More…

Synopsis

Functions

• def filterNativeEvent (eventType, message, result)

• def installNativeEventFilter (filterObj)

• def registerTimer (interval, timerType, object)

• def removeNativeEventFilter (filterObj)

Virtual functions

• def closingDown ()

• def flush ()

• def hasPendingEvents ()

• def interrupt ()

• def processEvents (flags)

• def registerSocketNotifier (notifier)

• def registerTimer (timerId, interval, timerType, object)

• def registeredTimers (object)

• def remainingTime (timerId)

• def startingUp ()

• def unregisterSocketNotifier (notifier)

• def unregisterTimer (timerId)

• def unregisterTimers (object)

• def wakeUp ()

Signals

• def aboutToBlock ()

• def awake ()

Static functions

• def instance ([thread=None])

Detailed Description

An event dispatcher receives events from the window system and other sources. It then sends them to the QCoreApplication or QApplication instance for processing and delivery. QAbstractEventDispatcher provides fine-grained control over event delivery.

For simple control of event processing use processEvents() .

For finer control of the application’s event loop, call instance() and call functions on the QAbstractEventDispatcher object that is returned. If you want to use your own instance of QAbstractEventDispatcher or of a QAbstractEventDispatcher subclass, you must install it with setEventDispatcher() or setEventDispatcher() before a default event dispatcher has been installed.

The main event loop is started by calling exec() , and stopped by calling exit() . Local event loops can be created using QEventLoop .

Programs that perform long operations can call processEvents() with a bitwise OR combination of various ProcessEventsFlag values to control which events should be delivered.

QAbstractEventDispatcher also allows the integration of an external event loop with the Qt event loop.

See also

QEventLoop QCoreApplication QThread

class PySide2.QtCore.QAbstractEventDispatcher([parent=None])

param parent:

PySide2.QtCore.QObject

Constructs a new event dispatcher with the given parent .

PySide2.QtCore.QAbstractEventDispatcher.aboutToBlock()

PySide2.QtCore.QAbstractEventDispatcher.awake()

PySide2.QtCore.QAbstractEventDispatcher.closingDown()

PySide2.QtCore.QAbstractEventDispatcher.filterNativeEvent(eventType, message, result)

Parameters:

• eventType – PySide2.QtCore.QByteArray

• message – void

• result – long

Return type:

bool

Sends message through the event filters that were set by installNativeEventFilter() . This function returns true as soon as an event filter returns true , and false otherwise to indicate that the processing of the event should continue.

Subclasses of QAbstractEventDispatcher must call this function for all messages received from the system to ensure compatibility with any extensions that may be used in the application. The type of event eventType is specific to the platform plugin chosen at run-time, and can be used to cast message to the right type. The result pointer is only used on Windows, and corresponds to the LRESULT pointer.

Note that the type of message is platform dependent. See QAbstractNativeEventFilter for details.

See also

installNativeEventFilter() nativeEventFilter()

PySide2.QtCore.QAbstractEventDispatcher.flush()

Depending from the event dispatcher implementation does nothing or calls sendPostedEvents() .

PySide2.QtCore.QAbstractEventDispatcher.hasPendingEvents()

Return type:

bool

Returns true if there is an event waiting; otherwise returns false. This function is an implementation detail for hasPendingEvents() and must not be called directly.

PySide2.QtCore.QAbstractEventDispatcher.installNativeEventFilter(filterObj)

Parameters:

filterObj – PySide2.QtCore.QAbstractNativeEventFilter

Installs an event filter filterObj for all native events received by the application.

The event filter filterObj receives events via its nativeEventFilter() function, which is called for all events received by all threads.

The nativeEventFilter() function should return true if the event should be filtered, (in this case, stopped). It should return false to allow normal Qt processing to continue: the native event can then be translated into a QEvent and handled by the standard Qt event filtering, e.g. installEventFilter() .

If multiple event filters are installed, the filter that was installed last is activated first.

Note

The filter function set here receives native messages, that is, MSG or XEvent structs.

For maximum portability, you should always try to use QEvent objects and installEventFilter() whenever possible.

See also

installEventFilter()

static PySide2.QtCore.QAbstractEventDispatcher.instance([thread=None])

Parameters:

thread – PySide2.QtCore.QThread

Return type:

PySide2.QtCore.QAbstractEventDispatcher

Returns a pointer to the event dispatcher object for the specified thread . If thread is None , the current thread is used. If no event dispatcher exists for the specified thread, this function returns None .

Note

If Qt is built without thread support, the thread argument is ignored.

PySide2.QtCore.QAbstractEventDispatcher.interrupt()

Interrupts event dispatching. The event dispatcher will return from processEvents() as soon as possible.

PySide2.QtCore.QAbstractEventDispatcher.processEvents(flags)

Parameters:

flags – ProcessEventsFlags

Return type:

bool

Processes pending events that match flags until there are no more events to process. Returns true if an event was processed; otherwise returns false .

This function is especially useful if you have a long running operation, and want to show its progress without allowing user input by using the ExcludeUserInputEvents flag.

If the WaitForMoreEvents flag is set in flags , the behavior of this function is as follows:

• If events are available, this function returns after processing them.

• If no events are available, this function will wait until more are available and return after processing newly available events.

If the WaitForMoreEvents flag is not set in flags , and no events are available, this function will return immediately.

Note

This function does not process events continuously; it returns after all available events are processed.

See also

hasPendingEvents()

PySide2.QtCore.QAbstractEventDispatcher.registerSocketNotifier(notifier)

Parameters:

notifier – PySide2.QtCore.QSocketNotifier

Registers notifier with the event loop. Subclasses must implement this method to tie a socket notifier into another event loop.

PySide2.QtCore.QAbstractEventDispatcher.registerTimer(interval, timerType, object)

Parameters:

• interval – int

• timerType – TimerType

• object – PySide2.QtCore.QObject

Return type:

int

Registers a timer with the specified interval and timerType for the given object and returns the timer id.

PySide2.QtCore.QAbstractEventDispatcher.registerTimer(timerId, interval, timerType, object)

Parameters:

• timerId – int

• interval – int

• timerType – TimerType

• object – PySide2.QtCore.QObject

Register a timer with the specified timerId , interval , and timerType for the given object .

PySide2.QtCore.QAbstractEventDispatcher.registeredTimers(object)

Parameters:

object – PySide2.QtCore.QObject

Return type:

Returns a list of registered timers for object . The TimerInfo struct has timerId , interval , and timerType members.

See also

TimerType

PySide2.QtCore.QAbstractEventDispatcher.remainingTime(timerId)

Parameters:

timerId – int

Return type:

int

Returns the remaining time in milliseconds with the given timerId . If the timer is inactive, the returned value will be -1. If the timer is overdue, the returned value will be 0.

See also

TimerType

PySide2.QtCore.QAbstractEventDispatcher.removeNativeEventFilter(filterObj)

Parameters:

filterObj – PySide2.QtCore.QAbstractNativeEventFilter

Removes the event filter filter from this object. The request is ignored if such an event filter has not been installed.

All event filters for this object are automatically removed when this object is destroyed.

It is always safe to remove an event filter, even during event filter filter activation (that is, even from within the nativeEventFilter() function).

See also

installNativeEventFilter() QAbstractNativeEventFilter

PySide2.QtCore.QAbstractEventDispatcher.startingUp()

PySide2.QtCore.QAbstractEventDispatcher.unregisterSocketNotifier(notifier)

Parameters:

notifier – PySide2.QtCore.QSocketNotifier

Unregisters notifier from the event dispatcher. Subclasses must reimplement this method to tie a socket notifier into another event loop. Reimplementations must call the base implementation.

PySide2.QtCore.QAbstractEventDispatcher.unregisterTimer(timerId)

Parameters:

timerId – int

Return type:

bool

Unregisters the timer with the given timerId . Returns true if successful; otherwise returns false .

See also

registerTimer() unregisterTimers()

PySide2.QtCore.QAbstractEventDispatcher.unregisterTimers(object)

Parameters:

object – PySide2.QtCore.QObject

Return type:

bool

Unregisters all the timers associated with the given object . Returns true if all timers were successful removed; otherwise returns false .

See also

unregisterTimer() registeredTimers()

PySide2.QtCore.QAbstractEventDispatcher.wakeUp()

Wakes up the event loop.

See also

awake()