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QWidget Class Reference

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

#include <qwidget.h>

Inherits QObject and QPaintDevice.

Inherited by QAxWidget, QButton, QFrame, QDialog, QComboBox, QDataBrowser, QDataView, QDateTimeEditBase, QDateTimeEdit, QDesktopWidget, QDial, QDockArea, QGLWidget, QHeader, QMainWindow, QMotifWidget, QNPWidget, QScrollBar, QSizeGrip, QSlider, QSpinBox, QSplashScreen, QStatusBar, QTabBar, QTabWidget, QWorkspace, and QXtWidget.

List of all member functions.

Public Members

Public Slots

Static Public Members

Properties

Protected Members

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 top-level widget. Usually, top-level widgets are windows with a frame and a title bar (although it is also possible to create top-level widgets without such decoration if suitable widget flags are used). In Qt, QMainWindow and the various subclasses of QDialog are the most common top-level windows.

A widget without a parent widget is always a top-level widget.

Non-top-level 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 top-level widget, 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, QListBox and QTabDialog, etc.

Groups of functions:

Context Functions
Window functions show(), hide(), raise(), lower(), close().
Top level windows caption(), setCaption(), icon(), setIcon(), iconText(), setIconText(), isActiveWindow(), setActiveWindow(), showMinimized(). showMaximized(), showFullScreen(), showNormal().
Window contents update(), repaint(), erase(), scroll(), updateMask().
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(), isDesktop(), isEnabled(), isEnabledTo(), isModal(), isPopup(), isTopLevel(), setEnabled(), hasMouseTracking(), setMouseTracking(), isUpdatesEnabled(), setUpdatesEnabled(), clipRegion().
Look and feel style(), setStyle(), cursor(), setCursor() font(), setFont(), palette(), setPalette(), backgroundMode(), setBackgroundMode(), colorGroup(), fontMetrics(), fontInfo().
Keyboard focus
functions 		isFocusEnabled(), 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().
Change handlers enabledChange(), fontChange(), paletteChange(), styleChange(), windowActivationChange().
System functions parentWidget(), topLevelWidget(), reparent(), polish(), winId(), find(), metric().
What's this help customWhatsThis()
Internal kernel
functions 		focusNextPrevChild(), wmapper(), clearWFlags(), getWFlags(), setWFlags(), testWFlags().

Every widget's constructor accepts two or three 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 top-level window. If not, it will be a child of parent, and be constrained by parent's geometry (unless you specify WType_TopLevel as widget flag).
  2. const char *name = 0 is the widget name of the new widget. You can access it using name(). The widget name is little used by programmers but is quite useful with GUI builders such as Qt Designer (you can name a widget in Qt Designer, and connect() to it using the name in your code). The dumpObjectTree() debugging function also uses it.
  3. WFlags f = 0 (where available) sets the widget flags; the default is suitable for almost all widgets, but to get, for example, a top-level widget without a window system frame, you must use special flags.

The tictac/tictac.cpp example program is good example of a simple widget. It contains a few event handlers (as all widgets must), a few custom routines that are specific to it (as all useful widgets do), and has a few 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:

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 hasMouse() function inside the parent widget's mousePressEvent().

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

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

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.

See also QEvent, QPainter, QGridLayout, QBoxLayout, and Abstract Widget Classes.

Member Type Documentation

QWidget::BackgroundOrigin

This enum defines the origin used to draw a widget's background pixmap.

The pixmap is drawn using the:

QWidget::FocusPolicy

This enum type defines the various policies a widget can have with respect to acquiring keyboard focus.

Member Function Documentation

explicit QWidget::QWidget ( QWidget * parent = 0, const char * name = 0, WFlags f = 0 )

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

If parent is 0, the new widget becomes a top-level 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 name is sent to the QObject constructor.

The widget flags argument, f, is normally 0, but it can be set to customize the window frame of a top-level widget (i.e. parent must be 0). To customize the frame, set the WStyle_Customize flag OR'ed with any of the Qt::WidgetFlags.

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.

Example: 

    QLabel *splashScreen = new QLabel( 0, "mySplashScreen",
                                WStyle_Customize | WStyle_Splash );

QWidget::~QWidget ()

Destroys the widget.

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

bool QWidget::acceptDrops () const

Returns TRUE if drop events are enabled for this widget; otherwise returns FALSE. See the "acceptDrops" property for details.

void QWidget::adjustSize () [virtual slot]

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).

See also sizeHint and childrenRect.

Example: xform/xform.cpp.

Reimplemented in QMessageBox.

bool QWidget::autoMask () const

Returns TRUE if the auto mask feature is enabled for the widget; otherwise returns FALSE. See the "autoMask" property for details.

const QBrush & QWidget::backgroundBrush () const

Returns the widget's background brush. See the "backgroundBrush" property for details.

const QColor & QWidget::backgroundColor () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code. Use paletteBackgroundColor() or eraseColor() instead.

BackgroundMode QWidget::backgroundMode () const

Returns the color role used for painting the background of the widget. See the "backgroundMode" property for details.

BackgroundOrigin QWidget::backgroundOrigin () const

Returns the origin of the widget's background. See the "backgroundOrigin" property for details.

const QPixmap * QWidget::backgroundPixmap () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code. Use paletteBackgroundPixmap() or erasePixmap() instead.

Examples: themes/metal.cpp and themes/wood.cpp.

QSize QWidget::baseSize () const

Returns the base size of the widget. See the "baseSize" property for details.

QString QWidget::caption () const

Returns the window caption (title). See the "caption" property for details.

QWidget * QWidget::childAt ( int x, int y, bool includeThis = FALSE ) const

Returns the visible child widget at pixel position (x, y) in the widget's own coordinate system.

If includeThis is TRUE, and there is no child visible at (x, y), the widget itself is returned.

QWidget * QWidget::childAt ( const QPoint & p, bool includeThis = FALSE ) 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.

If includeThis is TRUE, and there is no child visible at p, the widget itself is returned.

QRect QWidget::childrenRect () const

Returns the bounding rectangle of the widget's children. See the "childrenRect" property for details.

QRegion QWidget::childrenRegion () const

Returns the combined region occupied by the widget's children. See the "childrenRegion" property for details.

void QWidget::clearFocus () [slot]

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 focus, setFocus(), focusInEvent(), focusOutEvent(), focusPolicy, and QApplication::focusWidget().

void QWidget::clearMask ()

Removes any mask set by setMask().

See also setMask().

void QWidget::clearWFlags ( WFlags f ) [protected]

Clears the widget flags f.

Widget flags are a combination of Qt::WidgetFlags.

See also testWFlags(), getWFlags(), and setWFlags().

QRegion QWidget::clipRegion () 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.

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. The default implementation of QWidget::closeEvent() accepts the close event.

The QApplication::lastWindowClosed() signal is emitted when the last visible top level widget is closed.

Examples: dialog/mainwindow.cpp, mdi/application.cpp, popup/popup.cpp, and toplevel/options.ui.h.

bool QWidget::close ( bool alsoDelete ) [virtual]

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

Closes this widget. Returns TRUE if the widget was closed; otherwise returns FALSE.

If alsoDelete is TRUE or the widget has the WDestructiveClose widget flag, the widget is also deleted. The widget can prevent itself from being closed by rejecting the QCloseEvent it gets. 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 is closed.

Note that closing the QApplication::mainWidget() terminates the application.

See also closeEvent(), QCloseEvent, hide(), QApplication::quit(), QApplication::setMainWidget(), and QApplication::lastWindowClosed().

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

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

The default implementation calls e->accept(), which hides this widget. See the QCloseEvent documentation for more details.

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

Examples: action/application.cpp, application/application.cpp, chart/chartform.cpp, i18n/mywidget.cpp, mdi/application.cpp, popup/popup.cpp, and qwerty/qwerty.cpp.

const QColorGroup & QWidget::colorGroup () const

Returns the current color group of the widget palette. See the "colorGroup" property for details.

void QWidget::constPolish () const [slot]

Ensures that the widget is properly initialized by calling polish().

Call constPolish() from functions like sizeHint() that depends on the widget being initialized, and that may be called before show().

Warning: Do not call constPolish() on a widget from inside that widget's constructor.

See also polish().

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

See also event() and QContextMenuEvent.

Example: menu/menu.cpp.

void QWidget::create ( WId window = 0, bool initializeWindow = TRUE, bool destroyOldWindow = TRUE ) [virtual 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.

const QCursor & QWidget::cursor () const

Returns the cursor shape for this widget. See the "cursor" property for details.

bool QWidget::customWhatsThis () const [virtual]

Returns TRUE if the widget wants to handle What's This help manually; otherwise returns FALSE. See the "customWhatsThis" property for details.

void QWidget::destroy ( bool destroyWindow = TRUE, bool destroySubWindows = TRUE ) [virtual 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 * ) [virtual protected]

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

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.

Example: iconview/simple_dd/main.cpp.

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

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

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 * ) [virtual protected]

This event handler is called when a drag is in progress and the mouse enters this widget, and whenever it moves within the widget.

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::drawText ( int x, int y, const QString & str )

Draws the string str at position (x, y).

The y position is the base line position of the text. The text is drawn using the default font and the default foreground color.

This function is provided for convenience. You will generally get more flexible results and often higher speed by using a a painter instead.

See also font, foregroundColor(), and QPainter::drawText().

void QWidget::drawText ( const QPoint & pos, const QString & str )

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

Draws the string str at position pos.

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

This event handler is called when the drag is dropped on this widget.

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.

Example: iconview/simple_dd/main.cpp.

void QWidget::enabledChange ( bool oldEnabled ) [virtual protected]

This virtual function is called from setEnabled(). oldEnabled is the previous setting; you can get the new setting from isEnabled().

Reimplement this function if your widget needs to know when it becomes enabled or disabled. You will almost certainly need to update the widget using update().

The default implementation repaints the visible part of the widget.

See also enabled, enabled, repaint(), update(), and clipRegion().

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

This event handler can be reimplemented in a subclass to receive widget enter events.

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

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

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

Erases the specified area (x, y, w, h) in the widget without generating a paint event.

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

Child widgets are not affected.

See also repaint().

void QWidget::erase ()

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

This version erases the entire widget.

void QWidget::erase ( const QRect & r )

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

Erases the specified area r in the widget without generating a paint event.

void QWidget::erase ( const QRegion & reg )

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

Erases the area defined by reg, without generating a paint event.

Child widgets are not affected.

const QColor & QWidget::eraseColor () const

Returns the erase color of the widget.

See also setEraseColor(), setErasePixmap(), and backgroundColor().

const QPixmap * QWidget::erasePixmap () const

Returns the widget's erase pixmap.

See also setErasePixmap() and eraseColor().

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.

The main event handler first passes an event through all event filters that have been installed. If none of the filters intercept the event, it calls one of the specialized event handlers.

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().

This function returns TRUE if it is able to pass the event over to someone (i.e. someone wanted the event); otherwise returns FALSE.

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

Reimplemented from QObject.

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.

QFocusData * QWidget::focusData () [protected]

Returns the focus data for this widget's top-level widget.

Focus data always belongs to the top-level widget. The focus data list contains all the widgets in this top-level widget that can accept focus, in tab order. An iterator points to the current focus widget (focusWidget() returns a pointer to this widget).

This information is useful for implementing advanced versions of focusNextPrevChild().

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

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

A widget normally must setFocusPolicy() to something other than 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 toplevel widgets that do not specify a focusPolicy() ). It also calls setMicroFocusHint(), hinting any system-specific input tools about the focus of the user's attention.

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

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 is can find a new widget and 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" forwards or backwards, and call QWidget::focusNextPrevChild() only when it reaches the last or first link on the "page".

Child widgets call focusNextPrevChild() on their parent widgets, but only the top-level widget decides where to redirect focus. By overriding this method for an object, you thus gain control of focus traversal for all child widgets.

Warning: QScrollView uses it own logic for this function, which does the right thing in most cases. But if you are using a QScrollView and want complete control of the focus chain you'll need to override QScrollView::focusNextPrevChild() and your top-level widgets' focusNextPrevChild() functions.

See also focusData().

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

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

A widget normally must setFocusPolicy() to something other than 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 toplevel widgets that do not specify a focusPolicy() ). It also calls setMicroFocusHint(), hinting any system-specific input tools about the focus of the user's attention.

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

Example: qmag/qmag.cpp.

FocusPolicy QWidget::focusPolicy () const

Returns the way the widget accepts keyboard focus. See the "focusPolicy" property for details.

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

QFont QWidget::font () const

Returns the font currently set for the widget. See the "font" property for details.

void QWidget::fontChange ( const QFont & oldFont ) [virtual protected]

This virtual function is called from setFont(). oldFont is the previous font; you can get the new font from font().

Reimplement this function if your widget needs to know when its font changes. You will almost certainly need to update the widget using update().

The default implementation updates the widget including its geometry.

See also font, font, update(), and updateGeometry().

QFontInfo QWidget::fontInfo () const

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

See also font, fontMetrics(), and font.

QFontMetrics QWidget::fontMetrics () const

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

See also font, fontInfo(), and font.

Examples: drawdemo/drawdemo.cpp and qmag/qmag.cpp.

const QColor & QWidget::foregroundColor () const

Same as paletteForegroundColor()

QRect QWidget::frameGeometry () const

Returns geometry of the widget relative to its parent including any window frame. See the "frameGeometry" property for details.

QSize QWidget::frameSize () const

Returns the size of the widget including any window frame. See the "frameSize" property for details.

const QRect & QWidget::geometry () const

Returns the geometry of the widget relative to its parent and excluding the window frame. See the "geometry" property for details.

WFlags QWidget::getWFlags () const [protected]

Returns the widget flags for this this widget.

Widget flags are a combination of Qt::WidgetFlags.

See also testWFlags(), setWFlags(), and clearWFlags().

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().

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

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 cursor.

bool QWidget::hasFocus () const

Returns TRUE if this widget (or its focus proxy) has the keyboard input focus; otherwise returns FALSE. See the "focus" property for details.

bool QWidget::hasMouse () const

Returns TRUE if the widget is under the mouse cursor; otherwise returns FALSE. See the "underMouse" property for details.

bool QWidget::hasMouseTracking () const

Returns TRUE if mouse tracking is enabled for the widget; otherwise returns FALSE. See the "mouseTracking" property for details.

int QWidget::height () const

Returns the height of the widget excluding any window frame. See the "height" property for details.

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

Returns the preferred height for this widget, given the width w. The default implementation returns 0, indicating that the preferred height does not depend on the width.

Warning: Does not look at the widget's layout.

Reimplemented in QMenuBar and QTextEdit.

void QWidget::hide () [virtual slot]

Hides the widget.

You almost never have to reimplement this function. If you need to do something after a widget is hidden, use hideEvent() instead.

See also hideEvent(), hidden, show(), showMinimized(), visible, and close().

Examples: mdi/application.cpp, popup/popup.cpp, progress/progress.cpp, scrollview/scrollview.cpp, webbrowser/mainwindow.ui.h, and xform/xform.cpp.

Reimplemented in QMenuBar.

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

This event handler can be reimplemented in a subclass to receive widget hide events.

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

See also event() and QHideEvent.

Reimplemented in QScrollBar.

const QPixmap * QWidget::icon () const

Returns the widget's icon. See the "icon" property for details.

QString QWidget::iconText () const

Returns the widget's icon text. See the "iconText" property for details.

void QWidget::iconify () [slot]

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

void QWidget::imComposeEvent ( QIMEvent * 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 user has entered some text using an Input Method.

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

See also event() and QIMEvent.

void QWidget::imEndEvent ( QIMEvent * 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 user has finished inputting text via an Input Method.

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

See also event() and QIMEvent.

void QWidget::imStartEvent ( QIMEvent * 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 user begins entering text using an Input Method.

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

See also event() and QIMEvent.

bool QWidget::isActiveWindow () const

Returns TRUE if this widget is the active window; otherwise returns FALSE. See the "isActiveWindow" property for details.

bool QWidget::isDesktop () const

Returns TRUE if the widget is a desktop widget, i.e. represents the desktop; otherwise returns FALSE. See the "isDesktop" property for details.

bool QWidget::isDialog () const

Returns TRUE if the widget is a dialog widget; otherwise returns FALSE. See the "isDialog" property for details.

bool QWidget::isEnabled () const

Returns TRUE if the widget is enabled; otherwise returns FALSE. See the "enabled" property for details.

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 enabled and enabled.

bool QWidget::isEnabledToTLW () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

This function is deprecated. It is equivalent to isEnabled()

bool QWidget::isFocusEnabled () const

Returns TRUE if the widget accepts keyboard focus; otherwise returns FALSE. See the "focusEnabled" property for details.

bool QWidget::isFullScreen () const

Returns TRUE if the widget is full screen; otherwise returns FALSE. See the "fullScreen" property for details.

bool QWidget::isHidden () const

Returns TRUE if the widget is explicitly hidden; otherwise returns FALSE. See the "hidden" property for details.

bool QWidget::isInputMethodEnabled () const

Returns enables or disables the use of input methods for this widget. See the "inputMethodEnabled" property for details.

bool QWidget::isMaximized () const

Returns TRUE if this widget is maximized; otherwise returns FALSE. See the "maximized" property for details.

bool QWidget::isMinimized () const

Returns TRUE if this widget is minimized (iconified); otherwise returns FALSE. See the "minimized" property for details.

bool QWidget::isModal () const

Returns TRUE if the widget is a modal widget; otherwise returns FALSE. See the "isModal" property for details.

bool QWidget::isPopup () const

Returns TRUE if the widget is a popup widget; otherwise returns FALSE. See the "isPopup" property for details.

bool QWidget::isShown () const

Returns TRUE if the widget is shown; otherwise returns FALSE. See the "shown" property for details.

bool QWidget::isTopLevel () const

Returns TRUE if the widget is a top-level widget; otherwise returns FALSE. See the "isTopLevel" property for details.

bool QWidget::isUpdatesEnabled () const

Returns TRUE if updates are enabled; otherwise returns FALSE. See the "updatesEnabled" property for details.

bool QWidget::isVisible () const

Returns TRUE if the widget is visible; otherwise returns FALSE. See the "visible" property for details.

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 visible.

bool QWidget::isVisibleToTLW () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

This function is deprecated. It is equivalent to isVisible()

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(), focusPolicy, focusInEvent(), focusOutEvent(), event(), and QKeyEvent.

Example: picture/picture.cpp.

Reimplemented in QLineEdit and QTextEdit.

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(), focusPolicy, 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 sizePolicy.

Examples: chart/optionsform.cpp and fonts/simple-qfont-demo/viewer.cpp.

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

This event handler can be reimplemented in a subclass to receive widget leave events.

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 ( MSG * ) [virtual protected]

This special event handler can be reimplemented in a subclass to receive native Macintosh events.

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().

Example: scribble/scribble.cpp.

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.

int QWidget::maximumHeight () const

Returns the widget's maximum height. See the "maximumHeight" property for details.

QSize QWidget::maximumSize () const

Returns the widget's maximum size. See the "maximumSize" property for details.

int QWidget::maximumWidth () const

Returns the widget's maximum width. See the "maximumWidth" property for details.

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

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

Use the QPaintDeviceMetrics class instead.

m is the metric to get.

QRect QWidget::microFocusHint () const

Returns the currently set micro focus hint for this widget. See the "microFocusHint" property for details.

int QWidget::minimumHeight () const

Returns the widget's minimum height. See the "minimumHeight" property for details.

QSize QWidget::minimumSize () const

Returns the widget's minimum size. See the "minimumSize" property for details.

QSize QWidget::minimumSizeHint () const [virtual]

Returns the recommended minimum size for the widget. See the "minimumSizeHint" property for details.

Reimplemented in QLineEdit.

int QWidget::minimumWidth () const

Returns the widget's minimum width. See the "minimumWidth" property for details.

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 mouseTracking, mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(), event(), and QMouseEvent.

Examples: aclock/aclock.cpp, drawlines/connect.cpp, iconview/simple_dd/main.cpp, life/life.cpp, popup/popup.cpp, qmag/qmag.cpp, and scribble/scribble.cpp.

Reimplemented in QSizeGrip.

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.

Examples: biff/biff.cpp, drawlines/connect.cpp, iconview/simple_dd/main.cpp, life/life.cpp, qmag/qmag.cpp, scribble/scribble.cpp, and tooltip/tooltip.cpp.

Reimplemented in QSizeGrip.

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 mouseDoubleClickEvent(), mouseMoveEvent(), event(), and QMouseEvent.

Examples: drawlines/connect.cpp, hello/hello.cpp, popup/popup.cpp, qmag/qmag.cpp, scribble/scribble.cpp, showimg/showimg.cpp, and t14/cannon.cpp.

void QWidget::move ( const QPoint & ) [slot]

Sets the position of the widget within its parent widget. See the "pos" property for details.

void QWidget::move ( int x, int y ) [virtual slot]

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

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

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

This event handler can be reimplemented in a subclass to receive widget move events. 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(), pos, and QMoveEvent.

bool QWidget::ownCursor () const

Returns TRUE if the widget uses its own cursor; otherwise returns FALSE. See the "ownCursor" property for details.

bool QWidget::ownFont () const

Returns TRUE if the widget uses its own font; otherwise returns FALSE. See the "ownFont" property for details.

bool QWidget::ownPalette () const

Returns TRUE if the widget uses its own palette; otherwise returns FALSE. See the "ownPalette" property for details.

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

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

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 QCanvas 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. There are a couple of exceptions and QPaintEvent::erased() tells you whether the widget has been erased or not.

The background can be set using setBackgroundMode(), setPaletteBackgroundColor() or setBackgroundPixmap(). The documentation for setBackgroundMode() elaborates on the background; we recommend reading it.

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

Examples: drawlines/connect.cpp, forever/forever.cpp, qmag/qmag.cpp, scribble/scribble.cpp, splitter/splitter.cpp, t8/cannon.cpp, and t9/cannon.cpp.

Reimplemented in QButton, QFrame, QGLWidget, QSizeGrip, QStatusBar, and QTabBar.

const QPalette & QWidget::palette () const

Returns the widget's palette. See the "palette" property for details.

const QColor & QWidget::paletteBackgroundColor () const

Returns the background color of the widget. See the "paletteBackgroundColor" property for details.

const QPixmap * QWidget::paletteBackgroundPixmap () const

Returns the background pixmap of the widget. See the "paletteBackgroundPixmap" property for details.

void QWidget::paletteChange ( const QPalette & oldPalette ) [virtual protected]

This virtual function is called from setPalette(). oldPalette is the previous palette; you can get the new palette from palette().

Reimplement this function if your widget needs to know when its palette changes.

See also palette and palette.

const QColor & QWidget::paletteForegroundColor () const

Returns the foreground color of the widget. See the "paletteForegroundColor" property for details.

QWidget * QWidget::parentWidget ( bool sameWindow = FALSE ) const

Returns the parent of this widget, or 0 if it does not have any parent widget. If sameWindow is TRUE and the widget is top level returns 0; otherwise returns the widget's parent.

Example: mdi/application.cpp.

void QWidget::polish () [virtual slot]

Delayed initialization of a widget.

This function will be called after a widget has been fully created and before it is shown the very first time.

Polishing is useful for final initialization which depends on having an instantiated widget. This is something a constructor cannot guarantee since the initialization of the subclasses might not be finished.

After this function, the widget has a proper font and palette and QApplication::polish() has been called.

Remember to call QWidget's implementation first when reimplementing this function to ensure that your program does not end up in infinite recursion.

See also constPolish() and QApplication::polish().

Example: menu/menu.cpp.

QPoint QWidget::pos () const

Returns the position of the widget within its parent widget. See the "pos" property for details.

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

This special event handler can be reimplemented in a subclass to receive native Qt/Embedded events.

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().

Example: showimg/showimg.cpp.

void QWidget::recreate ( QWidget * parent, WFlags f, const QPoint & p, bool showIt = FALSE )

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

This method is provided to aid porting from Qt 1.0 to 2.0. It has been renamed reparent() in Qt 2.0.

QRect QWidget::rect () const

Returns the internal geometry of the widget excluding any window frame. See the "rect" property for details.

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::repaint ( int x, int y, int w, int h, bool erase = TRUE ) [slot]

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

If erase is TRUE, Qt erases the area (x, y, w, h) before the paintEvent() call.

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

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(), updatesEnabled, and erase().

Example: qwerty/qwerty.cpp.

void QWidget::repaint () [slot]

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

This version erases and repaints the entire widget.

void QWidget::repaint ( bool erase ) [slot]

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

This version repaints the entire widget.

void QWidget::repaint ( const QRect & r, bool erase = TRUE ) [slot]

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

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

Erases the widget region r if erase is TRUE.

void QWidget::repaint ( const QRegion & reg, bool erase = TRUE ) [slot]

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

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

Erases the widget region reg if erase is TRUE.

Only use repaint if your widget needs to be repainted immediately, for example when doing some animation. In all other cases, use update(). Calling update() many times in a row will generate a single paint event.

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(), updatesEnabled, and erase().

void QWidget::reparent ( QWidget * parent, WFlags f, const QPoint & p, bool showIt = FALSE ) [virtual]

Reparents the widget. The widget gets a new parent, new widget flags (f, but as usual, use 0) at a new position in its new parent (p).

If showIt is TRUE, show() is called once the widget has been reparented.

If the new parent widget is in a different top-level widget, 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, reparent() calls clearFocus() for that widget.

If the new parent widget is in the same top-level widget as the old parent, reparent doesn't change the tab order or keyboard focus.

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

See also getWFlags().

Example: toplevel/options.ui.h.

void QWidget::reparent (