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

Inherited by: QApplication
Synopsis¶
Functions¶
def
applicationStateChanged
(state)def
commitDataRequest
(sessionManager)def
devicePixelRatio
()def
focusObjectChanged
(focusObject)def
focusWindowChanged
(focusWindow)def
fontChanged
(font)def
fontDatabaseChanged
()def
isSavingSession
()def
isSessionRestored
()def
lastWindowClosed
()def
layoutDirectionChanged
(direction)def
paletteChanged
(pal)def
primaryScreenChanged
(screen)def
saveStateRequest
(sessionManager)def
screenAdded
(screen)def
screenRemoved
(screen)def
sessionId
()def
sessionKey
()
Static functions¶
def
allWindows
()def
applicationDisplayName
()def
applicationState
()def
changeOverrideCursor
(arg__1)def
clipboard
()def
desktopFileName
()def
desktopSettingsAware
()def
focusObject
()def
focusWindow
()def
font
()def
inputMethod
()def
isLeftToRight
()def
isRightToLeft
()def
keyboardModifiers
()def
layoutDirection
()def
modalWindow
()def
mouseButtons
()def
overrideCursor
()def
palette
()def
platformName
()def
primaryScreen
()def
queryKeyboardModifiers
()def
quitOnLastWindowClosed
()def
restoreOverrideCursor
()def
screenAt
(point)def
screens
()def
setApplicationDisplayName
(name)def
setDesktopFileName
(name)def
setDesktopSettingsAware
(on)def
setFont
(arg__1)def
setHighDpiScaleFactorRoundingPolicy
(policy)def
setLayoutDirection
(direction)def
setOverrideCursor
(arg__1)def
setPalette
(pal)def
setQuitOnLastWindowClosed
(quit)def
setWindowIcon
(icon)def
styleHints
()def
sync
()def
topLevelAt
(pos)def
topLevelWindows
()def
windowIcon
()
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()
andstyleHints()
. 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()
andpostEvent()
.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 oftopLevelWindows()
, 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()
andcommitDataRequest()
andsaveStateRequest()
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
QCoreApplication
QAbstractEventDispatcher
QEventLoop
-
class
PySide6.QtGui.
QGuiApplication
¶ PySide6.QtGui.QGuiApplication(arg__1)
- Parameters
arg__1 – list of strings
-
static
PySide6.QtGui.QGuiApplication.
allWindows
()¶ - Return type
Returns a list of all the windows in the application.
The list is empty if there are no windows.
See also
-
static
PySide6.QtGui.QGuiApplication.
applicationDisplayName
()¶ - Return type
str
See also
-
PySide6.QtGui.QGuiApplication.
applicationDisplayNameChanged
()¶
-
static
PySide6.QtGui.QGuiApplication.
applicationState
()¶ - Return type
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.
-
PySide6.QtGui.QGuiApplication.
applicationStateChanged
(state)¶ - Parameters
state –
ApplicationState
This signal is emitted when the state
of the application changes.
See also
-
static
PySide6.QtGui.QGuiApplication.
changeOverrideCursor
(arg__1)¶ - Parameters
arg__1 –
PySide6.QtGui.QCursor
Changes the currently active application override cursor to cursor
.
This function has no effect if setOverrideCursor()
was not called.
See also
setOverrideCursor()
overrideCursor()
restoreOverrideCursor()
setCursor()
-
static
PySide6.QtGui.QGuiApplication.
clipboard
()¶ - Return type
Returns the object for interacting with the clipboard.
-
PySide6.QtGui.QGuiApplication.
commitDataRequest
(sessionManager)¶ - Parameters
sessionManager –
PySide6.QtGui.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 DirectConnection
when connecting to this signal.
See also
isSessionRestored()
sessionId()
saveStateRequest()
Session Management
-
static
PySide6.QtGui.QGuiApplication.
desktopFileName
()¶ - Return type
str
See also
-
static
PySide6.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
.
See also
-
PySide6.QtGui.QGuiApplication.
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.
See also
-
static
PySide6.QtGui.QGuiApplication.
focusObject
()¶ - Return type
Returns the QObject
in currently active window that will be final receiver of events tied to focus, such as key events.
-
PySide6.QtGui.QGuiApplication.
focusObjectChanged
(focusObject)¶ - Parameters
focusObject –
PySide6.QtCore.QObject
This signal is emitted when final receiver of events tied to focus is changed. focusObject
is the new receiver.
See also
-
static
PySide6.QtGui.QGuiApplication.
focusWindow
()¶ - Return type
Returns the QWindow
that receives events tied to focus, such as key events.
-
PySide6.QtGui.QGuiApplication.
focusWindowChanged
(focusWindow)¶ - Parameters
focusWindow –
PySide6.QtGui.QWindow
This signal is emitted when the focused window changes. focusWindow
is the new focused window.
See also
-
static
PySide6.QtGui.QGuiApplication.
font
()¶ - Return type
Returns the default application font.
See also
-
PySide6.QtGui.QGuiApplication.
fontChanged
(font)¶ - Parameters
font –
PySide6.QtGui.QFont
Note
This function is deprecated.
This signal is emitted when the font
of the application changes. Use QEvent::ApplicationFontChanged instead.
See also
-
PySide6.QtGui.QGuiApplication.
fontDatabaseChanged
()¶
This signal is emitted when application fonts are loaded or removed.
-
static
PySide6.QtGui.QGuiApplication.
highDpiScaleFactorRoundingPolicy
()¶ - Return type
Returns the high-DPI scale factor rounding policy.
-
static
PySide6.QtGui.QGuiApplication.
inputMethod
()¶ - Return type
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
-
static
PySide6.QtGui.QGuiApplication.
isLeftToRight
()¶ - Return type
bool
Returns true
if the application’s layout direction is LeftToRight
; otherwise returns false
.
See also
-
static
PySide6.QtGui.QGuiApplication.
isRightToLeft
()¶ - Return type
bool
Returns true
if the application’s layout direction is RightToLeft
; otherwise returns false
.
See also
-
PySide6.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.
-
PySide6.QtGui.QGuiApplication.
isSessionRestored
()¶ - Return type
bool
Returns true
if the application has been restored from an earlier session; otherwise returns false
.
-
static
PySide6.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.
See also
-
PySide6.QtGui.QGuiApplication.
lastWindowClosed
()¶
This signal is emitted from exec()
when the last visible primary window (i.e. window with no parent) is closed.
By default, QGuiApplication
quits after this signal is emitted. This feature can be turned off by setting quitOnLastWindowClosed
to false
.
See also
-
static
PySide6.QtGui.QGuiApplication.
layoutDirection
()¶ - Return type
See also
-
PySide6.QtGui.QGuiApplication.
layoutDirectionChanged
(direction)¶ - Parameters
direction –
LayoutDirection
-
static
PySide6.QtGui.QGuiApplication.
modalWindow
()¶ - Return type
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
PySide6.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.
See also
-
static
PySide6.QtGui.QGuiApplication.
overrideCursor
()¶ - Return type
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
PySide6.QtGui.QGuiApplication.
palette
()¶ - Return type
Returns the current application palette.
Roles that have not been explicitly set will reflect the system’s platform theme.
See also
-
PySide6.QtGui.QGuiApplication.
paletteChanged
(pal)¶ - Parameters
pal –
PySide6.QtGui.QPalette
Note
This function is deprecated.
This signal is emitted when the palette
of the application changes. Use QEvent::ApplicationPaletteChanged instead.
See also
-
static
PySide6.QtGui.QGuiApplication.
platformName
()¶ - Return type
str
-
static
PySide6.QtGui.QGuiApplication.
primaryScreen
()¶ - Return type
-
PySide6.QtGui.QGuiApplication.
primaryScreenChanged
(screen)¶ - Parameters
screen –
PySide6.QtGui.QScreen
-
static
PySide6.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.
See also
-
static
PySide6.QtGui.QGuiApplication.
quitOnLastWindowClosed
()¶ - Return type
bool
See also
-
static
PySide6.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.
See also
-
PySide6.QtGui.QGuiApplication.
saveStateRequest
(sessionManager)¶ - Parameters
sessionManager –
PySide6.QtGui.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 DirectConnection
when connecting to this signal.
See also
isSessionRestored()
sessionId()
commitDataRequest()
Session Management
-
PySide6.QtGui.QGuiApplication.
screenAdded
(screen)¶ - Parameters
screen –
PySide6.QtGui.QScreen
This signal is emitted whenever a new screen screen
has been added to the system.
See also
-
static
PySide6.QtGui.QGuiApplication.
screenAt
(point)¶ - Parameters
point –
PySide6.QtCore.QPoint
- Return type
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()
.
-
PySide6.QtGui.QGuiApplication.
screenRemoved
(screen)¶ - Parameters
screen –
PySide6.QtGui.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.
See also
screens()
screenAdded()
destroyed()
setScreen()
-
static
PySide6.QtGui.QGuiApplication.
screens
()¶ - Return type
Returns a list of all the screens associated with the windowing system the application is connected to.
-
PySide6.QtGui.QGuiApplication.
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.
-
PySide6.QtGui.QGuiApplication.
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
PySide6.QtGui.QGuiApplication.
setApplicationDisplayName
(name)¶ - Parameters
name – str
See also
-
static
PySide6.QtGui.QGuiApplication.
setDesktopFileName
(name)¶ - Parameters
name – str
See also
-
static
PySide6.QtGui.QGuiApplication.
setDesktopSettingsAware
(on)¶ - Parameters
on – bool
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(); }See also
-
static
PySide6.QtGui.QGuiApplication.
setFont
(arg__1)¶ - Parameters
arg__1 –
PySide6.QtGui.QFont
Changes the default application font to font
.
See also
-
static
PySide6.QtGui.QGuiApplication.
setHighDpiScaleFactorRoundingPolicy
(policy)¶ - Parameters
policy –
HighDpiScaleFactorRoundingPolicy
Sets the high-DPI scale factor rounding policy for the application. The policy
decides how non-integer scale factors (such as Windows 150%) are handled.
The two principal options are whether fractional scale factors should be rounded to an integer or not. Keeping the scale factor as-is will make the user interface size match the OS setting exactly, but may cause painting errors, for example with the Windows style.
If rounding is wanted, then which type of rounding should be decided next. Mathematically correct rounding is supported but may not give the best visual results: Consider if you want to render 1.5x as 1x (“small UI”) or as 2x (“large UI”). See the HighDpiScaleFactorRoundingPolicy
enum for a complete list of all options.
This function must be called before creating the application object. The highDpiScaleFactorRoundingPolicy()
accessor will reflect the environment, if set.
The default value is Qt::HighDpiScaleFactorRoundingPolicy::PassThrough.
See also
-
static
PySide6.QtGui.QGuiApplication.
setLayoutDirection
(direction)¶ - Parameters
direction –
LayoutDirection
See also
-
static
PySide6.QtGui.QGuiApplication.
setOverrideCursor
(arg__1)¶ - Parameters
arg__1 –
PySide6.QtGui.QCursor
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();See also
overrideCursor()
restoreOverrideCursor()
changeOverrideCursor()
setCursor()
-
static
PySide6.QtGui.QGuiApplication.
setPalette
(pal)¶ - Parameters
pal –
PySide6.QtGui.QPalette
Changes the application palette to pal
.
The color roles from this palette are combined with the system’s platform theme to form the application’s final palette.
See also
-
static
PySide6.QtGui.QGuiApplication.
setQuitOnLastWindowClosed
(quit)¶ - Parameters
quit – bool
See also
-
static
PySide6.QtGui.QGuiApplication.
setWindowIcon
(icon)¶ - Parameters
icon –
PySide6.QtGui.QIcon
See also
-
static
PySide6.QtGui.QGuiApplication.
styleHints
()¶ - Return type
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
-
static
PySide6.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
PySide6.QtGui.QGuiApplication.
topLevelAt
(pos)¶ - Parameters
pos –
PySide6.QtCore.QPoint
- Return type
Returns the top level window at the given position pos
, if any.
-
static
PySide6.QtGui.QGuiApplication.
topLevelWindows
()¶ - Return type
Returns a list of the top-level windows in the application.
See also
-
static
PySide6.QtGui.QGuiApplication.
windowIcon
()¶ - Return type
See also
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