QGraphicsWidget Class

See also QGraphicsProxyWidget, QGraphicsItem, Widgets and Layouts

The value returned by the virtual type() function.

This property holds whether the widget background is filled automatically

If enabled, this property will cause Qt to fill the background of the widget before invoking the paint() method. The color used is defined by the QPalette::Window color role from the widget's palette.

In addition, Windows are always filled with QPalette::Window, unless the WA_OpaquePaintEvent or WA_NoSystemBackground attributes are set.

By default, this property is false.

Access functions:

• bool autoFillBackground() const

• void setAutoFillBackground(bool enabled)

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This property holds the way the widget accepts keyboard focus

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

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

If you enable a focus policy (i.e., not Qt::NoFocus), QGraphicsWidget will automatically enable the ItemIsFocusable flag. Setting Qt::NoFocus on a widget will clear the ItemIsFocusable flag. If the widget currently has keyboard focus, the widget will automatically lose focus.

Access functions:

• focusPolicy() const

• void setFocusPolicy( policy)

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This property holds the widgets' font

This property provides the widget's font.

QFont consists of font properties that have been explicitly defined and properties implicitly inherited from the widget's parent. Hence, font() can return a different font compared to the one set with setFont(). This scheme allows you to define single entries in a font without affecting the font's inherited entries.

When a widget's font changes, it resolves its entries against its parent widget. If the widget does not have a parent widget, it resolves its entries against the scene. The widget then sends itself a FontChange event and notifies all its descendants so that they can resolve their fonts as well.

By default, this property contains the application's default font.

Access functions:

• font() const

• void setFont(const &font)

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This property holds the geometry of the widget

Sets the item's geometry to rect. The item's position and size are modified as a result of calling this function. The item is first moved, then resized.

A side effect of calling this function is that the widget will receive a move event and a resize event. Also, if the widget has a layout assigned, the layout will activate.

Access functions:

• virtual void setGeometry(const &rect) override

• void setGeometry(qreal x, qreal y, qreal w, qreal h)

Notifier signal:

• void geometryChanged()

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This property holds the layout of the widget

Any existing layout manager is deleted before the new layout is assigned. If layout is nullptr, the widget is left without a layout. Existing subwidgets' geometries will remain unaffected.

QGraphicsWidget takes ownership of layout.

All widgets that are currently managed by layout or all of its sublayouts, are automatically reparented to this item. The layout is then invalidated, and the child widget geometries are adjusted according to this item's geometry() and contentsMargins(). Children who are not explicitly managed by layout remain unaffected by the layout after it has been assigned to this widget.

If no layout is currently managing this widget, layout() will return nullptr.

Access functions:

• *layout() const

• void setLayout( *layout)

Notifier signal:

• void layoutChanged()

This property holds the layout direction for this widget.

This property modifies this widget's and all of its descendants' Qt::WA_RightToLeft attribute. It also sets this widget's Qt::WA_SetLayoutDirection attribute.

The widget's layout direction determines the order in which the layout manager horizontally arranges subwidgets of this widget. The default value depends on the language and locale of the application, and is typically in the same direction as words are read and written. With Qt::LeftToRight, the layout starts placing subwidgets from the left side of this widget towards the right. Qt::RightToLeft does the opposite - the layout will place widgets starting from the right edge moving towards the left.

Subwidgets inherit their layout direction from the parent. Top-level widget items inherit their layout direction from QGraphicsScene::layoutDirection. If you change a widget's layout direction by calling setLayoutDirection(), the widget will send itself a LayoutDirectionChange event, and then propagate the new layout direction to all its descendants.

Access functions:

• layoutDirection() const

• void setLayoutDirection( direction)

• void unsetLayoutDirection()

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This property holds the maximum size of the widget

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This property holds the minimum size of the widget

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This property holds the widget's palette

This property provides the widget's palette. The palette provides colors and brushes for color groups (e.g., QPalette::Button) and states (e.g., QPalette::Inactive), loosely defining the general look of the widget and its children.

QPalette consists of color groups that have been explicitly defined, and groups that are implicitly inherited from the widget's parent. Because of this, palette() can return a different palette than what has been set with setPalette(). This scheme allows you to define single entries in a palette without affecting the palette's inherited entries.

When a widget's palette changes, it resolves its entries against its parent widget, or if it doesn't have a parent widget, it resolves against the scene. It then sends itself a PaletteChange event, and notifies all its descendants so they can resolve their palettes as well.

By default, this property contains the application's default palette.

Access functions:

• palette() const

• void setPalette(const &palette)

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This property holds the preferred size of the widget

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This property holds the size of the widget

Calling resize() resizes the widget to a size bounded by minimumSize() and maximumSize(). This property only affects the widget's width and height (e.g., its right and bottom edges); the widget's position and top-left corner remains unaffected.

Resizing a widget triggers the widget to immediately receive a GraphicsSceneResize event with the widget's old and new size. If the widget has a layout assigned when this event arrives, the layout will be activated and it will automatically update any child widgets's geometry.

This property does not affect any layout of the parent widget. If the widget itself is managed by a parent layout; e.g., it has a parent widget with a layout assigned, that layout will not activate.

By default, this property contains a size with zero width and height.

Access functions:

• size() const

• void resize(const &size)

• void resize(qreal w, qreal h)

Notifier signal:

• void geometryChanged()

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This property holds the size policy for the widget

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This property holds the widget's window flags

Window flags are a combination of a window type (e.g., Qt::Dialog) and several flags giving hints on the behavior of the window. The behavior is platform-dependent.

By default, this property contains no window flags.

Windows are panels. If you set the Qt::Window flag, the ItemIsPanel flag will be set automatically. If you clear the Qt::Window flag, the ItemIsPanel flag is also cleared. Note that the ItemIsPanel flag can be set independently of Qt::Window.

Access functions:

• windowFlags() const

• void setWindowFlags( wFlags)

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This property holds the window title (caption).

This property is only used for windows.

By default, if no title has been set, this property contains an empty string.

Access functions:

• windowTitle() const

• void setWindowTitle(const &title)

Constructs a QGraphicsWidget instance. The optional parent argument is passed to QGraphicsItem's constructor. The optional wFlags argument specifies the widget's window flags (e.g., whether the widget should be a window, a tool, a popup, etc).

Destroys the QGraphicsWidget instance.

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

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

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

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

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

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Adjusts the size of the widget to its effective preferred size hint.

This function is called implicitly when the item is shown for the first time.

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Reimplements: QGraphicsItem::boundingRect() const.

This event handler can be reimplemented to handle state changes.

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

Change events include: QEvent::ActivationChange, QEvent::EnabledChange, QEvent::FontChange, QEvent::StyleChange, QEvent::PaletteChange, QEvent::ParentChange, QEvent::LayoutDirectionChange, and QEvent::ContentsRectChange.

Call this function to close the widget.

Returns true if the widget was closed; otherwise returns false. This slot will first send a QCloseEvent to the widget, which may or may not accept the event. If the event was ignored, nothing happens. If the event was accepted, it will hide() the widget.

If the widget has the Qt::WA_DeleteOnClose attribute set it will be deleted.

This event handler, for event, can be reimplemented in a subclass to receive widget close events. The default implementation accepts the event.

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Reimplements: QGraphicsObject::event(QEvent *ev).

Handles the event. QGraphicsWidget handles the following events:

Reimplements: QGraphicsItem::focusInEvent(QFocusEvent *event).

Finds a new widget to give the keyboard focus to, as appropriate for Tab and Shift+Tab, and returns true if it can find a new widget; returns false otherwise. If next is true, this function searches forward; if next is false, it searches backward.

Sometimes, you will want to reimplement this function to provide special focus handling for your widget and its subwidgets. For example, a web browser might reimplement it to move its current active link forward or backward, and call the base implementation only when it reaches the last or first link on the page.

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

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Reimplements: QGraphicsItem::focusOutEvent(QFocusEvent *event).

If this widget, a child or descendant of this widget currently has input focus, this function will return a pointer to that widget. If no descendant widget has input focus, nullptr is returned.

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This signal gets emitted whenever the geometry is changed in setGeometry().

Reimplements: QGraphicsLayoutItem::getContentsMargins(qreal *left, qreal *top, qreal *right, qreal *bottom) const.

Gets the widget's contents margins. The margins are stored in left, top, right and bottom, as pointers to qreals. Each argument can be omitted by passing nullptr.

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Gets the widget's window frame margins. The margins are stored in left, top, right and bottom as pointers to qreals. Each argument can be omitted by passing nullptr.

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This event handler, for event, can be reimplemented in a subclass to receive notifications for QEvent::GrabKeyboard events.

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This event handler, for event, can be reimplemented in a subclass to receive notifications for QEvent::GrabMouse events.

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Adds a shortcut to Qt's shortcut system that watches for the given key sequence in the given context. If the context is Qt::ApplicationShortcut, the shortcut applies to the application as a whole. Otherwise, it is either local to this widget, Qt::WidgetShortcut, or to the window itself, Qt::WindowShortcut. For widgets that are not part of a window (i.e., top-level widgets and their children), Qt::WindowShortcut shortcuts apply to the scene.

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

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This event handler, for Hide events, is delivered after the widget has been hidden, for example, setVisible(false) has been called for the widget or one of its ancestors when the widget was previously shown.

You can reimplement this event handler to detect when your widget is hidden. Calling QEvent::accept() or QEvent::ignore() on event has no effect.

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Reimplements: QGraphicsItem::hoverLeaveEvent(QGraphicsSceneHoverEvent *event).

Reimplements: QGraphicsItem::hoverMoveEvent(QGraphicsSceneHoverEvent *event).

Populates a style option object for this widget based on its current state, and stores the output in option. The default implementation populates option with the following properties.

Subclasses of QGraphicsWidget should call the base implementation, and then test the type of option using qstyleoption_cast<>() or test QStyleOption::Type before storing widget-specific options.

For example:

void MyGroupBoxWidget::initStyleOption(QStyleOption *option) const
{
    QGraphicsWidget::initStyleOption(option);
    if (QStyleOptionGroupBox *box = qstyleoption_cast<QStyleOptionGroupBox *>(option)) {
        // Add group box specific state.
        box->flat = isFlat();
        ...
    }
}

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

A QGraphicsWidget should only have one of each action.

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

A QGraphicsWidget can have at most one of each action.

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Returns true if this widget's window is in the active window, or if the widget does not have a window but is in an active scene (i.e., a scene that currently has focus).

The active window is the window that either contains a child widget that currently has input focus, or that itself has input focus.

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Reimplements: QGraphicsItem::itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value).

QGraphicsWidget uses the base implementation of this function to catch and deliver events related to state changes in the item. Because of this, it is very important that subclasses call the base implementation.

change specifies the type of change, and value is the new value.

For example, QGraphicsWidget uses ItemVisibleChange to deliver Show and Hide events, ItemPositionHasChanged to deliver Move events, and ItemParentChange both to deliver ParentChange events, and for managing the focus chain.

QGraphicsWidget enables the ItemSendsGeometryChanges flag by default in order to track position changes.

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Returns this widget's layout, or nullptr if no layout is currently managing this widget.

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This event handler, for GraphicsSceneMove events, is delivered after the widget has moved (e.g., its local position has changed).

This event is only delivered when the item is moved locally. Calling setTransform() or moving any of the item's ancestors does not affect the item's local position.

You can reimplement this event handler to detect when your widget has moved. Calling QEvent::accept() or QEvent::ignore() on event has no effect.

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Reimplements: QGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget).

This virtual function is called by QGraphicsScene to draw the window frame for windows using painter, option, and widget, in local coordinates. The base implementation uses the current style to render the frame and title bar.

You can reimplement this function in a subclass of QGraphicsWidget to provide custom rendering of the widget's window frame.

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This event is delivered to the item by the scene at some point after it has been constructed, but before it is shown or otherwise accessed through the scene. You can use this event handler to do last-minute initializations of the widget which require the item to be fully constructed.

The base implementation does nothing.

Returns the item's local rect as a QRectF. This function is equivalent to QRectF(QPointF(), size()).

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

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

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This is an overloaded function.

Constructs a resize with the given width (w) and height (h). This convenience function is equivalent to calling resize(QSizeF(w, h)).

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This event handler, for GraphicsSceneResize events, is delivered after the widget has been resized (i.e., its local size has changed). event contains both the old and the new size.

This event is only delivered when the widget is resized locally; calling setTransform() on the widget or any of its ancestors or view, does not affect the widget's local size.

You can reimplement this event handler to detect when your widget has been resized. Calling QEvent::accept() or QEvent::ignore() on event has no effect.

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Reimplements: QGraphicsItem::sceneEvent(QEvent *event).

QGraphicsWidget's implementation of sceneEvent() simply passes event to QGraphicsWidget::event(). You can handle all events for your widget in event() or in any of the convenience functions; you should not have to reimplement this function in a subclass of QGraphicsWidget.

Returns true if event has been recognized and processed; otherwise, returns false.

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If on is true, this function enables attribute; otherwise attribute is disabled.

See the class documentation for QGraphicsWidget for a complete list of which attributes are supported, and what they are for.

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Sets the widget's contents margins to margins.

Contents margins are used by the assigned layout to define the placement of subwidgets and layouts. Margins are particularly useful for widgets that constrain subwidgets to only a section of its own geometry. For example, a group box with a layout will place subwidgets inside its frame, but below the title.

Changing a widget's contents margins will always trigger an update(), and any assigned layout will be activated automatically. The widget will then receive a ContentsRectChange event.

This function was introduced in Qt 5.14.

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This is an overloaded function.

Sets the widget's contents margins to left, top, right and bottom.

This convenience function is equivalent to calling setGeometry(QRectF( x, y, w, h)).

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Sets the layout for this widget to layout. Any existing layout manager is deleted before the new layout is assigned. If layout is nullptr, the widget is left without a layout. Existing subwidgets' geometries will remain unaffected.

All widgets that are currently managed by layout or all of its sublayouts, are automatically reparented to this item. The layout is then invalidated, and the child widget geometries are adjusted according to this item's geometry() and contentsMargins(). Children who are not explicitly managed by layout remain unaffected by the layout after it has been assigned to this widget.

QGraphicsWidget takes ownership of layout.

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

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

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Sets the widget's style to style. QGraphicsWidget does not take ownership of style.

If no style is assigned, or style is nullptr, the widget will use QGraphicsScene::style() (if this has been set). Otherwise the widget will use QApplication::style().

This function sets the Qt::WA_SetStyle attribute if style is not nullptr; otherwise it clears the attribute.

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

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

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

not like this:

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

If first is nullptr, this indicates that second should be the first widget to receive input focus should the scene gain Tab focus (i.e., the user hits Tab so that focus passes into the scene). If second is nullptr, this indicates that first should be the first widget to gain focus if the scene gained BackTab focus.

By default, tab order is defined implicitly using widget creation order.

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Sets the widget's window frame margins to margins. The default frame margins are provided by the style, and they depend on the current window flags.

If you would like to draw your own window decoration, you can set your own frame margins to override the default margins.

This function was introduced in Qt 5.14.

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This is an overloaded function.

Sets the widget's window frame margins to left, top, right and bottom.

Reimplements: QGraphicsItem::shape() const.

This event handler, for Show events, is delivered before the widget has been shown, for example, setVisible(true) has been called for the widget or one of its ancestors when the widget was previously hidden.

You can reimplement this event handler to detect when your widget is shown. Calling QEvent::accept() or QEvent::ignore() on event has no effect.

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Reimplements: QGraphicsLayoutItem::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const.

Returns a pointer to the widget's style. If this widget does not have any explicitly assigned style, the scene's style is returned instead. In turn, if the scene does not have any assigned style, this function returns QApplication::style().

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Returns true if attribute is enabled for this widget; otherwise, returns false.

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Reimplements: QGraphicsItem::type() const.

This event handler, for event, can be reimplemented in a subclass to receive notifications for QEvent::UngrabKeyboard events.

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This event handler, for event, can be reimplemented in a subclass to receive notifications for QEvent::UngrabMouse events.

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Resets the window frame margins to the default value, provided by the style.

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Reimplements: QGraphicsLayoutItem::updateGeometry().

If this widget is currently managed by a layout, this function notifies the layout that the widget's size hints have changed and the layout may need to resize and reposition the widget accordingly.

Call this function if the widget's sizeHint() has changed.

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This event handler, for event, receives events for the window frame if this widget is a window. Its base implementation provides support for default window frame interaction such as moving, resizing, etc.

You can reimplement this handler in a subclass of QGraphicsWidget to provide your own custom window frame interaction support.

Returns true if event has been recognized and processed; otherwise, returns false.

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Returns the widget's geometry in parent coordinates including any window frame.

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Returns the widget's local rect including any window frame.

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Returns the window frame section at position pos, or Qt::NoSection if there is no window frame section at this position.

This function is used in QGraphicsWidget's base implementation for window frame interaction.

You can reimplement this function if you want to customize how a window can be interactively moved or resized. For instance, if you only want to allow a window to be resized by the bottom right corner, you can reimplement this function to return Qt::NoSection for all sections except Qt::BottomRightSection.

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Returns the widgets window type.

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