QGuiApplication¶
The
QGuiApplication
class manages the GUI application’s control flow and main settings. More…
Inherited by: QApplication
Synopsis¶
Functions¶
def
devicePixelRatio
()def
isSavingSession
()def
isSessionRestored
()def
sessionId
()def
sessionKey
()
Signals¶
def
applicationStateChanged
(state)def
commitDataRequest
(sessionManager)def
focusObjectChanged
(focusObject)def
focusWindowChanged
(focusWindow)def
fontChanged
(font)def
fontDatabaseChanged
()def
lastWindowClosed
()def
layoutDirectionChanged
(direction)def
paletteChanged
(pal)def
primaryScreenChanged
(screen)def
saveStateRequest
(sessionManager)def
screenAdded
(screen)def
screenRemoved
(screen)
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
setFallbackSessionManagementEnabled
(arg__1)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, useQCoreApplication
instead, as it does not depend on the Qt GUI module. ForQWidget
based Qt applications, useQApplication
instead, as it provides some functionality needed for creatingQWidget
instances.The
QGuiApplication
object is accessible through theinstance()
function, which returns a pointer equivalent to the globalqApp
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 ofargv
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()
.See also
QCoreApplication
QAbstractEventDispatcher
QEventLoop
- class PySide2.QtGui.QGuiApplication¶
PySide2.QtGui.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.
See also
- static PySide2.QtGui.QGuiApplication.applicationDisplayName()¶
- Return type:
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
- PySide2.QtGui.QGuiApplication.applicationDisplayNameChanged()¶
- static PySide2.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.
- PySide2.QtGui.QGuiApplication.applicationStateChanged(state)¶
- Parameters:
state –
ApplicationState
- static PySide2.QtGui.QGuiApplication.changeOverrideCursor(arg__1)¶
- Parameters:
arg__1 –
PySide2.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 PySide2.QtGui.QGuiApplication.clipboard()¶
- Return type:
Returns the object for interacting with the clipboard.
- PySide2.QtGui.QGuiApplication.commitDataRequest(sessionManager)¶
- Parameters:
sessionManager –
PySide2.QtGui.QSessionManager
- static PySide2.QtGui.QGuiApplication.desktopFileName()¶
- Return type:
str
This property holds the base name of the desktop entry for this application.
This is the file name, without the full path, 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 .
- static PySide2.QtGui.QGuiApplication.desktopSettingsAware()¶
- Return type:
bool
Returns
true
if Qt is set to use the system’s standard colors, fonts, etc.; otherwise returnsfalse
. The default istrue
.See also
- PySide2.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 PySide2.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.
- PySide2.QtGui.QGuiApplication.focusObjectChanged(focusObject)¶
- Parameters:
focusObject –
PySide2.QtCore.QObject
- static PySide2.QtGui.QGuiApplication.focusWindow()¶
- Return type:
Returns the
QWindow
that receives events tied to focus, such as key events.
- PySide2.QtGui.QGuiApplication.focusWindowChanged(focusWindow)¶
- Parameters:
focusWindow –
PySide2.QtGui.QWindow
- static PySide2.QtGui.QGuiApplication.font()¶
- Return type:
Returns the default application font.
See also
- PySide2.QtGui.QGuiApplication.fontChanged(font)¶
- Parameters:
font –
PySide2.QtGui.QFont
- PySide2.QtGui.QGuiApplication.fontDatabaseChanged()¶
- static PySide2.QtGui.QGuiApplication.highDpiScaleFactorRoundingPolicy()¶
- Return type:
Returns the high-DPI scale factor rounding policy.
- static PySide2.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 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 aftercommitDataRequest()
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()
istrue
, 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.See also
setFallbackSessionManagementEnabled()
allowsInteraction()
saveStateRequest()
commitDataRequest()
Session Management
- static PySide2.QtGui.QGuiApplication.isLeftToRight()¶
- Return type:
bool
Returns
true
if the application’s layout direction isLeftToRight
; otherwise returnsfalse
.See also
- static PySide2.QtGui.QGuiApplication.isRightToLeft()¶
- Return type:
bool
Returns
true
if the application’s layout direction isRightToLeft
; otherwise returnsfalse
.See also
- PySide2.QtGui.QGuiApplication.isSavingSession()¶
- Return type:
bool
Returns
true
if the application is currently saving the session; otherwise returnsfalse
.This is
true
whencommitDataRequest()
andsaveStateRequest()
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 returnsfalse
.
- 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
andKeyRelease
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
- PySide2.QtGui.QGuiApplication.lastWindowClosed()¶
- static PySide2.QtGui.QGuiApplication.layoutDirection()¶
- Return type:
This property holds the default layout direction for this application.
On system start-up, the default layout direction depends on the application’s language.
The notifier signal was introduced in Qt 5.4.
See also
layoutDirection
isLeftToRight()
isRightToLeft()
- PySide2.QtGui.QGuiApplication.layoutDirectionChanged(direction)¶
- Parameters:
direction –
LayoutDirection
- static PySide2.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 toWindowModal
orApplicationModal
. 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
andMouseButtonRelease
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 PySide2.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 PySide2.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
- PySide2.QtGui.QGuiApplication.paletteChanged(pal)¶
- Parameters:
pal –
PySide2.QtGui.QPalette
- static PySide2.QtGui.QGuiApplication.platformName()¶
- Return type:
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)kms
is an experimental platform plugin using kernel modesetting and DRM (Direct Rendering Manager).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
openwfd
qnx
windows
wayland
is a platform plugin for modern Linux desktops and some embedded systems.xcb
is the X11 plugin used on regular desktop Linux platforms.
For more information about the platform plugins for embedded Linux devices, see Qt for Embedded Linux.
- static PySide2.QtGui.QGuiApplication.primaryScreen()¶
- Return type:
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 signal was introduced in Qt 5.6.
See also
- PySide2.QtGui.QGuiApplication.primaryScreenChanged(screen)¶
- Parameters:
screen –
PySide2.QtGui.QScreen
- 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.See also
- static PySide2.QtGui.QGuiApplication.quitOnLastWindowClosed()¶
- Return type:
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 applications quits when the last visible primary window (i.e. window with no parent) is closed.See also
quit()
close()
- 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.See also
- PySide2.QtGui.QGuiApplication.saveStateRequest(sessionManager)¶
- Parameters:
sessionManager –
PySide2.QtGui.QSessionManager
- PySide2.QtGui.QGuiApplication.screenAdded(screen)¶
- Parameters:
screen –
PySide2.QtGui.QScreen
- static PySide2.QtGui.QGuiApplication.screenAt(point)¶
- Parameters:
point –
PySide2.QtCore.QPoint
- Return type:
Returns the screen at
point
, orNone
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 windowQWidget::windowHandle()->screen()
), usevirtualSiblingAt()
.
- PySide2.QtGui.QGuiApplication.screenRemoved(screen)¶
- Parameters:
screen –
PySide2.QtGui.QScreen
- 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:
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.
- PySide2.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 PySide2.QtGui.QGuiApplication.setApplicationDisplayName(name)¶
- Parameters:
name – 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
- static PySide2.QtGui.QGuiApplication.setDesktopFileName(name)¶
- Parameters:
name – str
This property holds the base name of the desktop entry for this application.
This is the file name, without the full path, 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 .
- static PySide2.QtGui.QGuiApplication.setDesktopSettingsAware(on)¶
- Parameters:
on – bool
Sets whether Qt should use the system’s standard colors, fonts, etc., to
on
. By default, this istrue
.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 PySide2.QtGui.QGuiApplication.setFallbackSessionManagementEnabled(arg__1)¶
- Parameters:
arg__1 – bool
Sets whether
QGuiApplication
will use fallback session management toenabled
.See also
- static PySide2.QtGui.QGuiApplication.setFont(arg__1)¶
- Parameters:
arg__1 –
PySide2.QtGui.QFont
Changes the default application font to
font
.See also
- static PySide2.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, for applications that have AA_EnableHighDpiScaling enabled.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, and can be overridden by setting the QT_SCALE_FACTOR_ROUNDING_POLICY environment variable. The
highDpiScaleFactorRoundingPolicy()
accessor will reflect the environment, if set.The default value is Qt::HighDpiScaleFactorRoundingPolicy::Round. On Qt for Android the default is Qt::HighDpiScaleFactorRoundingPolicy::PassThrough, which preserves historical behavior from earlier Qt versions.
See also
- static PySide2.QtGui.QGuiApplication.setLayoutDirection(direction)¶
- Parameters:
direction –
LayoutDirection
This property holds the default layout direction for this application.
On system start-up, the default layout direction depends on the application’s language.
The notifier signal was introduced in Qt 5.4.
See also
layoutDirection
isLeftToRight()
isRightToLeft()
- static PySide2.QtGui.QGuiApplication.setOverrideCursor(arg__1)¶
- Parameters:
arg__1 –
PySide2.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 PySide2.QtGui.QGuiApplication.setPalette(pal)¶
- Parameters:
pal –
PySide2.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 PySide2.QtGui.QGuiApplication.setQuitOnLastWindowClosed(quit)¶
- Parameters:
quit – 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 applications quits when the last visible primary window (i.e. window with no parent) is closed.See also
quit()
close()
- static PySide2.QtGui.QGuiApplication.setWindowIcon(icon)¶
- Parameters:
icon –
PySide2.QtGui.QIcon
This property holds the default window icon.
See also
setIcon()
Setting the Application Icon
- static PySide2.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 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 toprocessEvents()
;This function is timeconsuming and its use is discouraged.
- static PySide2.QtGui.QGuiApplication.topLevelAt(pos)¶
- Parameters:
pos –
PySide2.QtCore.QPoint
- Return type:
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
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