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The QWidget class is the base class of all user interface objects. More...
#include <qwidget.h>
Inherits QObject and QPaintDevice.
Inherited by QButton, QFrame, QDialog, QComboBox, QDataBrowser, QDataView, QDateTimeEdit, QDesktopWidget, QDial, QDockArea, QGLWidget, QHeader, QMainWindow, QNPWidget, QScrollBar, QSizeGrip, QSlider, QSpinBox, QSplashScreen, QStatusBar, QTabBar, QTabWidget, QToolBox, and QWorkspace.
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.
Every widget's constructor accepts two or three standard arguments:
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.
This enum defines the origin used to draw a widget's background pixmap.
The pixmap is drawn using the:
This enum type defines the various policies a widget can have with respect to acquiring keyboard focus.
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 );
All this widget's children are deleted first. The application exits if this widget is the main widget.
Returns TRUE if drop events are enabled for this widget; otherwise returns FALSE. See the "acceptDrops" property for details.
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.
Returns TRUE if the auto mask feature is enabled for the widget; otherwise returns FALSE. See the "autoMask" property for details.
Returns the widget's background brush. See the "backgroundBrush" property for details.
Returns the color role used for painting the background of the widget. See the "backgroundMode" property for details.
Returns the origin of the widget's background. See the "backgroundOrigin" property for details.
Examples: themes/metal.cpp and themes/wood.cpp.
Returns the base size of the widget. See the "baseSize" property for details.
Returns the window caption (title). See the "caption" property for details.
If includeThis is TRUE, and there is no child visible at (x, y), the widget itself is returned.
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.
Returns the bounding rectangle of the widget's children. See the "childrenRect" property for details.
Returns the combined region occupied by the widget's children. See the "childrenRegion" property for details.
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().
See also setMask().
Clears the widget flags f.
Widget flags are a combination of Qt::WidgetFlags.
See also testWFlags(), getWFlags(), and setWFlags().
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.
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: mdi/application.cpp and popup/popup.cpp.
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().
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.
Returns the current color group of the widget palette. See the "colorGroup" property for details.
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().
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.
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.
Returns the cursor shape for this widget. See the "cursor" property for details.
Returns TRUE if the widget wants to handle What's This help manually; otherwise returns FALSE. See the "customWhatsThis" property for details.
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.
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.
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.
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.
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().
Draws the string str at position pos.
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.
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().
An event is sent to the widget when the mouse cursor enters the widget.
See also leaveEvent(), mouseMoveEvent(), and 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().
This version erases the entire widget.
Erases the specified area r in the widget without generating a paint event.
Erases the area defined by reg, without generating a paint event.
Child widgets are not affected.
Returns the erase color of the widget.
See also setEraseColor(), setErasePixmap(), and backgroundColor().
See also setErasePixmap() and eraseColor().
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.
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.
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().
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.
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.
See also focusData().
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.
Returns the way the widget accepts keyboard focus. See the "focusPolicy" property for details.
See also setFocusProxy().
Returns the font currently set for the widget. See the "font" property for details.
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().
Returns the font info for the widget's current font. Equivalent to QFontInto(widget->font()).
See also font, fontMetrics(), and font.
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.
Returns geometry of the widget relative to its parent including any window frame. See the "frameGeometry" property for details.
Returns the size of the widget including any window frame. See the "frameSize" property for details.
Returns the geometry of the widget relative to its parent and excluding the window frame. See the "geometry" property for details.
Returns the widget flags for this this widget.
Widget flags are a combination of Qt::WidgetFlags.
See also testWFlags(), setWFlags(), and clearWFlags().
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().
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().
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.
Returns TRUE if this widget (or its focus proxy) has the keyboard input focus; otherwise returns FALSE. See the "focus" property for details.
Returns TRUE if the widget is under the mouse cursor; otherwise returns FALSE. See the "underMouse" property for details.
Returns TRUE if mouse tracking is enabled for the widget; otherwise returns FALSE. See the "mouseTracking" property for details.
Returns the height of the widget excluding any window frame. See the "height" property for details.
Warning: Does not look at the widget's layout.
Reimplemented in QMenuBar and QTextEdit.
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, and xform/xform.cpp.
Reimplemented in QMenuBar.
Hide events are sent to widgets immediately after they have been hidden.
See also event() and QHideEvent.
Reimplemented in QScrollBar.
Returns the widget's icon. See the "icon" property for details.
Returns the widget's icon text. See the "iconText" property for details.
The default implementation calls e->ignore(), which rejects the Input Method event. See the QIMEvent documentation for more details.
See also event() and QIMEvent.
The default implementation calls e->ignore(), which rejects the Input Method event. See the QIMEvent documentation for more details.
See also event() and QIMEvent.
The default implementation calls e->ignore(), which rejects the Input Method event. See the QIMEvent documentation for more details.
See also event() and QIMEvent.
Returns TRUE if this widget is the active window; otherwise returns FALSE. See the "isActiveWindow" property for details.
Returns TRUE if the widget is a desktop widget, i.e. represents the desktop; otherwise returns FALSE. See the "isDesktop" property for details.
Returns TRUE if the widget is a dialog widget; otherwise returns FALSE. See the "isDialog" property for details.
Returns TRUE if the widget is enabled; otherwise returns FALSE. See the "enabled" property for details.
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().
This function is deprecated. It is equivalent to isEnabled()
Returns TRUE if the widget accepts keyboard focus; otherwise returns FALSE. See the "focusEnabled" property for details.
Returns TRUE if the widget is full screen; otherwise returns FALSE. See the "fullScreen" property for details.
Returns TRUE if the widget is explicitly hidden; otherwise returns FALSE. See the "hidden" property for details.
Returns enables or disables the use of input methods for this widget. See the "inputMethodEnabled" property for details.
Returns TRUE if this widget is maximized; otherwise returns FALSE. See the "maximized" property for details.
Returns TRUE if this widget is minimized (iconified); otherwise returns FALSE. See the "minimized" property for details.
Returns TRUE if the widget is a modal widget; otherwise returns FALSE. See the "isModal" property for details.
Returns TRUE if the widget is a popup widget; otherwise returns FALSE. See the "isPopup" property for details.
Returns TRUE if the widget is shown; otherwise returns FALSE. See the "shown" property for details.
Returns TRUE if the widget is a top-level widget; otherwise returns FALSE. See the "isTopLevel" property for details.
Returns TRUE if updates are enabled; otherwise returns FALSE. See the "updatesEnabled" property for details.
Returns TRUE if the widget is visible; otherwise returns FALSE. See the "visible" property for details.
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.
This function is deprecated. It is equivalent to isVisible()
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.
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.
If no widget in this application is currently grabbing the keyboard, 0 is returned.
See also grabMouse() and mouseGrabber().
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.
A leave event is sent to the widget when the mouse cursor leaves the widget.
See also enterEvent(), mouseMoveEvent(), and event().
After this call the widget will be visually behind (and therefore obscured by) any overlapping sibling widgets.
See also raise() and stackUnder().
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().
See also mapTo(), mapFromParent(), mapFromGlobal(), and underMouse.
See also mapToGlobal(), mapFrom(), and mapFromParent().
Same as mapFromGlobal() if the widget has no parent.
See also mapToParent(), mapFrom(), mapFromGlobal(), and underMouse.
See also mapFrom(), mapToParent(), mapToGlobal(), and underMouse.
See also mapFromGlobal(), mapTo(), and mapToParent().
Example: scribble/scribble.cpp.
Same as mapToGlobal() if the widget has no parent.
See also mapFromParent(), mapTo(), mapToGlobal(), and underMouse.
Returns the widget's maximum height. See the "maximumHeight" property for details.
Returns the widget's maximum size. See the "maximumSize" property for details.
Returns the widget's maximum width. See the "maximumWidth" property for details.
Use the QPaintDeviceMetrics class instead.
m is the metric to get.
Returns the currently set micro focus hint for this widget. See the "microFocusHint" property for details.
Returns the widget's minimum height. See the "minimumHeight" property for details.
Returns the widget's minimum size. See the "minimumSize" property for details.
Returns the recommended minimum size for the widget. See the "minimumSizeHint" property for details.
Reimplemented in QLineEdit.
Returns the widget's minimum width. See the "minimumWidth" property for details.
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.
If no widget in this application is currently grabbing the mouse, 0 is returned.
See also grabMouse() and keyboardGrabber().
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.
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.
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.
Sets the position of the widget within its parent widget. See the "pos" property for details.
This corresponds to move( QSize(x, y) ).
The old position is accessible through QMoveEvent::oldPos().
See also resizeEvent(), event(), pos, and QMoveEvent.
Returns TRUE if the widget uses its own cursor; otherwise returns FALSE. See the "ownCursor" property for details.
Returns TRUE if the widget uses its own font; otherwise returns FALSE. See the "ownFont" property for details.
Returns TRUE if the widget uses its own palette; otherwise returns FALSE. See the "ownPalette" property for details.
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.
Returns the widget's palette. See the "palette" property for details.
Returns the background color of the widget. See the "paletteBackgroundColor" property for details.
Returns the background pixmap of the widget. See the "paletteBackgroundPixmap" property for details.
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.
Returns the foreground color of the widget. See the "paletteForegroundColor" property for details.
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.
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.
Returns the position of the widget within its parent widget. See the "pos" property for details.
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().
After this call the widget will be visually in front of any overlapping sibling widgets.
See also lower() and stackUnder().
Example: showimg/showimg.cpp.
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.
Returns the internal geometry of the widget excluding any window frame. See the "rect" property for details.
See also grabKeyboard(), grabMouse(), and releaseMouse().
See also grabMouse(), grabKeyboard(), and releaseKeyboard().
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.
This version erases and repaints the entire widget.
This version repaints the entire widget.
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.
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().
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().
A convenience version of reparent that does not take widget flags as argument.
Calls reparent(parent, getWFlags() & ~WType_Mask, p, showIt).
Sets the size of the widget excluding any window frame. See the "size" property for details.
This corresponds to resize( QSize(w, h) ).
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.
Widgets that have been created with the WNoAutoErase flag will not be erased. Nevertheless, they will receive a paint event for their entire area afterwards. Again, no drawing needs to be done inside this handler.
The default implementation calls updateMask() if the widget has automatic masking enabled.
See also moveEvent(), event(), size, QResizeEvent, and paintEvent().
Examples: drawdemo/drawdemo.cpp, menu/menu.cpp, qmag/qmag.cpp, scribble/scribble.cpp, showimg/showimg.cpp, tooltip/tooltip.cpp, and xform/xform.cpp.
Reimplemented in QFrame and QGLWidget.
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.
See also QScrollView, erase(), and bitBlt().
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, erase(), and bitBlt().
Sets whether drop events are enabled for this widget to on. See the "acceptDrops" property for details.
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 setActiveWindow() 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, topLevelWidget(), and show().
Sets whether the auto mask feature is enabled for the widget. See the "autoMask" property for details.
Examples: customlayout/main.cpp, desktop/desktop.cpp, hello/main.cpp, movies/main.cpp, and splitter/splitter.cpp.
Sets the color role used for painting the background of the widget. See the "backgroundMode" property for details.
Sets the widget's own background mode to m and the visual background mode to visual. The visual background mode is used with the designable properties backgroundColor, foregroundColor and backgroundPixmap.
For complex controls, the logical background mode sometimes differs from a widget's own background mode. A spinbox for example has PaletteBackground as background mode (typically dark gray), while it's embedded lineedit control uses PaletteBase (typically white). Since the lineedit covers most of the visual area of a spinbox, it defines PaletteBase to be its visual background mode. Changing the backgroundColor property thus changes the lineedit control's background, which is exactly what the user expects in Qt Designer.
Sets the origin of the widget's background. See the "backgroundOrigin" property for details.
Example: desktop/desktop.cpp.
Sets the base size of the widget. See the "baseSize" property for details.
This corresponds to setBaseSize( QSize(basew, baseh) ). Sets the widgets base size to width basew and height baseh.
Sets the window caption (title). See the "caption" property for details.
Sets the cursor shape for this widget. See the "cursor" property for details.
See the enabled documentation for more information.
See also isEnabledTo(), QKeyEvent, QMouseEvent, and enabledChange().
Sets whether the widget is enabled. See the "enabled" property for details.
The erase color is the color the widget is to be cleared to before paintEvent() is called. If there is an erase pixmap (set using setErasePixmap()), then this property has an indeterminate value.
See also erasePixmap(), backgroundColor(), backgroundMode, and palette.
This pixmap is used to clear the widget before paintEvent() is called.
See also sizeHint, minimumSize, maximumSize, and setFixedSize().
Examples: fonts/simple-qfont-demo/viewer.cpp, layout/layout.cpp, qdir/qdir.cpp, and showimg/showimg.cpp.
See also maximumSize and minimumSize.
Sets the width of the widget to w and the height to h.
See also sizeHint, minimumSize, maximumSize, and setFixedSize().
Examples: progressbar/progressbar.cpp and qdir/qdir.cpp.
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.
See also focus, clearFocus(), focusInEvent(), focusOutEvent(), focusPolicy, QApplication::focusWidget(), grabKeyboard(), and grabMouse().
Examples: addressbook/centralwidget.cpp, lineedits/lineedits.cpp, mdi/application.cpp, popup/popup.cpp, rot13/rot13.cpp, t8/main.cpp, and wizard/wizard.cpp.
Sets the way the widget accepts keyboard focus. See the "focusPolicy" property for details.
Some widgets, such as QComboBox, can "have focus", but create a child widget to actually handle the focus. QComboBox, for example, creates a QLineEdit which handles the focus.
setFocusProxy() sets the widget which will actually get focus when "this widget" gets it. If there is a focus proxy, focusPolicy(), setFocusPolicy(), setFocus() and hasFocus() all operate on the focus proxy.
See also focusProxy().
Sets the font currently set for the widget. See the "font" property for details.
Reimplemented in QComboBox, QLabel, and QTabDialog.
Use setFont(const QFont& font) instead.
Sets the geometry of the widget relative to its parent and excluding the window frame. See the "geometry" property for details.
This corresponds to setGeometry( QRect(x, y, w, h) ).
Sets whether the widget is explicitly hidden to hide. See the "hidden" property for details.
Sets the widget's icon. See the "icon" property for details.
Sets the widget's icon text. See the "iconText" property for details.
Sets enables or disables the use of input methods for this widget to b. See the "inputMethodEnabled" property for details.
By default key compression is off, so widgets receive one key press event for each key press (or more, since autorepeat is usually on). If you turn it on and your program doesn't keep up with key input, Qt may try to compress key events so that more than one character can be processed in each event.
For example, a word processor widget might receive 2, 3 or more characters in each QKeyEvent::text(), if the layout recalculation takes too long for the CPU.
If a widget supports multiple character unicode input, it is always safe to turn the compression on.
Qt performs key event compression only for printable characters. Modifier keys, cursor movement keys, function keys and miscellaneous action keys (e.g. Escape, Enter, Backspace, PrintScreen) will stop key event compression, even if there are more compressible key events available.
Not all platforms support this compression, in which case turning it on will have no effect.
See also QKeyEvent::text().
Note that this effect can be slow if the region is particularly complex.
See also clearMask().
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 clearMask().
Sets the widget's maximum height to maxh. See the "maximumHeight" property for details.
Sets the widget's maximum size. See the "maximumSize" property for details.
This function corresponds to setMaximumSize( QSize(maxw, maxh) ). Sets the maximum width to maxw and the maximum height to maxh.
Sets the widget's maximum width to maxw. See the "maximumWidth" property for details.
The text argument should be TRUE if this is a position for text input.
In the Windows version of Qt, this method sets the system caret, which is used for user Accessibility focus handling. If text is TRUE, it also sets the IME composition window in Far East Asian language input systems.
In the X11 version of Qt, if text is TRUE, this method sets the XIM "spot" point for complex language input handling.
The font f is a rendering hint to the currently active input method. If f is 0 the widget's font is used.
See also microFocusHint.
Sets the widget's minimum height to minh. See the "minimumHeight" property for details.
Sets the widget's minimum size. See the "minimumSize" property for details.
This function corresponds to setMinimumSize( QSize(minw, minh) ). Sets the minimum width to minw and the minimum height to minh.
Sets the widget's minimum width to minw. See the "minimumWidth" property for details.
Sets whether mouse tracking is enabled for the widget to enable. See the "mouseTracking" property for details.
Sets the widget's palette. See the "palette" property for details.
Reimplemented in QComboBox, QScrollBar, and QSlider.
Use setPalette( const QPalette& p ) instead.
Sets the background color of the widget. See the "paletteBackgroundColor" property for details.
Sets the background pixmap of the widget. See the "paletteBackgroundPixmap" property for details.
Sets the foreground color of the widget. See the "paletteForegroundColor" property for details.
Sets whether the widget is shown to show. See the "shown" property for details.
Sets the size increment of the widget. See the "sizeIncrement" property for details.
Sets the x (width) size increment to w and the y (height) size increment to h.
Sets the default layout behavior of the widget. See the "sizePolicy" property for details.
Sets the size policy of the widget to hor, ver and hfw (height for width).
See also QSizePolicy::QSizePolicy().
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().
Examples: grapher/grapher.cpp and progressbar/progressbar.cpp.
Sets the widget's GUI style to style using the QStyleFactory.
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 focusPolicy and setFocusProxy().
Example: customlayout/main.cpp.
Sets whether updates are enabled to enable. See the "updatesEnabled" property for details.
Sets the widget flags f.
Widget flags are a combination of Qt::WidgetFlags.
See also testWFlags(), getWFlags(), and clearWFlags().
If its size or position has changed, Qt guarantees that a widget gets move and resize events just before it is shown.
You almost never have to reimplement this 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 polish().
See also showEvent(), hide(), showMinimized(), showMaximized(), showNormal(), visible, and polish().
Examples: aclock/main.cpp, life/main.cpp, popup/popup.cpp, showimg/main.cpp, t1/main.cpp, t3/main.cpp, and t4/main.cpp.
Reimplemented in QDialog and QMenuBar.
Non-spontaneous show events are sent to widgets immediately before they are shown. The spontaneous show events of top-level widgets are delivered afterwards.
See also event() and QShowEvent.
Example: qdir/qdir.cpp.
Calling this function only affects top-level widgets.
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 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.
Future X11 window managers that follow modern post-ICCCM specifications may support full-screen mode properly.
See also showNormal(), showMaximized(), show(), hide(), and visible.
Calling this function only affects top-level widgets.
On X11, this function may not work properly with certain window managers. See the Window Geometry documentation for an explanation.
See also showNormal(), showMinimized(), show(), hide(), and visible.
Examples: canvas/main.cpp, helpviewer/main.cpp, mdi/application.cpp, qwerty/main.cpp, qwerty/qwerty.cpp, and scribble/main.cpp.
Calling this function only affects top-level widgets.
See also showNormal(), showMaximized(), show(), hide(), visible, and minimized.
Calling this function only affects top-level widgets.
See also showMinimized(), showMaximized(), show(), hide(), and visible.
Example: mdi/application.cpp.
Returns the size of the widget excluding any window frame. See the "size" property for details.
Returns the recommended size for the widget. See the "sizeHint" property for details.
Reimplemented in QSizeGrip.
Returns the size increment of the widget. See the "sizeIncrement" property for details.
Returns the default layout behavior of the widget. See the "sizePolicy" property for details.
To make this work, the widget itself and w must be siblings.
See also QWidget::setStyle(), QApplication::setStyle(), and QApplication::style().
Reimplement this function if your widget needs to know when its GUI style changes. You will almost certainly need to update the widget using update().
The default implementation updates the widget including its geometry.
See also QApplication::setStyle(), style(), update(), and updateGeometry().
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.
Returns the bitwise AND of the widget flags and f.
Widget flags are a combination of Qt::WidgetFlags.
See also getWFlags(), setWFlags(), and clearWFlags().
If the widget is a top-level, the widget itself is returned.
Typical usage is changing the window caption:
aWidget->topLevelWidget()->setCaption( "New Caption" );
See also isTopLevel.
Resets the cursor shape for this widget. See the "cursor" property for details.
Resets the font currently set for the widget. See the "font" property for details.
Resets the widget's palette. See the "palette" property for details.
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 WRepaintNoErase widget flag is set, the widget is responsible for painting all its pixels itself.
See also repaint(), paintEvent(), updatesEnabled, erase(), and setWFlags().
Examples: desktop/desktop.cpp and scrollview/scrollview.cpp.
Updates a rectangle (x, y, w, h) inside 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 and a call to repaint() does.
Calling update() several times normally results in just one paintEvent() call.
If w is negative, it is replaced with width() - x. If h is negative, it is replaced width height() - y.
Qt normally erases the specified area before the paintEvent() call. If the WRepaintNoErase widget flag is set, the widget is responsible for painting all its pixels itself.
See also repaint(), paintEvent(), updatesEnabled, and erase().
Updates a rectangle r inside 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 and a call to repaint() does.
Calling update() several times normally results in just one paintEvent() call.
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.
See also autoMask, setMask(), and clearMask().
Returns the visible rectangle. See the "visibleRect" property for details.
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.
Returns the width of the widget excluding any window frame. See the "width" property for details.
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::winEventFilter().
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().
This virtual function is called for a widget when its window is activated or deactivated by the window system. oldActive is the previous state; you can get the new setting from isActiveWindow().
Reimplement this function if your widget needs to know when its window becomes activated or deactivated.
The default implementation updates the visible part of the widget if the inactive and the active colorgroup are different for colors other than the highlight and link colors.
See also setActiveWindow(), isActiveWindow, update(), and palette.
Returns the x coordinate of the widget relative to its parent including any window frame. See the "x" property for details.
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().
Returns the y coordinate of the widget relative to its parent and including any window frame. See the "y" property for details.
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::isDesktop()), 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.
Set this property's value with setAcceptDrops() and get this property's value with acceptDrops().
This property holds whether the auto mask feature is enabled for the widget.
Transparent widgets use a mask to define their visible region. QWidget has some built-in support to make the task of recalculating the mask easier. When setting auto mask to TRUE, updateMask() will be called whenever the widget is resized or changes its focus state. Note that you must reimplement updateMask() (which should include a call to setMask()) or nothing will happen.
Note: when you re-implement resizeEvent(), focusInEvent() or focusOutEvent() in your custom widgets and still want to ensure that the auto mask calculation works, you should add:
if ( autoMask() )
updateMask();
at the end of your event handlers. This is true for all member functions that change the appearance of the widget in a way that requires a recalculation of the mask.
While being a technically appealing concept, masks have a big drawback: when using complex masks that cannot be expressed easily with relatively simple regions, they can be very slow on some window systems. The classic example is a transparent label. The complex shape of its contents makes it necessary to represent its mask by a bitmap, which consumes both memory and time. If all you want is to blend the background of several neighboring widgets together seamlessly, you will probably want to use setBackgroundOrigin() rather than a mask.
See also updateMask(), setMask(), clearMask(), and backgroundOrigin.
Set this property's value with setAutoMask() and get this property's value with autoMask().
This property holds the widget's background brush.
The background brush depends on a widget's palette and its background mode.
See also backgroundColor(), backgroundPixmap(), eraseColor(), palette, and QApplication::setPalette().
Get this property's value with backgroundBrush().
This property holds the color role used for painting the background of the widget.
setPaletteBackgroundColor() reads this property to determine which entry of the palette to set.
For most widgets the default suffices (PaletteBackground, typically gray), but some need to use PaletteBase (the background color for text output, typically white) or another role.
QListBox, which is "sunken" and uses the base color to contrast with its environment, does this in its constructor:
setBackgroundMode( PaletteBase );
You will never need to set the background mode of a built-in widget in Qt, but you might consider setting it in your custom widgets, so that setPaletteBackgroundColor() works as expected.
Note that two of the BackgroundMode values make no sense for setBackgroundMode(), namely FixedPixmap and FixedColor. You must call setBackgroundPixmap() and setPaletteBackgroundColor() instead.
Set this property's value with setBackgroundMode() and get this property's value with backgroundMode().
This property holds the origin of the widget's background.
The origin is either WidgetOrigin (the default), ParentOrigin, WindowOrigin or AncestorOrigin.
This only makes a difference if the widget has a background pixmap, in which case positioning matters. Using WindowOrigin for several neighboring widgets makes the background blend together seamlessly. AncestorOrigin allows blending backgrounds seamlessly when an ancestor of the widget has an origin other than QWindowOrigin.
See also backgroundPixmap() and backgroundMode.
Set this property's value with setBackgroundOrigin() and get this property's value with backgroundOrigin().
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().
See also sizeIncrement.
Set this property's value with setBaseSize() and get this property's value with baseSize().
This property holds the window caption (title).
This property only makes sense for top-level widgets. If no caption has been set, the caption is QString::null.
Set this property's value with setCaption() and get this property's value with caption().
This property holds the bounding rectangle of the widget's children.
Hidden children are excluded.
See also childrenRegion and geometry.
Get this property's value with childrenRect().
This property holds the combined region occupied by the widget's children.
Hidden children are excluded.
See also childrenRect and geometry.
Get this property's value with childrenRegion().
This property holds the current color group of the widget palette.
The color group is determined by the state of the widget. A disabled widget has the QPalette::disabled() color group, a widget with keyboard focus has the QPalette::active() color group, and an inactive widget has the QPalette::inactive() color group.
See also palette.
Get this property's value with colorGroup().
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( 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 top-level widgets.
See also QApplication::setOverrideCursor().
Set this property's value with setCursor(), get this property's value with cursor(), and reset this property's value with unsetCursor().
This property holds whether the widget wants to handle What's This help manually.
The default implementation of customWhatsThis() returns FALSE, which means the widget will not receive any events in Whats This mode.
The widget may leave What's This mode by calling QWhatsThis::leaveWhatsThisMode(), with or without actually displaying any help text.
You can also reimplement customWhatsThis() if your widget is a "passive interactor" supposed to work under all circumstances. Simply don't call QWhatsThis::leaveWhatsThisMode() in that case.
See also QWhatsThis::inWhatsThisMode() and QWhatsThis::leaveWhatsThisMode().
Get this property's value with customWhatsThis().
This property holds whether the widget is enabled.
An enabled widget receives keyboard and mouse events; a disabled widget does not. In fact, an enabled widget only receives keyboard events when it is in focus.
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 reimplement the enabledChange() function.
Disabling a widget implicitly disables all its children. Enabling respectively enables all child widgets unless they have been explicitly disabled.
See also enabled, isEnabledTo(), QKeyEvent, QMouseEvent, and enabledChange().
Set this property's value with setEnabled() and get this property's value with isEnabled().
This property holds whether this widget (or its focus proxy) has the keyboard input focus.
Effectively equivalent to qApp->focusWidget() == this.
See also setFocus(), clearFocus(), focusPolicy, and QApplication::focusWidget().
Get this property's value with hasFocus().
This property holds whether the widget accepts keyboard focus.
Keyboard focus is initially disabled (i.e. focusPolicy() == QWidget::NoFocus).
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(QWidget::StrongFocus).
See also focusPolicy, focusInEvent(), focusOutEvent(), keyPressEvent(), keyReleaseEvent(), and enabled.
Get this property's value with isFocusEnabled().
This property holds the way the widget accepts keyboard focus.
The policy is QWidget::TabFocus if the widget accepts keyboard focus by tabbing, QWidget::ClickFocus if the widget accepts focus by clicking, QWidget::StrongFocus if it accepts both, and QWidget::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(QWidget::StrongFocus).
See also focusEnabled, focusInEvent(), focusOutEvent(), keyPressEvent(), keyReleaseEvent(), and enabled.
Set this property's value with setFocusPolicy() and get this property's value with focusPolicy().
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 unsetFont() 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.
See also fontChange(), fontInfo(), fontMetrics(), and ownFont.
Set this property's value with setFont(), get this property's value with font(), and reset this property's value with unsetFont().
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 top-level widgets.
See also geometry, x, y, and pos.
Get this property's value with frameGeometry().
This property holds the size of the widget including any window frame.
Get this property's value with frameSize().
This property holds whether the widget is full screen.
Get this property's value with isFullScreen().
See also minimized and maximized.
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().
setGeometry() is virtual, and all other overloaded setGeometry() implementations in Qt call it.
Warning: Calling setGeometry() inside resizeEvent() or moveEvent() can lead to infinite recursion.
See the Window Geometry documentation for an overview of top-level widget geometry.
See also frameGeometry, rect, pos, size, moveEvent(), resizeEvent(), minimumSize, and maximumSize.
Set this property's value with setGeometry() and get this property's value with geometry().
This property holds the height of the widget excluding any window frame.
See the Window Geometry documentation for an overview of top-level widget geometry.
See also geometry, width, and size.
Get this property's value with height().
This property holds whether the widget is explicitly hidden.
If FALSE, the widget is visible or would become visible if all its ancestors became visible.
See also hide(), show(), visible, isVisibleTo(), and shown.
Set this property's value with setHidden() and get this property's value with isHidden().
This property holds the widget's icon.
This property only makes sense for top-level widgets. If no icon has been set, icon() returns 0.
See also iconText, caption, and Setting the Application Icon.
Set this property's value with setIcon() and get this property's value with icon().
This property holds the widget's icon text.
This property only makes sense for top-level widgets. If no icon text has been set, this functions returns QString::null.
Set this property's value with setIconText() and get this property's value with iconText().
This property holds enables or disables the use of input methods for this widget.
Most Widgets (as eg. buttons) that do not handle text input should have the input method disabled if they have focus. This is the default.
If a widget handles text input it should set this property to TRUE.
Set this property's value with setInputMethodEnabled() and get this property's value with isInputMethodEnabled().
This property holds whether this widget is the active window.
The active window is the window (or child of the window) that has keyboard focus.
When popup windows are visible, this property is TRUE for both the active window and for the popup.
See also setActiveWindow() and QApplication::activeWindow().
Get this property's value with isActiveWindow().
This property holds whether the widget is a desktop widget, i.e. represents the desktop.
A desktop widget is also a top-level widget.
See also isTopLevel and QApplication::desktop().
Get this property's value with isDesktop().
This property holds whether the widget is a dialog widget.
A dialog widget is a secondary top-level widget, i.e. a top-level widget with a parent.
See also isTopLevel and QDialog.
Get this property's value with isDialog().
This property holds whether the widget is a modal widget.
This property only makes sense for top-level widgets. A modal widget prevents widgets in all other top-level widgets from getting any input.
See also isTopLevel, isDialog, and QDialog.
Get this property's value with isModal().
This property holds whether the widget is a popup widget.
A popup widget is created by specifying the widget flag WType_Popup to the widget constructor. A popup widget is also a top-level widget.
See also isTopLevel.
Get this property's value with isPopup().
This property holds whether the widget is a top-level widget.
A top-level widget is a widget which usually has a frame and a caption (title). Popup and desktop widgets are also top-level widgets.
A top-level widget 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 top-level, even if a parent widget is specified in the constructor. This behavior is specified by the WType_TopLevel widget flag.
See also topLevelWidget(), isDialog, isModal, isPopup, isDesktop, and parentWidget().
Get this property's value with isTopLevel().
This property holds whether this widget is maximized.
This property is only relevant for top-level widgets.
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.
See also showMaximized(), visible, show(), hide(), showNormal(), and minimized.
Get this property's value with isMaximized().
This property holds the widget's maximum height.
This property corresponds to maximumSize().height().
See also maximumSize and maximumWidth.
Set this property's value with setMaximumHeight() and get this property's value with maximumHeight().
This property holds the widget's maximum size.
The widget cannot be resized to a larger size than the maximum widget size.
See also maximumWidth, maximumHeight, maximumSize, minimumSize, and sizeIncrement.
Set this property's value with setMaximumSize() and get this property's value with maximumSize().
This property holds the widget's maximum width.
This property corresponds to maximumSize().width().
See also maximumSize and maximumHeight.
Set this property's value with setMaximumWidth() and get this property's value with maximumWidth().
This property holds the currently set micro focus hint for this widget.
See the documentation of setMicroFocusHint() for more information.
Get this property's value with microFocusHint().
This property holds whether this widget is minimized (iconified).
This property is only relevant for top-level widgets.
See also showMinimized(), visible, show(), hide(), showNormal(), and maximized.
Get this property's value with isMinimized().
This property holds the widget's minimum height.
This property corresponds to minimumSize().height().
See also minimumSize and minimumWidth.
Set this property's value with setMinimumHeight() and get this property's value with minimumHeight().
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.
If you use a layout inside the widget, the minimum size will be set by the layout and not by setMinimumSize(), unless you set the layout's resize mode to QLayout::FreeResize.
See also minimumWidth, minimumHeight, maximumSize, sizeIncrement, and QLayout::resizeMode.
Set this property's value with setMinimumSize() and get this property's value with minimumSize().
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 minimumSizeHint.
See also QSize::isValid(), size, minimumSize, and sizePolicy.
Get this property's value with minimumSizeHint().
This property holds the widget's minimum width.
This property corresponds to minimumSize().width().
See also minimumSize and minimumHeight.
Set this property's value with setMinimumWidth() and get this property's value with minimumWidth().
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.
See also mouseMoveEvent() and QApplication::setGlobalMouseTracking().
Set this property's value with setMouseTracking() and get this property's value with hasMouseTracking().
This property holds whether the widget uses its own cursor.
If FALSE, the widget uses its parent widget's cursor.
See also cursor.
Get this property's value with ownCursor().
This property holds whether the widget uses its own font.
If FALSE, the widget uses its parent widget's font.
See also font.
Get this property's value with ownFont().
This property holds whether the widget uses its own palette.
If FALSE, the widget uses its parent widget's palette.
See also palette.
Get this property's value with ownPalette().
This property holds the widget's palette.
As long as no special palette has been set, or after unsetPalette() has been called, 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.
Instead of defining an entirely new palette, you can also use the paletteBackgroundColor, paletteBackgroundPixmap and paletteForegroundColor convenience properties to change a widget's background and foreground appearance only.
See also ownPalette, colorGroup, and QApplication::palette().
Set this property's value with setPalette(), get this property's value with palette(), and reset this property's value with unsetPalette().
This property holds the background color of the widget.
The palette background color is usually set implicitly by setBackgroundMode(), although it can also be set explicitly by setPaletteBackgroundColor(). setPaletteBackgroundColor() is a convenience function that creates and sets a modified QPalette with setPalette(). The palette is modified according to the widget's background mode. For example, if the background mode is PaletteButton the color used for the palette's QColorGroup::Button color entry is set.
If there is a background pixmap (set using setPaletteBackgroundPixmap()), then the return value of this function is indeterminate.
See also paletteBackgroundPixmap, paletteForegroundColor, palette, and colorGroup.
Set this property's value with setPaletteBackgroundColor(), get this property's value with paletteBackgroundColor(), and reset this property's value with unsetPalette().
This property holds the background pixmap of the widget.
The palette background pixmap is usually set implicitly by setBackgroundMode(), although it can also be set explicitly by setPaletteBackgroundPixmap(). setPaletteBackgroundPixmap() is a convenience function that creates and sets a modified QPalette with setPalette(). The palette is modified according to the widget's background mode. For example, if the background mode is PaletteButton the pixmap used for the palette's QColorGroup::Button color entry is set.
If there is a plain background color (set using setPaletteBackgroundColor()), then this function returns 0.
See also paletteBackgroundColor, paletteForegroundColor, palette, and colorGroup.
Set this property's value with setPaletteBackgroundPixmap(), get this property's value with paletteBackgroundPixmap(), and reset this property's value with unsetPalette().
This property holds the foreground color of the widget.
setPaletteForegroundColor() is a convenience function that creates and sets a modified QPalette with setPalette(). The palette is modified according to the widget's background mode. For example, if the background mode is PaletteButton the palette entry QColorGroup::ButtonText is set to color.
See also palette, QApplication::setPalette(), backgroundMode, foregroundColor(), backgroundMode, and setEraseColor().
Set this property's value with setPaletteForegroundColor(), get this property's value with paletteForegroundColor(), and reset this property's value with unsetPalette().
This property holds the position of the widget within its parent widget.
If the widget is a top-level widget, 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 top-level widget geometry.
See also frameGeometry, size, x, and y.
Set this property's value with move() and get this property's value with pos().
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 top-level widget geometry.
See also size.
Get this property's value with rect().
This property holds whether the widget is shown.
If TRUE, the widget is visible or would become visible if all its ancestors became visible.
See also hide(), show(), visible, isVisibleTo(), and hidden.
Set this property's value with setShown() and get this property's value with isShown().
This property holds the size of the widget excluding any window frame.
When resizing, the widget, if visible, 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(). Furthermore, the size is always at least QSize(1, 1). For toplevel widgets, the minimum size might be larger, depending on the window manager.
If you want a top-level window to have a fixed size, call setResizeMode( QLayout::FreeResize ) on its layout.
resize() is virtual, and all other overloaded resize() implementations in Qt call it.
Warning: Calling resize() or setGeometry() inside resizeEvent() can lead to infinite recursion.
See also pos, geometry, minimumSize, maximumSize, and resizeEvent().
Set this property's value with resize() and get this property's value with size().
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.
See also QSize::isValid(), minimumSizeHint, sizePolicy, minimumSize, and updateGeometry().
Get this property's value with sizeHint().
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 top-level widgets.
Warning: The size increment has no effect under Windows, and may be disregarded by the window manager on X.
See also size, minimumSize, and maximumSize.
Set this property's value with setSizeIncrement() and get this property's value with sizeIncrement().
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().
See also sizeHint, QLayout, QSizePolicy, and updateGeometry().
Set this property's value with setSizePolicy() and get this property's value with sizePolicy().
This property holds whether the widget is under the mouse cursor.
This value is not updated properly during drag and drop operations.
See also QEvent::Enter and QEvent::Leave.
Get this property's value with hasMouse().
This property holds whether updates are enabled.
Calling update() and repaint() has no effect if updates are disabled. Paint events from the window system are processed normally even 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.
Example:
setUpdatesEnabled( FALSE );
bigVisualChanges();
setUpdatesEnabled( TRUE );
repaint();
See also update(), repaint(), and paintEvent().
Set this property's value with setUpdatesEnabled() and get this property's value with isUpdatesEnabled().
This property holds whether the widget is visible.
Calling show() sets the widget to visible status if all its parent widgets up to the top-level widget are visible. If an ancestor is not visible, the widget won't become visible until all its ancestors are shown.
Calling 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 top-level widgets 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.
See also show(), hide(), hidden, isVisibleTo(), minimized, showEvent(), and hideEvent().
Get this property's value with isVisible().
This property holds the visible rectangle.
This property is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.
No longer necessary, you can simply call repaint(). If you do not need the rectangle for repaint(), use clipRegion() instead.
Get this property's value with visibleRect().
This property holds the width of the widget excluding any window frame.
See the Window Geometry documentation for an overview of top-level widget geometry.
See also geometry, height, and size.
Get this property's value with width().
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 top-level widget geometry.
See also frameGeometry, y, and pos.
Get this property's value with x().
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 top-level widget geometry.
See also frameGeometry, x, and pos.
Get this property's value with y().
This file is part of the Qt toolkit. Copyright © 1995-2003 Trolltech. All Rights Reserved.
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