QtBase  v6.3.1
Public Slots | Signals | Public Member Functions | Static Public Member Functions | Protected Member Functions | Properties | Friends | Related Functions | List of all members
QApplication Class Reference

The QApplication class manages the GUI application's control flow and main settings. More...

#include <qapplication.h>

Inheritance diagram for QApplication:
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Public Slots

void setStyleSheet (const QString &sheet)
 
void setAutoSipEnabled (const bool enabled)
 
bool autoSipEnabled () const
 
static void closeAllWindows ()
 
static void aboutQt ()
 
- Public Slots inherited from QCoreApplication
static void quit ()
 
static void exit (int retcode=0)
 
- Public Slots inherited from QObject
void deleteLater ()
 

Signals

void focusChanged (QWidget *old, QWidget *now)
 
- Signals inherited from QGuiApplication
void fontDatabaseChanged ()
 
void screenAdded (QScreen *screen)
 
void screenRemoved (QScreen *screen)
 
void primaryScreenChanged (QScreen *screen)
 
void lastWindowClosed ()
 
void focusObjectChanged (QObject *focusObject)
 
void focusWindowChanged (QWindow *focusWindow)
 
void applicationStateChanged (Qt::ApplicationState state)
 
void layoutDirectionChanged (Qt::LayoutDirection direction)
 
void commitDataRequest (QSessionManager &sessionManager)
 
void saveStateRequest (QSessionManager &sessionManager)
 
void applicationDisplayNameChanged ()
 
- Signals inherited from QCoreApplication
void aboutToQuit (QPrivateSignal)
 
void organizationNameChanged ()
 
void organizationDomainChanged ()
 
void applicationNameChanged ()
 
void applicationVersionChanged ()
 
- Signals inherited from QObject
void destroyed (QObject *=nullptr)
 
void objectNameChanged (const QString &objectName, QPrivateSignal)
 

Public Member Functions

 QApplication (int &argc, char **argv, int=ApplicationFlags)
 
virtual ~QApplication ()
 
bool notify (QObject *, QEvent *) override
 
QString styleSheet () const
 
- Public Member Functions inherited from QGuiApplication
 QGuiApplication (int &argc, char **argv, int=ApplicationFlags)
 
 ~QGuiApplication ()
 
qreal devicePixelRatio () const
 
bool isSessionRestored () const
 
QString sessionId () const
 
QString sessionKey () const
 
bool isSavingSession () const
 
- Public Member Functions inherited from QCoreApplication
 QCoreApplication (int &argc, char **argv, int=ApplicationFlags)
 
 ~QCoreApplication ()
 
void installNativeEventFilter (QAbstractNativeEventFilter *filterObj)
 
void removeNativeEventFilter (QAbstractNativeEventFilter *filterObj)
 
- Public Member Functions inherited from QObject
Q_INVOKABLE QObject (QObject *parent=nullptr)
 
virtual ~QObject ()
 
virtual bool eventFilter (QObject *watched, QEvent *event)
 
QString objectName () const
 
void setObjectName (const QString &name)
 
QBindable< QString > bindableObjectName ()
 
bool isWidgetType () const
 
bool isWindowType () const
 
bool signalsBlocked () const noexcept
 
bool blockSignals (bool b) noexcept
 
QThread * thread () const
 
void moveToThread (QThread *thread)
 
int startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
 
void killTimer (int id)
 
template<typename T >
T findChild (const QString &aName=QString(), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
template<typename T >
QList< T > findChildren (const QString &aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
template<typename T >
QList< T > findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
const QObjectList & children () const
 
void setParent (QObject *parent)
 
void installEventFilter (QObject *filterObj)
 
void removeEventFilter (QObject *obj)
 
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
 
void dumpObjectInfo () const
 
bool setProperty (const char *name, const QVariant &value)
 
QVariant property (const char *name) const
 
QList< QByteArray > dynamicPropertyNames () const
 
QBindingStorage * bindingStorage ()
 
const QBindingStorage * bindingStorage () const
 
QObject * parent () const
 
bool inherits (const char *classname) const
 

Static Public Member Functions

static QStyle * style ()
 
static void setStyle (QStyle *)
 
static QStyle * setStyle (const QString &)
 
static QPalette palette (const QWidget *)
 
static QPalette palette (const char *className)
 
static void setPalette (const QPalette &, const char *className=nullptr)
 
static QFont font ()
 
static QFont font (const QWidget *)
 
static QFont font (const char *className)
 
static void setFont (const QFont &, const char *className=nullptr)
 
static QWidgetList allWidgets ()
 
static QWidgetList topLevelWidgets ()
 
static QWidget * activePopupWidget ()
 
static QWidget * activeModalWidget ()
 
static QWidget * focusWidget ()
 
static QWidget * activeWindow ()
 
static void setActiveWindow (QWidget *act)
 
static QWidget * widgetAt (const QPoint &p)
 
static QWidget * widgetAt (int x, int y)
 
static QWidget * topLevelAt (const QPoint &p)
 
static QWidget * topLevelAt (int x, int y)
 
static void beep ()
 
static void alert (QWidget *widget, int duration=0)
 
static void setCursorFlashTime (int)
 
static int cursorFlashTime ()
 
static void setDoubleClickInterval (int)
 
static int doubleClickInterval ()
 
static void setKeyboardInputInterval (int)
 
static int keyboardInputInterval ()
 
static void setStartDragTime (int ms)
 
static int startDragTime ()
 
static void setStartDragDistance (int l)
 
static int startDragDistance ()
 
static bool isEffectEnabled (Qt::UIEffect)
 
static void setEffectEnabled (Qt::UIEffect, bool enable=true)
 
static int exec ()
 
static QPalette palette ()
 
- Static Public Member Functions inherited from QGuiApplication
static void setApplicationDisplayName (const QString &name)
 
static QString applicationDisplayName ()
 
static void setDesktopFileName (const QString &name)
 
static QString desktopFileName ()
 
static QWindowList allWindows ()
 
static QWindowList topLevelWindows ()
 
static QWindow * topLevelAt (const QPoint &pos)
 
static void setWindowIcon (const QIcon &icon)
 
static QIcon windowIcon ()
 
static QString platformName ()
 
static QWindow * modalWindow ()
 
static QWindow * focusWindow ()
 
static QObject * focusObject ()
 
static QScreen * primaryScreen ()
 
static QList< QScreen * > screens ()
 
static QScreen * screenAt (const QPoint &point)
 
static QCursor * overrideCursor ()
 
static void setOverrideCursor (const QCursor &)
 
static void changeOverrideCursor (const QCursor &)
 
static void restoreOverrideCursor ()
 
static QFont font ()
 
static void setFont (const QFont &)
 
static QClipboard * clipboard ()
 
static QPalette palette ()
 
static void setPalette (const QPalette &pal)
 
static Qt::KeyboardModifiers keyboardModifiers ()
 
static Qt::KeyboardModifiers queryKeyboardModifiers ()
 
static Qt::MouseButtons mouseButtons ()
 
static void setLayoutDirection (Qt::LayoutDirection direction)
 
static Qt::LayoutDirection layoutDirection ()
 
static bool isRightToLeft ()
 
static bool isLeftToRight ()
 
static QStyleHints * styleHints ()
 
static void setDesktopSettingsAware (bool on)
 
static bool desktopSettingsAware ()
 
static QInputMethod * inputMethod ()
 
static QPlatformNativeInterface * platformNativeInterface ()
 
static QFunctionPointer platformFunction (const QByteArray &function)
 
static void setQuitOnLastWindowClosed (bool quit)
 
static bool quitOnLastWindowClosed ()
 
static Qt::ApplicationState applicationState ()
 
static void setHighDpiScaleFactorRoundingPolicy (Qt::HighDpiScaleFactorRoundingPolicy policy)
 
static Qt::HighDpiScaleFactorRoundingPolicy highDpiScaleFactorRoundingPolicy ()
 
static int exec ()
 
static void sync ()
 
- Static Public Member Functions inherited from QCoreApplication
static QStringList arguments ()
 
static void setAttribute (Qt::ApplicationAttribute attribute, bool on=true)
 [95] More...
 
static bool testAttribute (Qt::ApplicationAttribute attribute)
 
static void setOrganizationDomain (const QString &orgDomain)
 
static QString organizationDomain ()
 
static void setOrganizationName (const QString &orgName)
 [11] More...
 
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 ()
 
static int exec ()
 
static void processEvents (QEventLoop::ProcessEventsFlags flags=QEventLoop::AllEvents)
 
static void processEvents (QEventLoop::ProcessEventsFlags flags, int maxtime)
 
static bool sendEvent (QObject *receiver, QEvent *event)
 
static void postEvent (QObject *receiver, QEvent *event, int priority=Qt::NormalEventPriority)
 
static void sendPostedEvents (QObject *receiver=nullptr, int event_type=0)
 
static void removePostedEvents (QObject *receiver, int eventType=0)
 
static QAbstractEventDispatcher * eventDispatcher ()
 
static void setEventDispatcher (QAbstractEventDispatcher *eventDispatcher)
 
static bool startingUp ()
 
static bool closingDown ()
 
static QString applicationDirPath ()
 
static QString applicationFilePath ()
 
static qint64 applicationPid () Q_DECL_CONST_FUNCTION
 
static bool installTranslator (QTranslator *messageFile)
 
static bool removeTranslator (QTranslator *messageFile)
 
static QString translate (const char *context, const char *key, const char *disambiguation=nullptr, int n=-1)
 
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)
 
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::FunctionPointer< Func2 >::Object *receiver, Func2 slot, Qt::ConnectionType type=Qt::AutoConnection)
 
static QMetaObject::Connection ::type connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 slot)
 
static QMetaObject::Connection ::type connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, const QObject *context, Func2 slot, Qt::ConnectionType type=Qt::AutoConnection)
 
template<typename Func1 , typename Func2 >
static std::enable_if< QtPrivate::FunctionPointer< Func2 >::ArgumentCount==-1 &&!std::is_convertible_v< Func2, const char * >, QMetaObject::Connection >::type connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 slot)
 
template<typename Func1 , typename Func2 >
static std::enable_if< QtPrivate::FunctionPointer< Func2 >::ArgumentCount==-1 &&!std::is_convertible_v< Func2, const char * >, QMetaObject::Connection >::type connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, const QObject *context, Func2 slot, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool disconnect (const QObject *sender, const char *signal, const QObject *receiver, const char *member)
 
static bool disconnect (const QObject *sender, const QMetaMethod &signal, const QObject *receiver, const QMetaMethod &member)
 
static bool disconnect (const QMetaObject::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
 
bool compressEvent (QEvent *, QObject *receiver, QPostEventList *) override
 
- Protected Member Functions inherited from QGuiApplication
 QGuiApplication (QGuiApplicationPrivate &p)
 
- Protected Member Functions inherited from QCoreApplication
 QCoreApplication (QCoreApplicationPrivate &p)
 
- Protected Member Functions inherited from QObject
QObject * sender () const
 
int senderSignalIndex () const
 
int receivers (const char *signal) const
 
bool isSignalConnected (const QMetaMethod &signal) const
 
virtual void timerEvent (QTimerEvent *event)
 
virtual void childEvent (QChildEvent *event)
 
virtual void customEvent (QEvent *event)
 
virtual void connectNotify (const QMetaMethod &signal)
 
virtual void disconnectNotify (const QMetaMethod &signal)
 
 QObject (QObjectPrivate &dd, QObject *parent=nullptr)
 

Properties

int cursorFlashTime
 the text cursor's flash (blink) time in milliseconds More...
 
int doubleClickInterval
 the time limit in milliseconds that distinguishes a double click from two consecutive mouse clicks More...
 
int keyboardInputInterval
 the time limit in milliseconds that distinguishes a key press from two consecutive key presses More...
 
int startDragTime
 the time in milliseconds that a mouse button must be held down before a drag and drop operation will begin More...
 
int startDragDistance
 the minimum distance required for a drag and drop operation to start. More...
 
QString styleSheet
 the application style sheet More...
 
bool autoSipEnabled
 toggles automatic SIP (software input panel) visibility More...
 
- Properties inherited from QGuiApplication
QIcon windowIcon
 the default window icon More...
 
QString applicationDisplayName
 the user-visible name of this application More...
 
QString desktopFileName
 the base name of the desktop entry for this application More...
 
Qt::LayoutDirection layoutDirection
 the default layout direction for this application More...
 
QString platformName
 The name of the underlying platform plugin. More...
 
bool quitOnLastWindowClosed
 whether the application implicitly quits when the last window is closed. More...
 
QScreen * primaryScreen
 the primary (or default) screen of the application. More...
 
- Properties inherited from QCoreApplication
QString applicationName
 the name of this application More...
 
QString applicationVersion
 the version of this application More...
 
QString organizationName
 the name of the organization that wrote this application More...
 
QString organizationDomain
 the Internet domain of the organization that wrote this application More...
 
bool quitLockEnabled
 Whether the use of the QEventLoopLocker feature can cause the application to quit. More...
 
- Properties inherited from QObject
QString objectName
 the name of this object More...
 

Friends

class QGraphicsWidget
 
class QGraphicsItem
 
class QGraphicsScene
 
class QGraphicsScenePrivate
 
class QWidget
 
class QWidgetPrivate
 
class QWidgetWindow
 
class QTranslator
 
class QWidgetAnimator
 
class QShortcut
 
class QLineEdit
 
class QWidgetTextControl
 
class QAction
 
class QGestureManager
 

Related Functions

(Note that these are not member functions.)

bool qt_sendSpontaneousEvent (QObject *receiver, QEvent *event)
 
- Related Functions inherited from QCoreApplication
void qAddPostRoutine (QtCleanUpFunction ptr)
 
void qRemovePostRoutine (QtCleanUpFunction ptr)
 
void * resolveInterface (const char *name, int revision) const
 
- Related Functions inherited from QObject
template< class T > T qobject_cast (const QObject *object)
 
template< typename T > T qFindChildqFindChildren (const QObject *obj, const QString &name)()
 
template< typename T > QList< T > qFindChildrenqFindChildren (const QObject *obj, const QString &name)()
 
 QObjectList
 

Additional Inherited Members

- Public Types inherited from QCoreApplication
enum  { ApplicationFlags = QT_VERSION }
 
- Protected Attributes inherited from QObject
QScopedPointer< QObjectData > d_ptr
 

Detailed Description

The QApplication class manages the GUI application's control flow and main settings.

\inmodule QtWidgets

QApplication specializes QGuiApplication with some functionality needed for QWidget-based applications. It handles widget specific initialization, finalization.

For any GUI application using Qt, there is precisely one QApplication object, no matter whether the application has 0, 1, 2 or more windows at any given time. For non-QWidget based Qt applications, use QGuiApplication instead, as it does not depend on the \l QtWidgets library.

Some GUI applications provide a special batch mode ie. provide command line arguments for executing tasks without manual intervention. In such non-GUI mode, it is often sufficient to instantiate a plain QCoreApplication to avoid unnecessarily initializing resources needed for a graphical user interface. The following example shows how to dynamically create an appropriate type of application instance:

The QApplication object is accessible through the instance() function that returns a pointer equivalent to the global qApp pointer.

QApplication's main areas of responsibility are: \list

Since the QApplication object does so much initialization, it {must} be created before any other objects related to the user interface are created. QApplication also deals with common command line arguments. Hence, it is usually a good idea to create it before any interpretation or modification of argv is done in the application itself.

\table \header

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See also
QCoreApplication, QAbstractEventDispatcher, QEventLoop, QSettings

Definition at line 67 of file qapplication.h.

Constructor & Destructor Documentation

◆ QApplication()

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

Initializes the window system and constructs an application object with argc command line arguments in argv.

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

The global qApp pointer refers to this application object. Only one application object should be created.

This application object must be constructed before any \l{QPaintDevice} {paint devices} (including widgets, pixmaps, bitmaps etc.).

Note
argc and argv might be changed as Qt removes command line arguments that it recognizes.

All Qt programs automatically support the following command line options: \list

  • -style= style, sets the application GUI style. Possible values depend on your system configuration. If you compiled Qt with additional styles or have additional styles as plugins these will be available to the -style command line option. You can also set the style for all Qt applications by setting the QT_STYLE_OVERRIDE environment variable.
  • -style style, is the same as listed above.
  • -stylesheet= stylesheet, sets the application \l styleSheet. The value must be a path to a file that contains the Style Sheet.
    Note
    Relative URLs in the Style Sheet file are relative to the Style Sheet file's path.
  • -stylesheet stylesheet, is the same as listed above.
  • -widgetcount, prints debug message at the end about number of widgets left undestroyed and maximum number of widgets existed at the same time
  • -reverse, sets the application's layout direction to Qt::RightToLeft
  • -qmljsdebugger=, activates the QML/JS debugger with a specified port. The value must be of format port:1234[,block], where block is optional and will make the application wait until a debugger connects to it. \endlist
See also
QCoreApplication::arguments()

Definition at line 478 of file qapplication.cpp.

◆ ~QApplication()

QApplication::~QApplication ( )
virtual

Cleans up any window system resources that were allocated by this application. Sets the global variable qApp to \nullptr.

Definition at line 678 of file qapplication.cpp.

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Member Function Documentation

◆ aboutQt

void QApplication::aboutQt ( )
staticslot

Displays a simple message box about Qt. The message includes the version number of Qt being used by the application.

This is useful for inclusion in the \uicontrol Help menu of an application, as shown in the \l{mainwindows/menus}{Menus} example.

This function is a convenience slot for QMessageBox::aboutQt().

Definition at line 1639 of file qapplication.cpp.

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◆ activeModalWidget()

QWidget * QApplication::activeModalWidget ( )
static

Returns the active modal widget.

A modal widget is a special top-level widget which is a subclass of QDialog that specifies the modal parameter of the constructor as true. A modal widget must be closed before the user can continue with other parts of the program.

Modal widgets are organized in a stack. This function returns the active modal widget at the top of the stack.

See also
activePopupWidget(), topLevelWidgets()

Definition at line 667 of file qapplication.cpp.

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◆ activePopupWidget()

QWidget * QApplication::activePopupWidget ( )
static

Returns the active popup widget.

A popup widget is a special top-level widget that sets the Qt::WType_Popup widget flag, e.g. the QMenu widget. When the application opens a popup widget, all events are sent to the popup. Normal widgets and modal widgets cannot be accessed before the popup widget is closed.

Only other popup widgets may be opened when a popup widget is shown. The popup widgets are organized in a stack. This function returns the active popup widget at the top of the stack.

See also
activeModalWidget(), topLevelWidgets()

Definition at line 646 of file qapplication.cpp.

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◆ activeWindow()

QWidget * QApplication::activeWindow ( )
static

Returns the application top-level window that has the keyboard input focus, or \nullptr if no application window has the focus. There might be an activeWindow() even if there is no focusWidget(), for example if no widget in that window accepts key events.

See also
QWidget::setFocus(), QWidget::hasFocus(), focusWidget()

Definition at line 1560 of file qapplication.cpp.

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◆ alert()

void QApplication::alert ( QWidget *  widget,
int  msec = 0 
)
static
Since
4.3

Causes an alert to be shown for widget if the window is not the active window. The alert is shown for msec milliseconds. If msec is zero (the default), then the alert is shown indefinitely until the window becomes active again.

Currently this function does nothing on Qt for Embedded Linux.

On \macos, this works more at the application level and will cause the application icon to bounce in the dock.

On Windows, this causes the window's taskbar entry to flash for a time. If msec is zero, the flashing will stop and the taskbar entry will turn a different color (currently orange).

On X11, this will cause the window to be marked as "demands attention", the window must not be hidden (i.e. not have hide() called on it, but be visible in some sort of way) in order for this to work.

Definition at line 3543 of file qapplication.cpp.

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◆ allWidgets()

QWidgetList QApplication::allWidgets ( )
static

Returns a list of all the widgets in the application.

The list is empty (QList::isEmpty()) if there are no widgets.

Note
Some of the widgets may be hidden.

Example:

See also
topLevelWidgets(), QWidget::isVisible()

Definition at line 1476 of file qapplication.cpp.

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◆ autoSipEnabled

bool QApplication::autoSipEnabled ( ) const
slot

Definition at line 870 of file qapplication.cpp.

◆ beep()

void QApplication::beep ( )
static

Sounds the bell, using the default volume and sound. The function is not available in Qt for Embedded Linux.

Definition at line 3724 of file qapplication.cpp.

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◆ closeAllWindows

void QApplication::closeAllWindows ( )
staticslot

Closes all top-level windows.

This function is particularly useful for applications with many top-level windows.

The windows are closed in random order, until one window does not accept the close event. The application quits when the last window was successfully closed, unless \l quitOnLastWindowClosed is set to false. To trigger application termination from e.g. a menu, use QCoreApplication::quit() instead of this function.

See also
quitOnLastWindowClosed, lastWindowClosed(), QWidget::close(), QWidget::closeEvent(), lastWindowClosed(), QCoreApplication::quit(), topLevelWidgets(), QWidget::isWindow()

Definition at line 1624 of file qapplication.cpp.

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◆ compressEvent()

bool QApplication::compressEvent ( QEvent *  event,
QObject *  receiver,
QPostEventList *  postedEvents 
)
overrideprotectedvirtual

Reimplemented from QGuiApplication.

Definition at line 806 of file qapplication.cpp.

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◆ cursorFlashTime()

static int QApplication::cursorFlashTime ( )
static

◆ doubleClickInterval()

static int QApplication::doubleClickInterval ( )
static

◆ event()

bool QApplication::event ( QEvent *  e)
overrideprotectedvirtual

\reimp

Reimplemented from QGuiApplication.

Reimplemented in MyApplication.

Definition at line 1664 of file qapplication.cpp.

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◆ exec()

int QApplication::exec ( )
static

Enters the main event loop and waits until exit() is called, then returns the value that was set 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.

Generally, no user interaction can take place before calling exec(). As a special case, modal widgets like QMessageBox can be used before calling exec(), because modal widgets call exec() to start a local event loop.

To make your application perform idle processing, i.e., executing a special function whenever there are no pending events, use a QTimer with 0 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. This is because, on some platforms the QApplication::exec() call may not return. For example, on the Windows platform, 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 QApplication::exec() call.

See also
quitOnLastWindowClosed, QCoreApplication::quit(), QCoreApplication::exit(), QCoreApplication::processEvents(), QCoreApplication::exec()

Definition at line 2629 of file qapplication.cpp.

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◆ focusChanged

void QApplication::focusChanged ( QWidget *  old,
QWidget *  now 
)
signal
Since
4.1

This signal is emitted when the widget that has keyboard focus changed from old to now, i.e., because the user pressed the tab-key, clicked into a widget or changed the active window. Both old and now can be \nullptr.

The signal is emitted after both widget have been notified about the change through QFocusEvent.

See also
QWidget::setFocus(), QWidget::clearFocus(), Qt::FocusReason
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◆ focusWidget()

QWidget * QApplication::focusWidget ( )
static

Returns the application widget that has the keyboard input focus, or \nullptr if no widget in this application has the focus.

See also
QWidget::setFocus(), QWidget::hasFocus(), activeWindow(), focusChanged()

Definition at line 1490 of file qapplication.cpp.

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◆ font() [1/3]

QFont QApplication::font ( )
static

Returns the default application font.

See also
fontMetrics(), QWidget::font()

Definition at line 1266 of file qapplication.cpp.

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◆ font() [2/3]

QFont QApplication::font ( const char *  className)
static

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

Returns the font for widgets of the given className.

See also
setFont(), QWidget::font()

Definition at line 1317 of file qapplication.cpp.

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◆ font() [3/3]

QFont QApplication::font ( const QWidget *  widget)
static

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

Returns the default font for the widget. If a default font was not registered for the {widget}'s class, it returns the default font of its nearest registered superclass.

See also
fontMetrics(), setFont(), QWidget::setFont()

Definition at line 1281 of file qapplication.cpp.

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◆ isEffectEnabled()

bool QApplication::isEffectEnabled ( Qt::UIEffect  effect)
static

Returns true if effect is enabled; otherwise returns false.

By default, Qt will try to use the desktop settings. To prevent this, call setDesktopSettingsAware(false).

Note
All effects are disabled on screens running at less than 16-bit color depth.
See also
setEffectEnabled(), Qt::UIEffect

Definition at line 3710 of file qapplication.cpp.

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◆ keyboardInputInterval()

static int QApplication::keyboardInputInterval ( )
static

◆ notify()

bool QApplication::notify ( QObject *  receiver,
QEvent *  e 
)
overridevirtual

\reimp

Reimplemented from QGuiApplication.

Definition at line 2636 of file qapplication.cpp.

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◆ palette() [1/3]

QPalette QGuiApplication::palette
static

Returns the current application palette.

Roles that have not been explicitly set will reflect the system's platform theme.

See also
setPalette()

Definition at line 134 of file qguiapplication.cpp.

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◆ palette() [2/3]

QPalette QApplication::palette ( const char *  className)
static

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

Returns the palette for widgets of the given className.

See also
setPalette(), QWidget::palette()

Definition at line 1145 of file qapplication.cpp.

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◆ palette() [3/3]

QPalette QApplication::palette ( const QWidget *  widget)
static

If a widget is passed, the default palette for the widget's class is returned. This may or may not be the application palette. In most cases there is no special palette for certain types of widgets, but one notable exception is the popup menu under Windows, if the user has defined a special background color for menus in the display settings.

See also
setPalette(), QWidget::palette()

Definition at line 1122 of file qapplication.cpp.

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◆ setActiveWindow()

void QApplication::setActiveWindow ( QWidget *  active)
static

Sets the active window to the active widget in response to a system event. The function is called from the platform specific event handlers.

Warning
This function does not set the keyboard focus to the active widget. Call QWidget::activateWindow() instead.

It sets the activeWindow() and focusWidget() attributes and sends proper \l{QEvent::WindowActivate}{WindowActivate}/\l{QEvent::WindowDeactivate} {WindowDeactivate} and \l{QEvent::FocusIn}{FocusIn}/\l{QEvent::FocusOut} {FocusOut} events to all appropriate widgets. The window will then be painted in active state (e.g. cursors in line edits will blink), and it will have tool tips enabled.

See also
activeWindow(), QWidget::activateWindow()

Definition at line 1791 of file qapplication.cpp.

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◆ setAutoSipEnabled

void QApplication::setAutoSipEnabled ( const bool  enabled)
slot

Definition at line 865 of file qapplication.cpp.

◆ setCursorFlashTime()

void QApplication::setCursorFlashTime ( int  msecs)
static

Definition at line 3575 of file qapplication.cpp.

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◆ setDoubleClickInterval()

void QApplication::setDoubleClickInterval ( int  ms)
static

Definition at line 3593 of file qapplication.cpp.

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◆ setEffectEnabled()

void QApplication::setEffectEnabled ( Qt::UIEffect  effect,
bool  enable = true 
)
static

Enables the UI effect effect if enable is true, otherwise the effect will not be used.

Note
All effects are disabled on screens running at less than 16-bit color depth.
See also
isEffectEnabled(), Qt::UIEffect, setDesktopSettingsAware()

Definition at line 3683 of file qapplication.cpp.

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◆ setFont()

void QApplication::setFont ( const QFont &  font,
const char *  className = nullptr 
)
static

Changes the default application font to font. If className is passed, the change applies only to classes that inherit className (as reported by QObject::inherits()).

On application start-up, the default font depends on the window system. It can vary depending on both the window system version and the locale. This function lets you override the default font; but overriding may be a bad idea because, for example, some locales need extra large fonts to support their special characters.

Warning
Do not use this function in conjunction with \l{Qt Style Sheets}. The font of an application can be customized using the "font" style sheet property. To set a bold font for all QPushButtons, set the application styleSheet() as "QPushButton { font: bold }"
See also
font(), fontMetrics(), QWidget::setFont()

Definition at line 1348 of file qapplication.cpp.

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◆ setKeyboardInputInterval()

void QApplication::setKeyboardInputInterval ( int  ms)
static

Definition at line 3612 of file qapplication.cpp.

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◆ setPalette()

void QApplication::setPalette ( const QPalette &  palette,
const char *  className = nullptr 
)
static

Changes the application palette to palette.

If className is passed, the change applies only to widgets that inherit className (as reported by QObject::inherits()). If className is left 0, the change affects all widgets, thus overriding any previously set class specific palettes.

The palette may be changed according to the current GUI style in QStyle::polish().

Warning
Do not use this function in conjunction with \l{Qt Style Sheets}. When using style sheets, the palette of a widget can be customized using the "color", "background-color", "selection-color", "selection-background-color" and "alternate-background-color".
Note
Some styles do not use the palette for all drawing, for instance, if they make use of native theme engines. This is the case for the Windows Vista and \macos styles.
See also
QWidget::setPalette(), palette(), QStyle::polish()

Definition at line 1179 of file qapplication.cpp.

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◆ setStartDragDistance()

void QApplication::setStartDragDistance ( int  l)
static

Definition at line 2567 of file qapplication.cpp.

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◆ setStartDragTime()

void QApplication::setStartDragTime ( int  ms)
static

Definition at line 2534 of file qapplication.cpp.

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◆ setStyle() [1/2]

QStyle * QApplication::setStyle ( const QString &  style)
static

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

Requests a QStyle object for style from the QStyleFactory.

The string must be one of the QStyleFactory::keys(), typically one of "windows", "windowsvista", "fusion", or "macos". Style names are case insensitive.

Returns \nullptr if an unknown style is passed, otherwise the QStyle object returned is set as the application's GUI style.

Warning
To ensure that the application's style is set correctly, it is best to call this function before the QApplication constructor, if possible.

Definition at line 1075 of file qapplication.cpp.

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◆ setStyle() [2/2]

void QApplication::setStyle ( QStyle *  style)
static

Sets the application's GUI style to style. Ownership of the style object is transferred to QApplication, so QApplication will delete the style object on application exit or when a new style is set and the old style is still the parent of the application object.

Example usage:

When switching application styles, the color palette is set back to the initial colors or the system defaults. This is necessary since certain styles have to adapt the color palette to be fully style-guide compliant.

Setting the style before a palette has been set, i.e., before creating QApplication, will cause the application to use QStyle::standardPalette() for the palette.

Warning
Qt style sheets are currently not supported for custom QStyle subclasses. We plan to address this in some future release.
See also
style(), QStyle, setPalette(), desktopSettingsAware()

Definition at line 970 of file qapplication.cpp.

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◆ setStyleSheet

void QApplication::setStyleSheet ( const QString &  sheet)
slot

Definition at line 882 of file qapplication.cpp.

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◆ startDragDistance()

static int QApplication::startDragDistance ( )
static

◆ startDragTime()

static int QApplication::startDragTime ( )
static

◆ style()

QStyle * QApplication::style ( )
static

Returns the application's style object.

See also
setStyle(), QStyle

Definition at line 906 of file qapplication.cpp.

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◆ styleSheet()

QString QApplication::styleSheet ( ) const

Definition at line 877 of file qapplication.cpp.

◆ topLevelAt() [1/2]

QWidget * QApplication::topLevelAt ( const QPoint &  point)
static

Returns the top-level widget at the given point; returns \nullptr if there is no such widget.

Definition at line 316 of file qapplication.cpp.

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◆ topLevelAt() [2/2]

QWidget * QApplication::topLevelAt ( int  x,
int  y 
)
inlinestatic

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

Returns the top-level widget at the point ({x}, {y}); returns 0 if there is no such widget.

Definition at line 122 of file qapplication.h.

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◆ topLevelWidgets()

QWidgetList QApplication::topLevelWidgets ( )
static

Returns a list of the top-level widgets (windows) in the application.

Note
Some of the top-level widgets may be hidden, for example a tooltip if no tooltip is currently shown.

Example:

See also
allWidgets(), QWidget::isWindow(), QWidget::isHidden()

Definition at line 1450 of file qapplication.cpp.

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◆ widgetAt() [1/2]

QWidget * QApplication::widgetAt ( const QPoint &  point)
static

Returns the widget at global screen position point, or \nullptr if there is no Qt widget there.

This function can be slow.

See also
QCursor::pos(), QWidget::grabMouse(), QWidget::grabKeyboard()

Definition at line 757 of file qapplication.cpp.

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◆ widgetAt() [2/2]

QWidget * QApplication::widgetAt ( int  x,
int  y 
)
inlinestatic

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

Returns the widget at global screen position (x, y), or \nullptr if there is no Qt widget there.

Definition at line 120 of file qapplication.h.

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Friends And Related Function Documentation

◆ QAction

friend class QAction
friend

Definition at line 195 of file qapplication.h.

◆ QGestureManager

friend class QGestureManager
friend

Definition at line 198 of file qapplication.h.

◆ QGraphicsItem

friend class QGraphicsItem
friend

Definition at line 182 of file qapplication.h.

◆ QGraphicsScene

friend class QGraphicsScene
friend

Definition at line 183 of file qapplication.h.

◆ QGraphicsScenePrivate

friend class QGraphicsScenePrivate
friend

Definition at line 184 of file qapplication.h.

◆ QGraphicsWidget

friend class QGraphicsWidget
friend

Definition at line 181 of file qapplication.h.

◆ QLineEdit

friend class QLineEdit
friend

Definition at line 192 of file qapplication.h.

◆ QShortcut

friend class QShortcut
friend

Definition at line 191 of file qapplication.h.

◆ qt_sendSpontaneousEvent()

bool qt_sendSpontaneousEvent ( QObject *  receiver,
QEvent *  event 
)
related

\macro qApp

A global pointer referring to the unique application object. It is equivalent to QCoreApplication::instance(), but cast as a QApplication pointer, so only valid when the unique application object is a QApplication.

See also
QCoreApplication::instance(), qGuiApp

Definition at line 3740 of file qapplication.cpp.

◆ QTranslator

friend class QTranslator
friend

Definition at line 188 of file qapplication.h.

◆ QWidget

friend class QWidget
friend

Definition at line 185 of file qapplication.h.

◆ QWidgetAnimator

friend class QWidgetAnimator
friend

Definition at line 189 of file qapplication.h.

◆ QWidgetPrivate

friend class QWidgetPrivate
friend

Definition at line 186 of file qapplication.h.

◆ QWidgetTextControl

friend class QWidgetTextControl
friend

Definition at line 193 of file qapplication.h.

◆ QWidgetWindow

friend class QWidgetWindow
friend

Definition at line 187 of file qapplication.h.

Property Documentation

◆ autoSipEnabled

QApplication::autoSipEnabled
readwrite

toggles automatic SIP (software input panel) visibility

Since
4.5

Set this property to true to automatically display the SIP when entering widgets that accept keyboard input. This property only affects widgets with the WA_InputMethodEnabled attribute set, and is typically used to launch a virtual keyboard on devices which have very few or no keys.

{ The property only has an effect on platforms that use software input panels.}

The default is platform dependent.

Definition at line 202 of file qapplication.h.

◆ cursorFlashTime

int QApplication::cursorFlashTime
readwrite

the text cursor's flash (blink) time in milliseconds

The flash time is the time required to display, invert and restore the caret display. Usually the text cursor is displayed for half the cursor flash time, then hidden for the same amount of time, but this may vary.

The default value on X11 is 1000 milliseconds. On Windows, the \uicontrol{Control Panel} value is used and setting this property sets the cursor flash time for all applications.

We recommend that widgets do not cache this value as it may change at any time if the user changes the global desktop settings.

Note
This property may hold a negative value, for instance if cursor blinking is disabled.

Definition at line 202 of file qapplication.h.

◆ doubleClickInterval

int QApplication::doubleClickInterval
readwrite

the time limit in milliseconds that distinguishes a double click from two consecutive mouse clicks

The default value on X11 is 400 milliseconds. On Windows and Mac OS, the operating system's value is used.

Definition at line 202 of file qapplication.h.

◆ keyboardInputInterval

int QApplication::keyboardInputInterval
readwrite

the time limit in milliseconds that distinguishes a key press from two consecutive key presses

Since
4.2

The default value on X11 is 400 milliseconds. On Windows and Mac OS, the operating system's value is used.

Definition at line 202 of file qapplication.h.

◆ startDragDistance

int QApplication::startDragDistance
readwrite

the minimum distance required for a drag and drop operation to start.

If you support drag and drop in your application, and want to start a drag and drop operation after the user has moved the cursor a certain distance with a button held down, you should use this property's value as the minimum distance required.

For example, if the mouse position of the click is stored in startPos and the current position (e.g. in the mouse move event) is currentPos, you can find out if a drag should be started with code like this:

Qt uses this value internally, e.g. in QFileDialog.

The default value (if the platform doesn't provide a different default) is 10 pixels.

See also
startDragTime(), QPoint::manhattanLength(), {Drag and Drop}

Definition at line 202 of file qapplication.h.

◆ startDragTime

int QApplication::startDragTime
readwrite

the time in milliseconds that a mouse button must be held down before a drag and drop operation will begin

If you support drag and drop in your application, and want to start a drag and drop operation after the user has held down a mouse button for a certain amount of time, you should use this property's value as the delay.

Qt also uses this delay internally, e.g. in QTextEdit and QLineEdit, for starting a drag.

The default value is 500 ms.

See also
startDragDistance(), {Drag and Drop}

Definition at line 202 of file qapplication.h.

◆ styleSheet

QApplication::styleSheet
readwrite

the application style sheet

Since
4.2

By default, this property returns an empty string unless the user specifies the {-stylesheet} option on the command line when running the application.

See also
QWidget::setStyle(), {Qt Style Sheets}

Definition at line 202 of file qapplication.h.

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