class QGuiApplication

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

Inheritance diagram of PySide6.QtGui.QGuiApplication

Inherited by: QApplication

Synopsis

Properties

Methods

Signals

Static functions

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

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(), notify() .

Windows

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

Advanced cursor handling

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

Session management

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

Miscellaneous

startingUp(), closingDown().

See also

QCoreApplicationQAbstractEventDispatcherQEventLoop

Note

Properties can be used directly when from __feature__ import true_property is used or via accessor functions otherwise.

property applicationDisplayNameᅟ: str

This property holds the user-visible name of this application.

This name is shown to the user, for instance in window titles. It can be translated, if necessary.

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

See also

applicationName

Access functions:
property desktopFileNameᅟ: str

This property holds the base name of the desktop entry for this application.

This is the file name, without the full path or the trailing “.desktop” extension of the desktop entry that represents this application according to the freedesktop desktop entry specification.

This property gives a precise indication of what desktop entry represents the application and it is needed by the windowing system to retrieve such information without resorting to imprecise heuristics.

The latest version of the freedesktop desktop entry specification can be obtained here .

Access functions:
property layoutDirectionᅟ: Qt.LayoutDirection

This property holds the default layout direction for this application.

On system start-up, or when the direction is explicitly set to Qt::LayoutDirectionAuto, the default layout direction depends on the application’s language.

The notifier signal was introduced in Qt 5.4.

Access functions:
property platformNameᅟ: str

This property holds The name of the underlying platform plugin..

The QPA platform plugins are located in qtbase\src\plugins\platforms. At the time of writing, the following platform plugin names are supported:

  • android

  • cocoa is a platform plugin for macOS.

  • directfb

  • eglfs is a platform plugin for running Qt5 applications on top of EGL and OpenGL ES 2.0 without an actual windowing system (like X11 or Wayland). For more information, see EGLFS.

  • ios (also used for tvOS)

  • linuxfb writes directly to the framebuffer. For more information, see LinuxFB.

  • minimal is provided as an examples for developers who want to write their own platform plugins. However, you can use the plugin to run GUI applications in environments without a GUI, such as servers.

  • minimalegl is an example plugin.

  • offscreen

  • qnx

  • windows

  • wayland is a platform plugin for the Wayland display server protocol, used on some Linux desktops and embedded systems.

  • xcb is a plugin for the X11 window system, used on some desktop Linux platforms.

Note

Calling this function without a QGuiApplication will return the default platform name, if available. The default platform name is not affected by the -platform command line option, or the QT_QPA_PLATFORM environment variable.

For more information about the platform plugins for embedded Linux devices, see Qt for Embedded Linux.

Access functions:
property primaryScreenᅟ: QScreen

This property holds the primary (or default) screen of the application..

This will be the screen where QWindows are initially shown, unless otherwise specified.

The primaryScreenChanged signal was introduced in Qt 5.6.

See also

screens()

Access functions:
property quitOnLastWindowClosedᅟ: bool

This property holds whether the application implicitly quits when the last window is closed..

The default is true.

If this property is true, the application will attempt to quit when the last visible primary window (i.e. top level window with no transient parent) is closed.

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

See also

close()

Access functions:
property windowIconᅟ: QIcon

This property holds the default window icon.

See also

setIcon() Setting the Application Icon

Access functions:
__init__()
__init__(arg__1)
Parameters:

arg__1 – list of strings

static allWindows()
Return type:

.list of QWindow

Returns a list of all the windows in the application.

The list is empty if there are no windows.

static applicationDisplayName()
Return type:

str

See also

setApplicationDisplayName()

Getter of property applicationDisplayNameᅟ .

applicationDisplayNameChanged()

Notification signal of property applicationDisplayNameᅟ .

static 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.

applicationStateChanged(state)
Parameters:

state – ApplicationState

This signal is emitted when the state of the application changes.

static changeOverrideCursor(arg__1)
Parameters:

arg__1 – QCursor

static clipboard()
Return type:

QClipboard

commitDataRequest(sessionManager)
Parameters:

sessionManager – QSessionManager

This signal deals with session management. It is emitted when the QSessionManager wants the application to commit all its data.

Usually this means saving all open files, after getting permission from the user. Furthermore you may want to provide a means by which the user can cancel the shutdown.

You should not exit the application within this signal. Instead, the session manager may or may not do this afterwards, depending on the context.

Warning

Within this signal, no user interaction is possible, unless you ask the manager for explicit permission. See allowsInteraction() and allowsErrorInteraction() for details and example usage.

Note

You should use Qt::DirectConnection when connecting to this signal.

See also

isSessionRestored() sessionId() saveStateRequest() Session Management

static desktopFileName()
Return type:

str

See also

setDesktopFileName()

Getter of property desktopFileNameᅟ .

static desktopSettingsAware()
Return type:

bool

devicePixelRatio()
Return type:

float

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.

exec_()
Return type:

int

static 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.

focusObjectChanged(focusObject)
Parameters:

focusObject – QObject

This signal is emitted when final receiver of events tied to focus is changed. focusObject is the new receiver.

See also

focusObject()

static focusWindow()
Return type:

QWindow

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

focusWindowChanged(focusWindow)
Parameters:

focusWindow – QWindow

This signal is emitted when the focused window changes. focusWindow is the new focused window.

See also

focusWindow()

static font()
Return type:

QFont

fontChanged(font)
Parameters:

font – QFont

Note

This function is deprecated.

Handle QEvent::ApplicationFontChange instead.

This signal is emitted when the font of the application changes. Use QEvent::ApplicationFontChanged instead.

See also

font()

fontDatabaseChanged()

This signal is emitted when the available fonts have changed.

This can happen when application fonts are added or removed, or when the system fonts change.

static highDpiScaleFactorRoundingPolicy()
Return type:

HighDpiScaleFactorRoundingPolicy

static inputMethod()
Return type:

QInputMethod

static isLeftToRight()
Return type:

bool

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

static isRightToLeft()
Return type:

bool

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

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.

isSessionRestored()
Return type:

bool

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

static keyboardModifiers()
Return type:

Combination of KeyboardModifier

Returns the current state of the modifier keys on the keyboard. The current state is updated synchronously as the event queue is emptied of events that will spontaneously change the keyboard state (QEvent::KeyPress and QEvent::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 Qt::NoModifier is returned.

lastWindowClosed()

This signal is emitted from exec() when the last visible primary window (i.e. top level window with no transient parent) is closed.

By default, QGuiApplication quits after this signal is emitted. This feature can be turned off by setting quitOnLastWindowClosed to false.

static layoutDirection()
Return type:

LayoutDirection

See also

setLayoutDirection()

Getter of property layoutDirectionᅟ .

layoutDirectionChanged(direction)
Parameters:

direction – LayoutDirection

Notification signal of property layoutDirectionᅟ .

static 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 Qt::WindowModal or Qt::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

setModality()

static mouseButtons()
Return type:

Combination of MouseButton

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 (QEvent::MouseButtonPress and QEvent::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 Qt::NoButton is returned.

nativeInterface()
Return type:

object

static 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 palette()
Return type:

QPalette

paletteChanged(pal)
Parameters:

pal – QPalette

Note

This function is deprecated.

Handle QEvent::ApplicationPaletteChange instead.

This signal is emitted when the palette of the application changes. Use QEvent::ApplicationPaletteChanged instead.

See also

palette()

static platformFunction(function)
Parameters:

function – QByteArray

Return type:

QFunctionPointer

static platformName()
Return type:

str

Getter of property platformNameᅟ .

static primaryScreen()
Return type:

QScreen

Getter of property primaryScreenᅟ .

primaryScreenChanged(screen)
Parameters:

screen – QScreen

Notification signal of property primaryScreenᅟ .

static queryKeyboardModifiers()
Return type:

Combination of KeyboardModifier

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 quitOnLastWindowClosed()
Return type:

bool

See also

setQuitOnLastWindowClosed()

Getter of property quitOnLastWindowClosedᅟ .

static restoreOverrideCursor()

Undoes the last setOverrideCursor() .

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

saveStateRequest(sessionManager)
Parameters:

sessionManager – QSessionManager

This signal deals with session management. It is invoked when the session manager wants the application to preserve its state for a future session.

For example, a text editor would create a temporary file that includes the current contents of its edit buffers, the location of the cursor and other aspects of the current editing session.

You should never exit the application within this signal. Instead, the session manager may or may not do this afterwards, depending on the context. Furthermore, most session managers will very likely request a saved state immediately after the application has been started. This permits the session manager to learn about the application’s restart policy.

Warning

Within this signal, no user interaction is possible, unless you ask the manager for explicit permission. See allowsInteraction() and allowsErrorInteraction() for details.

Note

You should use Qt::DirectConnection when connecting to this signal.

See also

isSessionRestored() sessionId() commitDataRequest() Session Management

screenAdded(screen)
Parameters:

screen – QScreen

This signal is emitted whenever a new screen screen has been added to the system.

static screenAt(point)
Parameters:

point – QPoint

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. If you wish to search only the virtual desktop siblings of a known screen (for example siblings of the screen of your application window QWidget::windowHandle()->screen()), use virtualSiblingAt() .

screenRemoved(screen)
Parameters:

screen – QScreen

This signal is emitted whenever a screen is removed from the system. It provides an opportunity to manage the windows on the screen before Qt falls back to moving them to the primary screen.

static screens()
Return type:

.list of QScreen

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

sessionId()
Return type:

str

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.

sessionKey()
Return type:

str

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 setApplicationDisplayName(name)
Parameters:

name – str

See also

applicationDisplayName()

Setter of property applicationDisplayNameᅟ .

setBadgeNumber(number)
Parameters:

number – int

Sets the application’s badge to number.

Useful for providing feedback to the user about the number of unread messages or similar.

The badge will be overlaid on the application’s icon in the Dock on macOS, the home screen icon on iOS, or the task bar on Windows and Linux.

If the number is outside the range supported by the platform, the number will be clamped to the supported range. If the number does not fit within the badge, the number may be visually elided.

Setting the number to 0 will clear the badge.

See also

applicationName

static setDesktopFileName(name)
Parameters:

name – str

See also

desktopFileName()

Setter of property desktopFileNameᅟ .

static setDesktopSettingsAware(on)
Parameters:

on – bool

static setFont(arg__1)
Parameters:

arg__1 – QFont

static setHighDpiScaleFactorRoundingPolicy(policy)
Parameters:

policy – HighDpiScaleFactorRoundingPolicy

static setLayoutDirection(direction)
Parameters:

direction – LayoutDirection

See also

layoutDirection()

Setter of property layoutDirectionᅟ .

static setOverrideCursor(arg__1)
Parameters:

arg__1 – QCursor

Return type:

QtGuiHelper::QOverrideCursorGuard*

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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 setOverrideCursor() is called.

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

Every setOverrideCursor() 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()

See also

overrideCursor() restoreOverrideCursor() setCursor()

static setPalette(pal)
Parameters:

pal – QPalette

static setQuitOnLastWindowClosed(quit)
Parameters:

quit – bool

See also

quitOnLastWindowClosed()

Setter of property quitOnLastWindowClosedᅟ .

static setWindowIcon(icon)
Parameters:

icon – QIcon

See also

windowIcon()

Setter of property windowIconᅟ .

static styleHints()
Return type:

QStyleHints

static sync()
static topLevelAt(pos)
Parameters:

pos – QPoint

Return type:

QWindow

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

static topLevelWindows()
Return type:

.list of QWindow

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

See also

allWindows()

static windowIcon()
Return type:

QIcon

See also

setWindowIcon()

Getter of property windowIconᅟ .