QGuiApplication 类

QGuiApplication 类管理 GUI 应用程序的控制流和主要设置。 更多...

Header: #include <QGuiApplication>
CMake: find_package(Qt6 COMPONENTS Gui REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: QT += gui
Since: Qt 5.0
继承: QCoreApplication




QGuiApplication (int & argc , char ** argv )
virtual ~QGuiApplication ()
qreal devicePixelRatio () const
bool isSavingSession () const
bool isSessionRestored () const
QString sessionId () const
QString sessionKey () const


virtual bool notify (QObject * object , QEvent * event ) override


void applicationDisplayNameChanged ()
void applicationStateChanged (Qt::ApplicationState state )
void commitDataRequest (QSessionManager & manager )
void focusObjectChanged (QObject * focusObject )
void focusWindowChanged (QWindow * focusWindow )
void fontDatabaseChanged ()
void lastWindowClosed ()
void layoutDirectionChanged (Qt::LayoutDirection direction )
void primaryScreenChanged (QScreen * screen )
void saveStateRequest (QSessionManager & manager )
void screenAdded (QScreen * screen )
void screenRemoved (QScreen * screen )


QWindowList allWindows ()
QString applicationDisplayName ()
Qt::ApplicationState applicationState ()
void changeOverrideCursor (const QCursor & cursor )
QClipboard * clipboard ()
QString desktopFileName ()
bool desktopSettingsAware ()
int exec ()
QObject * focusObject ()
QWindow * focusWindow ()
QFont font ()
Qt::HighDpiScaleFactorRoundingPolicy highDpiScaleFactorRoundingPolicy ()
QInputMethod * inputMethod ()
bool isLeftToRight ()
bool isRightToLeft ()
Qt::KeyboardModifiers keyboardModifiers ()
Qt::LayoutDirection layoutDirection ()
QWindow * modalWindow ()
Qt::MouseButtons mouseButtons ()
QCursor * overrideCursor ()
QPalette palette ()
QString platformName ()
QScreen * primaryScreen ()
Qt::KeyboardModifiers queryKeyboardModifiers ()
bool quitOnLastWindowClosed ()
void restoreOverrideCursor ()
QScreen * screenAt (const QPoint & point )
QList<QScreen *> screens ()
void setApplicationDisplayName (const QString & name )
void setDesktopFileName (const QString & name )
void setDesktopSettingsAware (bool on )
void setFont (const QFont & font )
void setHighDpiScaleFactorRoundingPolicy (Qt::HighDpiScaleFactorRoundingPolicy policy )
void setLayoutDirection (Qt::LayoutDirection direction )
void setOverrideCursor (const QCursor & cursor )
void setPalette (const QPalette & pal )
void setQuitOnLastWindowClosed (bool quit )
void setWindowIcon (const QIcon & icon )
QStyleHints * styleHints ()
void sync ()
QWindow * topLevelAt (const QPoint & pos )
QWindowList topLevelWindows ()
QIcon windowIcon ()


virtual bool event (QEvent * e ) override


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 实例。

QGuiApplication 对象是可访问的透过 instance () 函数,返回指针相当于全局 qApp 指针。

QApplication 主要负责的领域:

  • It initializes the application with the user's desktop settings, such as palette (), font () 和 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 () 和 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 (),获取列表为 topLevelWindows (),等。
  • It manages the application's mouse cursor handling, see setOverrideCursor ()
  • It provides support for sophisticated 会话管理 . 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 () 和 commitDataRequest () 和 saveStateRequest () 了解细节。

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.

另请参阅 QCoreApplication , QAbstractEventDispatcher ,和 QEventLoop .


[since 5.0] applicationDisplayName : QString


此名称将展示给用户,例如在窗口标题中。 可以翻译它,若有必要。


该特性在 Qt 5.0 引入。


QString applicationDisplayName ()
void setApplicationDisplayName (const QString & name )


void applicationDisplayNameChanged ()

另请参阅 applicationName .

[since 5.7] desktopFileName : QString


这是表示此应用程序桌面条目的文件名 (不带完整路径),根据 freedesktop 桌面条目规范。


可以获得最新版本的 freedesktop 桌面条目规范 here .

该特性在 Qt 5.7 引入。


QString desktopFileName ()
void setDesktopFileName (const QString & name )

layoutDirection : Qt::LayoutDirection



通知信号在 Qt 5.4 引入。


Qt::LayoutDirection layoutDirection ()
void setLayoutDirection (Qt::LayoutDirection direction )


void layoutDirectionChanged (Qt::LayoutDirection direction )

另请参阅 QWidget::layoutDirection , isLeftToRight (),和 isRightToLeft ().

[read-only] platformName : const QString

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 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 .


QString platformName ()

[read-only] primaryScreen : QScreen * const

此特性保持应用程序的首要 (或默认) 屏幕。

这将是最初展示 QWindows 的屏幕,除非另有指定。

primaryScreenChanged 信号在 Qt 5.6 引入。


QScreen * primaryScreen ()


void primaryScreenChanged (QScreen * screen )

另请参阅 screens ().

quitOnLastWindowClosed : bool


默认为 true .

若此特性为 true ,应用程序离开,当最后可见首要窗口 (即:窗口没有父级) 被关闭时。


bool quitOnLastWindowClosed ()
void setQuitOnLastWindowClosed (bool quit )

另请参阅 quit () 和 QWindow::close ().

windowIcon : QIcon



QIcon windowIcon ()
void setWindowIcon (const QIcon & icon )

另请参阅 QWindow::setIcon () 和 设置应用程序图标 .


QGuiApplication:: QGuiApplication ( int & argc , char ** argv )

Initializes the window system and constructs an application object with argc command line arguments in argv .

警告: The data referred to by argc and argv must stay valid for the entire lifetime of the QGuiApplication object. In addition, argc must be greater than zero and argv must contain at least one valid character string.

全局 qApp pointer refers to this application object. Only one application object should be created.

This application object must be constructed before any paint devices (including pixmaps, bitmaps etc.).

注意: argc and argv might be changed as Qt removes command line arguments that it recognizes.

Supported Command Line Options

All Qt programs automatically support a set of command-line options that allow modifying the way Qt will interact with the windowing system. Some of the options are also accessible via environment variables, which are the preferred form if the application can launch GUI sub-processes or other applications (environment variables will be inherited by child processes). When in doubt, use the environment variables.

The options currently supported are the following:

  • -platform platformName [:options] , specifies the Qt Platform Abstraction (QPA) plugin.

    Overrides the QT_QPA_PLATFORM 环境变量。

  • -platformpluginpath path , specifies the path to platform plugins.

    Overrides the QT_QPA_PLATFORM_PLUGIN_PATH 环境变量。

  • -platformtheme platformTheme , specifies the platform theme.

    Overrides the QT_QPA_PLATFORMTHEME 环境变量。

  • -plugin plugin , specifies additional plugins to load. The argument may appear multiple times.

    Concatenated with the plugins in the QT_QPA_GENERIC_PLUGINS 环境变量。

  • -qmljsdebugger= , activates the QML/JS debugger with a specified port. The value must be of format port:1234 [,block] ,其中 block is optional and will make the application wait until a debugger connects to it.
  • -qwindowgeometry geometry , specifies window geometry for the main window using the X11-syntax. For example: -qwindowgeometry 100x100+50+50
  • -qwindowicon , sets the default window icon
  • -qwindowtitle , sets the title of the first window
  • -reverse , sets the application's layout direction to Qt::RightToLeft . This option is intended to aid debugging and should not be used in production. The default value is automatically detected from the user's locale (see also QLocale::textDirection ()).
  • -session session , restores the application from an earlier session .

The following standard command line options are available for X11:

  • -display hostname:screen_number , switches displays on X11.

    Overrides the DISPLAY 环境变量。

  • -geometry geometry , same as -qwindowgeometry .

Platform-Specific Arguments

You can specify platform-specific arguments for the -platform option. Place them after the platform plugin name following a colon as a comma-separated list. For example, -platform windows:dialogs=xp,fontengine=freetype .

The following parameters are available for -platform windows :

  • altgr , detect the key AltGr found on some keyboards as Qt::GroupSwitchModifier (since Qt 5.12).
  • darkmode=[1|2] controls how Qt responds to the activation of the Dark Mode for applications introduced in Windows 10 1903 (since Qt 5.15).

    A value of 1 causes Qt to switch the window borders to black when Dark Mode for applications is activated and no High Contrast Theme is in use. This is intended for applications that implement their own theming.

    A value of 2 will in addition cause the Windows Vista style to be deactivated and switch to the Windows style using a simplified palette in dark mode. This is currently experimental pending the introduction of new style that properly adapts to dark mode.

  • dialogs=[xp|none] , xp uses XP-style native dialogs and none disables them.
  • fontengine=freetype , uses the FreeType font engine.
  • fontengine=directwrite , uses the experimental DirectWrite font database and defaults to using the DirectWrite font engine (which is otherwise only used for some font types or font properties.) This affects font selection and aims to provide font naming more consistent with other platforms, but does not support all font formats, such as Postscript Type-1 or Microsoft FNT fonts.
  • menus=[native|none] , controls the use of native menus.

    Native menus are implemented using Win32 API and are simpler than QMenu -based menus in for example that they do allow for placing widgets on them or changing properties like fonts and do not provide hover signals. They are mainly intended for Qt Quick. By default, they will be used if the application is not an instance of QApplication or for Qt Quick Controls 2 applications (since Qt 5.10).

  • nocolorfonts Turn off DirectWrite Color fonts (since Qt 5.8).
  • nodirectwrite Turn off DirectWrite fonts (since Qt 5.8).
  • nomousefromtouch Ignores mouse events synthesized from touch events by the operating system.
  • nowmpointer Switches from Pointer Input Messages handling to legacy mouse handling (since Qt 5.12).
  • reverse Activates Right-to-left mode (experimental). Windows title bars will be shown accordingly in Right-to-left locales (since Qt 5.13).
  • tabletabsoluterange=<value> Sets a value for mouse mode detection of WinTab tablets (Legacy, since Qt 5.3).

The following parameter is available for -platform cocoa (on macOS):

  • fontengine=freetype , uses the FreeType font engine.

For more information about the platform-specific arguments available for embedded Linux platforms, see Qt for Embedded Linux .

另请参阅 arguments () 和 QGuiApplication::platformName .

[signal, since 5.2] void QGuiApplication:: applicationStateChanged ( Qt::ApplicationState state )

此信号被发射当 state 对于应用程序改变。

该函数在 Qt 5.2 引入。

另请参阅 applicationState ().

[signal] void QGuiApplication:: commitDataRequest ( QSessionManager & manager )

This signal deals with 会话管理 . 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.

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

注意: 应使用 Qt::DirectConnection when connecting to this signal.

另请参阅 isSessionRestored (), sessionId (), saveStateRequest (),和 会话管理 .

[signal] void QGuiApplication:: focusObjectChanged ( QObject * focusObject )

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

另请参阅 focusObject ().

[signal] void QGuiApplication:: focusWindowChanged ( QWindow * focusWindow )

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

另请参阅 focusWindow ().

[signal] void QGuiApplication:: fontDatabaseChanged ()


另请参阅 QFontDatabase::addApplicationFont (), QFontDatabase::addApplicationFontFromData (), QFontDatabase::removeAllApplicationFonts (),和 QFontDatabase::removeApplicationFont ().

[signal] void QGuiApplication:: lastWindowClosed ()

此信号被发射从 exec () 当最后可见首要窗口 (即:窗口没有父级) 被关闭时。

默认情况下, QGuiApplication 离开在此信号被发射之后。可以关闭此特征通过设置 quitOnLastWindowClosed to false .

另请参阅 QWindow::close () 和 QWindow::isTopLevel ().

[signal] void QGuiApplication:: saveStateRequest ( QSessionManager & manager )

This signal deals with 会话管理 . It is invoked when the 会话管理器 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.

警告: Within this signal, no user interaction is possible, unless you ask the manager for explicit permission. See QSessionManager::allowsInteraction () 和 QSessionManager::allowsErrorInteraction () 了解细节。

注意: 应使用 Qt::DirectConnection when connecting to this signal.

另请参阅 isSessionRestored (), sessionId (), commitDataRequest (),和 会话管理 .

[signal] void QGuiApplication:: screenAdded ( QScreen * screen )

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

另请参阅 screens (), primaryScreen ,和 screenRemoved ().

[signal, since 5.4] void QGuiApplication:: screenRemoved ( QScreen * screen )

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.

该函数在 Qt 5.4 引入。

另请参阅 screens (), screenAdded (), QObject::destroyed (),和 QWindow::setScreen ().

[virtual] QGuiApplication:: ~QGuiApplication ()


[static] QWindowList QGuiApplication:: allWindows ()

Returns a list of all the windows in the application.

The list is empty if there are no windows.

另请参阅 topLevelWindows ().

[static, since 5.2] Qt::ApplicationState QGuiApplication:: applicationState ()


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.

该函数在 Qt 5.2 引入。

[static] void QGuiApplication:: changeOverrideCursor (const QCursor & cursor )

Changes the currently active application override cursor to cursor .

此函数不起作用若 setOverrideCursor () 未被调用。

另请参阅 setOverrideCursor (), overrideCursor (), restoreOverrideCursor (),和 QWidget::setCursor ().

[static] QClipboard *QGuiApplication:: clipboard ()


[static] bool QGuiApplication:: desktopSettingsAware ()

返回 true 若 Qt 被设为使用系统标准颜色、字体、等;否则返回 false 。默认为 true .

另请参阅 setDesktopSettingsAware ().

qreal QGuiApplication:: devicePixelRatio () const

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 QWindow::devicePixelRatio () 代替。

另请参阅 QWindow::devicePixelRatio ().

[override virtual protected] bool QGuiApplication:: event ( QEvent * e )

重实现: QCoreApplication::event (QEvent *e).

[static] int QGuiApplication:: exec ()

进入主事件循环并等待,直到 exit () is called, and then returns the value that was set to exit () (其为 0 若 exit () 被调用凭借 quit ()).

有必要调用此函数以启动事件处理。主事件循环从窗口系统接收事件,并将其分派给应用程序 Widget。

Generally, no user interaction can take place before calling exec().

To make your application perform idle processing, e.g., executing a special function whenever there are no pending events, use a QTimer 采用 0 超时。更高级空闲处理方案可以达成使用 processEvents ().

推荐把清理代码连接到 aboutToQuit() 信号,而非将其放入应用程序的 main() function. This is because, on some platforms, the QApplication::exec () call may not return.

另请参阅 quitOnLastWindowClosed , quit (), exit (), processEvents (),和 QCoreApplication::exec ().

[static] QObject *QGuiApplication:: focusObject ()

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

[static] QWindow *QGuiApplication:: focusWindow ()

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

[static] QFont QGuiApplication:: font ()


另请参阅 setFont ().

[static, since 5.14] Qt::HighDpiScaleFactorRoundingPolicy QGuiApplication:: highDpiScaleFactorRoundingPolicy ()

Returns the high-DPI scale factor rounding policy.

该函数在 Qt 5.14 引入。

另请参阅 setHighDpiScaleFactorRoundingPolicy ().

[static] QInputMethod *QGuiApplication:: inputMethod ()

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.

另请参阅 QInputMethod .

[static] bool QGuiApplication:: isLeftToRight ()

返回 true 若应用程序的布局方向是 Qt::LeftToRight ;否则返回 false .

另请参阅 layoutDirection () 和 isRightToLeft ().

[static] bool QGuiApplication:: isRightToLeft ()

返回 true 若应用程序的布局方向是 Qt::RightToLeft ;否则返回 false .

另请参阅 layoutDirection () 和 isLeftToRight ().

[since 5.0] bool QGuiApplication:: isSavingSession () const

返回 true 若应用程序目前正在保存 session ;否则返回 false .

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

该函数在 Qt 5.0 引入。

另请参阅 sessionId (), commitDataRequest (),和 saveStateRequest ().

bool QGuiApplication:: isSessionRestored () const

返回 true if the application has been restored from an earlier session ;否则返回 false .

另请参阅 sessionId (), commitDataRequest (),和 saveStateRequest ().

[static] Qt::KeyboardModifiers QGuiApplication:: keyboardModifiers ()

返回键盘修饰符键的当前状态。当前状态会被同步更新,当事件队列中的自发改变键盘状态的事件被清空时 ( QEvent::KeyPress and QEvent::KeyRelease 事件)。

应注意,这可能不反映调用时在输入设备上保持的实际键,但反映上述事件之一最后报告的修饰符。若没有保持键, Qt::NoModifier 被返回。

另请参阅 mouseButtons () 和 queryKeyboardModifiers ().

返回最近展示的模态窗口。若没有可见的模态窗口,此函数返回 0。

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.

另请参阅 Qt::WindowModality and QWindow::setModality ().

[static] Qt::MouseButtons QGuiApplication:: 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 ( QEvent::MouseButtonPress and QEvent::MouseButtonRelease 事件)。

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 被返回。

另请参阅 keyboardModifiers ().

[override virtual] bool QGuiApplication:: notify ( QObject * object , QEvent * event )

重实现: QCoreApplication::notify (QObject *receiver, QEvent *event).

[static] QCursor *QGuiApplication:: overrideCursor ()


此函数返回 nullptr 若应用程序光标没有定义 (即:内部光标堆栈为空)。

另请参阅 setOverrideCursor () 和 restoreOverrideCursor ().

[static] QPalette QGuiApplication:: palette ()



另请参阅 setPalette ().

[static] Qt::KeyboardModifiers QGuiApplication:: queryKeyboardModifiers ()

查询并返回键盘修饰符键的状态。不像 keyboardModifiers 此方法返回调用方法时保持在输入设备上的实际键。

它不依赖由此进程已接收的键按下事件,譬如:这使得当移动窗口时校验修饰符成为可能。注意:在大多数情况下,应使用 keyboardModifiers (),其更快更准确,因为它包含的修饰符状态 (如同接收当前处理事件时状态)。

另请参阅 keyboardModifiers ().

[static] void QGuiApplication:: restoreOverrideCursor ()

撤消最后 setOverrideCursor ().

setOverrideCursor () 已调用 2 次,调用 restoreOverrideCursor() 将激活第 1 次光标设置。第 2 次调用此函数将还原原始 Widget 光标。

另请参阅 setOverrideCursor () 和 overrideCursor ().

[static, since 5.10] QScreen *QGuiApplication:: screenAt (const QPoint & point )

返回屏幕,位于 point ,或 nullptr 若在任何屏幕之外。

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 QScreen::virtualSiblingAt ().

该函数在 Qt 5.10 引入。

[static] QList < QScreen *> QGuiApplication:: screens ()


QString QGuiApplication:: sessionId () const

返回当前 session's 标识符。

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.

另请参阅 isSessionRestored (), sessionKey (), commitDataRequest (),和 saveStateRequest ().

QString QGuiApplication:: sessionKey () const

返回会话键,在当前 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.

另请参阅 isSessionRestored (), sessionId (), commitDataRequest (),和 saveStateRequest ().

[static] void QGuiApplication:: setDesktopSettingsAware ( bool on )

将 Qt 是否应使用系统标准颜色、字体等设为 on 。默认情况下,这是 true .

此函数必须先被调用才创建 QGuiApplication 对象,像这样:

int main(int argc, char *argv[])
    QApplication app(argc, argv);
    // ...
    return app.exec();

另请参阅 desktopSettingsAware ().

[static] void QGuiApplication:: setFont (const QFont & font )

把默认应用程序字体改为 font .

另请参阅 font ().

[static, since 5.14] void QGuiApplication:: setHighDpiScaleFactorRoundingPolicy ( Qt::HighDpiScaleFactorRoundingPolicy policy )

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 Qt::HighDpiScaleFactorRoundingPolicy enum for a complete list of all options.

This function must be called before creating the application object. The QGuiApplication::highDpiScaleFactorRoundingPolicy () accessor will reflect the environment, if set.

默认值为 Qt::HighDpiScaleFactorRoundingPolicy::PassThrough .

该函数在 Qt 5.14 引入。

另请参阅 highDpiScaleFactorRoundingPolicy ().

[static] void QGuiApplication:: setOverrideCursor (const QCursor & cursor )

将应用程序覆盖光标设为 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 curently active application override cursor.

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


calculateHugeMandelbrot();              // lunch time...

另请参阅 overrideCursor (), restoreOverrideCursor (), changeOverrideCursor (),和 QWidget::setCursor ().

[static] void QGuiApplication:: setPalette (const QPalette & pal )

将应用程序调色板更改为 pal .

The color roles from this palette are combined with the system's platform theme to form the application's final palette.

另请参阅 palette ().

[static] QStyleHints *QGuiApplication:: styleHints ()


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.

另请参阅 QStyleHints .

[static, since 5.2] void 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 QCoreApplication::processEvents (), then the platform plugin will sync up with the windowsystem, and finally Qts events will be delived by another call to QCoreApplication::processEvents ();

This function is timeconsuming and its use is discouraged.

该函数在 Qt 5.2 引入。

[static] QWindow *QGuiApplication:: topLevelAt (const QPoint & pos )

返回顶层窗口在给定位置 pos ,若有的话。

[static] QWindowList QGuiApplication:: topLevelWindows ()


另请参阅 allWindows ().



A global pointer referring to the unique application object. Only valid for use when that object is a QGuiApplication .

另请参阅 QCoreApplication::instance () 和 qApp .