QGuiApplication

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

Inheritance diagram of PySide2.QtGui.QGuiApplication

Inherited by: QApplication

Synopsis

Functions

Signals

Detailed Description

QGuiApplication contains the main event loop, where all events from the window system and other sources are processed and dispatched. It also handles the application’s initialization and finalization, and provides session management. In addition, QGuiApplication handles most of the system-wide and application-wide settings.

For any GUI application using Qt, there is precisely one QGuiApplication object no matter whether the application has 0, 1, 2 or more windows at any given time. For non-GUI Qt applications, use QCoreApplication instead, as it does not depend on the Qt GUI module. For QWidget based Qt applications, use QApplication instead, as it provides some functionality needed for creating QWidget instances.

The QGuiApplication object is accessible through the instance() function, which returns a pointer equivalent to the global qApp pointer.

QGuiApplication ‘s main areas of responsibility are:

  • It initializes the application with the user’s desktop settings, such as palette() , font() and styleHints() . 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. You can send your own events to windows by using sendEvent() and postEvent() .

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

  • 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 window is at a certain position using topLevelAt() , get a list of topLevelWindows() , etc.

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

  • It provides support for sophisticated session management. This makes it possible for applications to terminate gracefully when the user logs out, to cancel a shutdown process if termination isn’t possible and even to preserve the entire application’s state for a future session. See isSessionRestored() , sessionId() and commitDataRequest() and saveStateRequest() for details.

Since the QGuiApplication object does so much initialization, it must be created before any other objects related to the user interface are created. QGuiApplication 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() , styleHints() , palette() , setPalette() , font() , setFont() .

Event handling

exec() , processEvents() , exit() , quit() . sendEvent() , postEvent() , sendPostedEvents() , removePostedEvents() , hasPendingEvents() , notify() .

Windows

allWindows() , topLevelWindows() , focusWindow() , clipboard() , topLevelAt() .

Advanced cursor handling

overrideCursor() , setOverrideCursor() , restoreOverrideCursor() .

Session management

isSessionRestored() , sessionId() , commitDataRequest() , saveStateRequest() .

Miscellaneous

startingUp() , closingDown() .

class QGuiApplication

QGuiApplication(arg__1)

Parameters

arg__1 – list of strings

static PySide2.QtGui.QGuiApplication.allWindows()
Return type

Returns a list of all the windows in the application.

The list is empty if there are no windows.

static PySide2.QtGui.QGuiApplication.applicationDisplayName()
Return type

unicode

PySide2.QtGui.QGuiApplication.applicationDisplayNameChanged()
static PySide2.QtGui.QGuiApplication.applicationState()
Return type

ApplicationState

Returns the current state of the application.

You can react to application state changes to perform actions such as stopping/resuming CPU-intensive tasks, freeing/loading resources or saving/restoring application data.

PySide2.QtGui.QGuiApplication.applicationStateChanged(state)
Parameters

stateApplicationState

static PySide2.QtGui.QGuiApplication.changeOverrideCursor(arg__1)
Parameters

arg__1QCursor

Changes the currently active application override cursor to cursor .

This function has no effect if setOverrideCursor() was not called.

static PySide2.QtGui.QGuiApplication.clipboard()
Return type

QClipboard

Returns the object for interacting with the clipboard.

PySide2.QtGui.QGuiApplication.commitDataRequest(sessionManager)
Parameters

sessionManagerQSessionManager

static PySide2.QtGui.QGuiApplication.desktopFileName()
Return type

unicode

static PySide2.QtGui.QGuiApplication.desktopSettingsAware()
Return type

bool

Returns true if Qt is set to use the system’s standard colors, fonts, etc.; otherwise returns false . The default is true .

PySide2.QtGui.QGuiApplication.devicePixelRatio()
Return type

qreal

Returns the highest screen device pixel ratio found on the system. This is the ratio between physical pixels and device-independent pixels.

Use this function only when you don’t know which window you are targeting. If you do know the target window, use devicePixelRatio() instead.

static PySide2.QtGui.QGuiApplication.focusObject()
Return type

QObject

Returns the QObject in currently active window that will be final receiver of events tied to focus, such as key events.

PySide2.QtGui.QGuiApplication.focusObjectChanged(focusObject)
Parameters

focusObjectQObject

static PySide2.QtGui.QGuiApplication.focusWindow()
Return type

QWindow

Returns the QWindow that receives events tied to focus, such as key events.

PySide2.QtGui.QGuiApplication.focusWindowChanged(focusWindow)
Parameters

focusWindowQWindow

static PySide2.QtGui.QGuiApplication.font()
Return type

QFont

Returns the default application font.

See also

setFont()

PySide2.QtGui.QGuiApplication.fontChanged(font)
Parameters

fontQFont

PySide2.QtGui.QGuiApplication.fontDatabaseChanged()
static PySide2.QtGui.QGuiApplication.inputMethod()
Return type

QInputMethod

returns the input method.

The input method returns properties about the state and position of the virtual keyboard. It also provides information about the position of the current focused input element.

See also

QInputMethod

static PySide2.QtGui.QGuiApplication.isFallbackSessionManagementEnabled()
Return type

bool

Returns whether QGuiApplication will use fallback session management.

The default is true .

If this is true and the session manager allows user interaction, QGuiApplication will try to close toplevel windows after commitDataRequest() has been emitted. If a window cannot be closed, session shutdown will be canceled and the application will keep running.

Fallback session management only benefits applications that have an “are you sure you want to close this window?” feature or other logic that prevents closing a toplevel window depending on certain conditions, and that do nothing to explicitly implement session management. In applications that do implement session management using the proper session management API, fallback session management interferes and may break session management logic.

Warning

If all windows are closed due to fallback session management and quitOnLastWindowClosed() is true , the application will quit before it is explicitly instructed to quit through the platform’s session management protocol. That violation of protocol may prevent the platform session manager from saving application state.

static PySide2.QtGui.QGuiApplication.isLeftToRight()
Return type

bool

Returns true if the application’s layout direction is LeftToRight ; otherwise returns false .

static PySide2.QtGui.QGuiApplication.isRightToLeft()
Return type

bool

Returns true if the application’s layout direction is RightToLeft ; otherwise returns false .

PySide2.QtGui.QGuiApplication.isSavingSession()
Return type

bool

Returns true if the application is currently saving the session; otherwise returns false .

This is true when commitDataRequest() and saveStateRequest() are emitted, but also when the windows are closed afterwards by session management.

PySide2.QtGui.QGuiApplication.isSessionRestored()
Return type

bool

Returns true if the application has been restored from an earlier session; otherwise returns false .

static PySide2.QtGui.QGuiApplication.keyboardModifiers()
Return type

KeyboardModifiers

Returns the current state of the modifier keys on the keyboard. The current state is updated sychronously as the event queue is emptied of events that will spontaneously change the keyboard state ( KeyPress and KeyRelease events).

It should be noted this may not reflect the actual keys held on the input device at the time of calling but rather the modifiers as last reported in one of the above events. If no keys are being held NoModifier is returned.

PySide2.QtGui.QGuiApplication.lastWindowClosed()
static PySide2.QtGui.QGuiApplication.layoutDirection()
Return type

LayoutDirection

PySide2.QtGui.QGuiApplication.layoutDirectionChanged(direction)
Parameters

directionLayoutDirection

static PySide2.QtGui.QGuiApplication.modalWindow()
Return type

QWindow

Returns the most recently shown modal window. If no modal windows are visible, this function returns zero.

A modal window is a window which has its modality property set to WindowModal or ApplicationModal . A modal window must be closed before the user can continue with other parts of the program.

Modal window are organized in a stack. This function returns the modal window at the top of the stack.

See also

WindowModality setModality()

static PySide2.QtGui.QGuiApplication.mouseButtons()
Return type

MouseButtons

Returns the current state of the buttons on the mouse. The current state is updated synchronously as the event queue is emptied of events that will spontaneously change the mouse state ( MouseButtonPress and MouseButtonRelease events).

It should be noted this may not reflect the actual buttons held on the input device at the time of calling but rather the mouse buttons as last reported in one of the above events. If no mouse buttons are being held NoButton is returned.

static PySide2.QtGui.QGuiApplication.overrideCursor()
Return type

QCursor

Returns the active application override cursor.

This function returns None if no application cursor has been defined (i.e. the internal cursor stack is empty).

static PySide2.QtGui.QGuiApplication.palette()
Return type

QPalette

Returns the default application palette.

See also

setPalette()

PySide2.QtGui.QGuiApplication.paletteChanged(pal)
Parameters

palQPalette

static PySide2.QtGui.QGuiApplication.platformName()
Return type

unicode

static PySide2.QtGui.QGuiApplication.primaryScreen()
Return type

QScreen

PySide2.QtGui.QGuiApplication.primaryScreenChanged(screen)
Parameters

screenQScreen

static PySide2.QtGui.QGuiApplication.queryKeyboardModifiers()
Return type

KeyboardModifiers

Queries and returns the state of the modifier keys on the keyboard. Unlike keyboardModifiers , this method returns the actual keys held on the input device at the time of calling the method.

It does not rely on the keypress events having been received by this process, which makes it possible to check the modifiers while moving a window, for instance. Note that in most cases, you should use keyboardModifiers() , which is faster and more accurate since it contains the state of the modifiers as they were when the currently processed event was received.

static PySide2.QtGui.QGuiApplication.quitOnLastWindowClosed()
Return type

bool

static PySide2.QtGui.QGuiApplication.restoreOverrideCursor()

Undoes the last setOverrideCursor() .

If setOverrideCursor() has been called twice, calling will activate the first cursor set. Calling this function a second time restores the original widgets’ cursors.

PySide2.QtGui.QGuiApplication.saveStateRequest(sessionManager)
Parameters

sessionManagerQSessionManager

PySide2.QtGui.QGuiApplication.screenAdded(screen)
Parameters

screenQScreen

static PySide2.QtGui.QGuiApplication.screenAt(point)
Parameters

pointQPoint

Return type

QScreen

Returns the screen at point , or None if outside of any screen.

The point is in relation to the virtualGeometry() of each set of virtual siblings. If the point maps to more than one set of virtual siblings the first match is returned.

PySide2.QtGui.QGuiApplication.screenRemoved(screen)
Parameters

screenQScreen

static PySide2.QtGui.QGuiApplication.screens()
Return type

Returns a list of all the screens associated with the windowing system the application is connected to.

PySide2.QtGui.QGuiApplication.sessionId()
Return type

unicode

Returns the current session’s identifier.

If the application has been restored from an earlier session, this identifier is the same as it was in that previous session. The session identifier is guaranteed to be unique both for different applications and for different instances of the same application.

PySide2.QtGui.QGuiApplication.sessionKey()
Return type

unicode

Returns the session key in the current session.

If the application has been restored from an earlier session, this key is the same as it was when the previous session ended.

The session key changes every time the session is saved. If the shutdown process is cancelled, another session key will be used when shutting down again.

static PySide2.QtGui.QGuiApplication.setApplicationDisplayName(name)
Parameters

name – unicode

static PySide2.QtGui.QGuiApplication.setDesktopFileName(name)
Parameters

name – unicode

static PySide2.QtGui.QGuiApplication.setDesktopSettingsAware(on)
Parameters

onbool

Sets whether Qt should use the system’s standard colors, fonts, etc., to on . By default, this is true .

This function must be called before creating the QGuiApplication object, like this:

int main(int argc, char *argv[])
{
    QApplication::setDesktopSettingsAware(false);
    QApplication app(argc, argv);
    ...
    return app.exec();
}
static PySide2.QtGui.QGuiApplication.setFallbackSessionManagementEnabled(arg__1)
Parameters

arg__1bool

Sets whether QGuiApplication will use fallback session management to enabled .

static PySide2.QtGui.QGuiApplication.setFont(arg__1)
Parameters

arg__1QFont

Changes the default application font to font .

See also

font()

static PySide2.QtGui.QGuiApplication.setLayoutDirection(direction)
Parameters

directionLayoutDirection

static PySide2.QtGui.QGuiApplication.setOverrideCursor(arg__1)
Parameters

arg__1QCursor

Sets the application override cursor to cursor .

Application override cursors are intended for showing the user that the application is in a special state, for example during an operation that might take some time.

This cursor will be displayed in all the application’s widgets until restoreOverrideCursor() or another is called.

Application cursors are stored on an internal stack. pushes the cursor onto the stack, and restoreOverrideCursor() pops the active cursor off the stack. changeOverrideCursor() changes the curently active application override cursor.

Every must eventually be followed by a corresponding restoreOverrideCursor() , otherwise the stack will never be emptied.

Example:

QGuiApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
calculateHugeMandelbrot();              // lunch time...
QGuiApplication::restoreOverrideCursor();
static PySide2.QtGui.QGuiApplication.setPalette(pal)
Parameters

palQPalette

Changes the default application palette to pal .

See also

palette()

static PySide2.QtGui.QGuiApplication.setQuitOnLastWindowClosed(quit)
Parameters

quitbool

static PySide2.QtGui.QGuiApplication.setWindowIcon(icon)
Parameters

iconQIcon

See also

windowIcon()

static PySide2.QtGui.QGuiApplication.styleHints()
Return type

QStyleHints

Returns the application’s style hints.

The style hints encapsulate a set of platform dependent properties such as double click intervals, full width selection and others.

The hints can be used to integrate tighter with the underlying platform.

See also

QStyleHints

static PySide2.QtGui.QGuiApplication.sync()

Function that can be used to sync Qt state with the Window Systems state.

This function will first empty Qts events by calling processEvents() , then the platform plugin will sync up with the windowsystem, and finally Qts events will be delived by another call to processEvents() ;

This function is timeconsuming and its use is discouraged.

static PySide2.QtGui.QGuiApplication.topLevelAt(pos)
Parameters

posQPoint

Return type

QWindow

Returns the top level window at the given position pos , if any.

static PySide2.QtGui.QGuiApplication.topLevelWindows()
Return type

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

See also

allWindows()

static PySide2.QtGui.QGuiApplication.windowIcon()
Return type

QIcon

See also

setWindowIcon()