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# QWidget Class Reference

The QWidget class is the base class of all user interface objects. More...

    #include <QWidget>

Part of the QtGui module.

Inherits QObject and QPaintDevice.

Inherited by Q3DataBrowser, Q3DataView, Q3DateTimeEdit, Q3DateTimeEditBase, Q3DockArea, Q3Header, Q3MainWindow, QAbstractButton, QAbstractSlider, QAbstractSpinBox, QAxWidget, QComboBox, QDesignerFormWindowInterface, QDesignerObjectInspectorInterface, QDesignerPropertyEditorInterface, QDesignerWidgetBoxInterface, QDesktopWidget, QDialog, QDockWidget, QFocusFrame, QFrame, QGLWidget, QGroupBox, QLineEdit, QMainWindow, QMenu, QMenuBar, QProgressBar, QRubberBand, QSizeGrip, QSplashScreen, QSplitterHandle, QStatusBar, QTabBar, QTabWidget, QToolBar, QWorkspace, QX11EmbedContainer, and QX11EmbedWidget.

- List of all members, including inherited members
- Obsolete members
- Qt 3 support members

### Properties

acceptDrops : bool accessibleDescription : QString accessibleName : QString baseSize : QSize childrenRect : const QRect childrenRegion : const QRegion contextMenuPolicy : Qt::ContextMenuPolicy cursor : QCursor enabled : bool focus : const bool focusPolicy : Qt::FocusPolicy font : QFont frameGeometry : const QRect frameSize : const QSize fullScreen : const bool geometry : QRect height : const int isActiveWindow : const bool layoutDirection : Qt::LayoutDirection maximized : const bool maximumHeight : int maximumSize : QSize maximumWidth : int minimized : const bool minimumHeight : int minimumSize : QSize | minimumSizeHint : const QSize minimumWidth : int modal : const bool mouseTracking : bool normalGeometry : const QRect palette : QPalette pos : QPoint rect : const QRect size : QSize sizeHint : const QSize sizeIncrement : QSize sizePolicy : QSizePolicy statusTip : QString toolTip : QString updatesEnabled : bool visible : bool whatsThis : QString width : const int windowFlags : Qt::WindowFlags windowIcon : QIcon windowIconText : QString windowModified : bool windowOpacity : double windowTitle : QString x : const int y : const int

- 1 property inherited from QObject

### Public Functions

- QWidget ( QWidget * parent = 0, Qt::WFlags f = 0 )
- ~QWidget ()
- bool acceptDrops () const
- QString accessibleDescription () const
- QString accessibleName () const
- QList<QAction *> actions () const
- void activateWindow ()
- void addAction ( QAction * action )
- void addActions ( QList<QAction *> actions )
- void adjustSize ()
- QPalette::ColorRole backgroundRole () const
- QSize baseSize () const
- QWidget * childAt ( int x, int y ) const
- QWidget * childAt ( const QPoint & p ) const
- QRect childrenRect () const
- QRegion childrenRegion () const
- void clearFocus ()
- void clearMask ()
- QRect contentsRect () const
- Qt::ContextMenuPolicy contextMenuPolicy () const
- QCursor cursor () const
- void ensurePolished () const
- Qt::FocusPolicy focusPolicy () const
- QWidget * focusProxy () const
- QWidget * focusWidget () const
- const QFont & font () const
- QFontInfo fontInfo () const
- QFontMetrics fontMetrics () const
- QPalette::ColorRole foregroundRole () const
- QRect frameGeometry () const
- QSize frameSize () const
- const QRect & geometry () const
- void getContentsMargins ( int * left, int * top, int * right, int * bottom ) const
- virtual HDC getDC () const
- void grabKeyboard ()
- void grabMouse ()
- void grabMouse ( const QCursor & cursor )
- int grabShortcut ( const QKeySequence & key, Qt::ShortcutContext context = Qt::WindowShortcut )
- bool hasFocus () const
- bool hasMouseTracking () const
- int height () const
- virtual int heightForWidth ( int w ) const
- QInputContext * inputContext ()
- virtual QVariant inputMethodQuery ( Qt::InputMethodQuery query ) const
- void insertAction ( QAction * before, QAction * action )
- void insertActions ( QAction * before, QList<QAction *> actions )
- bool isActiveWindow () const
- bool isAncestorOf ( const QWidget * child ) const
- bool isEnabled () const
- bool isEnabledTo ( QWidget * ancestor ) const
- bool isFullScreen () const
- bool isHidden () const
- bool isMaximized () const
- bool isMinimized () const
- bool isModal () const
- bool isVisible () const
- bool isVisibleTo ( QWidget * ancestor ) const
- bool isWindow () const
- bool isWindowModified () const
- QLayout * layout () const
- Qt::LayoutDirection layoutDirection () const
- QPoint mapFrom ( QWidget * parent, const QPoint & pos ) const
- QPoint mapFromGlobal ( const QPoint & pos ) const
- QPoint mapFromParent ( const QPoint & pos ) const
- QPoint mapTo ( QWidget * parent, const QPoint & pos ) const
- QPoint mapToGlobal ( const QPoint & pos ) const
- QPoint mapToParent ( const QPoint & pos ) const
- QRegion mask () const
- int maximumHeight () const
- QSize maximumSize () const
- int maximumWidth () const
- int minimumHeight () const
- QSize minimumSize () const
- virtual QSize minimumSizeHint () const
- int minimumWidth () const
- void move ( const QPoint & )
- void move ( int x, int y )
- QWidget * nextInFocusChain () const
- QRect normalGeometry () const
- void overrideWindowFlags ( Qt::WindowFlags flags )
- virtual QPaintEngine * paintEngine () const
- const QPalette & palette () const
- QWidget * parentWidget () const
- QPoint pos () const
- QRect rect () const
- virtual void releaseDC ( HDC hdc ) const
- void releaseKeyboard ()
- void releaseMouse ()
- void releaseShortcut ( int id )
- void removeAction ( QAction * action )
- void repaint ( int x, int y, int w, int h )
- void repaint ( const QRect & r )
- void repaint ( const QRegion & rgn )
- void resize ( const QSize & )
- void resize ( int w, int h )
- void scroll ( int dx, int dy )
- void scroll ( int dx, int dy, const QRect & r )
- void setAcceptDrops ( bool on )
- void setAccessibleDescription ( const QString & description )
- void setAccessibleName ( const QString & name )
- void setAttribute ( Qt::WidgetAttribute attribute, bool on = true )
- void setBackgroundRole ( QPalette::ColorRole role )
- void setBaseSize ( const QSize & )
- void setBaseSize ( int basew, int baseh )
- void setContentsMargins ( int left, int top, int right, int bottom )
- void setContextMenuPolicy ( Qt::ContextMenuPolicy policy )
- void setCursor ( const QCursor & )
- void setFixedHeight ( int h )
- void setFixedSize ( const QSize & s )
- void setFixedSize ( int w, int h )
- void setFixedWidth ( int w )
- void setFocus ( Qt::FocusReason reason )
- void setFocusPolicy ( Qt::FocusPolicy policy )
- void setFocusProxy ( QWidget * w )
- void setFont ( const QFont & )
- void setForegroundRole ( QPalette::ColorRole role )
- void setGeometry ( const QRect & )
- void setGeometry ( int x, int y, int w, int h )
- void setInputContext ( QInputContext * context )
- void setLayout ( QLayout * l )
- void setLayoutDirection ( Qt::LayoutDirection direction )
- void setMask ( const QBitmap & bitmap )
- void setMask ( const QRegion & region )
- void setMaximumHeight ( int maxh )
- void setMaximumSize ( const QSize & )
- void setMaximumSize ( int maxw, int maxh )
- void setMaximumWidth ( int maxw )
- void setMinimumHeight ( int minh )
- void setMinimumSize ( const QSize & )
- void setMinimumSize ( int minw, int minh )
- void setMinimumWidth ( int minw )
- void setMouseTracking ( bool enable )
- void setPalette ( const QPalette & )
- void setParent ( QWidget * parent )
- void setParent ( QWidget * parent, Qt::WFlags f )
- void setShortcutEnabled ( int id, bool enable = true )
- void setSizeIncrement ( const QSize & )
- void setSizeIncrement ( int w, int h )
- void setSizePolicy ( QSizePolicy )
- void setSizePolicy ( QSizePolicy::Policy horizontal, QSizePolicy::Policy vertical )
- void setStatusTip ( const QString & )
- void setStyle ( QStyle * style )
- void setToolTip ( const QString & )
- void setUpdatesEnabled ( bool enable )
- void setWhatsThis ( const QString & )
- void setWindowFlags ( Qt::WindowFlags type )
- void setWindowIcon ( const QIcon & icon )
- void setWindowIconText ( const QString & )
- void setWindowOpacity ( qreal level )
- void setWindowRole ( const QString & role )
- void setWindowState ( Qt::WindowStates windowState )
- void setWindowTitle ( const QString & )
- QSize size () const
- virtual QSize sizeHint () const
- QSize sizeIncrement () const
- QSizePolicy sizePolicy () const
- void stackUnder ( QWidget * w )
- QString statusTip () const
- QStyle * style () const
- bool testAttribute ( Qt::WidgetAttribute attribute ) const
- QString toolTip () const
- bool underMouse () const
- void unsetCursor ()
- void unsetLayoutDirection ()
- void update ( int x, int y, int w, int h )
- void update ( const QRect & r )
- void update ( const QRegion & rgn )
- void updateGeometry ()
- bool updatesEnabled () const
- QRegion visibleRegion () const
- QString whatsThis () const
- int width () const
- WId winId () const
- QWidget * window () const
- Qt::WindowFlags windowFlags () const
- QIcon windowIcon () const
- QString windowIconText () const
- qreal windowOpacity () const
- QString windowRole () const
- Qt::WindowStates windowState () const
- QString windowTitle () const
- Qt::WindowType windowType () const
- int x () const
- Qt::HANDLE x11PictureHandle () const
- int y () const

- 28 public functions inherited from QObject
- 10 public functions inherited from QPaintDevice

### Public Slots

- bool close ()
- void hide ()
- void lower ()
- void raise ()
- void repaint ()
- void setDisabled ( bool disable )
- void setEnabled ( bool )
- void setFocus ()
- void setHidden ( bool hidden )
- virtual void setVisible ( bool visible )
- void setWindowModified ( bool )
- void show ()
- void showFullScreen ()
- void showMaximized ()
- void showMinimized ()
- void showNormal ()
- void update ()

- 1 public slot inherited from QObject

### Signals

- void customContextMenuRequested ( const QPoint & pos )

- 1 signal inherited from QObject

### Static Public Members

- QWidget * find ( WId id )
- QWidget * keyboardGrabber ()
- QWidget * mouseGrabber ()
- void setTabOrder ( QWidget * first, QWidget * second )

- 4 static public members inherited from QObject

### Protected Functions

- virtual void actionEvent ( QActionEvent * event )
- virtual void changeEvent ( QEvent * e )
- virtual void closeEvent ( QCloseEvent * e )
- virtual void contextMenuEvent ( QContextMenuEvent * e )
- void create ( WId window = 0, bool initializeWindow = true, bool destroyOldWindow = true )
- void destroy ( bool destroyWindow = true, bool destroySubWindows = true )
- virtual void dragEnterEvent ( QDragEnterEvent * event )
- virtual void dragLeaveEvent ( QDragLeaveEvent * event )
- virtual void dragMoveEvent ( QDragMoveEvent * event )
- virtual void dropEvent ( QDropEvent * event )
- virtual void enterEvent ( QEvent * event )
- virtual bool event ( QEvent * e )
- virtual void focusInEvent ( QFocusEvent * event )
- bool focusNextChild ()
- virtual bool focusNextPrevChild ( bool next )
- virtual void focusOutEvent ( QFocusEvent * event )
- bool focusPreviousChild ()
- virtual void hideEvent ( QHideEvent * event )
- virtual void inputMethodEvent ( QInputMethodEvent * e )
- virtual void keyPressEvent ( QKeyEvent * e )
- virtual void keyReleaseEvent ( QKeyEvent * e )
- virtual void leaveEvent ( QEvent * event )
- virtual bool macEvent ( EventHandlerCallRef caller, EventRef event )
- virtual int metric ( PaintDeviceMetric m ) const
- virtual void mouseDoubleClickEvent ( QMouseEvent * e )
- virtual void mouseMoveEvent ( QMouseEvent * e )
- virtual void mousePressEvent ( QMouseEvent * e )
- virtual void mouseReleaseEvent ( QMouseEvent * e )
- virtual void moveEvent ( QMoveEvent * event )
- virtual void paintEvent ( QPaintEvent * event )
- virtual bool qwsEvent ( QWSEvent * event )
- void resetInputContext ()
- virtual void resizeEvent ( QResizeEvent * event )
- virtual void showEvent ( QShowEvent * event )
- virtual void tabletEvent ( QTabletEvent * e )
- void updateMicroFocus ()
- virtual void wheelEvent ( QWheelEvent * e )
- virtual bool winEvent ( MSG * message, long * result )
- virtual bool x11Event ( XEvent * event )

- 7 protected functions inherited from QObject

## Detailed Description

The QWidget class is the base class of all user interface objects.

The widget is the atom of the user interface: it receives mouse, keyboard and other events from the window system, and paints a representation of itself on the screen. Every widget is rectangular, and they are sorted in a Z-order. A widget is clipped by its parent and by the widgets in front of it.

A widget that isn't embedded in a parent widget is called a window. Usually, windows have a frame and a title bar, although it is also possible to create windows without such decoration using suitable window flags). In Qt, QMainWindow and the various subclasses of QDialog are the most common window types.

A widget without a parent widget is always an independent window.

Non-window widgets are child widgets. These are child windows in their parent widgets. You cannot usually distinguish a child widget from its parent visually. Most other widgets in Qt are useful only as child widgets. (It is possible to make, say, a button into a window, but most people prefer to put their buttons inside other widgets, e.g. QDialog.)

If you want to use a QWidget to hold child widgets you will probably want to add a layout to the parent QWidget. (See Layouts.)

QWidget has many member functions, but some of them have little direct functionality: for example, QWidget has a font property, but never uses this itself. There are many subclasses which provide real functionality, such as QPushButton, QListWidget and QTabWidget, etc.

### Groups of functions:

Context | Functions
--- | ---
Window functions | show(), hide(), raise(), lower(), close().
Top-level windows | isWindowModified(), setWindowModified(), windowTitle(), setWindowTitle(), windowIcon(), setWindowIcon(), windowIconText(), setWindowIconText(), isActiveWindow(), activateWindow(), showMinimized(). showMaximized(), showFullScreen(), showNormal().
Window contents | update(), repaint(), scroll().
Geometry | pos(), size(), rect(), x(), y(), width(), height(), sizePolicy(), setSizePolicy(), sizeHint(), updateGeometry(), layout(), move(), resize(), setGeometry(), frameGeometry(), geometry(), childrenRect(), adjustSize(), mapFromGlobal(), mapFromParent() mapToGlobal(), mapToParent(), maximumSize(), minimumSize(), sizeIncrement(), setMaximumSize(), setMinimumSize(), setSizeIncrement(), setBaseSize(), setFixedSize()
Mode | isVisible(), isVisibleTo(), isMinimized(), isEnabled(), isEnabledTo(), isModal(), isWindow(), setEnabled(), hasMouseTracking(), setMouseTracking(), updatesEnabled(), setUpdatesEnabled(), visibleRegion().
Look and feel | style(), setStyle(), cursor(), setCursor() font(), setFont(), palette(), setPalette(), backgroundRole(), setBackgroundRole(), fontMetrics(), fontInfo().
Keyboard focus functions | setFocusPolicy(), focusPolicy(), hasFocus(), setFocus(), clearFocus(), setTabOrder(), setFocusProxy().
Mouse and keyboard grabbing | grabMouse(), releaseMouse(), grabKeyboard(), releaseKeyboard(), mouseGrabber(), keyboardGrabber().
Event handlers | event(), mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(), mouseMoveEvent(), keyPressEvent(), keyReleaseEvent(), focusInEvent(), focusOutEvent(), wheelEvent(), enterEvent(), leaveEvent(), paintEvent(), moveEvent(), resizeEvent(), closeEvent(), dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), dropEvent(), childEvent(), showEvent(), hideEvent(), customEvent(). changeEvent(),
System functions | parentWidget(), window(), setParent(), winId(), find(), metric().
What's this help | setWhatsThis()
Focus functions | focusNextChild(), focusPreviousChild()

Every widget's constructor accepts one or two standard arguments:

1. `QWidget *parent = 0` is the parent of the new widget. If it is 0 (the default), the new widget will be a window. If not, it will be a child of parent, and be constrained by parent's geometry (unless you specify `Qt::Window` as window flag).
2. `Qt::WFlags f = 0` (where available) sets the window flags; the default is suitable for almost all widgets, but to get, for example, a window without a window system frame, you must use special flags.

The widgets/calculator example program is good example of a simple widget. It contains event handlers (as all widgets must), routines that are specific to it (as all useful widgets do), and has children and connections. Everything it does is done in response to an event: this is by far the most common way to design GUI applications.

You will need to supply the content for your widgets yourself, but here is a brief run-down of the events, starting with the most common ones:

- paintEvent() - called whenever the widget needs to be repainted. Every widget which displays output must implement it. Painting using a QPainter can only take place in a paintEvent() or a function called by a paintEvent().
- resizeEvent() - called when the widget has been resized.
- mousePressEvent() - called when a mouse button is pressed. There are six mouse-related events, but the mouse press and mouse release events are by far the most important. A widget receives mouse press events when the mouse is inside it, or when it has grabbed the mouse using grabMouse().
- mouseReleaseEvent() - called when a mouse button is released. A widget receives mouse release events when it has received the corresponding mouse press event. This means that if the user presses the mouse inside your widget, then drags the mouse to somewhere else, then releases, your widget receives the release event. There is one exception: if a popup menu appears while the mouse button is held down, this popup immediately steals the mouse events.
- mouseDoubleClickEvent() - not quite as obvious as it might seem. If the user double-clicks, the widget receives a mouse press event (perhaps a mouse move event or two if they don't hold the mouse quite steady), a mouse release event and finally this event. It is not possible to distinguish a click from a double click until you've seen whether the second click arrives. (This is one reason why most GUI books recommend that double clicks be an extension of single clicks, rather than trigger a different action.)

If your widget only contains child widgets, you probably do not need to implement any event handlers. If you want to detect a mouse click in a child widget call the child's underMouse() function inside the parent widget's mousePressEvent().

Widgets that accept keyboard input need to reimplement a few more event handlers:

- keyPressEvent() - called whenever a key is pressed, and again when a key has been held down long enough for it to auto-repeat. Note that the Tab and Shift+Tab keys are only passed to the widget if they are not used by the focus-change mechanisms. To force those keys to be processed by your widget, you must reimplement QWidget::event().
- focusInEvent() - called when the widget gains keyboard focus (assuming you have called setFocusPolicy()). Well written widgets indicate that they own the keyboard focus in a clear but discreet way.
- focusOutEvent() - called when the widget loses keyboard focus.

Some widgets will also need to reimplement some of the less common event handlers:

- mouseMoveEvent() - called whenever the mouse moves while a button is held down. This is useful for, for example, dragging. If you call setMouseTracking(true), you get mouse move events even when no buttons are held down. (See also the drag and drop information.)
- keyReleaseEvent() - called whenever a key is released, and also while it is held down if the key is auto-repeating. In that case the widget receives a key release event and immediately a key press event for every repeat. Note that the Tab and Shift+Tab keys are only passed to the widget if they are not used by the focus-change mechanisms. To force those keys to be processed by your widget, you must reimplement QWidget::event().
- wheelEvent() -- called whenever the user turns the mouse wheel while the widget has the focus.
- enterEvent() - called when the mouse enters the widget's screen space. (This excludes screen space owned by any children of the widget.)
- leaveEvent() - called when the mouse leaves the widget's screen space.
- moveEvent() - called when the widget has been moved relative to its parent.
- closeEvent() - called when the user closes the widget (or when close() is called).

There are also some rather obscure events. They are listed in `qevent.h` and you need to reimplement event() to handle them. The default implementation of event() handles Tab and Shift+Tab (to move the keyboard focus), and passes on most other events to one of the more specialized handlers above.

When implementing a widget, there are a few more things to consider.

- In the constructor, be sure to set up your member variables early on, before there's any chance that you might receive an event.
- It is almost always useful to reimplement sizeHint() and to set the correct size policy with setSizePolicy(), so users of your class can set up layout management more easily. A size policy lets you supply good defaults for the layout management handling, so that other widgets can contain and manage yours easily. sizeHint() indicates a "good" size for the widget.
- If your widget is a window, setWindowTitle() and setWindowIcon() set the title bar and icon respectively.

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

See also QEvent, QPainter, QGridLayout, and QBoxLayout.

## Property Documentation

### acceptDrops : bool

This property holds whether drop events are enabled for this widget.

Setting this property to true announces to the system that this widget may be able to accept drop events.

If the widget is the desktop (QWidget::(windowType() == Qt::Desktop)), this may fail if another application is using the desktop; you can call acceptDrops() to test if this occurs.

Warning: Do not modify this property in a Drag&Drop event handler.

Access functions:

- bool acceptDrops () const
- void setAcceptDrops ( bool on )

### accessibleDescription : QString

This property holds the widget's description as seen by assistive technologies.

Access functions:

- QString accessibleDescription () const
- void setAccessibleDescription ( const QString & description )

See also QAccessibleInterface::text().

### accessibleName : QString

This property holds the widget's name as seen by assistive technologies.

Access functions:

- QString accessibleName () const
- void setAccessibleName ( const QString & name )

See also QAccessibleInterface::text().

### baseSize : QSize

This property holds the base size of the widget.

The base size is used to calculate a proper widget size if the widget defines sizeIncrement().

Access functions:

- QSize baseSize () const
- void setBaseSize ( const QSize & )
- void setBaseSize ( int basew, int baseh )

See also setSizeIncrement().

### childrenRect : const QRect

This property holds the bounding rectangle of the widget's children.

Hidden children are excluded.

Access functions:

- QRect childrenRect () const

See also childrenRegion() and geometry().

### childrenRegion : const QRegion

This property holds the combined region occupied by the widget's children.

Hidden children are excluded.

Access functions:

- QRegion childrenRegion () const

See also childrenRect() and geometry().

### contextMenuPolicy : Qt::ContextMenuPolicy

This property holds how the widget shows a context menu.

The default value of this property is Qt::DefaultContextMenu, which means the contextMenuEvent() handler is called. Other values are Qt::NoContextMenu, Qt::ActionsContextMenu, and Qt::CustomContextMenu. With Qt::CustomContextMenu, the signal customContextMenuRequested() is emitted.

Access functions:

- Qt::ContextMenuPolicy contextMenuPolicy () const
- void setContextMenuPolicy ( Qt::ContextMenuPolicy policy )

See also contextMenuEvent() and customContextMenuRequested().

### cursor : QCursor

This property holds the cursor shape for this widget.

The mouse cursor will assume this shape when it's over this widget. See the list of predefined cursor objects for a range of useful shapes.

An editor widget might use an I-beam cursor:

        setCursor(Qt::IBeamCursor);

If no cursor has been set, or after a call to unsetCursor(), the parent's cursor is used. The function unsetCursor() has no effect on windows.

Access functions:

- QCursor cursor () const
- void setCursor ( const QCursor & )
- void unsetCursor ()

See also QApplication::setOverrideCursor().

### enabled : bool

This property holds whether the widget is enabled.

An enabled widget handles keyboard and mouse events; a disabled widget does not.

Some widgets display themselves differently when they are disabled. For example a button might draw its label grayed out. If your widget needs to know when it becomes enabled or disabled, you can use the changeEvent() with type QEvent::EnabledChange.

Disabling a widget implicitly disables all its children. Enabling respectively enables all child widgets unless they have been explicitly disabled.

Access functions:

- bool isEnabled () const
- void setEnabled ( bool )

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

### focus : const bool

This property holds whether this widget (or its focus proxy) has the keyboard input focus.

Effectively equivalent to `QApplication::focusWidget() == this`.

Access functions:

- bool hasFocus () const

See also setFocus(), clearFocus(), setFocusPolicy(), and QApplication::focusWidget().

### focusPolicy : Qt::FocusPolicy

This property holds the way the widget accepts keyboard focus.

The policy is `Qt::TabFocus` if the widget accepts keyboard focus by tabbing, `Qt::ClickFocus` if the widget accepts focus by clicking, `Qt::StrongFocus` if it accepts both, and `Qt::NoFocus` (the default) if it does not accept focus at all.

You must enable keyboard focus for a widget if it processes keyboard events. This is normally done from the widget's constructor. For instance, the QLineEdit constructor calls setFocusPolicy(Qt::StrongFocus).

Access functions:

- Qt::FocusPolicy focusPolicy () const
- void setFocusPolicy ( Qt::FocusPolicy policy )

See also focusInEvent(), focusOutEvent(), keyPressEvent(), keyReleaseEvent(), and enabled.

### font : QFont

This property holds the font currently set for the widget.

The fontInfo() function reports the actual font that is being used by the widget.

As long as no special font has been set, or after setFont(QFont()) is called, this is either a special font for the widget class, the parent's font or (if this widget is a top level widget), the default application font.

This code fragment sets a 12 point helvetica bold font:

        QFont f("Helvetica", 12, QFont::Bold);
        setFont(f);

In addition to setting the font, setFont() informs all children about the change.

Access functions:

- const QFont & font () const
- void setFont ( const QFont & )

See also fontInfo() and fontMetrics().

### frameGeometry : const QRect

This property holds geometry of the widget relative to its parent including any window frame.

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

Access functions:

- QRect frameGeometry () const

See also geometry(), x(), y(), and pos().

### frameSize : const QSize

This property holds the size of the widget including any window frame.

Access functions:

- QSize frameSize () const

### fullScreen : const bool

This property holds whether the widget is full screen.

Access functions:

- bool isFullScreen () const

See also windowState(), minimized, and maximized.

### geometry : QRect

This property holds the geometry of the widget relative to its parent and excluding the window frame.

When changing the geometry, the widget, if visible, receives a move event (moveEvent()) and/or a resize event (resizeEvent()) immediately. If the widget is not currently visible, it is guaranteed to receive appropriate events before it is shown.

The size component is adjusted if it lies outside the range defined by minimumSize() and maximumSize().

Warning: Calling setGeometry() inside resizeEvent() or moveEvent() can lead to infinite recursion.

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- const QRect & geometry () const
- void setGeometry ( int x, int y, int w, int h )
- void setGeometry ( const QRect & )

See also frameGeometry(), rect(), move(), resize(), moveEvent(), resizeEvent(), minimumSize(), and maximumSize().

### height : const int

This property holds the height of the widget excluding any window frame.

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- int height () const

See also geometry, width, and size.

### isActiveWindow : const bool

This property holds whether this widget's window is the active window.

The active window is the window that contains the widget that has keyboard focus.

When popup windows are visible, this property is true for both the active window and for the popup.

Access functions:

- bool isActiveWindow () const

See also activateWindow() and QApplication::activeWindow().

### layoutDirection : Qt::LayoutDirection

This property holds the layout direction for this widget.

Access functions:

- Qt::LayoutDirection layoutDirection () const
- void setLayoutDirection ( Qt::LayoutDirection direction )
- void unsetLayoutDirection ()

See also QApplication::layoutDirection.

### maximized : const bool

This property holds whether this widget is maximized.

This property is only relevant for windows.

Note that due to limitations in some window-systems, this does not always report the expected results (e.g. if the user on X11 maximizes the window via the window manager, Qt has no way of distinguishing this from any other resize). This is expected to improve as window manager protocols evolve.

Access functions:

- bool isMaximized () const

See also windowState(), showMaximized(), visible, show(), hide(), showNormal(), and minimized.

### maximumHeight : int

This property holds the widget's maximum height.

This property corresponds to maximumSize().height().

Access functions:

- int maximumHeight () const
- void setMaximumHeight ( int maxh )

See also maximumSize and maximumWidth.

### maximumSize : QSize

This property holds the widget's maximum size.

The widget cannot be resized to a larger size than the maximum widget size.

Access functions:

- QSize maximumSize () const
- void setMaximumSize ( const QSize & )
- void setMaximumSize ( int maxw, int maxh )

See also maximumWidth, maximumHeight, minimumSize, and sizeIncrement.

### maximumWidth : int

This property holds the widget's maximum width.

This property corresponds to maximumSize().width().

Access functions:

- int maximumWidth () const
- void setMaximumWidth ( int maxw )

See also maximumSize and maximumHeight.

### minimized : const bool

This property holds whether this widget is minimized (iconified).

This property is only relevant for windows.

Access functions:

- bool isMinimized () const

See also showMinimized(), visible, show(), hide(), showNormal(), and maximized.

### minimumHeight : int

This property holds the widget's minimum height.

This property corresponds to minimumSize().height().

Access functions:

- int minimumHeight () const
- void setMinimumHeight ( int minh )

See also minimumSize and minimumWidth.

### minimumSize : QSize

This property holds the widget's minimum size.

The widget cannot be resized to a smaller size than the minimum widget size. The widget's size is forced to the minimum size if the current size is smaller.

The minimum size set by this function will override the minimum size defined by QLayout.

Access functions:

- QSize minimumSize () const
- void setMinimumSize ( const QSize & )
- void setMinimumSize ( int minw, int minh )

See also minimumWidth, minimumHeight, maximumSize, and sizeIncrement.

### minimumSizeHint : const QSize

This property holds the recommended minimum size for the widget.

If the value of this property is an invalid size, no minimum size is recommended.

The default implementation of minimumSizeHint() returns an invalid size if there is no layout for this widget, and returns the layout's minimum size otherwise. Most built-in widgets reimplement minimumSizeHint().

QLayout will never resize a widget to a size smaller than the minimum size hint unless minimumSize() is set or the size policy is set to `QSizePolicy::Ignore`. If minimumSize() is set, the minimum size hint will be ignored.

Access functions:

- virtual QSize minimumSizeHint () const

See also QSize::isValid(), resize(), setMinimumSize(), and sizePolicy().

### minimumWidth : int

This property holds the widget's minimum width.

This property corresponds to minimumSize().width().

Access functions:

- int minimumWidth () const
- void setMinimumWidth ( int minw )

See also minimumSize and minimumHeight.

### modal : const bool

This property holds whether the widget is a modal widget.

This property only makes sense for windows. A modal widget prevents widgets in all other windows from getting any input.

Access functions:

- bool isModal () const

See also isWindow() and QDialog.

### mouseTracking : bool

This property holds whether mouse tracking is enabled for the widget.

If mouse tracking is disabled (the default), the widget only receives mouse move events when at least one mouse button is pressed while the mouse is being moved.

If mouse tracking is enabled, the widget receives mouse move events even if no buttons are pressed.

Access functions:

- bool hasMouseTracking () const
- void setMouseTracking ( bool enable )

See also mouseMoveEvent().

### normalGeometry : const QRect

This property holds the geometry a toplevel widget has when it is not maximized or fullscreen.

For child widgets this property always holds an empty rect.

Access functions:

- QRect normalGeometry () const

See also QWidget::windowState() and QWidget::geometry.

### palette : QPalette

This property holds the widget's palette.

As long as no special palette has been set, this is either a special palette for the widget class, the parent's palette or (if this widget is a top level widget), the default application palette.

Access functions:

- const QPalette & palette () const
- void setPalette ( const QPalette & )

See also QApplication::palette().

### pos : QPoint

This property holds the position of the widget within its parent widget.

If the widget is a window, the position is that of the widget on the desktop, including its frame.

When changing the position, the widget, if visible, receives a move event (moveEvent()) immediately. If the widget is not currently visible, it is guaranteed to receive an event before it is shown.

move() is virtual, and all other overloaded move() implementations in Qt call it.

Warning: Calling move() or setGeometry() inside moveEvent() can lead to infinite recursion.

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- QPoint pos () const
- void move ( int x, int y )
- void move ( const QPoint & )

See also frameGeometry, size, x(), and y().

### rect : const QRect

This property holds the internal geometry of the widget excluding any window frame.

The rect property equals QRect(0, 0, width(), height()).

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- QRect rect () const

See also size.

### size : QSize

This property holds the size of the widget excluding any window frame.

If the widget is visible when it is being resized, it receives a resize event (resizeEvent()) immediately. If the widget is not currently visible, it is guaranteed to receive an event before it is shown.

The size is adjusted if it lies outside the range defined by minimumSize() and maximumSize(). For windows, the minimum size is always at least QSize(1, 1), and it might be larger, depending on the window manager.

Warning: Calling resize() or setGeometry() inside resizeEvent() can lead to infinite recursion.

Access functions:

- QSize size () const
- void resize ( int w, int h )
- void resize ( const QSize & )

See also pos, geometry, minimumSize, maximumSize, and resizeEvent().

### sizeHint : const QSize

This property holds the recommended size for the widget.

If the value of this property is an invalid size, no size is recommended.

The default implementation of sizeHint() returns an invalid size if there is no layout for this widget, and returns the layout's preferred size otherwise.

Access functions:

- virtual QSize sizeHint () const

See also QSize::isValid(), minimumSizeHint(), sizePolicy(), setMinimumSize(), and updateGeometry().

### sizeIncrement : QSize

This property holds the size increment of the widget.

When the user resizes the window, the size will move in steps of sizeIncrement().width() pixels horizontally and sizeIncrement.height() pixels vertically, with baseSize() as the basis. Preferred widget sizes are for non-negative integers i and j:

        width = baseSize().width() + i * sizeIncrement().width();
        height = baseSize().height() + j * sizeIncrement().height();

Note that while you can set the size increment for all widgets, it only affects windows.

Warning: The size increment has no effect under Windows, and may be disregarded by the window manager on X.

Access functions:

- QSize sizeIncrement () const
- void setSizeIncrement ( const QSize & )
- void setSizeIncrement ( int w, int h )

See also size, minimumSize, and maximumSize.

### sizePolicy : QSizePolicy

This property holds the default layout behavior of the widget.

If there is a QLayout that manages this widget's children, the size policy specified by that layout is used. If there is no such QLayout, the result of this function is used.

The default policy is Preferred/Preferred, which means that the widget can be freely resized, but prefers to be the size sizeHint() returns. Button-like widgets set the size policy to specify that they may stretch horizontally, but are fixed vertically. The same applies to lineedit controls (such as QLineEdit, QSpinBox or an editable QComboBox) and other horizontally orientated widgets (such as QProgressBar). QToolButton's are normally square, so they allow growth in both directions. Widgets that support different directions (such as QSlider, QScrollBar or QHeader) specify stretching in the respective direction only. Widgets that can provide scrollbars (usually subclasses of QScrollView) tend to specify that they can use additional space, and that they can make do with less than sizeHint().

Access functions:

- QSizePolicy sizePolicy () const
- void setSizePolicy ( QSizePolicy )
- void setSizePolicy ( QSizePolicy::Policy horizontal, QSizePolicy::Policy vertical )

See also sizeHint(), QLayout, QSizePolicy, and updateGeometry().

### statusTip : QString

This property holds the widget's status tip.

Access functions:

- QString statusTip () const
- void setStatusTip ( const QString & )

See also toolTip and whatsThis.

### toolTip : QString

This property holds the widget's tooltip.

Access functions:

- QString toolTip () const
- void setToolTip ( const QString & )

See also QToolTip, statusTip, and whatsThis.

### updatesEnabled : bool

This property holds whether updates are enabled.

An updates enabled widget receives paint events and has a system background; a disabled widget does not. This also implies that calling update() and repaint() has no effect if updates are disabled.

setUpdatesEnabled() is normally used to disable updates for a short period of time, for instance to avoid screen flicker during large changes. In Qt, widgets normally do not generate screen flicker, but on X11 the server might erase regions on the screen when widgets get hidden before they can be replaced by other widgets. Disabling updates solves this.

Example:

        setUpdatesEnabled(false);
        bigVisualChanges();
        setUpdatesEnabled(true);

Disabling a widget implicitly disables all its children. Enabling respectively enables all child widgets unless they have been explicitly disabled. Re-enabling updates implicitly calls update() on the widget.

Access functions:

- bool updatesEnabled () const
- void setUpdatesEnabled ( bool enable )

See also paintEvent().

### visible : bool

This property holds whether the widget is visible.

Calling setVisible(true) or show() sets the widget to visible status if all its parent widgets up to the window are visible. If an ancestor is not visible, the widget won't become visible until all its ancestors are shown. If its size or position has changed, Qt guarantees that a widget gets move and resize events just before it is shown. If the widget has not been resized yet, Qt will adjust the widget's size to a useful default using adjustSize().

Calling setVisible(false) or hide() hides a widget explicitly. An explicitly hidden widget will never become visible, even if all its ancestors become visible, unless you show it.

A widget receives show and hide events when its visibility status changes. Between a hide and a show event, there is no need to waste CPU cycles preparing or displaying information to the user. A video application, for example, might simply stop generating new frames.

A widget that happens to be obscured by other windows on the screen is considered to be visible. The same applies to iconified windows and windows that exist on another virtual desktop (on platforms that support this concept). 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.

You almost never have to reimplement the setVisible() function. If you need to change some settings before a widget is shown, use showEvent() instead. If you need to do some delayed initialization use the Polish event delivered to the event() method

Access functions:

- bool isVisible () const
- virtual void setVisible ( bool visible )

See also show(), hide(), isHidden(), isVisibleTo(), isMinimized(), showEvent(), and hideEvent().

### whatsThis : QString

This property holds the widget's What's This help text.

Access functions:

- QString whatsThis () const
- void setWhatsThis ( const QString & )

See also QWhatsThis, QWidget::toolTip, and QWidget::statusTip.

### width : const int

This property holds the width of the widget excluding any window frame.

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- int width () const

See also geometry, height, and size.

### windowFlags : Qt::WindowFlags

Window flags are a combination of a type (e.g. Qt::Dialog) and zero or more hints to the window system (e.g. Qt::FramelessWindowHint).

If the widget had type Qt::Widget or Qt::SubWindow and becomes a window (Qt::Window, Qt::Dialog, etc.), it is put at position (0, 0) on the desktop. If the widget is a window and becomes a Qt::Widget or Qt::SubWindow, it is put at position (0, 0) relative to its parent widget.

Access functions:

- Qt::WindowFlags windowFlags () const
- void setWindowFlags ( Qt::WindowFlags type )

See also windowType().

### windowIcon : QIcon

This property holds the widget's icon.

This property only makes sense for windows. If no icon has been set, windowIcon() returns the application icon (QApplication::windowIcon()).

Access functions:

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

See also windowIconText and windowTitle.

### windowIconText : QString

This property holds the widget's icon text.

This property only makes sense for windows. If no icon text has been set, this functions returns an empty string.

Access functions:

- QString windowIconText () const
- void setWindowIconText ( const QString & )

See also windowIcon and windowTitle.

### windowModified : bool

This property holds whether the document shown in the window has unsaved changes.

A modified window is a window whose content has changed but has not been saved to disk. This flag will have different effects varied by the platform. On Mac OS X the close button will have a modified look; on other platforms, the window title will have an '*' (asterisk).

The window title must contain a "[*]" placeholder, which indicates where the '*' should appear. Normally, it should appear right after the file name (e.g., "document1.txt[*] - Text Editor"). If the window isn't modified, the placeholder is simply removed.

Access functions:

- bool isWindowModified () const
- void setWindowModified ( bool )

See also windowTitle.

### windowOpacity : double

This property holds the level of opacity for the window.

The valid range of opacity is from 1.0 (completely opaque) to 0.0 (completely transparent).

By default the value of this property is 1.0.

This feature is only present on Mac OS X and Windows 2000 and up.

Warning: Changing this property from opaque to transparent might issue a paint event that needs to be processed before the window is displayed correctly. This affects mainly the use of QPixmap::grabWindow(). Also note that semi-transparent windows update and resize significantly slower than opaque windows.

Access functions:

- qreal windowOpacity () const
- void setWindowOpacity ( qreal level )

### windowTitle : QString

This property holds the window title (caption).

This property only makes sense for windows. If no caption has been set, the title is an empty string.

If you use the windowModified mechanism, the window title must contain a "[*]" placeholder, which indicates where the '*' should appear. Normally, it should appear right after the file name (e.g., "document1.txt[*] - Text Editor"). If the windowModified property is false (the default), the placeholder is simply removed.

Access functions:

- QString windowTitle () const
- void setWindowTitle ( const QString & )

See also windowIcon, windowIconText, and windowModified.

### x : const int

This property holds the x coordinate of the widget relative to its parent including any window frame.

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- int x () const

See also frameGeometry, y, and pos.

### y : const int

This property holds the y coordinate of the widget relative to its parent and including any window frame.

See the Window Geometry documentation for an overview of window geometry.

Access functions:

- int y () const

See also frameGeometry, x, and pos.

## Member Function Documentation

### QWidget::QWidget ( QWidget * parent = 0, Qt::WFlags f = 0 )

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

If parent is 0, 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 0). 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.

### QWidget::~QWidget ()

Destroys the widget.

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

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

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.

### 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 flash the task bar entry blue to indicate that the window has done something. This is because Microsoft do not allow an application to interrupt what the user is currently doing in another application.

See also isActiveWindow(), window(), and show().

### void QWidget::addAction ( QAction * action )

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

All QWidgets have 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.

See also removeAction() 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 the contents.

Uses sizeHint() if valid (i.e if the size hint's width and height are >= 0), otherwise sets the size to the children rectangle (the union of all child widget geometries). For toplevel widgets, the function also takes the screen size into account.

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().

### void QWidget::changeEvent ( QEvent * e ) `[virtual protected]`

This event handler can be reimplemented to handle state changes.

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

### 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 0.

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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 is about to lose 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().

### bool QWidget::close () `[slot]`

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 top level widget with the Qt::WA_QuitOnClose attribute set is closed. By default this attribute is set for all widgets except transient top level widgets such as splash screens, popup menus, and dialogs.

### void QWidget::closeEvent ( QCloseEvent * e ) `[virtual protected]`

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

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

### QRect QWidget::contentsRect () const

Returns the area inside the widget's margins.

See also setContentsMargins() and getContentsMargins().

### void QWidget::contextMenuEvent ( QContextMenuEvent * e ) `[virtual protected]`

This event handler, for event e, 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 calls e->ignore(), which rejects the context event. See the QContextMenuEvent documentation for more details.

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

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

Creates a new widget window if window is 0, otherwise sets the widget's window to window.

Initializes the window (sets the geometry etc.) if initializeWindow is true. If initializeWindow is false, no initialization is performed. This parameter only makes sense if window is a valid window.

Destroys the old window if destroyOldWindow is true. If destroyOldWindow is false, you are responsible for destroying the window yourself (using platform native code).

The QWidget constructor calls create(0,true,true) to create a window for this widget.

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

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 request in widget coordinates.

See also mapToGlobal(), QMenu, and contextMenuPolicy.

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

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.

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

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.

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

See also QTextDrag, QImageDrag, and QDragEnterEvent.

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

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 QTextDrag, QImageDrag, and QDragLeaveEvent.

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

This event handler is called if a drag is in progress, and when any of the following conditions occurs: 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 QTextDrag, QImageDrag, and QDragMoveEvent.

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

This event handler is called when the drag is dropped on this widget which are 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 QTextDrag, QImageDrag, and QDropEvent.

### void QWidget::ensurePolished () const

Ensures that the widget has been polished by QStyle (i.e., has 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).

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().

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

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().

### bool QWidget::event ( QEvent * e ) `[virtual protected]`

This is the main event handler; it handles event e. 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.

Reimplemented from QObject.

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

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

Returns a pointer to the widget with window identifer/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, 0 is returned.

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

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.

### bool QWidget::focusNextChild () `[protected]`

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.

This is the same as focusNextPrevChild(true).

See also focusPreviousChild().

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

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 "forwards", if next is false, it searches "backwards".

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().

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

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.

### bool QWidget::focusPreviousChild () `[protected]`

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.

This is the same as focusNextPrevChild(false).

See also focusNextChild().

### QWidget * QWidget::focusProxy () const

Returns the focus proxy, or 0 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 QFontInto(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().

### void QWidget::getContentsMargins ( int * left, int * top, int * right, int * bottom ) const

Returns the widget's contents margins for left, top, right, and bottom.

See also setContentsMargins() and contentsRect().

### HDC QWidget::getDC () const `[virtual]`

Returns the window system handle of the widget, for low-level access. Using this function is not portable.

An HDC aquired with getDC() has to be released with releaseDC().

Warning: Using this function is not portable.

Reimplemented from QPaintDevice.

### void QWidget::grabKeyboard ()

Grabs the keyboard input.

This widget reveives 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.

Warning: Bugs in mouse-grabbing applications very often lock the terminal. Use this function with extreme caution, and consider using the `-nograb` command line option while debugging.

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.

Note that only visible widgets can grab mouse input. If isVisible() returns false for a widget, that widget cannot call grabMouse().

focusWidget()

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

### void QWidget::grabMouse ( const QCursor & cursor )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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().

Warning: Grabbing the mouse might lock the terminal.

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 not `OnApplication`, the shortcut is local to this widget; otherwise it applies to the application as a whole.

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.

Warning: You should not normally need to use this function; instead create QActions with the shortcut key sequences you require (if you also want equivalent menu options and toolbar buttons), or create QShortcuts if you just need key sequences. Both QAction and QShortcut handle all the event filtering for you, and provide signals which are triggered when the user triggers the key sequence, so are much easier to use than this low-level function.

See also releaseShortcut() and setShortcutEnabled().

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

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.

### void QWidget::hide () `[slot]`

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

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

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

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.

### QInputContext * QWidget::inputContext ()

This function returns the QInputContext for this widget. By default the input context is inherited from the widgets parent. For toplevels it is inherited from QApplication.

You can override this and set a special input context for this widget by using the setInputContext() method.

See also setInputContext().

### void QWidget::inputMethodEvent ( QInputMethodEvent * e ) `[virtual protected]`

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

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

See also event() and QInputMethodEvent.

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

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, and QInputContext.

### 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 0 or before is not a valid action for this widget.

See also addAction().

### 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 0 or before is not a valid action for this widget.

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

### 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 ( 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) is equivalent to isEnabled().

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 visiblity, 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 or as children of visible widgets, or if hide() or setVisible(false) was called.

### bool QWidget::isVisibleTo ( 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

whether the widget is an independent window

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().

### void QWidget::keyPressEvent ( QKeyEvent * e ) `[virtual protected]`

This event handler, for event e, 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 ignore() the event if you do not understand it, so that the widget's parent can interpret it.

The default implementation closes popup widgets if the user presses Esc. Otherwise the event is ignored.

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

### void QWidget::keyReleaseEvent ( QKeyEvent * e ) `[virtual protected]`

This event handler, for event e, 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 ignore() the release if you do not understand it, so that the widget's parent can interpret it.

The default implementation ignores the event.

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

### QWidget * QWidget::keyboardGrabber () `[static]`

Returns the widget that is currently grabbing the keyboard input.

If no widget in this application is currently grabbing the keyboard, 0 is returned.

See also grabMouse() and mouseGrabber().

### QLayout * QWidget::layout () const

Returns the layout engine that manages the geometry of this widget's children.

If the widget does not have a layout, layout() returns 0.

See also setLayout() and sizePolicy().

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

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().

### void QWidget::lower () `[slot]`

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().

### bool QWidget::macEvent ( EventHandlerCallRef caller, EventRef event ) `[virtual protected]`

This special event handler can be reimplemented in a subclass to receive native Macintosh events which are passed from the caller with the event details in the event parameter.

In your reimplementation of this function, if you want to stop the event being handled by Qt, return true. 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.

Warning: This function is not portable.

See also QApplication::macEventFilter().

### QPoint QWidget::mapFrom ( 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 0 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 ( QWidget * parent, const QPoint & pos ) const

Translates the widget coordinate pos to the coordinate system of parent. The parent must not be 0 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(), and QRegion::isEmpty().

### int QWidget::metric ( PaintDeviceMetric m ) const `[virtual protected]`

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

m is the metric to get.

Reimplemented from QPaintDevice.

### void QWidget::mouseDoubleClickEvent ( QMouseEvent * e ) `[virtual protected]`

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

The default implementation generates a normal mouse press event.

Note that the widgets gets a mousePressEvent() and a mouseReleaseEvent() before the mouseDoubleClickEvent().

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

### QWidget * QWidget::mouseGrabber () `[static]`

Returns the widget that is currently grabbing the mouse input.

If no widget in this application is currently grabbing the mouse, 0 is returned.

See also grabMouse() and keyboardGrabber().

### void QWidget::mouseMoveEvent ( QMouseEvent * e ) `[virtual protected]`

This event handler, for event e, 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.

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

### void QWidget::mousePressEvent ( QMouseEvent * e ) `[virtual protected]`

This event handler, for event e, 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(), and QMouseEvent.

### void QWidget::mouseReleaseEvent ( QMouseEvent * e ) `[virtual protected]`

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

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

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

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.

### QWidget * QWidget::nextInFocusChain () const

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

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

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

Warning: Do not call this function unless you really know what you're doing.

See also setWindowFlags().

### QPaintEngine * QWidget::paintEngine () const `[virtual]`

Returns the widget's paint engine.

Reimplemented from QPaintDevice.

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

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

A paint event is a request to repaint all or part of the widget. It can happen as a result of repaint() or update(), or because the widget was obscured and has now been uncovered, or for 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::unite()). repaint() does not permit this optimization, so we suggest using update() when possible.

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

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

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

Note: Under X11 it is possible to toggle the global double buffering by calling `qt_x11_set_global_double_buffer()`. Example usage:

        ...
        extern void qt_x11_set_global_double_buffer(bool);
        qt_x11_set_global_double_buffer(false);
        ...

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

### QWidget * QWidget::parentWidget () const

Returns the parent of this widget, or 0 if it does not have any parent widget.

### bool QWidget::qwsEvent ( QWSEvent * event ) `[virtual protected]`

This special event handler can be reimplemented in a subclass to receive native Qt/Embedded events which are passed in the event parameter.

In your reimplementation of this function, if you want to stop the event being handled by Qt, return true. 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.

Warning: This function is not portable.

See also QApplication::qwsEventFilter().

### void QWidget::raise () `[slot]`

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().

### void QWidget::releaseDC ( HDC hdc ) const `[virtual]`

Releases the HDC hdc aquired by a previous call to getDC().

Warning: Using this function is not portable.

Reimplemented from QPaintDevice.

### 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).

Warning: You should not normally need to use this function since Qt's shortcut system removes shortcuts automatically when their parent widget is destroyed. It is best to use QAction or QShortcut to handle shortcuts, since they are easier to use than this low-level function. Note also that this is an expensive operation.

See also grabShortcut() and setShortcutEnabled().

### void QWidget::removeAction ( QAction * action )

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

### void QWidget::repaint () `[slot]`

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.

Warning: If you call repaint() in a function which may itself be called from paintEvent(), you may get infinite recursion. The update() function never causes recursion.

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

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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 & r )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

This version repaints a rectangle r inside the widget.

### void QWidget::repaint ( const QRegion & rgn )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

This version repaints a region rgn inside the widget.

### void QWidget::resetInputContext () `[protected]`

This function is called when text widgets need to be neutral state to execute text operations properly. See qlineedit.cpp and qtextedit.cpp as example.

Ordinary reset that along with changing focus to another widget, moving the cursor, etc, is implicitly handled via unfocusInputContext() because whether reset or not when such situation is a responsibility of input methods. So we delegate the responsibility to the input context via unfocusInputContext(). See 'Preedit preservation' section of the class description of QInputContext for further information.

See also QInputContext and QInputContext::reset().

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

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, and paintEvent().

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

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

After scrolling, scroll() sends a paint event for the the part that is read but not written. For example, when scrolling 10 pixels rightwards, the leftmost ten pixels of the widget need repainting. The paint event may be delivered immediately or later, depending on some heuristics (note that you might have to force processing of paint events using QApplication::sendPostedEvents() when using scroll() and move() in combination).

See also QScrollView and bitBlt().

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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 QScrollView and bitBlt().

### 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.

See also backgroundRole() and foregroundRole().

### 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 getContentsMargins().

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

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().

### 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.

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 member function, provided for convenience. It behaves essentially like the above 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.

First, a focus out event is sent to the focus widget (if any) to tell it that it is about to lose the focus. Then a focus in event is sent to this widget 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.

Warning: If you call setFocus() in a function which may itself be called from focusOutEvent() or focusInEvent(), you may get an infinite recursion.

setFocusPolicy() QApplication::focusWidget() grabKeyboard() grabMouse(), {Keyboard Focus}

See also hasFocus(), clearFocus(), focusInEvent(), and focusOutEvent().

### void QWidget::setFocus () `[slot]`

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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.

### void QWidget::setFocusProxy ( QWidget * w )

Sets the widget's focus proxy to widget w. If w is 0, 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.

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.

See also foregroundRole() and backgroundRole().

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

Convenience function, equivalent to setVisible(!hidden).

### void QWidget::setInputContext ( QInputContext * context )

This function sets the input context context on this widget.

See also inputContext().

### void QWidget::setLayout ( QLayout * l )

Sets the layout engine for this widget to l.

There can be only one top-level layout for a widget.

See also layout().

### 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.

See also clearMask().

### void QWidget::setMask ( const QRegion & region )

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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 setMask() and clearMask().

### void QWidget::setParent ( QWidget * parent )

Sets the parent of the widget to parent. 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.

Warning: It is very unlikely that you will ever need this function. If you have a widget that changes its content dynamically, it is far easier to use QStackedWidget.

See also setWindowFlags().

### void QWidget::setParent ( QWidget * parent, Qt::WFlags f )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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

### 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.

Warning: You should not normally need to use this function since Qt's shortcut system enables/disables shortcuts automatically as widgets become hidden/visible and gain or lose focus. It is best to use QAction or QShortcut to handle shortcuts, since they are easier to use than this low-level function.

See also grabShortcut() and releaseShortcut().

### void QWidget::setStyle ( QStyle * style )

Sets the widget's GUI style to style. 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.

Warning: This function is particularly useful for demonstration purposes, where you want to show Qt's styling capabilities. Real applications should avoid it and use one consistent GUI style instead.

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

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

Moves the second widget around the ring of focus widgets so that keyboard focus moves from the first widget to the second widget when the Tab key is pressed.

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:

        setTabOrder(c, d); // c to d   WRONG
        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.

### void QWidget::setWindowRole ( const QString & role )

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

### 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 mormal 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);

Note: On some window systems `Qt::WindowActive` is not immediate, and may be ignored in certain cases.

See also Qt::WindowState and windowState().

### void QWidget::show () `[slot]`

Shows the widget and its child widgets. This function is equivalent to setVisible(true).

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

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

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::showFullScreen () `[slot]`

Shows the widget in full-screen mode.

Calling this function only affects windows.

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

Full-screen mode works fine under Windows, but has certain problems under X. These problems are due to limitations of the ICCCM protocol that specifies the communication between X11 clients and the window manager. ICCCM simply does not understand the concept of non-decorated full-screen windows. Therefore, the best we can do is to request a borderless window and place and resize it to fill the entire screen. Depending on the window manager, this may or may not work. The borderless window is requested using MOTIF hints, which are at least partially supported by virtually all modern window managers.

An alternative would be to bypass the window manager entirely and create a window with the Qt::WX11BypassWM 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.

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

### void QWidget::showMaximized () `[slot]`

Shows the widget maximized.

Calling this function only affects windows.

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

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

### void QWidget::showMinimized () `[slot]`

Shows the widget minimized, as an icon.

Calling this function only affects windows.

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

### void QWidget::showNormal () `[slot]`

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().

### 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

Returns the GUI style for this widget

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

### void QWidget::tabletEvent ( QTabletEvent * e ) `[virtual protected]`

This event handler, for event e, 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.

See also QTabletEvent::ignore(), QTabletEvent::accept(), event(), 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::update () `[slot]`

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::WRepaintNoErase` widget flag is set, the widget is responsible for painting all its pixels itself.

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

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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

### void QWidget::update ( const QRect & r )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

This version updates a rectangle r inside the widget.

### void QWidget::update ( const QRegion & rgn )

This is an overloaded member function, provided for convenience. It behaves essentially like the above 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.

### void QWidget::updateMicroFocus () `[protected]`

Updates the widget's micro focus.

See also QInputContext.

### 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.

### void QWidget::wheelEvent ( QWheelEvent * e ) `[virtual protected]`

This event handler, for event e, 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 QWheelEvent::ignore(), QWheelEvent::accept(), event(), and QWheelEvent.

### bool QWidget::winEvent ( MSG * message, long * result ) `[virtual protected]`

This special event handler can be reimplemented in a subclass to receive native Windows events 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 to the value that the window procedure should return. 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.

Warning: This function is not portable.

See also QApplication::winEventFilter().

### 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.

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().

### QString QWidget::windowRole () const

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

See also 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.

### bool QWidget::x11Event ( XEvent * event ) `[virtual protected]`

This special event handler can be reimplemented in a subclass to receive native X11 events which are passed in the event parameter.

In your reimplementation of this function, if you want to stop the event being handled by Qt, return true. 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.

Warning: This function is not portable.

See also QApplication::x11EventFilter().

### Qt::HANDLE QWidget::x11PictureHandle () const

Returns the X11 Picture handle of the widget for XRender support. Use of this function is not portable. This function will return 0 if XRender support is not compiled into Qt, if the XRender extension is not supported on the X11 display, or if the handle could not be created.