QApplication

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

Synopsis

Functions

• def autoSipEnabled ()

• def focusChanged (old, now)

• def setAutoSipEnabled (enabled)

• def setStyleSheet (sheet)

• def styleSheet ()

Static functions

• def aboutQt ()

• def activeModalWidget ()

• def activePopupWidget ()

• def activeWindow ()

• def alert (widget[, duration=0])

• def allWidgets ()

• def beep ()

• def closeAllWindows ()

• def cursorFlashTime ()

• def doubleClickInterval ()

• def focusWidget ()

• def font (arg__1)

• def font (className)

• def fontMetrics ()

• def isEffectEnabled (arg__1)

• def keyboardInputInterval ()

• def palette (arg__1)

• def palette (className)

• def setActiveWindow (act)

• def setCursorFlashTime (arg__1)

• def setDoubleClickInterval (arg__1)

• def setEffectEnabled (arg__1[, enable=true])

• def setFont (arg__1[, className=None])

• def setKeyboardInputInterval (arg__1)

• def setPalette (arg__1[, className=None])

• def setStartDragDistance (l)

• def setStartDragTime (ms)

• def setStyle (arg__1)

• def setStyle (arg__1)

• def setWheelScrollLines (arg__1)

• def startDragDistance ()

• def startDragTime ()

• def style ()

• def topLevelAt (x, y)

• def topLevelWidgets ()

• def wheelScrollLines ()

• def widgetAt (p)

• def widgetAt (x, y)

Detailed Description

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 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:

def main():
    useGUI = not '-no-gui' in sys.argv
    app = QApplication(sys.argv) if useGUI else QCoreApplication(sys.argv)
    ...
    return app.exec_()

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:

• It initializes the application with the user’s desktop settings such as palette() , font() and doubleClickInterval() . It keeps track of these properties in case the user changes the desktop globally, for example through some kind of control panel.

• It performs event handling, meaning that it receives events from the underlying window system and dispatches them to the relevant widgets. By using sendEvent() and postEvent() you can send your own events to widgets.

• It parses common command line arguments and sets its internal state accordingly. See the constructor documentation below for more details.

• It defines the application’s look and feel, which is encapsulated in a QStyle object. This can be changed at runtime with setStyle() .

• It provides localization of strings that are visible to the user via translate() .

• It provides some magical objects like the clipboard() .

• It knows about the application’s windows. You can ask which widget is at a certain position using , get a list of topLevelWidgets() and closeAllWindows() , etc.

• It manages the application’s mouse cursor handling, see setOverrideCursor()

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.

Groups of functions
System settings	desktopSettingsAware() , setDesktopSettingsAware() , cursorFlashTime() , setCursorFlashTime() , doubleClickInterval() , setDoubleClickInterval() , setKeyboardInputInterval() , wheelScrollLines() , setWheelScrollLines() , palette() , setPalette() , font() , setFont() , fontMetrics() .
Event handling	exec() , processEvents() , exit() , quit() . sendEvent() , postEvent() , sendPostedEvents() , removePostedEvents() , notify() .
GUI Styles	style() , setStyle() .
Text handling	installTranslator() , removeTranslator() translate() .
Widgets	allWidgets() , topLevelWidgets() , activePopupWidget() , activeModalWidget() , clipboard() , focusWidget() , activeWindow() , .
Advanced cursor handling	overrideCursor() , setOverrideCursor() , restoreOverrideCursor() .
Miscellaneous	closeAllWindows() , startingUp() , closingDown() .

See also

QCoreApplication QAbstractEventDispatcher QEventLoop QSettings

class PySide6.QtWidgets.QApplication

PySide6.QtWidgets.QApplication(arg__1)

Parameters

arg__1 – list of strings

static PySide6.QtWidgets.QApplication.aboutQt()

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 Help menu of an application, as shown in the Menus example.

This function is a convenience slot for aboutQt() .

static PySide6.QtWidgets.QApplication.activeModalWidget()

Return type

PySide6.QtWidgets.QWidget

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()

static PySide6.QtWidgets.QApplication.activePopupWidget()

Return type

PySide6.QtWidgets.QWidget

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()

static PySide6.QtWidgets.QApplication.activeWindow()

Return type

PySide6.QtWidgets.QWidget

Returns the application top-level window that has the keyboard input focus, or None if no application window has the focus. There might be an even if there is no focusWidget() , for example if no widget in that window accepts key events.

See also

setFocus() hasFocus() focusWidget()

static PySide6.QtWidgets.QApplication.alert(widget[, duration=0])

Parameters

• widget – PySide6.QtWidgets.QWidget

• duration – int

static PySide6.QtWidgets.QApplication.allWidgets()

Return type

Returns a list of all the widgets in the application.

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

Note

Some of the widgets may be hidden.

Example:

def updateAllWidgets():
    for widget in QApplication.allWidgets()
        widget.update()

See also

topLevelWidgets() isVisible()

PySide6.QtWidgets.QApplication.autoSipEnabled()

Return type

bool

See also

setAutoSipEnabled()

static PySide6.QtWidgets.QApplication.beep()

static PySide6.QtWidgets.QApplication.closeAllWindows()

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 quitOnLastWindowClosed is set to false. To trigger application termination from e.g. a menu, use quit() instead of this function.

See also

quitOnLastWindowClosed lastWindowClosed() close() closeEvent() lastWindowClosed() quit() topLevelWidgets() isWindow()

static PySide6.QtWidgets.QApplication.cursorFlashTime()

Return type

int

See also

setCursorFlashTime()

static PySide6.QtWidgets.QApplication.doubleClickInterval()

Return type

int

See also

setDoubleClickInterval()

PySide6.QtWidgets.QApplication.focusChanged(old, now)

Parameters

• old – PySide6.QtWidgets.QWidget

• now – PySide6.QtWidgets.QWidget

static PySide6.QtWidgets.QApplication.focusWidget()

Return type

PySide6.QtWidgets.QWidget

Returns the application widget that has the keyboard input focus, or None if no widget in this application has the focus.

See also

setFocus() hasFocus() activeWindow() focusChanged()

static PySide6.QtWidgets.QApplication.font(arg__1)

Parameters

arg__1 – PySide6.QtWidgets.QWidget

Return type

PySide6.QtGui.QFont

This is an overloaded function.

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() setFont()

static PySide6.QtWidgets.QApplication.font(className)

Parameters

className – str

Return type

PySide6.QtGui.QFont

This is an overloaded function.

Returns the font for widgets of the given className.

See also

setFont() font()

static PySide6.QtWidgets.QApplication.fontMetrics()

Return type

PySide6.QtGui.QFontMetrics

Note

This function is deprecated.

Use the QFontMetricsF constructor instead Returns display (screen) font metrics for the application font.

See also

font() setFont() fontMetrics()

static PySide6.QtWidgets.QApplication.isEffectEnabled(arg__1)

Parameters

arg__1 – UIEffect

Return type

bool

static PySide6.QtWidgets.QApplication.keyboardInputInterval()

Return type

int

See also

setKeyboardInputInterval()

static PySide6.QtWidgets.QApplication.palette(arg__1)

Parameters

arg__1 – PySide6.QtWidgets.QWidget

Return type

PySide6.QtGui.QPalette

See also

setPalette()

static PySide6.QtWidgets.QApplication.palette(className)

Parameters

className – str

Return type

PySide6.QtGui.QPalette

This is an overloaded function.

Returns the palette for widgets of the given className.

See also

setPalette() palette()

static PySide6.QtWidgets.QApplication.setActiveWindow(act)

Parameters

act – PySide6.QtWidgets.QWidget

See also

activeWindow()

PySide6.QtWidgets.QApplication.setAutoSipEnabled(enabled)

Parameters

enabled – bool

See also

autoSipEnabled()

static PySide6.QtWidgets.QApplication.setCursorFlashTime(arg__1)

Parameters

arg__1 – int

See also

cursorFlashTime()

static PySide6.QtWidgets.QApplication.setDoubleClickInterval(arg__1)

Parameters

arg__1 – int

See also

doubleClickInterval()

static PySide6.QtWidgets.QApplication.setEffectEnabled(arg__1[, enable=true])

Parameters

• arg__1 – UIEffect

• enable – bool

static PySide6.QtWidgets.QApplication.setFont(arg__1[, className=None])

Parameters

• arg__1 – PySide6.QtGui.QFont

• className – str

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

static PySide6.QtWidgets.QApplication.setKeyboardInputInterval(arg__1)

Parameters

arg__1 – int

See also

keyboardInputInterval()

static PySide6.QtWidgets.QApplication.setPalette(arg__1[, className=None])

Parameters

• arg__1 – PySide6.QtGui.QPalette

• className – str

Changes the application palette to palette.

If className is passed, the change applies only to widgets that inherit className (as reported by 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 polish() .

Warning

Do not use this function in conjunction with 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

setPalette() palette() polish()

static PySide6.QtWidgets.QApplication.setStartDragDistance(l)

Parameters

l – int

See also

startDragDistance()

static PySide6.QtWidgets.QApplication.setStartDragTime(ms)

Parameters

ms – int

See also

startDragTime()

static PySide6.QtWidgets.QApplication.setStyle(arg__1)

Parameters

arg__1 – PySide6.QtWidgets.QStyle

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:

QApplication.setStyle(QWindowsStyle())

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 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()

static PySide6.QtWidgets.QApplication.setStyle(arg__1)

Parameters

arg__1 – str

Return type

PySide6.QtWidgets.QStyle

PySide6.QtWidgets.QApplication.setStyleSheet(sheet)

Parameters

sheet – str

See also

styleSheet()

static PySide6.QtWidgets.QApplication.setWheelScrollLines(arg__1)

Parameters

arg__1 – int

See also

wheelScrollLines()

static PySide6.QtWidgets.QApplication.startDragDistance()

Return type

int

See also

setStartDragDistance()

static PySide6.QtWidgets.QApplication.startDragTime()

Return type

int

See also

setStartDragTime()

static PySide6.QtWidgets.QApplication.style()

Return type

PySide6.QtWidgets.QStyle

Returns the application’s style object.

See also

setStyle() QStyle

PySide6.QtWidgets.QApplication.styleSheet()

Return type

str

See also

setStyleSheet()

static PySide6.QtWidgets.QApplication.topLevelAt(x, y)

Parameters

• x – int

• y – int

Return type

PySide6.QtWidgets.QWidget

static PySide6.QtWidgets.QApplication.topLevelWidgets()

Return type

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:

def showAllHiddenTopLevelWidgets():
    for widget in QApplication.topLevelWidgets():
        if widget.isHidden():
            widget.show()

See also

allWidgets() isHidden()

static PySide6.QtWidgets.QApplication.wheelScrollLines()

Return type

int

See also

setWheelScrollLines()

static PySide6.QtWidgets.QApplication.widgetAt(p)

Parameters

p – PySide6.QtCore.QPoint

Return type

PySide6.QtWidgets.QWidget

static PySide6.QtWidgets.QApplication.widgetAt(x, y)

Parameters

• x – int

• y – int

Return type

PySide6.QtWidgets.QWidget