\inmodule QtCore More...

#include <qcoreapplication.h>

Inheritance diagram for QCoreApplication:

Collaboration diagram for QCoreApplication:

Public Types
enum	{ ApplicationFlags = QT_VERSION }

Public Slots
static void	quit ()
	\threadsafe

static void	exit (int retcode=0)
	Tells the application to exit with a return code.

Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe

Signals
void	aboutToQuit (QPrivateSignal)
	This signal is emitted when the application is about to quit the main event loop, e.g.

void	organizationNameChanged ()

void	organizationDomainChanged ()

void	applicationNameChanged ()

void	applicationVersionChanged ()

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.

Public Member Functions
	QCoreApplication (int &argc, char **argv, int=ApplicationFlags)
	Constructs a Qt core application.

	~QCoreApplication ()
	Destroys the QCoreApplication object.

virtual bool	notify (QObject , QEvent )
	Sends event to receiver: {receiver}->event(event).

void	installNativeEventFilter (QAbstractNativeEventFilter *filterObj)
	Installs an event filter filterObj for all native events received by the application in the main thread.

void	removeNativeEventFilter (QAbstractNativeEventFilter *filterObj)
	Removes an event filterObject from this 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	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`.

Static Public Member Functions
static QStringList	arguments ()

static void	setAttribute (Qt::ApplicationAttribute attribute, bool on=true)
	Sets the attribute attribute if on is true; otherwise clears the attribute.

static bool	testAttribute (Qt::ApplicationAttribute attribute)
	Returns `true` if attribute attribute is set; otherwise returns `false`.

static void	setOrganizationDomain (const QString &orgDomain)

static QString	organizationDomain ()

static void	setOrganizationName (const QString &orgName)
	[11]

static QString	organizationName ()

static void	setApplicationName (const QString &application)

static QString	applicationName ()

static void	setApplicationVersion (const QString &version)

static QString	applicationVersion ()

static void	setSetuidAllowed (bool allow)

static bool	isSetuidAllowed ()

static QCoreApplication *	instance () noexcept
	Returns a pointer to the application's QCoreApplication (or QGuiApplication/QApplication) instance.

static bool	instanceExists () noexcept

static int	exec ()
	Enters the main event loop and waits until exit() is called.

static void	processEvents (QEventLoop::ProcessEventsFlags flags=QEventLoop::AllEvents)
	Processes some pending events for the calling thread according to the specified flags.

static void	processEvents (QEventLoop::ProcessEventsFlags flags, int maxtime)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Processes pending events for the calling thread for ms milliseconds or until there are no more events to process, whichever is shorter.

static void	processEvents (QEventLoop::ProcessEventsFlags flags, QDeadlineTimer deadline)

static bool	sendEvent (QObject receiver, QEvent event)
	Sends event event directly to receiver receiver, using the notify() function.

static void	postEvent (QObject receiver, QEvent event, int priority=Qt::NormalEventPriority)

static void	sendPostedEvents (QObject *receiver=nullptr, int event_type=0)
	Immediately dispatches all events which have been previously queued with QCoreApplication::postEvent() and which are for the object receiver and have the event type event_type.

static void	removePostedEvents (QObject *receiver, int eventType=0)

static QAbstractEventDispatcher *	eventDispatcher ()
	Returns a pointer to the event dispatcher object for the main thread.

static void	setEventDispatcher (QAbstractEventDispatcher *eventDispatcher)
	Sets the event dispatcher for the main thread to eventDispatcher.

static bool	startingUp ()
	Returns `true` if an application object has not been created yet; otherwise returns `false`.

static bool	closingDown ()
	Returns `true` if the application objects are being destroyed; otherwise returns `false`.

static QString	applicationDirPath ()
	Returns the directory that contains the application executable.

static QString	applicationFilePath ()
	Returns the file path of the application executable.

static qint64	applicationPid () Q_DECL_CONST_FUNCTION

static bool	installTranslator (QTranslator *messageFile)
	Adds the translation file translationFile to the list of translation files to be used for translations.

static bool	removeTranslator (QTranslator *messageFile)
	Removes the translation file translationFile from the list of translation files used by this application.

static QString	translate (const char context, const char key, const char *disambiguation=nullptr, int n=-1)
	\threadsafe

static bool	isQuitLockEnabled ()

static void	setQuitLockEnabled (bool enabled)

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
bool	event (QEvent *) override
	\reimp

	QCoreApplication (QCoreApplicationPrivate &p)

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)

Properties
QString	applicationName
	the name of this application

QString	applicationVersion
	the version of this application

QString	organizationName
	the name of the organization that wrote this application

QString	organizationDomain
	the Internet domain of the organization that wrote this application

bool	quitLockEnabled
	Whether the use of the QEventLoopLocker feature can cause the application to quit.

Properties inherited from QObject
QString	objectName
	the name of this object

Friends
class	QEventLoopLocker

class	QApplication

class	QApplicationPrivate

class	QGuiApplication

class	QGuiApplicationPrivate

class	QWidget

class	QWidgetWindow

class	QWidgetPrivate

class	QWindowPrivate

class	QEventDispatcherUNIXPrivate

class	QCocoaEventDispatcherPrivate

class	QCommandLineParserPrivate

bool	qt_sendSpontaneousEvent (QObject receiver, QEvent event)

Q_CORE_EXPORT QString	qAppName ()

Related Symbols
(Note that these are not member symbols.)
void	qAddPostRoutine (QtCleanUpFunction ptr)
	\macro Q_COREAPP_STARTUP_FUNCTION(QtStartUpFunction ptr)

void	qRemovePostRoutine (QtCleanUpFunction ptr)
	\threadsafe

void *	resolveInterface (const char *name, int revision) const
	\macro Q_DECLARE_TR_FUNCTIONS(context)

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)

Additional Inherited Members
Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr

Detailed Description

\inmodule QtCore

The QCoreApplication class provides an event loop for Qt applications without UI.

This class is used by non-GUI applications to provide their event loop. For non-GUI application that uses Qt, there should be exactly one QCoreApplication object. For GUI applications, see QGuiApplication. For applications that use the Qt Widgets module, see QApplication.

QCoreApplication contains the main event loop, where all events from the operating system (e.g., timer and network events) and other sources are processed and dispatched. It also handles the application's initialization and finalization, as well as system-wide and application-wide settings.

Definition at line 40 of file qcoreapplication.h.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

Enumerator
ApplicationFlags

Definition at line 65 of file qcoreapplication.h.

Constructor & Destructor Documentation

◆ QCoreApplication() [1/2]

QCoreApplication::QCoreApplication	(	int &	argc,
		char **	argv,
		int	= ApplicationFlags )

Constructs a Qt core application.

Core applications are applications without a graphical user interface. Such applications are used at the console or as server processes.

The argc and argv arguments are processed by the application, and made available in a more convenient form by the arguments() function.

Warning: The data referred to by argc and argv must stay valid for the entire lifetime of the QCoreApplication object. In addition, argc must be greater than zero and argv must contain at least one valid character string.

Definition at line 752 of file qcoreapplication.cpp.

◆ ~QCoreApplication()

QCoreApplication::~QCoreApplication ( )

Destroys the QCoreApplication object.

Definition at line 896 of file qcoreapplication.cpp.

◆ QCoreApplication() [2/2]

QCoreApplication::QCoreApplication ( QCoreApplicationPrivate & p )

protected

Definition at line 726 of file qcoreapplication.cpp.

Member Function Documentation

◆ aboutToQuit

void QCoreApplication::aboutToQuit ( QPrivateSignal )

signal

This signal is emitted when the application is about to quit the main event loop, e.g.

when the event loop level drops to zero. This may happen either after a call to quit() from inside the application or when the user shuts down the entire desktop session.

The signal is particularly useful if your application has to do some last-second cleanup. Note that no user interaction is possible in this state.

Note: At this point the main event loop is still running, but will not process further events on return except QEvent::DeferredDelete events for objects deleted via deleteLater(). If event processing is needed, use a nested event loop or call QCoreApplication::processEvents() manually.

See also: quit()

◆ applicationDirPath()

QString QCoreApplication::applicationDirPath ( )

static

Returns the directory that contains the application executable.

For example, if you have installed Qt in the {C:\Qt} directory, and you run the {regexp} example, this function will return "C:/Qt/examples/tools/regexp".

On \macos and iOS this will point to the directory actually containing the executable, which may be inside an application bundle (if the application is bundled).

On Android this will point to the directory actually containing the executable, which may be inside the application APK (if it was built with uncompressed libraries support).

Warning: On Linux, this function will try to get the path from the {/proc} file system. If that fails, it assumes that {argv[0]} contains the absolute file name of the executable. The function also assumes that the current directory has not been changed by the application.

See also: applicationFilePath()

Definition at line 2379 of file qcoreapplication.cpp.

◆ applicationFilePath()

QString QCoreApplication::applicationFilePath ( )

static

Returns the file path of the application executable.

For example, if you have installed Qt in the {/usr/local/qt} directory, and you run the {regexp} example, this function will return "/usr/local/qt/examples/tools/regexp/regexp".

Warning: On Linux, this function will try to get the path from the {/proc} file system. If that fails, it assumes that {argv[0]} contains the absolute file name of the executable. The function also assumes that the current directory has not been changed by the application.

See also: applicationDirPath()

Definition at line 2430 of file qcoreapplication.cpp.

◆ applicationName()

static QString QCoreApplication::applicationName ( )

static

◆ applicationNameChanged

void QCoreApplication::applicationNameChanged ( )

signal

Primarily for QML, see organizationNameChanged.

◆ applicationPid()

qint64 QCoreApplication::applicationPid ( )

static

Since: 4.4

Returns the current process ID for the application.

Definition at line 2494 of file qcoreapplication.cpp.

◆ applicationVersion()

static QString QCoreApplication::applicationVersion ( )

static

◆ applicationVersionChanged

void QCoreApplication::applicationVersionChanged ( )

signal

Primarily for QML, see organizationNameChanged.

◆ arguments()

QStringList QCoreApplication::arguments ( )

static

Since: 4.1

Returns the list of command-line arguments.

Usually arguments().at(0) is the program name, arguments().at(1) is the first argument, and arguments().last() is the last argument. See the note below about Windows.

Calling this function is slow - you should store the result in a variable when parsing the command line.

Warning: On Unix, this list is built from the argc and argv parameters passed to the constructor in the main() function. The string-data in argv is interpreted using QString::fromLocal8Bit(); hence it is not possible to pass, for example, Japanese command line arguments on a system that runs in a Latin1 locale. Most modern Unix systems do not have this limitation, as they are Unicode-based.

On Windows, the list is built from the argc and argv parameters only if modified argv/argc parameters are passed to the constructor. In that case, encoding problems might occur.

Otherwise, the arguments() are constructed from the return value of \l{https://docs.microsoft.com/en-us/windows/win32/api/processenv/nf-processenv-getcommandlinea}{GetCommandLine()}. As a result of this, the string given by arguments().at(0) might not be the program name on Windows, depending on how the application was started.

See also: applicationFilePath(), QCommandLineParser

Definition at line 2557 of file qcoreapplication.cpp.

◆ closingDown()

bool QCoreApplication::closingDown ( )

static

Returns true if the application objects are being destroyed; otherwise returns false.

See also: startingUp()

Definition at line 1306 of file qcoreapplication.cpp.

◆ event()

bool QCoreApplication::event ( QEvent * e )

overrideprotectedvirtual

\reimp

Reimplemented from QObject.

Reimplemented in QDesigner, and QGuiApplication.

Definition at line 2016 of file qcoreapplication.cpp.

◆ eventDispatcher()

QAbstractEventDispatcher * QCoreApplication::eventDispatcher ( )

static

Returns a pointer to the event dispatcher object for the main thread.

If no event dispatcher exists for the thread, this function returns \nullptr.

Definition at line 3225 of file qcoreapplication.cpp.

◆ exec()

int QCoreApplication::exec ( )

static

Enters the main event loop and waits until exit() is called.

Returns the value that was passed to exit() (which is 0 if exit() is called via quit()).

It is necessary to call this function to start event handling. The main event loop receives events from the window system and dispatches these to the application widgets.

To make your application perform idle processing (by executing a special function whenever there are no pending events), use a QChronoTimer with 0ns timeout. More advanced idle processing schemes can be achieved using processEvents().

We recommend that you connect clean-up code to the \l{QCoreApplication::}{aboutToQuit()} signal, instead of putting it in your application's {main()} function because on some platforms the exec() call may not return. For example, on Windows when the user logs off, the system terminates the process after Qt closes all top-level windows. Hence, there is no guarantee that the application will have time to exit its event loop and execute code at the end of the {main()} function after the exec() call.

See also: quit(), exit(), processEvents(), QApplication::exec()

Definition at line 1435 of file qcoreapplication.cpp.

◆ exit

void QCoreApplication::exit ( int returnCode = 0 )

staticslot

Tells the application to exit with a return code.

After this function has been called, the application leaves the main event loop and returns from the call to exec(). The exec() function returns returnCode. If the event loop is not running, this function does nothing.

By convention, a returnCode of 0 means success, and any non-zero value indicates an error.

It's good practice to always connect signals to this slot using a \l{Qt::}{QueuedConnection}. If a signal connected (non-queued) to this slot is emitted before control enters the main event loop (such as before "int main" calls \l{QCoreApplication::}{exec()}), the slot has no effect and the application never exits. Using a queued connection ensures that the slot will not be invoked until after control enters the main event loop.

Note that unlike the C library function of the same name, this function does return to the caller – it is event processing that stops.

Note also that this function is not thread-safe. It should be called only from the main thread (the thread that the QCoreApplication object is processing events on). To ask the application to exit from another thread, either use QCoreApplication::quit() or instead call this function from the main thread with QMetaMethod::invokeMethod().

See also: quit(), exec()

Definition at line 1507 of file qcoreapplication.cpp.

◆ installNativeEventFilter()

void QCoreApplication::installNativeEventFilter ( QAbstractNativeEventFilter * filterObj )

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

The event filter filterObj receives events via its \l {QAbstractNativeEventFilter::}{nativeEventFilter()} function, which is called for all native events received in the main thread.

The QAbstractNativeEventFilter::nativeEventFilter() function should return true if the event should be filtered, i.e. 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 \l{QEvent} {event} filtering, e.g. QObject::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, i.e. MSG or XCB event structs.; Native event filters will be disabled in the application when the Qt::AA_PluginApplication attribute is set.

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

See also: QObject::installEventFilter()

Since: 5.0

Definition at line 3187 of file qcoreapplication.cpp.

◆ installTranslator()

bool QCoreApplication::installTranslator ( QTranslator * translationFile )

static

Adds the translation file translationFile to the list of translation files to be used for translations.

Multiple translation files can be installed. Translations are searched for in the reverse order in which they were installed, so the most recently installed translation file is searched first and the first translation file installed is searched last. The search stops as soon as a translation containing a matching string is found.

Installing or removing a QTranslator, or changing an installed QTranslator generates a \l{QEvent::LanguageChange}{LanguageChange} event for the QCoreApplication instance. A QApplication instance will propagate the event to all toplevel widgets, where a reimplementation of changeEvent can re-translate the user interface by passing user-visible strings via the tr() function to the respective property setters. User-interface classes generated by \QD provide a retranslateUi() function that can be called.

The function returns true on success and false on failure.

Note: QCoreApplication does not take ownership of translationFile.

See also: removeTranslator(), translate(), QTranslator::load(), {Writing Source Code for Translation#Prepare for Dynamic Language Changes}{Prepare for Dynamic Language Changes}

Definition at line 2177 of file qcoreapplication.cpp.

◆ instance()

static QCoreApplication * QCoreApplication::instance ( )

inlinestaticnoexcept

Returns a pointer to the application's QCoreApplication (or QGuiApplication/QApplication) instance.

If no instance has been allocated, \nullptr is returned.

Definition at line 94 of file qcoreapplication.h.

◆ instanceExists()

static bool QCoreApplication::instanceExists ( )

inlinestaticnoexcept

Definition at line 95 of file qcoreapplication.h.

◆ isQuitLockEnabled()

bool QCoreApplication::isQuitLockEnabled ( )

static

Definition at line 1064 of file qcoreapplication.cpp.

◆ isSetuidAllowed()

bool QCoreApplication::isSetuidAllowed ( )

static

Since: 5.3

Returns true if the application is allowed to run setuid on UNIX platforms.

See also: QCoreApplication::setSetuidAllowed()

Definition at line 982 of file qcoreapplication.cpp.

◆ notify()

bool QCoreApplication::notify	(	QObject *	receiver,
		QEvent *	event )

virtual

Sends event to receiver: {receiver}->event(event).

Returns the value that is returned from the receiver's event handler. Note that this function is called for all events sent to any object in any thread.

For certain types of events (e.g. mouse and key events), the event will be propagated to the receiver's parent and so on up to the top-level object if the receiver is not interested in the event (i.e., it returns false).

There are five different ways that events can be processed; reimplementing this virtual function is just one of them. All five approaches are listed below: \list 1

Reimplementing \l {QWidget::}{paintEvent()}, \l {QWidget::}{mousePressEvent()} and so on. This is the most common, easiest, and least powerful way.

Reimplementing this function. This is very powerful, providing complete control; but only one subclass can be active at a time.

Installing an event filter on QCoreApplication::instance(). Such an event filter is able to process all events for all widgets, so it's just as powerful as reimplementing notify(); furthermore, it's possible to have more than one application-global event filter. Global event filters even see mouse events for \l{QWidget::isEnabled()}{disabled widgets}. Note that application event filters are only called for objects that live in the main thread.

Reimplementing QObject::event() (as QWidget does). If you do this you get Tab key presses, and you get to see the events before any widget-specific event filters.

Installing an event filter on the object. Such an event filter gets all the events, including Tab and Shift+Tab key press events, as long as they do not change the focus widget. \endlist

{Future direction:} This function will not be called for objects that live outside the main thread in Qt 7. Applications that need that functionality should find other solutions for their event inspection needs in the meantime. The change may be extended to the main thread, causing this function to be deprecated.

Warning: If you override this function, you must ensure all threads that process events stop doing so before your application object begins destruction. This includes threads started by other libraries that you may be using, but does not apply to Qt's own threads.

See also: QObject::event(), installNativeEventFilter()

Reimplemented in QApplication, and QGuiApplication.

Definition at line 1182 of file qcoreapplication.cpp.

◆ organizationDomain()

static QString QCoreApplication::organizationDomain ( )

static

◆ organizationDomainChanged

void QCoreApplication::organizationDomainChanged ( )

signal

Primarily for QML, see organizationNameChanged.

◆ organizationName()

static QString QCoreApplication::organizationName ( )

static

◆ organizationNameChanged

void QCoreApplication::organizationNameChanged ( )

signal

While not useful from C++ due to how organizationName is normally set once on startup, this is still needed for QML so that bindings are reevaluated after that initial change.

◆ postEvent()

void QCoreApplication::postEvent	(	QObject *	receiver,
		QEvent *	event,
		int	priority = Qt::NormalEventPriority )

static

Since: 4.3

Adds the event event, with the object receiver as the receiver of the event, to an event queue and returns immediately.

The event must be allocated on the heap since the post event queue will take ownership of the event and delete it once it has been posted. It is {not safe} to access the event after it has been posted.

When control returns to the main event loop, all events that are stored in the queue will be sent using the notify() function.

Events are sorted in descending priority order, i.e. events with a high priority are queued before events with a lower priority. The priority can be any integer value, i.e. between INT_MAX and INT_MIN, inclusive; see Qt::EventPriority for more details. Events with equal priority will be processed in the order posted.

\threadsafe

See also: sendEvent(), notify(), sendPostedEvents(), Qt::EventPriority

Definition at line 1627 of file qcoreapplication.cpp.

◆ processEvents() [1/3]

void QCoreApplication::processEvents	(	QEventLoop::ProcessEventsFlags	flags,
		int	ms )

static

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Processes pending events for the calling thread for ms milliseconds or until there are no more events to process, whichever is shorter.

This is equivalent to calling:

QCoreApplication::processEvents(flags, QDeadlineTimer(ms));

QCoreApplication::processEvents

static void processEvents(QEventLoop::ProcessEventsFlags flags=QEventLoop::AllEvents)

Processes some pending events for the calling thread according to the specified flags.

Definition qcoreapplication.cpp:1341

QDeadlineTimer

\inmodule QtCore

Definition qdeadlinetimer.h:23

flags

GLbitfield flags

Definition qopengles2ext.h:1026

Definition at line 1361 of file qcoreapplication.cpp.

◆ processEvents() [2/3]

void QCoreApplication::processEvents	(	QEventLoop::ProcessEventsFlags	flags,
		QDeadlineTimer	deadline )

static

Since: 6.7 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Processes pending events for the calling thread untile deadline has expired, or until there are no more events to process, whichever happens first.

Use of this function is discouraged. Instead, prefer to move long operations out of the GUI thread into an auxiliary one and to completely avoid nested event loop processing. If event processing is really necessary, consider using \l QEventLoop instead.

Calling this function processes events only for the calling thread.

Note: Unlike the \l{QCoreApplication::processEvents(QEventLoop::ProcessEventsFlags flags)}{processEvents()} overload, this function also processes events that are posted while the function runs.; All events that were queued before the timeout will be processed, however long it takes.

\threadsafe

See also: exec(), QTimer, QChronoTimer, QEventLoop::processEvents()

Definition at line 1390 of file qcoreapplication.cpp.

◆ processEvents() [3/3]

void QCoreApplication::processEvents ( QEventLoop::ProcessEventsFlags flags = QEventLoop::AllEvents )

static

Processes some pending events for the calling thread according to the specified flags.

Use of this function is discouraged. Instead, prefer to move long operations out of the GUI thread into an auxiliary one and to completely avoid nested event loop processing. If event processing is really necessary, consider using \l QEventLoop instead.

In the event that you are running a local loop which calls this function continuously, without an event loop, the \l{QEvent::DeferredDelete}{DeferredDelete} events will not be processed. This can affect the behaviour of widgets, e.g. QToolTip, that rely on \l{QEvent::DeferredDelete}{DeferredDelete} events to function properly. An alternative would be to call \l{QCoreApplication::sendPostedEvents()}{sendPostedEvents()} from within that local loop.

Calling this function processes events only for the calling thread, and returns after all available events have been processed. Available events are events queued before the function call. This means that events that are posted while the function runs will be queued until a later round of event processing.

\threadsafe

See also: exec(), QTimer, QChronoTimer, QEventLoop::processEvents(), sendPostedEvents()

Definition at line 1341 of file qcoreapplication.cpp.

◆ quit

void QCoreApplication::quit ( )

staticslot

\threadsafe

Asks the application to quit.

The request may be ignored if the application prevents the quit, for example if one of its windows can't be closed. The application can affect this by handling the QEvent::Quit event on the application level, or QEvent::Close events for the individual windows.

If the quit is not interrupted the application will exit with return code 0 (success).

To exit the application without a chance of being interrupted, call exit() directly. Note that method is not thread-safe.

It's good practice to always connect signals to this slot using a \l{Qt::}{QueuedConnection}. If a signal connected (non-queued) to this slot is emitted before control enters the main event loop (such as before "int main" calls \l{QCoreApplication::}{exec()}), the slot has no effect and the application never exits. Using a queued connection ensures that the slot will not be invoked until after control enters the main event loop.

Example:

QPushButton *quitButton = new QPushButton("Quit");

connect(quitButton, &QPushButton::clicked, &app, &QCoreApplication::quit, Qt::QueuedConnection);

{Thread-safety note}: this function may be called from any thread to thread-safely cause the currently-running main application loop to exit. However, thread-safety is not guaranteed if the QCoreApplication object is being destroyed at the same time.

See also: exit(), aboutToQuit()

Definition at line 2102 of file qcoreapplication.cpp.

◆ removeNativeEventFilter()

void QCoreApplication::removeNativeEventFilter ( QAbstractNativeEventFilter * filterObject )

Removes an event filterObject 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 activation (i.e. from the nativeEventFilter() function).

See also: installNativeEventFilter()

Since: 5.0

Definition at line 3213 of file qcoreapplication.cpp.

◆ removePostedEvents()

void QCoreApplication::removePostedEvents	(	QObject *	receiver,
		int	eventType = 0 )

static

Since: 4.3

Removes all events of the given eventType that were posted using postEvent() for receiver.

The events are not dispatched, instead they are removed from the queue. You should never need to call this function. If you do call it, be aware that killing events may cause receiver to break one or more invariants.

If receiver is \nullptr, the events of eventType are removed for all objects. If eventType is 0, all the events are removed for receiver. You should never call this function with eventType of 0.

\threadsafe

Definition at line 1920 of file qcoreapplication.cpp.

◆ removeTranslator()

bool QCoreApplication::removeTranslator ( QTranslator * translationFile )

static

Removes the translation file translationFile from the list of translation files used by this application.

(It does not delete the translation file from the file system.)

The function returns true on success and false on failure.

See also: installTranslator(), translate(), QObject::tr()

Definition at line 2213 of file qcoreapplication.cpp.

◆ sendEvent()

bool QCoreApplication::sendEvent	(	QObject *	receiver,
		QEvent *	event )

static

Sends event event directly to receiver receiver, using the notify() function.

Returns the value that was returned from the event handler.

The event is not deleted when the event has been sent. The normal approach is to create the event on the stack, for example:

QMouseEvent event(QEvent::MouseButtonPress, pos, 0, 0, 0);

QApplication::sendEvent(mainWindow, &event);

See also: postEvent(), notify()

Definition at line 1543 of file qcoreapplication.cpp.

◆ sendPostedEvents()

void QCoreApplication::sendPostedEvents	(	QObject *	receiver = nullptr,
		int	event_type = 0 )

static

Immediately dispatches all events which have been previously queued with QCoreApplication::postEvent() and which are for the object receiver and have the event type event_type.

Events from the window system are not dispatched by this function, but by processEvents().

If receiver is \nullptr, the events of event_type are sent for all objects. If event_type is 0, all the events are sent for receiver.

Note: This method must be called from the thread in which its QObject parameter, receiver, lives.

See also: postEvent()

Definition at line 1738 of file qcoreapplication.cpp.

◆ setApplicationName()

void QCoreApplication::setApplicationName ( const QString & application )

static

Definition at line 2702 of file qcoreapplication.cpp.

◆ setApplicationVersion()

void QCoreApplication::setApplicationVersion ( const QString & version )

static

Definition at line 2755 of file qcoreapplication.cpp.

◆ setAttribute()

QCoreApplication::setAttribute	(	Qt::ApplicationAttribute	attribute,
		bool	on = true )

static

Sets the attribute attribute if on is true; otherwise clears the attribute.

[95]

Note: Some application attributes must be set before creating a QCoreApplication instance. Refer to the Qt::ApplicationAttribute documentation for more information.

See also: testAttribute()

[96]

Definition at line 997 of file qcoreapplication.cpp.

◆ setEventDispatcher()

void QCoreApplication::setEventDispatcher ( QAbstractEventDispatcher * eventDispatcher )

static

Sets the event dispatcher for the main thread to eventDispatcher.

This is only possible as long as there is no event dispatcher installed yet. That is, before QCoreApplication has been instantiated. This method takes ownership of the object.

Definition at line 3238 of file qcoreapplication.cpp.

◆ setOrganizationDomain()

void QCoreApplication::setOrganizationDomain ( const QString & orgDomain )

static

Definition at line 2664 of file qcoreapplication.cpp.

◆ setOrganizationName()

void QCoreApplication::setOrganizationName ( const QString & orgName )

static

[11]

[12]

Definition at line 2627 of file qcoreapplication.cpp.

◆ setQuitLockEnabled()

void QCoreApplication::setQuitLockEnabled ( bool enabled )

static

Definition at line 1071 of file qcoreapplication.cpp.

◆ setSetuidAllowed()

void QCoreApplication::setSetuidAllowed ( bool allow )

static

Since: 5.3

Allows the application to run setuid on UNIX platforms if allow is true.

If allow is false (the default) and Qt detects the application is running with an effective user id different than the real user id, the application will be aborted when a QCoreApplication instance is created.

Qt is not an appropriate solution for setuid programs due to its large attack surface. However some applications may be required to run in this manner for historical reasons. This flag will prevent Qt from aborting the application when this is detected, and must be set before a QCoreApplication instance is created.

Note: It is strongly recommended not to enable this option since it introduces security risks. If this application does enable the flag and starts child processes, it should drop the privileges as early as possible by calling {setuid(2)} for itself, or at the latest by using the QProcess::UnixProcessParameters::ResetIds flag.

Definition at line 969 of file qcoreapplication.cpp.

◆ startingUp()

bool QCoreApplication::startingUp ( )

static

Returns true if an application object has not been created yet; otherwise returns false.

See also: closingDown()

Definition at line 1294 of file qcoreapplication.cpp.

◆ testAttribute()

bool QCoreApplication::testAttribute ( Qt::ApplicationAttribute attribute )

static

Returns true if attribute attribute is set; otherwise returns false.

See also: setAttribute()

Definition at line 1038 of file qcoreapplication.cpp.

◆ translate()

QString QCoreApplication::translate	(	const char *	context,
		const char *	sourceText,
		const char *	disambiguation = nullptr,
		int	n = -1 )

static

\threadsafe

Returns the translation text for sourceText, by querying the installed translation files. The translation files are searched from the most recently installed file back to the first installed file.

QObject::tr() provides this functionality more conveniently.

context is typically a class name (e.g., "MyDialog") and sourceText is either English text or a short identifying text.

disambiguation is an identifying string, for when the same sourceText is used in different roles within the same context. By default, it is \nullptr.

See the \l QTranslator and \l QObject::tr() documentation for more information about contexts, disambiguations and comments.

n is used in conjunction with n to support plural forms. See QObject::tr() for details.

If none of the translation files contain a translation for sourceText in context, this function returns a QString equivalent of sourceText.

This function is not virtual. You can use alternative translation techniques by subclassing \l QTranslator.

See also: QObject::tr(), installTranslator(), removeTranslator(), {Internationalization and Translations}

Definition at line 2295 of file qcoreapplication.cpp.

Friends And Related Symbol Documentation

◆ qAddPostRoutine()

void qAddPostRoutine ( QtCleanUpFunction ptr )

\macro Q_COREAPP_STARTUP_FUNCTION(QtStartUpFunction ptr)

Since: 5.1

\reentrant

Adds a global function that will be called from the QCoreApplication constructor. This macro is normally used to initialize libraries for program-wide functionality, without requiring the application to call into the library for initialization.

The function specified by ptr should take no arguments and should return nothing. For example:

// Called once QCoreApplication exists
static void preRoutineMyDebugTool()
{
    MyDebugTool* tool = new MyDebugTool(QCoreApplication::instance());
    QCoreApplication::instance()->installEventFilter(tool);
}
 
Q_COREAPP_STARTUP_FUNCTION(preRoutineMyDebugTool)

Note that the startup function will run at the end of the QCoreApplication constructor, before any GUI initialization. If GUI code is required in the function, use a timer (or a queued invocation) to perform the initialization later on, from the event loop.

If QCoreApplication is deleted and another QCoreApplication is created, the startup function will be invoked again.

Note: This macro is not suitable for use in library code that is then statically linked into an application since the function may not be called at all due to being eliminated by the linker.

\threadsafe

Adds a global routine that will be called from the QCoreApplication destructor. This function is normally used to add cleanup routines for program-wide functionality.

The cleanup routines are called in the reverse order of their addition.

The function specified by ptr should take no arguments and should return nothing. For example:

static int *global_ptr = nullptr;
 
static void cleanup_ptr()
{
    delete [] global_ptr;
    global_ptr = nullptr;
}
 
void init_ptr()
{
    global_ptr = new int[100];      // allocate data
    qAddPostRoutine(cleanup_ptr);   // delete later
}

Note that for an application- or module-wide cleanup, qAddPostRoutine() is often not suitable. For example, if the program is split into dynamically loaded modules, the relevant module may be unloaded long before the QCoreApplication destructor is called. In such cases, if using qAddPostRoutine() is still desirable, qRemovePostRoutine() can be used to prevent a routine from being called by the QCoreApplication destructor. For example, if that routine was called before the module was unloaded.

For modules and libraries, using a reference-counted initialization manager or Qt's parent-child deletion mechanism may be better. Here is an example of a private class that uses the parent-child mechanism to call a cleanup function at the right time:

class MyPrivateInitStuff : public QObject
{
public:
    static MyPrivateInitStuff *initStuff(QObject *parent)
    {
        if (!p)
            p = new MyPrivateInitStuff(parent);
        return p;
    }
 
    ~MyPrivateInitStuff()
    {
        // cleanup goes here
    }
 
private:
    MyPrivateInitStuff(QObject *parent)
        : QObject(parent)
    {
        // initialization goes here
    }
 
    MyPrivateInitStuff *p;
};

By selecting the right parent object, this can often be made to clean up the module's data at the right moment.

Note: This function has been thread-safe since Qt 5.10.

See also: qRemovePostRoutine()

◆ QApplication

friend class QApplication

friend

Definition at line 243 of file qcoreapplication.h.

◆ QApplicationPrivate

friend class QApplicationPrivate

friend

Definition at line 244 of file qcoreapplication.h.

◆ qAppName

Q_CORE_EXPORT QString qAppName ( )

friend

Definition at line 550 of file qcoreapplication.cpp.

◆ QCocoaEventDispatcherPrivate

friend class QCocoaEventDispatcherPrivate

friend

Definition at line 253 of file qcoreapplication.h.

◆ QCommandLineParserPrivate

friend class QCommandLineParserPrivate

friend

Definition at line 257 of file qcoreapplication.h.

◆ QEventDispatcherUNIXPrivate

friend class QEventDispatcherUNIXPrivate

friend

Definition at line 252 of file qcoreapplication.h.

◆ QEventLoopLocker

friend class QEventLoopLocker

friend

Definition at line 59 of file qcoreapplication.h.

◆ QGuiApplication

friend class QGuiApplication

friend

Definition at line 245 of file qcoreapplication.h.

◆ QGuiApplicationPrivate

friend class QGuiApplicationPrivate

friend

Definition at line 246 of file qcoreapplication.h.

◆ qRemovePostRoutine()

void qRemovePostRoutine ( QtCleanUpFunction ptr )

\threadsafe

Since: 5.3

Removes the cleanup routine specified by ptr from the list of routines called by the QCoreApplication destructor. The routine must have been previously added to the list by a call to qAddPostRoutine(), otherwise this function has no effect.

Note: This function has been thread-safe since Qt 5.10.

See also: qAddPostRoutine()

◆ qt_sendSpontaneousEvent

bool qt_sendSpontaneousEvent	(	QObject *	receiver,
		QEvent *	event )

friend

◆ QWidget

friend class QWidget

friend

Definition at line 247 of file qcoreapplication.h.

◆ QWidgetPrivate

friend class QWidgetPrivate

friend

Definition at line 249 of file qcoreapplication.h.

◆ QWidgetWindow

friend class QWidgetWindow

friend

Definition at line 248 of file qcoreapplication.h.

◆ QWindowPrivate

friend class QWindowPrivate

friend

Definition at line 250 of file qcoreapplication.h.

◆ resolveInterface()

void * resolveInterface	(	const char *	name,
		int	revision ) const

\macro Q_DECLARE_TR_FUNCTIONS(context)

The Q_DECLARE_TR_FUNCTIONS() macro declares and implements the translation function tr() with this signature:

static inline QString tr(const char *sourceText,

const char *comment = nullptr);

This macro is useful if you want to use QObject::tr() in classes that don't inherit from QObject.

Q_DECLARE_TR_FUNCTIONS() must appear at the very top of the class definition (before the first {public:} or {protected:}). For example:

class MyMfcView : public CView
{
    Q_DECLARE_TR_FUNCTIONS(MyMfcView)
 
public:
    MyMfcView();
    ...
};

The context parameter is normally the class name, but it can be any text.

See also: Q_OBJECT, QObject::tr()

Definition at line 3357 of file qcoreapplication.cpp.

Property Documentation

◆ applicationName

QString QCoreApplication::applicationName

readwrite

the name of this application

The application name is used in various Qt classes and modules, most prominently in \l{QSettings} when it is constructed using the default constructor. Other uses are in formatted logging output (see \l{qSetMessagePattern()}), in output by \l{QCommandLineParser}, in \l{QTemporaryDir} and \l{QTemporaryFile} default paths, and in some file locations of \l{QStandardPaths}. \l{Qt D-Bus}, \l{Accessibility}, and the XCB platform integration make use of the application name, too.

If not set, the application name defaults to the executable name.

See also: organizationName, organizationDomain, applicationVersion, applicationFilePath()

Definition at line 47 of file qcoreapplication.h.

◆ applicationVersion

QString QCoreApplication::applicationVersion

readwrite

the version of this application

Since: 4.4

If not set, the application version defaults to a platform-specific value determined from the main application executable or package (since Qt 5.9):

\table \header

Platform
Source \row
Windows (classic desktop)
PRODUCTVERSION parameter of the VERSIONINFO resource \row
macOS, iOS, tvOS, watchOS
CFBundleVersion property of the information property list \row
Android
android:versionName property of the AndroidManifest.xml manifest element \endtable

On other platforms, the default is the empty string.

See also: applicationName, organizationName, organizationDomain

Definition at line 49 of file qcoreapplication.h.

◆ organizationDomain

QString QCoreApplication::organizationDomain

readwrite

the Internet domain of the organization that wrote this application

The value is used by the QSettings class when it is constructed using the default constructor. This saves having to repeat this information each time a QSettings object is created.

On Mac, QSettings uses organizationDomain() as the organization if it's not an empty string; otherwise it uses organizationName(). On all other platforms, QSettings uses organizationName() as the organization.

See also: organizationName, applicationName, applicationVersion

Definition at line 53 of file qcoreapplication.h.

◆ organizationName

QString QCoreApplication::organizationName

readwrite

the name of the organization that wrote this application

The value is used by the QSettings class when it is constructed using the default constructor. This saves having to repeat this information each time a QSettings object is created.

On Mac, QSettings uses \l {QCoreApplication::}{organizationDomain()} as the organization if it's not an empty string; otherwise it uses organizationName(). On all other platforms, QSettings uses organizationName() as the organization.

See also: organizationDomain, applicationName

Definition at line 51 of file qcoreapplication.h.

◆ quitLockEnabled

bool QCoreApplication::quitLockEnabled

readwrite

Whether the use of the QEventLoopLocker feature can cause the application to quit.

When this property is true the release of the last remaining QEventLoopLocker operating on the application will attempt to quit the application.

Note that attempting a quit may not necessarily result in the application quitting, for example if there still are open windows, or the QEvent::Quit event is ignored.

The default is true.

See also: QEventLoopLocker

Definition at line 55 of file qcoreapplication.h.

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

qtbase/src/corelib/kernel/qcoreapplication.h (cb382450aaf773865267d0d74243e9026babea64)
qtbase/src/corelib/doc/snippets/code/src_corelib_io_qsettings.cpp (7d542e1daf09caadf6d3e36c4b09bdf94952c5a1)
qtbase/src/corelib/kernel/qcoreapplication.cpp (cb382450aaf773865267d0d74243e9026babea64)
qtbase/src/widgets/doc/snippets/code/doc_src_stylesheet.cpp (d6bdc5e9b6bcc9324c506c194bc168cdb6ec1da7)

Public Types

Public Slots

Signals

Public Member Functions

Static Public Member Functions

Protected Member Functions

Properties

Friends

Related Symbols

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ anonymous enum

Constructor & Destructor Documentation

◆ QCoreApplication() [1/2]

◆ ~QCoreApplication()

◆ QCoreApplication() [2/2]

Member Function Documentation

◆ aboutToQuit

◆ applicationDirPath()

◆ applicationFilePath()

◆ applicationName()

◆ applicationNameChanged

◆ applicationPid()

◆ applicationVersion()

◆ applicationVersionChanged

◆ arguments()

◆ closingDown()

◆ event()

◆ eventDispatcher()

◆ exec()

◆ exit

◆ installNativeEventFilter()

◆ installTranslator()

◆ instance()

◆ instanceExists()

◆ isQuitLockEnabled()

◆ isSetuidAllowed()

◆ notify()

◆ organizationDomain()

◆ organizationDomainChanged

◆ organizationName()

◆ organizationNameChanged

◆ postEvent()

◆ processEvents() [1/3]

◆ processEvents() [2/3]

◆ processEvents() [3/3]

◆ quit

◆ removeNativeEventFilter()

◆ removePostedEvents()

◆ removeTranslator()

◆ sendEvent()

◆ sendPostedEvents()

◆ setApplicationName()

◆ setApplicationVersion()

◆ setAttribute()

◆ setEventDispatcher()

◆ setOrganizationDomain()

◆ setOrganizationName()

◆ setQuitLockEnabled()

◆ setSetuidAllowed()

◆ startingUp()

◆ testAttribute()

◆ translate()

Friends And Related Symbol Documentation

◆ qAddPostRoutine()

◆ QApplication

◆ QApplicationPrivate

◆ qAppName

◆ QCocoaEventDispatcherPrivate

◆ QCommandLineParserPrivate

◆ QEventDispatcherUNIXPrivate

◆ QEventLoopLocker

◆ QGuiApplication

◆ QGuiApplicationPrivate

◆ qRemovePostRoutine()

◆ qt_sendSpontaneousEvent

◆ QWidget

◆ QWidgetPrivate

◆ QWidgetWindow