QGuiApplication Class

Member Function Documentation

QGuiApplication::QGuiApplication(int & argc, char ** argv, int flags = ApplicationFlags)

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

Warning: 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.

The global 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.).

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

All Qt programs automatically support the following command line options:

• -reverse, sets the application's layout direction to Qt::RightToLeft
• -qmljsdebugger=, activates the QML/JS debugger with a specified port. The value must be of format port:1234[,block], where block is optional and will make the application wait until a debugger connects to it.

See also arguments().

QGuiApplication::QGuiApplication(QGuiApplicationPrivate & p) [protected]

QGuiApplication::~QGuiApplication() [virtual]

Destructs the application.

QWindowList QGuiApplication::allWindows() [static]

Returns a list of all the windows in the application.

The list is empty if there are no windows.

See also topLevelWindows().

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

Changes the currently active application override cursor to cursor.

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

See also setOverrideCursor(), overrideCursor(), restoreOverrideCursor(), and QWidget::setCursor().

QClipboard * QGuiApplication::clipboard() [static]

Returns the object for interacting with the clipboard.

bool QGuiApplication::desktopSettingsAware() [static]

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

See also setDesktopSettingsAware().

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

Reimplemented from QObject::event().

int QGuiApplication::exec() [static]

Enters the main event loop and waits until exit() is called, and then returns the value that was set to exit() (which is 0 if exit() is called via quit()).

It is necessary to call this function to start event handling. The main event loop receives events from the window system and dispatches these to the application widgets.

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 with 0 timeout. More advanced idle processing schemes can be achieved using processEvents().

We recommend that you connect clean-up code to the aboutToQuit() signal, instead of putting it in your application's main() function. This is because, on some platforms, the QApplication::exec() call may not return.

See also quitOnLastWindowClosed, quit(), exit(), processEvents(), and QCoreApplication::exec().

QObject * QGuiApplication::focusObject() [static]

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

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

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

See also focusObject().

QWindow * QGuiApplication::focusWindow() [static]

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

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

This signal is emitted when the focused window changes.

See also focusWindow().

QFont QGuiApplication::font() [static]

Returns the default application font.

See also setFont().

void QGuiApplication::fontDatabaseChanged() [signal]

This signal is emitted when application fonts are loaded or removed.

See also QFontDatabase::addApplicationFont(), QFontDatabase::addApplicationFontFromData(), QFontDatabase::removeAllApplicationFonts(), and QFontDatabase::removeApplicationFont().

QInputMethod * QGuiApplication::inputMethod() [static]

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 QInputPanel.

bool QGuiApplication::isLeftToRight() [static]

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

See also layoutDirection() and isRightToLeft().

bool QGuiApplication::isRightToLeft() [static]

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

See also layoutDirection() and isLeftToRight().

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

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 (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.

See also mouseButtons() and queryKeyboardModifiers().

void QGuiApplication::lastWindowClosed() [signal]

QWindow * QGuiApplication::modalWindow() [static]

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 windowModality 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 Qt::WindowModality and QWindow::setWindowModality().

Qt::MouseButtons QGuiApplication::mouseButtons() [static]

Returns the current state of the buttons on the mouse. The current state is updated syncronously 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.

See also keyboardModifiers().

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

Reimplemented from QCoreApplication::notify().

QCursor * QGuiApplication::overrideCursor() [static]

Returns the active application override cursor.

This function returns 0 if no application cursor has been defined (i.e. the internal cursor stack is empty).

See also setOverrideCursor() and restoreOverrideCursor().

QPalette QGuiApplication::palette() [static]

Returns the default application palette.

See also setPalette().

QPlatformNativeInterface * QGuiApplication::platformNativeInterface() [static]

Returns the platform's native interface, for platform specific functionality.

QScreen * QGuiApplication::primaryScreen() [static]

Returns the primary (or default) screen of the application.

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

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

void QGuiApplication::restoreOverrideCursor() [static]

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.

See also setOverrideCursor() and overrideCursor().

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

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

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

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

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 desktopSettingsAware().

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

Changes the default application font to font.

See also font().

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

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 curently active application override cursor.

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

Example:

 QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
 calculateHugeMandelbrot();              // lunch time...
 QApplication::restoreOverrideCursor();

See also overrideCursor(), restoreOverrideCursor(), changeOverrideCursor(), and QWidget::setCursor().

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

Changes the default application palette to palette.

See also palette().

QStyleHints * QGuiApplication::styleHints() [static]

Returns the application's style hints.

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

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

See also QStyleHints.

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

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

QWindowList QGuiApplication::topLevelWindows() [static]

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

See also allWindows().