QWidget Class

Member Function Documentation

QWidget::QWidget(QWidget *parent = nullptr, Qt::WindowFlags f = Qt::WindowFlags())

Constructs a widget which is a child of parent, with widget flags set to f.

If parent is nullptr, the new widget becomes a window. If parent is another widget, this widget becomes a child window inside parent. The new widget is deleted when its parent is deleted.

The widget flags argument, f, is normally 0, but it can be set to customize the frame of a window (i.e. parent must be nullptr). To customize the frame, use a value composed from the bitwise OR of any of the window flags.

If you add a child widget to an already visible widget you must explicitly show the child to make it visible.

Note that the X11 version of Qt may not be able to deliver all combinations of style flags on all systems. This is because on X11, Qt can only ask the window manager, and the window manager can override the application's settings. On Windows, Qt can set whatever flags you want.

See also windowFlags.

[slot] bool QWidget::close()

Closes this widget. Returns true if the widget was closed; otherwise returns false.

First it sends the widget a QCloseEvent. The widget is hidden if it accepts the close event. If it ignores the event, nothing happens. The default implementation of QWidget::closeEvent() accepts the close event.

If the widget has the Qt::WA_DeleteOnClose flag, the widget is also deleted. A close events is delivered to the widget no matter if the widget is visible or not.

The QApplication::lastWindowClosed() signal is emitted when the last visible primary window (i.e. window with no parent) with the Qt::WA_QuitOnClose attribute set is closed. By default this attribute is set for all widgets except transient windows such as splash screens, tool windows, and popup menus.

[signal] void QWidget::customContextMenuRequested(const QPoint &pos)

This signal is emitted when the widget's contextMenuPolicy is Qt::CustomContextMenu, and the user has requested a context menu on the widget. The position pos is the position of the context menu event that the widget receives. Normally this is in widget coordinates. The exception to this rule is QAbstractScrollArea and its subclasses that map the context menu event to coordinates of the viewport().

See also mapToGlobal(), QMenu, and contextMenuPolicy.

[slot] void QWidget::hide()

Hides the widget. This function is equivalent to setVisible(false).

See also hideEvent(), isHidden(), show(), setVisible(), isVisible(), and close().

[slot] void QWidget::lower()

Lowers the widget to the bottom of the parent widget's stack.

After this call the widget will be visually behind (and therefore obscured by) any overlapping sibling widgets.

See also raise() and stackUnder().

[slot] void QWidget::raise()

Raises this widget to the top of the parent widget's stack.

After this call the widget will be visually in front of any overlapping sibling widgets.

See also lower() and stackUnder().

[slot] void QWidget::repaint()

Repaints the widget directly by calling paintEvent() immediately, unless updates are disabled or the widget is hidden.

We suggest only using repaint() if you need an immediate repaint, for example during animation. In almost all circumstances update() is better, as it permits Qt to optimize for speed and minimize flicker.

See also update(), paintEvent(), and setUpdatesEnabled().

[slot] void QWidget::setDisabled(bool disable)

Disables widget input events if disable is true; otherwise enables input events.

See the enabled documentation for more information.

See also isEnabledTo(), QKeyEvent, QMouseEvent, and changeEvent().

[slot] void QWidget::setFocus()

This is an overloaded function.

Gives the keyboard input focus to this widget (or its focus proxy) if this widget or one of its parents is the active window.

[slot] void QWidget::setHidden(bool hidden)

Convenience function, equivalent to setVisible(!hidden).

See also isHidden().

[slot] void QWidget::show()

Shows the widget and its child widgets.

This is equivalent to calling showFullScreen(), showMaximized(), or setVisible(true), depending on the platform's default behavior for the window flags.

See also raise(), showEvent(), hide(), setVisible(), showMinimized(), showMaximized(), showNormal(), isVisible(), and windowFlags().

[slot] void QWidget::showFullScreen()

Shows the widget in full-screen mode.

Calling this function only affects windows.

To return from full-screen mode, call showNormal() or close().

An alternative would be to bypass the window manager entirely and create a window with the Qt::X11BypassWindowManagerHint flag. This has other severe problems though, like totally broken keyboard focus and very strange effects on desktop changes or when the user raises other windows.

X11 window managers that follow modern post-ICCCM specifications support full-screen mode properly.

On macOS, showing a window full screen puts the entire application in full-screen mode, providing it with a dedicated desktop. Showing another window while the application runs in full-screen mode might automatically make that window full screen as well. To prevent that, exit full-screen mode by calling showNormal() or by close() on the full screen window before showing another window.

See also showNormal(), showMaximized(), show(), isVisible(), and close().

[slot] void QWidget::showMaximized()

Shows the widget maximized.

Calling this function only affects windows.

On X11, this function may not work properly with certain window managers. See the Window Geometry documentation for an explanation.

See also setWindowState(), showNormal(), showMinimized(), show(), hide(), and isVisible().

[slot] void QWidget::showMinimized()

Shows the widget minimized, as an icon.

Calling this function only affects windows.

See also showNormal(), showMaximized(), show(), hide(), isVisible(), and isMinimized().

[slot] void QWidget::showNormal()

Restores the widget after it has been maximized or minimized.

Calling this function only affects windows.

See also setWindowState(), showMinimized(), showMaximized(), show(), hide(), and isVisible().

[slot] void QWidget::update()

Updates the widget unless updates are disabled or the widget is hidden.

This function does not cause an immediate repaint; instead it schedules a paint event for processing when Qt returns to the main event loop. This permits Qt to optimize for more speed and less flicker than a call to repaint() does.

Calling update() several times normally results in just one paintEvent() call.

Qt normally erases the widget's area before the paintEvent() call. If the Qt::WA_OpaquePaintEvent widget attribute is set, the widget is responsible for painting all its pixels with an opaque color.

See also repaint(), paintEvent(), setUpdatesEnabled(), and Analog Clock Example.

[protected slot] void QWidget::updateMicroFocus()

Updates the widget's micro focus.

[signal] void QWidget::windowIconChanged(const QIcon &icon)

This signal is emitted when the window's icon has changed, with the new icon as an argument.

Note: Notifier signal for property windowIcon.

This function was introduced in Qt 5.2.

[signal] void QWidget::windowTitleChanged(const QString &title)

This signal is emitted when the window's title has changed, with the new title as an argument.

Note: Notifier signal for property windowTitle.

This function was introduced in Qt 5.2.

[virtual] QWidget::~QWidget()

Destroys the widget.

All this widget's children are deleted first. The application exits if this widget is the main widget.

[virtual protected] void QWidget::actionEvent(QActionEvent *event)

This event handler is called with the given event whenever the widget's actions are changed.

See also addAction(), insertAction(), removeAction(), actions(), and QActionEvent.

QList<QAction *> QWidget::actions() const

Returns the (possibly empty) list of this widget's actions.

See also contextMenuPolicy, insertAction(), and removeAction().

void QWidget::activateWindow()

Sets the top-level widget containing this widget to be the active window.

An active window is a visible top-level window that has the keyboard input focus.

This function performs the same operation as clicking the mouse on the title bar of a top-level window. On X11, the result depends on the Window Manager. If you want to ensure that the window is stacked on top as well you should also call raise(). Note that the window must be visible, otherwise activateWindow() has no effect.

On Windows, if you are calling this when the application is not currently the active one then it will not make it the active window. It will change the color of the taskbar entry to indicate that the window has changed in some way. This is because Microsoft does not allow an application to interrupt what the user is currently doing in another application.

See also isActiveWindow(), window(), show(), and QWindowsWindowFunctions::setWindowActivationBehavior().

void QWidget::addAction(QAction *action)

Appends the action action to this widget's list of actions.

All QWidgets have a list of QActions, however they can be represented graphically in many different ways. The default use of the QAction list (as returned by actions()) is to create a context QMenu.

A QWidget should only have one of each action and adding an action it already has will not cause the same action to be in the widget twice.

The ownership of action is not transferred to this QWidget.

See also removeAction(), insertAction(), actions(), and QMenu.

void QWidget::addActions(QList<QAction *> actions)

Appends the actions actions to this widget's list of actions.

See also removeAction(), QMenu, and addAction().

void QWidget::adjustSize()

Adjusts the size of the widget to fit its contents.

This function uses sizeHint() if it is valid, i.e., the size hint's width and height are >= 0. Otherwise, it sets the size to the children rectangle that covers all child widgets (the union of all child widget rectangles).

For windows, the screen size is also taken into account. If the sizeHint() is less than (200, 100) and the size policy is expanding, the window will be at least (200, 100). The maximum size of a window is 2/3 of the screen's width and height.

See also sizeHint() and childrenRect().

QPalette::ColorRole QWidget::backgroundRole() const

Returns the background role of the widget.

The background role defines the brush from the widget's palette that is used to render the background.

If no explicit background role is set, the widget inherts its parent widget's background role.

See also setBackgroundRole() and foregroundRole().

QBackingStore *QWidget::backingStore() const

Returns the QBackingStore this widget will be drawn into.

This function was introduced in Qt 5.0.

[virtual protected] void QWidget::changeEvent(QEvent *event)

This event handler can be reimplemented to handle state changes.

The state being changed in this event can be retrieved through the event supplied.

Change events include: QEvent::ToolBarChange, QEvent::ActivationChange, QEvent::EnabledChange, QEvent::FontChange, QEvent::StyleChange, QEvent::PaletteChange, QEvent::WindowTitleChange, QEvent::IconTextChange, QEvent::ModifiedChange, QEvent::MouseTrackingChange, QEvent::ParentChange, QEvent::WindowStateChange, QEvent::LanguageChange, QEvent::LocaleChange, QEvent::LayoutDirectionChange, QEvent::ReadOnlyChange.

QWidget *QWidget::childAt(int x, int y) const

Returns the visible child widget at the position (x, y) in the widget's coordinate system. If there is no visible child widget at the specified position, the function returns nullptr.

QWidget *QWidget::childAt(const QPoint &p) const

This is an overloaded function.

Returns the visible child widget at point p in the widget's own coordinate system.

void QWidget::clearFocus()

Takes keyboard input focus from the widget.

If the widget has active focus, a focus out event is sent to this widget to tell it that it has lost the focus.

This widget must enable focus setting in order to get the keyboard input focus, i.e. it must call setFocusPolicy().

See also hasFocus(), setFocus(), focusInEvent(), focusOutEvent(), setFocusPolicy(), and QApplication::focusWidget().

void QWidget::clearMask()

Removes any mask set by setMask().

See also setMask().

[virtual protected] void QWidget::closeEvent(QCloseEvent *event)

This event handler is called with the given event when Qt receives a window close request for a top-level widget from the window system.

By default, the event is accepted and the widget is closed. You can reimplement this function to change the way the widget responds to window close requests. For example, you can prevent the window from closing by calling ignore() on all events.

Main window applications typically use reimplementations of this function to check whether the user's work has been saved and ask for permission before closing. For example, the Application Example uses a helper function to determine whether or not to close the window:

void MainWindow::closeEvent(QCloseEvent *event)
{
    if (maybeSave()) {
        writeSettings();
        event->accept();
    } else {
        event->ignore();
    }
}

See also event(), hide(), close(), QCloseEvent, and Application Example.

QMargins QWidget::contentsMargins() const

The contentsMargins function returns the widget's contents margins.

This function was introduced in Qt 4.6.

See also setContentsMargins() and contentsRect().

QRect QWidget::contentsRect() const

Returns the area inside the widget's margins.

See also setContentsMargins() and contentsMargins().

[virtual protected] void QWidget::contextMenuEvent(QContextMenuEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive widget context menu events.

The handler is called when the widget's contextMenuPolicy is Qt::DefaultContextMenu.

The default implementation ignores the context event. See the QContextMenuEvent documentation for more details.

See also event(), QContextMenuEvent, and customContextMenuRequested().

[protected] void QWidget::create(WId window = 0, bool initializeWindow = true, bool destroyOldWindow = true)

Creates a new widget window.

The parameters window, initializeWindow, and destroyOldWindow are ignored in Qt 5. Please use QWindow::fromWinId() to create a QWindow wrapping a foreign window and pass it to QWidget::createWindowContainer() instead.

See also createWindowContainer() and QWindow::fromWinId().

[static] QWidget *QWidget::createWindowContainer(QWindow *window, QWidget *parent = nullptr, Qt::WindowFlags flags = Qt::WindowFlags())

Creates a QWidget that makes it possible to embed window into a QWidget-based application.

The window container is created as a child of parent and with window flags flags.

Once the window has been embedded into the container, the container will control the window's geometry and visibility. Explicit calls to QWindow::setGeometry(), QWindow::show() or QWindow::hide() on an embedded window is not recommended.

The container takes over ownership of window. The window can be removed from the window container with a call to QWindow::setParent().

The window container is attached as a native child window to the toplevel window it is a child of. When a window container is used as a child of a QAbstractScrollArea or QMdiArea, it will create a native window for every widget in its parent chain to allow for proper stacking and clipping in this use case. Creating a native window for the window container also allows for proper stacking and clipping. This must be done before showing the window container. Applications with many native child windows may suffer from performance issues.

The window container has a number of known limitations:

• Stacking order; The embedded window will stack on top of the widget hierarchy as an opaque box. The stacking order of multiple overlapping window container instances is undefined.
• Rendering Integration; The window container does not interoperate with QGraphicsProxyWidget, QWidget::render() or similar functionality.
• Focus Handling; It is possible to let the window container instance have any focus policy and it will delegate focus to the window via a call to QWindow::requestActivate(). However, returning to the normal focus chain from the QWindow instance will be up to the QWindow instance implementation itself. For instance, when entering a Qt Quick based window with tab focus, it is quite likely that further tab presses will only cycle inside the QML application. Also, whether QWindow::requestActivate() actually gives the window focus, is platform dependent.
• Using many window container instances in a QWidget-based application can greatly hurt the overall performance of the application.

[protected] void QWidget::destroy(bool destroyWindow = true, bool destroySubWindows = true)

Frees up window system resources. Destroys the widget window if destroyWindow is true.

destroy() calls itself recursively for all the child widgets, passing destroySubWindows for the destroyWindow parameter. To have more control over destruction of subwidgets, destroy subwidgets selectively first.

This function is usually called from the QWidget destructor.

[virtual protected] void QWidget::dragEnterEvent(QDragEnterEvent *event)

This event handler is called when a drag is in progress and the mouse enters this widget. The event is passed in the event parameter.

If the event is ignored, the widget won't receive any drag move events.

See the Drag-and-drop documentation for an overview of how to provide drag-and-drop in your application.

See also QDrag and QDragEnterEvent.

[virtual protected] void QWidget::dragLeaveEvent(QDragLeaveEvent *event)

This event handler is called when a drag is in progress and the mouse leaves this widget. The event is passed in the event parameter.

See the Drag-and-drop documentation for an overview of how to provide drag-and-drop in your application.

See also QDrag and QDragLeaveEvent.

[virtual protected] void QWidget::dragMoveEvent(QDragMoveEvent *event)

This event handler is called if a drag is in progress, and when any of the following conditions occur: the cursor enters this widget, the cursor moves within this widget, or a modifier key is pressed on the keyboard while this widget has the focus. The event is passed in the event parameter.

See the Drag-and-drop documentation for an overview of how to provide drag-and-drop in your application.

See also QDrag and QDragMoveEvent.

[virtual protected] void QWidget::dropEvent(QDropEvent *event)

This event handler is called when the drag is dropped on this widget. The event is passed in the event parameter.

See the Drag-and-drop documentation for an overview of how to provide drag-and-drop in your application.

See also QDrag and QDropEvent.

WId QWidget::effectiveWinId() const

Returns the effective window system identifier of the widget, i.e. the native parent's window system identifier.

If the widget is native, this function returns the native widget ID. Otherwise, the window ID of the first native parent widget, i.e., the top-level widget that contains this widget, is returned.

This function was introduced in Qt 4.4.

See also nativeParentWidget().

void QWidget::ensurePolished() const

Ensures that the widget and its children have been polished by QStyle (i.e., have a proper font and palette).

QWidget calls this function after it has been fully constructed but before it is shown the very first time. You can call this function if you want to ensure that the widget is polished before doing an operation, e.g., the correct font size might be needed in the widget's sizeHint() reimplementation. Note that this function is called from the default implementation of sizeHint().

Polishing is useful for final initialization that must happen after all constructors (from base classes as well as from subclasses) have been called.

If you need to change some settings when a widget is polished, reimplement event() and handle the QEvent::Polish event type.

Note: The function is declared const so that it can be called from other const functions (e.g., sizeHint()).

See also event().

[virtual protected] void QWidget::enterEvent(QEvent *event)

This event handler can be reimplemented in a subclass to receive widget enter events which are passed in the event parameter.

An event is sent to the widget when the mouse cursor enters the widget.

See also leaveEvent(), mouseMoveEvent(), and event().

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

Reimplements: QObject::event(QEvent *e).

This is the main event handler; it handles event event. You can reimplement this function in a subclass, but we recommend using one of the specialized event handlers instead.

Key press and release events are treated differently from other events. event() checks for Tab and Shift+Tab and tries to move the focus appropriately. If there is no widget to move the focus to (or the key press is not Tab or Shift+Tab), event() calls keyPressEvent().

Mouse and tablet event handling is also slightly special: only when the widget is enabled, event() will call the specialized handlers such as mousePressEvent(); otherwise it will discard the event.

This function returns true if the event was recognized, otherwise it returns false. If the recognized event was accepted (see QEvent::accepted), any further processing such as event propagation to the parent widget stops.

See also closeEvent(), focusInEvent(), focusOutEvent(), enterEvent(), keyPressEvent(), keyReleaseEvent(), leaveEvent(), mouseDoubleClickEvent(), mouseMoveEvent(), mousePressEvent(), mouseReleaseEvent(), moveEvent(), paintEvent(), resizeEvent(), QObject::event(), and QObject::timerEvent().

[static] QWidget *QWidget::find(WId id)

Returns a pointer to the widget with window identifier/handle id.

The window identifier type depends on the underlying window system, see qwindowdefs.h for the actual definition. If there is no widget with this identifier, nullptr is returned.

[virtual protected] void QWidget::focusInEvent(QFocusEvent *event)

This event handler can be reimplemented in a subclass to receive keyboard focus events (focus received) for the widget. The event is passed in the event parameter

A widget normally must setFocusPolicy() to something other than Qt::NoFocus in order to receive focus events. (Note that the application programmer can call setFocus() on any widget, even those that do not normally accept focus.)

The default implementation updates the widget (except for windows that do not specify a focusPolicy()).

See also focusOutEvent(), setFocusPolicy(), keyPressEvent(), keyReleaseEvent(), event(), and QFocusEvent.

[protected] bool QWidget::focusNextChild()

Finds a new widget to give the keyboard focus to, as appropriate for Tab, and returns true if it can find a new widget, or false if it can't.

See also focusPreviousChild().

[virtual protected] bool QWidget::focusNextPrevChild(bool next)

Finds a new widget to give the keyboard focus to, as appropriate for Tab and Shift+Tab, and returns true if it can find a new widget, or false if it can't.

If next is true, this function searches forward, if next is false, it searches backward.

Sometimes, you will want to reimplement this function. For example, a web browser might reimplement it to move its "current active link" forward or backward, and call focusNextPrevChild() only when it reaches the last or first link on the "page".

Child widgets call focusNextPrevChild() on their parent widgets, but only the window that contains the child widgets decides where to redirect focus. By reimplementing this function for an object, you thus gain control of focus traversal for all child widgets.

See also focusNextChild() and focusPreviousChild().

[virtual protected] void QWidget::focusOutEvent(QFocusEvent *event)

This event handler can be reimplemented in a subclass to receive keyboard focus events (focus lost) for the widget. The events is passed in the event parameter.

A widget normally must setFocusPolicy() to something other than Qt::NoFocus in order to receive focus events. (Note that the application programmer can call setFocus() on any widget, even those that do not normally accept focus.)

The default implementation updates the widget (except for windows that do not specify a focusPolicy()).

See also focusInEvent(), setFocusPolicy(), keyPressEvent(), keyReleaseEvent(), event(), and QFocusEvent.

[protected] bool QWidget::focusPreviousChild()

Finds a new widget to give the keyboard focus to, as appropriate for Shift+Tab, and returns true if it can find a new widget, or false if it can't.

See also focusNextChild().

QWidget *QWidget::focusProxy() const

Returns the focus proxy, or nullptr if there is no focus proxy.

See also setFocusProxy().

QWidget *QWidget::focusWidget() const

Returns the last child of this widget that setFocus had been called on. For top level widgets this is the widget that will get focus in case this window gets activated

This is not the same as QApplication::focusWidget(), which returns the focus widget in the currently active window.

QFontInfo QWidget::fontInfo() const

Returns the font info for the widget's current font. Equivalent to QFontInfo(widget->font()).

See also font(), fontMetrics(), and setFont().

QFontMetrics QWidget::fontMetrics() const

Returns the font metrics for the widget's current font. Equivalent to QFontMetrics(widget->font()).

See also font(), fontInfo(), and setFont().

QPalette::ColorRole QWidget::foregroundRole() const

Returns the foreground role.

The foreground role defines the color from the widget's palette that is used to draw the foreground.

If no explicit foreground role is set, the function returns a role that contrasts with the background role.

See also setForegroundRole() and backgroundRole().

QPixmap QWidget::grab(const QRect &rectangle = QRect(QPoint(0, 0), QSize(-1, -1)))

Renders the widget into a pixmap restricted by the given rectangle. If the widget has any children, then they are also painted in the appropriate positions.

If a rectangle with an invalid size is specified (the default), the entire widget is painted.

Note: This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.

This function was introduced in Qt 5.0.

See also render() and QPixmap.

void QWidget::grabGesture(Qt::GestureType gesture, Qt::GestureFlags flags = Qt::GestureFlags())

Subscribes the widget to a given gesture with specific flags.

This function was introduced in Qt 4.6.

See also ungrabGesture() and QGestureEvent.

void QWidget::grabKeyboard()

Grabs the keyboard input.

This widget receives all keyboard events until releaseKeyboard() is called; other widgets get no keyboard events at all. Mouse events are not affected. Use grabMouse() if you want to grab that.

The focus widget is not affected, except that it doesn't receive any keyboard events. setFocus() moves the focus as usual, but the new focus widget receives keyboard events only after releaseKeyboard() is called.

If a different widget is currently grabbing keyboard input, that widget's grab is released first.

See also releaseKeyboard(), grabMouse(), releaseMouse(), and focusWidget().

void QWidget::grabMouse()

Grabs the mouse input.

This widget receives all mouse events until releaseMouse() is called; other widgets get no mouse events at all. Keyboard events are not affected. Use grabKeyboard() if you want to grab that.

It is almost never necessary to grab the mouse when using Qt, as Qt grabs and releases it sensibly. In particular, Qt grabs the mouse when a mouse button is pressed and keeps it until the last button is released.

See also releaseMouse(), grabKeyboard(), and releaseKeyboard().

void QWidget::grabMouse(const QCursor &cursor)

This function overloads grabMouse().

Grabs the mouse input and changes the cursor shape.

The cursor will assume shape cursor (for as long as the mouse focus is grabbed) and this widget will be the only one to receive mouse events until releaseMouse() is called().

See also releaseMouse(), grabKeyboard(), releaseKeyboard(), and setCursor().

int QWidget::grabShortcut(const QKeySequence &key, Qt::ShortcutContext context = Qt::WindowShortcut)

Adds a shortcut to Qt's shortcut system that watches for the given key sequence in the given context. If the context is Qt::ApplicationShortcut, the shortcut applies to the application as a whole. Otherwise, it is either local to this widget, Qt::WidgetShortcut, or to the window itself, Qt::WindowShortcut.

If the same key sequence has been grabbed by several widgets, when the key sequence occurs a QEvent::Shortcut event is sent to all the widgets to which it applies in a non-deterministic order, but with the ``ambiguous'' flag set to true.

See also releaseShortcut() and setShortcutEnabled().

QGraphicsEffect *QWidget::graphicsEffect() const

The graphicsEffect function returns a pointer to the widget's graphics effect.

If the widget has no graphics effect, nullptr is returned.

This function was introduced in Qt 4.6.

See also setGraphicsEffect().

QGraphicsProxyWidget *QWidget::graphicsProxyWidget() const

Returns the proxy widget for the corresponding embedded widget in a graphics view; otherwise returns nullptr.

This function was introduced in Qt 4.5.

See also QGraphicsProxyWidget::createProxyForChildWidget() and QGraphicsScene::addWidget().

bool QWidget::hasEditFocus() const

Returns true if this widget currently has edit focus; otherwise false.

This feature is only available in Qt for Embedded Linux.

See also setEditFocus() and QApplication::navigationMode().

[virtual] bool QWidget::hasHeightForWidth() const

Returns true if the widget's preferred height depends on its width; otherwise returns false.

This function was introduced in Qt 5.0.

[virtual] int QWidget::heightForWidth(int w) const

Returns the preferred height for this widget, given the width w.

If this widget has a layout, the default implementation returns the layout's preferred height. if there is no layout, the default implementation returns -1 indicating that the preferred height does not depend on the width.

[virtual protected] void QWidget::hideEvent(QHideEvent *event)

This event handler can be reimplemented in a subclass to receive widget hide events. The event is passed in the event parameter.

Hide events are sent to widgets immediately after they have been hidden.

Note: A widget receives spontaneous show and hide events when its mapping status is changed by the window system, e.g. a spontaneous hide event when the user minimizes the window, and a spontaneous show event when the window is restored again. After receiving a spontaneous hide event, a widget is still considered visible in the sense of isVisible().

See also visible, event(), and QHideEvent.

[override virtual protected] void QWidget::initPainter(QPainter *painter) const

Initializes the painter pen, background and font to the same as the given widget's. This function is called automatically when the painter is opened on a QWidget.

[virtual protected] void QWidget::inputMethodEvent(QInputMethodEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive Input Method composition events. This handler is called when the state of the input method changes.

Note that when creating custom text editing widgets, the Qt::WA_InputMethodEnabled window attribute must be set explicitly (using the setAttribute() function) in order to receive input method events.

The default implementation calls event->ignore(), which rejects the Input Method event. See the QInputMethodEvent documentation for more details.

See also event() and QInputMethodEvent.

[virtual] QVariant QWidget::inputMethodQuery(Qt::InputMethodQuery query) const

This method is only relevant for input widgets. It is used by the input method to query a set of properties of the widget to be able to support complex input method operations as support for surrounding text and reconversions.

query specifies which property is queried.

See also inputMethodEvent(), QInputMethodEvent, QInputMethodQueryEvent, and inputMethodHints.

void QWidget::insertAction(QAction *before, QAction *action)

Inserts the action action to this widget's list of actions, before the action before. It appends the action if before is nullptr or before is not a valid action for this widget.

A QWidget should only have one of each action.

See also removeAction(), addAction(), QMenu, contextMenuPolicy, and actions().

void QWidget::insertActions(QAction *before, QList<QAction *> actions)

Inserts the actions actions to this widget's list of actions, before the action before. It appends the action if before is nullptr or before is not a valid action for this widget.

A QWidget can have at most one of each action.

See also removeAction(), QMenu, insertAction(), and contextMenuPolicy.

bool QWidget::isAncestorOf(const QWidget *child) const

Returns true if this widget is a parent, (or grandparent and so on to any level), of the given child, and both widgets are within the same window; otherwise returns false.

bool QWidget::isEnabledTo(const QWidget *ancestor) const

Returns true if this widget would become enabled if ancestor is enabled; otherwise returns false.

This is the case if neither the widget itself nor every parent up to but excluding ancestor has been explicitly disabled.

isEnabledTo(0) returns false if this widget or any if its ancestors was explicitly disabled.

The word ancestor here means a parent widget within the same window.

Therefore isEnabledTo(0) stops at this widget's window, unlike isEnabled() which also takes parent windows into considerations.

See also setEnabled() and enabled.

bool QWidget::isHidden() const

Returns true if the widget is hidden, otherwise returns false.

A hidden widget will only become visible when show() is called on it. It will not be automatically shown when the parent is shown.

To check visibility, use !isVisible() instead (notice the exclamation mark).

isHidden() implies !isVisible(), but a widget can be not visible and not hidden at the same time. This is the case for widgets that are children of widgets that are not visible.

Widgets are hidden if:

• they were created as independent windows,
• they were created as children of visible widgets,
• hide() or setVisible(false) was called.

bool QWidget::isVisibleTo(const QWidget *ancestor) const

Returns true if this widget would become visible if ancestor is shown; otherwise returns false.

The true case occurs if neither the widget itself nor any parent up to but excluding ancestor has been explicitly hidden.

This function will still return true if the widget is obscured by other windows on the screen, but could be physically visible if it or they were to be moved.

isVisibleTo(0) is identical to isVisible().

See also show(), hide(), and isVisible().

bool QWidget::isWindow() const

Returns true if the widget is an independent window, otherwise returns false.

A window is a widget that isn't visually the child of any other widget and that usually has a frame and a window title.

A window can have a parent widget. It will then be grouped with its parent and deleted when the parent is deleted, minimized when the parent is minimized etc. If supported by the window manager, it will also have a common taskbar entry with its parent.

QDialog and QMainWindow widgets are by default windows, even if a parent widget is specified in the constructor. This behavior is specified by the Qt::Window flag.

See also window(), isModal(), and parentWidget().

[virtual protected] void QWidget::keyPressEvent(QKeyEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive key press events for the widget.

A widget must call setFocusPolicy() to accept focus initially and have focus in order to receive a key press event.

If you reimplement this handler, it is very important that you call the base class implementation if you do not act upon the key.

The default implementation closes popup widgets if the user presses the key sequence for QKeySequence::Cancel (typically the Escape key). Otherwise the event is ignored, so that the widget's parent can interpret it.

Note that QKeyEvent starts with isAccepted() == true, so you do not need to call QKeyEvent::accept() - just do not call the base class implementation if you act upon the key.

See also keyReleaseEvent(), setFocusPolicy(), focusInEvent(), focusOutEvent(), event(), QKeyEvent, and Tetrix Example.

[virtual protected] void QWidget::keyReleaseEvent(QKeyEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive key release events for the widget.

A widget must accept focus initially and have focus in order to receive a key release event.

If you reimplement this handler, it is very important that you call the base class implementation if you do not act upon the key.

The default implementation ignores the event, so that the widget's parent can interpret it.

Note that QKeyEvent starts with isAccepted() == true, so you do not need to call QKeyEvent::accept() - just do not call the base class implementation if you act upon the key.

See also keyPressEvent(), QEvent::ignore(), setFocusPolicy(), focusInEvent(), focusOutEvent(), event(), and QKeyEvent.

[static] QWidget *QWidget::keyboardGrabber()

Returns the widget that is currently grabbing the keyboard input.

If no widget in this application is currently grabbing the keyboard, nullptr is returned.

See also grabMouse() and mouseGrabber().

QLayout *QWidget::layout() const

Returns the layout manager that is installed on this widget, or nullptr if no layout manager is installed.

The layout manager sets the geometry of the widget's children that have been added to the layout.

See also setLayout(), sizePolicy(), and Layout Management.

[virtual protected] void QWidget::leaveEvent(QEvent *event)

This event handler can be reimplemented in a subclass to receive widget leave events which are passed in the event parameter.

A leave event is sent to the widget when the mouse cursor leaves the widget.

See also enterEvent(), mouseMoveEvent(), and event().

QPoint QWidget::mapFrom(const QWidget *parent, const QPoint &pos) const

Translates the widget coordinate pos from the coordinate system of parent to this widget's coordinate system. The parent must not be nullptr and must be a parent of the calling widget.

See also mapTo(), mapFromParent(), mapFromGlobal(), and underMouse().

QPoint QWidget::mapFromGlobal(const QPoint &pos) const

Translates the global screen coordinate pos to widget coordinates.

See also mapToGlobal(), mapFrom(), and mapFromParent().

QPoint QWidget::mapFromParent(const QPoint &pos) const

Translates the parent widget coordinate pos to widget coordinates.

Same as mapFromGlobal() if the widget has no parent.

See also mapToParent(), mapFrom(), mapFromGlobal(), and underMouse().

QPoint QWidget::mapTo(const QWidget *parent, const QPoint &pos) const

Translates the widget coordinate pos to the coordinate system of parent. The parent must not be nullptr and must be a parent of the calling widget.

See also mapFrom(), mapToParent(), mapToGlobal(), and underMouse().

QPoint QWidget::mapToGlobal(const QPoint &pos) const

Translates the widget coordinate pos to global screen coordinates. For example, mapToGlobal(QPoint(0,0)) would give the global coordinates of the top-left pixel of the widget.

See also mapFromGlobal(), mapTo(), and mapToParent().

QPoint QWidget::mapToParent(const QPoint &pos) const

Translates the widget coordinate pos to a coordinate in the parent widget.

Same as mapToGlobal() if the widget has no parent.

See also mapFromParent(), mapTo(), mapToGlobal(), and underMouse().

QRegion QWidget::mask() const

Returns the mask currently set on a widget. If no mask is set the return value will be an empty region.

See also setMask(), clearMask(), QRegion::isEmpty(), and Shaped Clock Example.

[override virtual protected] int QWidget::metric(QPaintDevice::PaintDeviceMetric m) const

Reimplements: QPaintDevice::metric(QPaintDevice::PaintDeviceMetric metric) const.

Internal implementation of the virtual QPaintDevice::metric() function.

m is the metric to get.

[virtual protected] void QWidget::mouseDoubleClickEvent(QMouseEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive mouse double click events for the widget.

The default implementation calls mousePressEvent().

See also mousePressEvent(), mouseReleaseEvent(), mouseMoveEvent(), event(), and QMouseEvent.

[static] QWidget *QWidget::mouseGrabber()

Returns the widget that is currently grabbing the mouse input.

If no widget in this application is currently grabbing the mouse, nullptr is returned.

See also grabMouse() and keyboardGrabber().

[virtual protected] void QWidget::mouseMoveEvent(QMouseEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive mouse move events for the widget.

If mouse tracking is switched off, mouse move events only occur if a mouse button is pressed while the mouse is being moved. If mouse tracking is switched on, mouse move events occur even if no mouse button is pressed.

QMouseEvent::pos() reports the position of the mouse cursor, relative to this widget. For press and release events, the position is usually the same as the position of the last mouse move event, but it might be different if the user's hand shakes. This is a feature of the underlying window system, not Qt.

If you want to show a tooltip immediately, while the mouse is moving (e.g., to get the mouse coordinates with QMouseEvent::pos() and show them as a tooltip), you must first enable mouse tracking as described above. Then, to ensure that the tooltip is updated immediately, you must call QToolTip::showText() instead of setToolTip() in your implementation of mouseMoveEvent().

See also setMouseTracking(), mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(), event(), QMouseEvent, and Scribble Example.

[virtual protected] void QWidget::mousePressEvent(QMouseEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive mouse press events for the widget.

If you create new widgets in the mousePressEvent() the mouseReleaseEvent() may not end up where you expect, depending on the underlying window system (or X11 window manager), the widgets' location and maybe more.

The default implementation implements the closing of popup widgets when you click outside the window. For other widget types it does nothing.

See also mouseReleaseEvent(), mouseDoubleClickEvent(), mouseMoveEvent(), event(), QMouseEvent, and Scribble Example.

[virtual protected] void QWidget::mouseReleaseEvent(QMouseEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive mouse release events for the widget.

See also mousePressEvent(), mouseDoubleClickEvent(), mouseMoveEvent(), event(), QMouseEvent, and Scribble Example.

void QWidget::move(int x, int y)

This is an overloaded function.

This corresponds to move(QPoint(x, y)).

Note: Setter function for property pos.

[virtual protected] void QWidget::moveEvent(QMoveEvent *event)

This event handler can be reimplemented in a subclass to receive widget move events which are passed in the event parameter. When the widget receives this event, it is already at the new position.

The old position is accessible through QMoveEvent::oldPos().

See also resizeEvent(), event(), move(), and QMoveEvent.

[virtual protected] bool QWidget::nativeEvent(const QByteArray &eventType, void *message, long *result)

This special event handler can be reimplemented in a subclass to receive native platform events identified by eventType which are passed in the message parameter.

In your reimplementation of this function, if you want to stop the event being handled by Qt, return true and set result. The result parameter has meaning only on Windows. If you return false, this native event is passed back to Qt, which translates the event into a Qt event and sends it to the widget.

See also QAbstractNativeEventFilter.

QWidget *QWidget::nativeParentWidget() const

Returns the native parent for this widget, i.e. the next ancestor widget that has a system identifier, or nullptr if it does not have any native parent.

This function was introduced in Qt 4.4.

See also effectiveWinId().

QWidget *QWidget::nextInFocusChain() const

Returns the next widget in this widget's focus chain.

See also previousInFocusChain().

void QWidget::overrideWindowFlags(Qt::WindowFlags flags)

Sets the window flags for the widget to flags, without telling the window system.

See also setWindowFlags().

[override virtual] QPaintEngine *QWidget::paintEngine() const

Reimplements: QPaintDevice::paintEngine() const.

Returns the widget's paint engine.

Note that this function should not be called explicitly by the user, since it's meant for reimplementation purposes only. The function is called by Qt internally, and the default implementation may not always return a valid pointer.

[virtual protected] void QWidget::paintEvent(QPaintEvent *event)

This event handler can be reimplemented in a subclass to receive paint events passed in event.

A paint event is a request to repaint all or part of a widget. It can happen for one of the following reasons:

• repaint() or update() was invoked,
• the widget was obscured and has now been uncovered, or
• many other reasons.

Many widgets can simply repaint their entire surface when asked to, but some slow widgets need to optimize by painting only the requested region: QPaintEvent::region(). This speed optimization does not change the result, as painting is clipped to that region during event processing. QListView and QTableView do this, for example.

Qt also tries to speed up painting by merging multiple paint events into one. When update() is called several times or the window system sends several paint events, Qt merges these events into one event with a larger region (see QRegion::united()). The repaint() function does not permit this optimization, so we suggest using update() whenever possible.

When the paint event occurs, the update region has normally been erased, so you are painting on the widget's background.

The background can be set using setBackgroundRole() and setPalette().

Since Qt 4.0, QWidget automatically double-buffers its painting, so there is no need to write double-buffering code in paintEvent() to avoid flicker.

See also event(), repaint(), update(), QPainter, QPixmap, QPaintEvent, and Analog Clock Example.

QWidget *QWidget::parentWidget() const

Returns the parent of this widget, or nullptr if it does not have any parent widget.

QWidget *QWidget::previousInFocusChain() const

The previousInFocusChain function returns the previous widget in this widget's focus chain.

This function was introduced in Qt 4.6.

See also nextInFocusChain().

void QWidget::releaseKeyboard()

Releases the keyboard grab.

See also grabKeyboard(), grabMouse(), and releaseMouse().

void QWidget::releaseMouse()

Releases the mouse grab.

See also grabMouse(), grabKeyboard(), and releaseKeyboard().

void QWidget::releaseShortcut(int id)

Removes the shortcut with the given id from Qt's shortcut system. The widget will no longer receive QEvent::Shortcut events for the shortcut's key sequence (unless it has other shortcuts with the same key sequence).

See also grabShortcut() and setShortcutEnabled().

void QWidget::removeAction(QAction *action)

Removes the action action from this widget's list of actions.

See also insertAction(), actions(), and insertAction().

void QWidget::render(QPaintDevice *target, const QPoint &targetOffset = QPoint(), const QRegion &sourceRegion = QRegion(), QWidget::RenderFlags renderFlags = RenderFlags(DrawWindowBackground | DrawChildren))

Renders the sourceRegion of this widget into the target using renderFlags to determine how to render. Rendering starts at targetOffset in the target. For example:

QPixmap pixmap(widget->size());
widget->render(&pixmap);

If sourceRegion is a null region, this function will use QWidget::rect() as the region, i.e. the entire widget.

Ensure that you call QPainter::end() for the target device's active painter (if any) before rendering. For example:

QPainter painter(this);
...
painter.end();
myWidget->render(this);

This function was introduced in Qt 4.3.

void QWidget::render(QPainter *painter, const QPoint &targetOffset = QPoint(), const QRegion &sourceRegion = QRegion(), QWidget::RenderFlags renderFlags = RenderFlags(DrawWindowBackground | DrawChildren))

This is an overloaded function.

Renders the widget into the painter's QPainter::device().

Transformations and settings applied to the painter will be used when rendering.

See also QPainter::device().

void QWidget::repaint(int x, int y, int w, int h)

This is an overloaded function.

This version repaints a rectangle (x, y, w, h) inside the widget.

If w is negative, it is replaced with width() - x, and if h is negative, it is replaced width height() - y.

void QWidget::repaint(const QRect &rect)

This is an overloaded function.

This version repaints a rectangle rect inside the widget.

void QWidget::repaint(const QRegion &rgn)

This is an overloaded function.

This version repaints a region rgn inside the widget.

void QWidget::resize(int w, int h)

This is an overloaded function.

This corresponds to resize(QSize(w, h)).

Note: Setter function for property size.

[virtual protected] void QWidget::resizeEvent(QResizeEvent *event)

This event handler can be reimplemented in a subclass to receive widget resize events which are passed in the event parameter. When resizeEvent() is called, the widget already has its new geometry. The old size is accessible through QResizeEvent::oldSize().

The widget will be erased and receive a paint event immediately after processing the resize event. No drawing need be (or should be) done inside this handler.

See also moveEvent(), event(), resize(), QResizeEvent, paintEvent(), and Scribble Example.

bool QWidget::restoreGeometry(const QByteArray &geometry)

Restores the geometry and state of top-level widgets stored in the byte array geometry. Returns true on success; otherwise returns false.

If the restored geometry is off-screen, it will be modified to be inside the available screen geometry.

To restore geometry saved using QSettings, you can use code like this:

QSettings settings("MyCompany", "MyApp");
myWidget->restoreGeometry(settings.value("myWidget/geometry").toByteArray());

See the Window Geometry documentation for an overview of geometry issues with windows.

Use QMainWindow::restoreState() to restore the geometry and the state of toolbars and dock widgets.

This function was introduced in Qt 4.2.

See also saveGeometry(), QSettings, QMainWindow::saveState(), and QMainWindow::restoreState().

QByteArray QWidget::saveGeometry() const

Saves the current geometry and state for top-level widgets.

To save the geometry when the window closes, you can implement a close event like this:

void MyWidget::closeEvent(QCloseEvent *event)
{
    QSettings settings("MyCompany", "MyApp");
    settings.setValue("geometry", saveGeometry());
    QWidget::closeEvent(event);
}

See the Window Geometry documentation for an overview of geometry issues with windows.

Use QMainWindow::saveState() to save the geometry and the state of toolbars and dock widgets.

This function was introduced in Qt 4.2.

See also restoreGeometry(), QMainWindow::saveState(), and QMainWindow::restoreState().

QScreen *QWidget::screen() const

Returns the screen the widget is on.

This function was introduced in Qt 5.14.

See also windowHandle().

void QWidget::scroll(int dx, int dy)

Scrolls the widget including its children dx pixels to the right and dy downward. Both dx and dy may be negative.

After scrolling, the widgets will receive paint events for the areas that need to be repainted. For widgets that Qt knows to be opaque, this is only the newly exposed parts. For example, if an opaque widget is scrolled 8 pixels to the left, only an 8-pixel wide stripe at the right edge needs updating.

Since widgets propagate the contents of their parents by default, you need to set the autoFillBackground property, or use setAttribute() to set the Qt::WA_OpaquePaintEvent attribute, to make a widget opaque.

For widgets that use contents propagation, a scroll will cause an update of the entire scroll area.

See also Transparency and Double Buffering.

void QWidget::scroll(int dx, int dy, const QRect &r)

This is an overloaded function.

This version only scrolls r and does not move the children of the widget.

If r is empty or invalid, the result is undefined.

See also QScrollArea.

void QWidget::setAttribute(Qt::WidgetAttribute attribute, bool on = true)

Sets the attribute attribute on this widget if on is true; otherwise clears the attribute.

See also testAttribute().

void QWidget::setBackgroundRole(QPalette::ColorRole role)

Sets the background role of the widget to role.

The background role defines the brush from the widget's palette that is used to render the background.

If role is QPalette::NoRole, then the widget inherits its parent's background role.

Note that styles are free to choose any color from the palette. You can modify the palette or set a style sheet if you don't achieve the result you want with setBackgroundRole().

See also backgroundRole() and foregroundRole().

void QWidget::setBaseSize(int basew, int baseh)

This is an overloaded function.

This corresponds to setBaseSize(QSize(basew, baseh)). Sets the widgets base size to width basew and height baseh.

Note: Setter function for property baseSize.

void QWidget::setContentsMargins(int left, int top, int right, int bottom)

Sets the margins around the contents of the widget to have the sizes left, top, right, and bottom. The margins are used by the layout system, and may be used by subclasses to specify the area to draw in (e.g. excluding the frame).

Changing the margins will trigger a resizeEvent().

See also contentsRect() and contentsMargins().

void QWidget::setContentsMargins(const QMargins &margins)

This is an overloaded function.

The setContentsMargins function sets the margins around the widget's contents.

Sets the margins around the contents of the widget to have the sizes determined by margins. The margins are used by the layout system, and may be used by subclasses to specify the area to draw in (e.g. excluding the frame).

Changing the margins will trigger a resizeEvent().

This function was introduced in Qt 4.6.

See also contentsRect() and contentsMargins().

void QWidget::setEditFocus(bool enable)

If enable is true, make this widget have edit focus, in which case Qt::Key_Up and Qt::Key_Down will be delivered to the widget normally; otherwise, Qt::Key_Up and Qt::Key_Down are used to change focus.

This feature is only available in Qt for Embedded Linux.

See also hasEditFocus() and QApplication::navigationMode().

void QWidget::setFixedHeight(int h)

Sets both the minimum and maximum heights of the widget to h without changing the widths. Provided for convenience.

See also sizeHint(), minimumSize(), maximumSize(), and setFixedSize().

void QWidget::setFixedSize(const QSize &s)

Sets both the minimum and maximum sizes of the widget to s, thereby preventing it from ever growing or shrinking.

This will override the default size constraints set by QLayout.

To remove constraints, set the size to QWIDGETSIZE_MAX.

Alternatively, if you want the widget to have a fixed size based on its contents, you can call QLayout::setSizeConstraint(QLayout::SetFixedSize);

See also maximumSize and minimumSize.

void QWidget::setFixedSize(int w, int h)

This is an overloaded function.

Sets the width of the widget to w and the height to h.

void QWidget::setFixedWidth(int w)

Sets both the minimum and maximum width of the widget to w without changing the heights. Provided for convenience.

See also sizeHint(), minimumSize(), maximumSize(), and setFixedSize().

void QWidget::setFocus(Qt::FocusReason reason)

Gives the keyboard input focus to this widget (or its focus proxy) if this widget or one of its parents is the active window. The reason argument will be passed into any focus event sent from this function, it is used to give an explanation of what caused the widget to get focus. If the window is not active, the widget will be given the focus when the window becomes active.

First, a focus about to change event is sent to the focus widget (if any) to tell it that it is about to lose the focus. Then focus is changed, a focus out event is sent to the previous focus item and a focus in event is sent to the new item to tell it that it just received the focus. (Nothing happens if the focus in and focus out widgets are the same.)

setFocus() gives focus to a widget regardless of its focus policy, but does not clear any keyboard grab (see grabKeyboard()).

Be aware that if the widget is hidden, it will not accept focus until it is shown.

See also hasFocus(), clearFocus(), focusInEvent(), focusOutEvent(), setFocusPolicy(), focusWidget(), QApplication::focusWidget(), grabKeyboard(), grabMouse(), Keyboard Focus in Widgets, and QEvent::RequestSoftwareInputPanel.

void QWidget::setFocusProxy(QWidget *w)

Sets the widget's focus proxy to widget w. If w is nullptr, the function resets this widget to have no focus proxy.

Some widgets can "have focus", but create a child widget, such as QLineEdit, to actually handle the focus. In this case, the widget can set the line edit to be its focus proxy.

setFocusProxy() sets the widget which will actually get focus when "this widget" gets it. If there is a focus proxy, setFocus() and hasFocus() operate on the focus proxy. If "this widget" is the focus widget, then setFocusProxy() moves focus to the new focus proxy.

See also focusProxy().

void QWidget::setForegroundRole(QPalette::ColorRole role)

Sets the foreground role of the widget to role.

The foreground role defines the color from the widget's palette that is used to draw the foreground.

If role is QPalette::NoRole, the widget uses a foreground role that contrasts with the background role.

Note that styles are free to choose any color from the palette. You can modify the palette or set a style sheet if you don't achieve the result you want with setForegroundRole().

See also foregroundRole() and backgroundRole().

void QWidget::setGeometry(int x, int y, int w, int h)

This is an overloaded function.

This corresponds to setGeometry(QRect(x, y, w, h)).

Note: Setter function for property geometry.

void QWidget::setGraphicsEffect(QGraphicsEffect *effect)

The setGraphicsEffect function is for setting the widget's graphics effect.

Sets effect as the widget's effect. If there already is an effect installed on this widget, QWidget will delete the existing effect before installing the new effect.

If effect is the installed effect on a different widget, setGraphicsEffect() will remove the effect from the widget and install it on this widget.

QWidget takes ownership of effect.

This function was introduced in Qt 4.6.

See also graphicsEffect().

void QWidget::setLayout(QLayout *layout)

Sets the layout manager for this widget to layout.

If there already is a layout manager installed on this widget, QWidget won't let you install another. You must first delete the existing layout manager (returned by layout()) before you can call setLayout() with the new layout.

If layout is the layout manager on a different widget, setLayout() will reparent the layout and make it the layout manager for this widget.

Example:

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(formWidget);
    setLayout(layout);

An alternative to calling this function is to pass this widget to the layout's constructor.

The QWidget will take ownership of layout.

See also layout() and Layout Management.

void QWidget::setMask(const QBitmap &bitmap)

Causes only the pixels of the widget for which bitmap has a corresponding 1 bit to be visible. If the region includes pixels outside the rect() of the widget, window system controls in that area may or may not be visible, depending on the platform.

Note that this effect can be slow if the region is particularly complex.

The following code shows how an image with an alpha channel can be used to generate a mask for a widget:

    QLabel topLevelLabel;
    QPixmap pixmap(":/images/tux.png");
    topLevelLabel.setPixmap(pixmap);
    topLevelLabel.setMask(pixmap.mask());

The label shown by this code is masked using the image it contains, giving the appearance that an irregularly-shaped image is being drawn directly onto the screen.

Masked widgets receive mouse events only on their visible portions.

See also mask(), clearMask(), windowOpacity(), and Shaped Clock Example.

void QWidget::setMask(const QRegion &region)

This is an overloaded function.

Causes only the parts of the widget which overlap region to be visible. If the region includes pixels outside the rect() of the widget, window system controls in that area may or may not be visible, depending on the platform.

Note that this effect can be slow if the region is particularly complex.

See also windowOpacity.

void QWidget::setMaximumSize(int maxw, int maxh)

This is an overloaded function.

This function corresponds to setMaximumSize(QSize(maxw, maxh)). Sets the maximum width to maxw and the maximum height to maxh.

Note: Setter function for property maximumSize.

void QWidget::setMinimumSize(int minw, int minh)

This is an overloaded function.

This function corresponds to setMinimumSize(QSize(minw, minh)). Sets the minimum width to minw and the minimum height to minh.

Note: Setter function for property minimumSize.

void QWidget::setParent(QWidget *parent)

Sets the parent of the widget to parent, and resets the window flags. The widget is moved to position (0, 0) in its new parent.

If the new parent widget is in a different window, the reparented widget and its children are appended to the end of the tab chain of the new parent widget, in the same internal order as before. If one of the moved widgets had keyboard focus, setParent() calls clearFocus() for that widget.

If the new parent widget is in the same window as the old parent, setting the parent doesn't change the tab order or keyboard focus.

If the "new" parent widget is the old parent widget, this function does nothing.

See also setWindowFlags().

void QWidget::setParent(QWidget *parent, Qt::WindowFlags f)

This is an overloaded function.

This function also takes widget flags, f as an argument.

void QWidget::setShortcutAutoRepeat(int id, bool enable = true)

If enable is true, auto repeat of the shortcut with the given id is enabled; otherwise it is disabled.

This function was introduced in Qt 4.2.

See also grabShortcut() and releaseShortcut().

void QWidget::setShortcutEnabled(int id, bool enable = true)

If enable is true, the shortcut with the given id is enabled; otherwise the shortcut is disabled.

See also grabShortcut() and releaseShortcut().

void QWidget::setSizeIncrement(int w, int h)

This is an overloaded function.

Sets the x (width) size increment to w and the y (height) size increment to h.

Note: Setter function for property sizeIncrement.

void QWidget::setSizePolicy(QSizePolicy::Policy horizontal, QSizePolicy::Policy vertical)

This is an overloaded function.

Sets the size policy of the widget to horizontal and vertical, with standard stretch and no height-for-width.

Note: Setter function for property sizePolicy.

See also QSizePolicy::QSizePolicy().

void QWidget::setStyle(QStyle *style)

Sets the widget's GUI style to style. The ownership of the style object is not transferred.

If no style is set, the widget uses the application's style, QApplication::style() instead.

Setting a widget's style has no effect on existing or future child widgets.

See also style(), QStyle, QApplication::style(), and QApplication::setStyle().

[static] void QWidget::setTabOrder(QWidget *first, QWidget *second)

Puts the second widget after the first widget in the focus order.

It effectively removes the second widget from its focus chain and inserts it after the first widget.

Note that since the tab order of the second widget is changed, you should order a chain like this:

setTabOrder(a, b); // a to b
setTabOrder(b, c); // a to b to c
setTabOrder(c, d); // a to b to c to d

not like this:

// WRONG
setTabOrder(c, d); // c to d
setTabOrder(a, b); // a to b AND c to d
setTabOrder(b, c); // a to b to c, but not c to d

If first or second has a focus proxy, setTabOrder() correctly substitutes the proxy.

See also setFocusPolicy(), setFocusProxy(), and Keyboard Focus in Widgets.

void QWidget::setWindowFlag(Qt::WindowType flag, bool on = true)

Sets the window flag flag on this widget if on is true; otherwise clears the flag.

This function was introduced in Qt 5.9.

See also setWindowFlags(), windowFlags(), and windowType().

void QWidget::setWindowRole(const QString &role)

Sets the window's role to role. This only makes sense for windows on X11.

See also windowRole().

void QWidget::setWindowState(Qt::WindowStates windowState)

Sets the window state to windowState. The window state is a OR'ed combination of Qt::WindowState: Qt::WindowMinimized, Qt::WindowMaximized, Qt::WindowFullScreen, and Qt::WindowActive.

If the window is not visible (i.e. isVisible() returns false), the window state will take effect when show() is called. For visible windows, the change is immediate. For example, to toggle between full-screen and normal mode, use the following code:

w->setWindowState(w->windowState() ^ Qt::WindowFullScreen);

In order to restore and activate a minimized window (while preserving its maximized and/or full-screen state), use the following:

w->setWindowState((w->windowState() & ~Qt::WindowMinimized) | Qt::WindowActive);

Calling this function will hide the widget. You must call show() to make the widget visible again.

When the window state changes, the widget receives a changeEvent() of type QEvent::WindowStateChange.

See also Qt::WindowState and windowState().

void QWidget::setupUi(QWidget *widget)

Sets up the user interface for the specified widget.

See also Using a Designer UI File in Your C++ Application.

[virtual protected] void QWidget::showEvent(QShowEvent *event)

This event handler can be reimplemented in a subclass to receive widget show events which are passed in the event parameter.

Non-spontaneous show events are sent to widgets immediately before they are shown. The spontaneous show events of windows are delivered afterwards.

Note: A widget receives spontaneous show and hide events when its mapping status is changed by the window system, e.g. a spontaneous hide event when the user minimizes the window, and a spontaneous show event when the window is restored again. After receiving a spontaneous hide event, a widget is still considered visible in the sense of isVisible().

See also visible, event(), and QShowEvent.

void QWidget::stackUnder(QWidget *w)

Places the widget under w in the parent widget's stack.

To make this work, the widget itself and w must be siblings.

See also raise() and lower().

QStyle *QWidget::style() const

See also QWidget::setStyle(), QApplication::setStyle(), and QApplication::style().

[virtual protected] void QWidget::tabletEvent(QTabletEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive tablet events for the widget.

If you reimplement this handler, it is very important that you ignore() the event if you do not handle it, so that the widget's parent can interpret it.

The default implementation ignores the event.

If tablet tracking is switched off, tablet move events only occur if the stylus is in contact with the tablet, or at least one stylus button is pressed, while the stylus is being moved. If tablet tracking is switched on, tablet move events occur even while the stylus is hovering in proximity of the tablet, with no buttons pressed.

See also QEvent::ignore(), QEvent::accept(), event(), setTabletTracking(), and QTabletEvent.

bool QWidget::testAttribute(Qt::WidgetAttribute attribute) const

Returns true if attribute attribute is set on this widget; otherwise returns false.

See also setAttribute().

bool QWidget::underMouse() const

Returns true if the widget is under the mouse cursor; otherwise returns false.

This value is not updated properly during drag and drop operations.

See also enterEvent() and leaveEvent().

void QWidget::ungrabGesture(Qt::GestureType gesture)

Unsubscribes the widget from a given gesture type

This function was introduced in Qt 4.6.

See also grabGesture() and QGestureEvent.

void QWidget::update(int x, int y, int w, int h)

This is an overloaded function.

This version updates a rectangle (x, y, w, h) inside the widget.

void QWidget::update(const QRect &rect)

This is an overloaded function.

This version updates a rectangle rect inside the widget.

void QWidget::update(const QRegion &rgn)

This is an overloaded function.

This version repaints a region rgn inside the widget.

void QWidget::updateGeometry()

Notifies the layout system that this widget has changed and may need to change geometry.

Call this function if the sizeHint() or sizePolicy() have changed.

For explicitly hidden widgets, updateGeometry() is a no-op. The layout system will be notified as soon as the widget is shown.

QRegion QWidget::visibleRegion() const

Returns the unobscured region where paint events can occur.

For visible widgets, this is an approximation of the area not covered by other widgets; otherwise, this is an empty region.

The repaint() function calls this function if necessary, so in general you do not need to call it.

[virtual protected] void QWidget::wheelEvent(QWheelEvent *event)

This event handler, for event event, can be reimplemented in a subclass to receive wheel events for the widget.

If you reimplement this handler, it is very important that you ignore() the event if you do not handle it, so that the widget's parent can interpret it.

The default implementation ignores the event.

See also QEvent::ignore(), QEvent::accept(), event(), and QWheelEvent.

WId QWidget::winId() const

Returns the window system identifier of the widget.

Portable in principle, but if you use it you are probably about to do something non-portable. Be careful.

If a widget is non-native (alien) and winId() is invoked on it, that widget will be provided a native handle.

This value may change at run-time. An event with type QEvent::WinIdChange will be sent to the widget following a change in window system identifier.

See also find().

QWidget *QWidget::window() const

Returns the window for this widget, i.e. the next ancestor widget that has (or could have) a window-system frame.

If the widget is a window, the widget itself is returned.

Typical usage is changing the window title:

aWidget->window()->setWindowTitle("New Window Title");

See also isWindow().

QWindow *QWidget::windowHandle() const

If this is a native widget, return the associated QWindow. Otherwise return null.

Native widgets include toplevel widgets, QGLWidget, and child widgets on which winId() was called.

This function was introduced in Qt 5.0.

See also winId() and screen().

QString QWidget::windowRole() const

Returns the window's role, or an empty string.

See also setWindowRole(), windowIcon, and windowTitle.

Qt::WindowStates QWidget::windowState() const

Returns the current window state. The window state is a OR'ed combination of Qt::WindowState: Qt::WindowMinimized, Qt::WindowMaximized, Qt::WindowFullScreen, and Qt::WindowActive.

See also Qt::WindowState and setWindowState().

Qt::WindowType QWidget::windowType() const

Returns the window type of this widget. This is identical to windowFlags() & Qt::WindowType_Mask.

See also windowFlags.