The QGraphicsLayout class provides the base class for all layouts in Graphics View. More...

#include <qgraphicslayout.h>

Inheritance diagram for QGraphicsLayout:

Collaboration diagram for QGraphicsLayout:

Public Member Functions
	QGraphicsLayout (QGraphicsLayoutItem *parent=nullptr)
	Constructs a QGraphicsLayout object.

	~QGraphicsLayout ()
	Destroys the QGraphicsLayout object.

void	setContentsMargins (qreal left, qreal top, qreal right, qreal bottom)
	Sets the contents margins to left, top, right and bottom.

void	getContentsMargins (qreal left, qreal top, qreal right, qreal bottom) const override
	\reimp

void	activate ()
	Activates the layout, causing all items in the layout to be immediately rearranged.

bool	isActivated () const
	Returns `true` if the layout is currently being activated; otherwise, returns `false`.

virtual void	invalidate ()
	Clears any cached geometry and size hint information in the layout, and posts a \l{QEvent::LayoutRequest}{LayoutRequest} event to the managed parent QGraphicsLayoutItem.

virtual void	updateGeometry () override
	\reimp

virtual void	widgetEvent (QEvent *e)
	This virtual event handler receives all events for the managed widget.

virtual int	count () const =0
	This pure virtual function must be reimplemented in a subclass of QGraphicsLayout to return the number of items in the layout.

virtual QGraphicsLayoutItem *	itemAt (int i) const =0
	This pure virtual function must be reimplemented in a subclass of QGraphicsLayout to return a pointer to the item at index i.

virtual void	removeAt (int index)=0
	This pure virtual function must be reimplemented in a subclass of QGraphicsLayout to remove the item at index.

Public Member Functions inherited from QGraphicsLayoutItem
	QGraphicsLayoutItem (QGraphicsLayoutItem *parent=nullptr, bool isLayout=false)
	Constructs the QGraphicsLayoutItem object.

virtual	~QGraphicsLayoutItem ()
	Destroys the QGraphicsLayoutItem object.

void	setSizePolicy (const QSizePolicy &policy)
	Sets the size policy to policy.

void	setSizePolicy (QSizePolicy::Policy hPolicy, QSizePolicy::Policy vPolicy, QSizePolicy::ControlType controlType=QSizePolicy::DefaultType)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.This function is equivalent to calling setSizePolicy(QSizePolicy(hPolicy, vPolicy, controlType)).

QSizePolicy	sizePolicy () const
	Returns the current size policy.

void	setMinimumSize (const QSizeF &size)
	Sets the minimum size to size.

void	setMinimumSize (qreal w, qreal h)
	This convenience function is equivalent to calling setMinimumSize(QSizeF(w, h)).

QSizeF	minimumSize () const
	Returns the minimum size.

void	setMinimumWidth (qreal width)
	Sets the minimum width to width.

qreal	minimumWidth () const
	Returns the minimum width.

void	setMinimumHeight (qreal height)
	Sets the minimum height to height.

qreal	minimumHeight () const
	Returns the minimum height.

void	setPreferredSize (const QSizeF &size)
	Sets the preferred size to size.

void	setPreferredSize (qreal w, qreal h)
	This convenience function is equivalent to calling setPreferredSize(QSizeF(w, h)).

QSizeF	preferredSize () const
	Returns the preferred size.

void	setPreferredWidth (qreal width)
	Sets the preferred width to width.

qreal	preferredWidth () const
	Returns the preferred width.

void	setPreferredHeight (qreal height)
	Sets the preferred height to height.

qreal	preferredHeight () const
	Returns the preferred height.

void	setMaximumSize (const QSizeF &size)
	Sets the maximum size to size.

void	setMaximumSize (qreal w, qreal h)
	This convenience function is equivalent to calling setMaximumSize(QSizeF(w, h)).

QSizeF	maximumSize () const
	Returns the maximum size.

void	setMaximumWidth (qreal width)
	Sets the maximum width to width.

qreal	maximumWidth () const
	Returns the maximum width.

void	setMaximumHeight (qreal height)
	Sets the maximum height to height.

qreal	maximumHeight () const
	Returns the maximum height.

virtual void	setGeometry (const QRectF &rect)
	This virtual function sets the geometry of the QGraphicsLayoutItem to rect, which is in parent coordinates (e.g., the top-left corner of rect is equivalent to the item's position in parent coordinates).

QRectF	geometry () const
	Returns the item's geometry (e.g., position and size) as a QRectF.

virtual void	getContentsMargins (qreal left, qreal top, qreal right, qreal bottom) const
	This virtual function provides the left, top, right and bottom contents margins for this QGraphicsLayoutItem.

QRectF	contentsRect () const
	Returns the contents rect in local coordinates.

QSizeF	effectiveSizeHint (Qt::SizeHint which, const QSizeF &constraint=QSizeF()) const
	Returns the effective size hint for this QGraphicsLayoutItem.

virtual void	updateGeometry ()
	This virtual function discards any cached size hint information.

virtual bool	isEmpty () const

QGraphicsLayoutItem *	parentLayoutItem () const
	Returns the parent of this QGraphicsLayoutItem, or \nullptr if there is no parent, or if the parent does not inherit from QGraphicsLayoutItem (QGraphicsLayoutItem is often used through multiple inheritance with QObject-derived classes).

void	setParentLayoutItem (QGraphicsLayoutItem *parent)
	Sets the parent of this QGraphicsLayoutItem to parent.

bool	isLayout () const
	Returns `true` if this QGraphicsLayoutItem is a layout (e.g., is inherited by an object that arranges other QGraphicsLayoutItem objects); otherwise returns `false`.

QGraphicsItem *	graphicsItem () const
	Returns the QGraphicsItem that this layout item represents.

bool	ownedByLayout () const

Static Public Member Functions
static void	setInstantInvalidatePropagation (bool enable)

static bool	instantInvalidatePropagation ()

Protected Member Functions
	QGraphicsLayout (QGraphicsLayoutPrivate &, QGraphicsLayoutItem *)

void	addChildLayoutItem (QGraphicsLayoutItem *layoutItem)

Protected Member Functions inherited from QGraphicsLayoutItem
void	setGraphicsItem (QGraphicsItem *item)
	If the QGraphicsLayoutItem represents a QGraphicsItem, and it wants to take advantage of the automatic reparenting capabilities of QGraphicsLayout it should set this value.

void	setOwnedByLayout (bool ownedByLayout)

	QGraphicsLayoutItem (QGraphicsLayoutItemPrivate &dd)

virtual QSizeF	sizeHint (Qt::SizeHint which, const QSizeF &constraint=QSizeF()) const =0
	This pure virtual function returns the size hint for which of the QGraphicsLayoutItem, using the width or height of constraint to constrain the output.

Friends
class	QGraphicsWidget

Additional Inherited Members
Protected Attributes inherited from QGraphicsLayoutItem
QScopedPointer< QGraphicsLayoutItemPrivate >	d_ptr

Detailed Description

The QGraphicsLayout class provides the base class for all layouts in Graphics View.

Since: 4.4

\inmodule QtWidgets

QGraphicsLayout is an abstract class that defines a virtual API for arranging QGraphicsWidget children and other QGraphicsLayoutItem objects for a QGraphicsWidget. QGraphicsWidget assigns responsibility to a QGraphicsLayout through QGraphicsWidget::setLayout(). As the widget is resized, the layout will automatically arrange the widget's children. QGraphicsLayout inherits QGraphicsLayoutItem, so, it can be managed by any layout, including its own subclasses.

Definition at line 18 of file qgraphicslayout.h.

Constructor & Destructor Documentation

◆ QGraphicsLayout() [1/2]

QGraphicsLayout::QGraphicsLayout ( QGraphicsLayoutItem * parent = nullptr )

Constructs a QGraphicsLayout object.

parent is passed to QGraphicsLayoutItem's constructor and the QGraphicsLayoutItem's isLayout argument is set to true.

If parent is a QGraphicsWidget the layout will be installed on that widget. (Note that installing a layout will delete the old one installed.)

Definition at line 122 of file qgraphicslayout.cpp.

References QSizePolicy::DefaultType, QSizePolicy::Expanding, QGraphicsItem::isWidget(), parent, qWarning, QGraphicsLayoutItem::setOwnedByLayout(), and QGraphicsLayoutItem::setParentLayoutItem().

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◆ ~QGraphicsLayout()

QGraphicsLayout::~QGraphicsLayout ( )

Destroys the QGraphicsLayout object.

Definition at line 164 of file qgraphicslayout.cpp.

◆ QGraphicsLayout() [2/2]

QGraphicsLayout::QGraphicsLayout	(	QGraphicsLayoutPrivate &	dd,
		QGraphicsLayoutItem *	parent
	)

protected

Definition at line 143 of file qgraphicslayout.cpp.

References QSizePolicy::DefaultType, QSizePolicy::Expanding, QGraphicsItem::isWidget(), parent, qWarning, QGraphicsLayoutItem::setOwnedByLayout(), and QGraphicsLayoutItem::setParentLayoutItem().

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Member Function Documentation

◆ activate()

void QGraphicsLayout::activate ( )

Activates the layout, causing all items in the layout to be immediately rearranged.

This function is based on calling count() and itemAt(), and then calling setGeometry() on all items sequentially. When activated, the layout will adjust its geometry to its parent's contentsRect(). The parent will then invalidate any layout of its own.

If called in sequence or recursively, e.g., by one of the arranged items in response to being resized, this function will do nothing.

Note that the layout is free to use geometry caching to optimize this process. To forcefully invalidate any such cache, you can call invalidate() before calling activate().

See also: invalidate()

Definition at line 221 of file qgraphicslayout.cpp.

References QGraphicsLayoutItem::contentsRect(), d, instantInvalidatePropagation(), QGraphicsLayoutItem::isLayout(), QGraphicsLayoutItem::parentLayoutItem(), Q_ASSERT, QGraphicsWidget::resize(), QGraphicsWidget::setAttribute(), QGraphicsLayoutItem::setGeometry(), QGraphicsWidget::size, QGraphicsWidget::testAttribute(), QGraphicsLayoutItem::updateGeometry(), and Qt::WA_Resized.

Referenced by widgetEvent().

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◆ addChildLayoutItem()

void QGraphicsLayout::addChildLayoutItem ( QGraphicsLayoutItem * layoutItem )

protected

Since: 4.6

This function is a convenience function provided for custom layouts, and will go through all items in the layout and reparent their graphics items to the closest QGraphicsWidget ancestor of the layout.

If layoutItem is already in a different layout, it will be removed from that layout.

If custom layouts want special behaviour they can ignore to use this function, and implement their own behaviour.

See also: graphicsItem()

Definition at line 436 of file qgraphicslayout.cpp.

References d, and layoutItem().

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◆ count()

int QGraphicsLayout::count ( ) const

pure virtual

This pure virtual function must be reimplemented in a subclass of QGraphicsLayout to return the number of items in the layout.

The subclass is free to decide how to store the items.

See also: itemAt(), removeAt()

Implemented in QGraphicsAnchorLayout, QGraphicsGridLayout, and QGraphicsLinearLayout.

Referenced by QGraphicsLayoutItem::~QGraphicsLayoutItem(), QGraphicsLayoutItemPrivate::hasHeightForWidth(), QGraphicsLayoutItemPrivate::hasWidthForHeight(), and removeLayoutItemFromLayout().

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◆ getContentsMargins()

void QGraphicsLayout::getContentsMargins	(	qreal *	left,
		qreal *	top,
		qreal *	right,
		qreal *	bottom
	)		const

overridevirtual

\reimp

Reimplemented from QGraphicsLayoutItem.

Definition at line 196 of file qgraphicslayout.cpp.

References d, QStyle::PM_LayoutBottomMargin, QStyle::PM_LayoutLeftMargin, QStyle::PM_LayoutRightMargin, and QStyle::PM_LayoutTopMargin.

Referenced by QGraphicsGridLayout::setGeometry(), QGraphicsLinearLayout::setGeometry(), QGraphicsAnchorLayout::sizeHint(), QGraphicsGridLayout::sizeHint(), and QGraphicsLinearLayout::sizeHint().

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◆ instantInvalidatePropagation()

bool QGraphicsLayout::instantInvalidatePropagation ( )

static

Since: 4.8

See also: setInstantInvalidatePropagation()

returns true if the complete widget/layout hierarchy is rearranged in one go.

Definition at line 481 of file qgraphicslayout.cpp.

References g_instantInvalidatePropagation.

Referenced by activate(), QGraphicsLayoutPrivate::activateRecursive(), invalidate(), QGraphicsWidget::setGeometry(), updateGeometry(), and QGraphicsWidget::updateGeometry().

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◆ invalidate()

void QGraphicsLayout::invalidate ( )

virtual

Clears any cached geometry and size hint information in the layout, and posts a \l{QEvent::LayoutRequest}{LayoutRequest} event to the managed parent QGraphicsLayoutItem.

See also: activate(), setGeometry()

Reimplemented in QGraphicsAnchorLayout, QGraphicsGridLayout, and QGraphicsLinearLayout.

Definition at line 275 of file qgraphicslayout.cpp.

References instantInvalidatePropagation(), layoutItem(), QEvent::LayoutRequest, QCoreApplication::postEvent(), and updateGeometry().

Referenced by QGraphicsAnchorLayout::invalidate(), QGraphicsGridLayout::invalidate(), QGraphicsLinearLayout::invalidate(), setContentsMargins(), QGraphicsWidget::setLayout(), updateGeometry(), and widgetEvent().

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◆ isActivated()

bool QGraphicsLayout::isActivated ( ) const

Returns true if the layout is currently being activated; otherwise, returns false.

If the layout is being activated, this means that it is currently in the process of rearranging its items (i.e., the activate() function has been called, and has not yet returned).

See also: activate(), invalidate()

Definition at line 262 of file qgraphicslayout.cpp.

References d.

Referenced by widgetEvent().

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◆ itemAt()

QGraphicsLayoutItem * QGraphicsLayout::itemAt ( int i ) const

pure virtual

This pure virtual function must be reimplemented in a subclass of QGraphicsLayout to return a pointer to the item at index i.

The reimplementation can assume that i is valid (i.e., it respects the value of count()). Together with count(), it is provided as a means of iterating over all items in a layout.

The subclass is free to decide how to store the items, and the visual arrangement does not have to be reflected through this function.

See also: count(), removeAt()

Implemented in QGraphicsAnchorLayout, QGraphicsGridLayout, and QGraphicsLinearLayout.

Referenced by QGraphicsLayoutItem::~QGraphicsLayoutItem(), QGraphicsLayoutItemPrivate::hasHeightForWidth(), QGraphicsLayoutItemPrivate::hasWidthForHeight(), and removeLayoutItemFromLayout().

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◆ removeAt()

void QGraphicsLayout::removeAt ( int index )

pure virtual

This pure virtual function must be reimplemented in a subclass of QGraphicsLayout to remove the item at index.

The reimplementation can assume that index is valid (i.e., it respects the value of count()).

The implementation must ensure that the parentLayoutItem() of the removed item does not point to this layout, since the item is considered to be removed from the layout hierarchy.

If the layout is to be reused between applications, we recommend that the layout deletes the item, but the graphics view framework does not depend on this.

The subclass is free to decide how to store the items.

See also: itemAt(), count()

Implemented in QGraphicsAnchorLayout, QGraphicsGridLayout, and QGraphicsLinearLayout.

Referenced by QGraphicsLayoutItem::~QGraphicsLayoutItem(), and removeLayoutItemFromLayout().

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◆ setContentsMargins()

void QGraphicsLayout::setContentsMargins	(	qreal	left,
		qreal	top,
		qreal	right,
		qreal	bottom
	)

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

The default contents margins for toplevel layouts are style dependent (by querying the pixelMetric for QStyle::PM_LayoutLeftMargin, QStyle::PM_LayoutTopMargin, QStyle::PM_LayoutRightMargin and QStyle::PM_LayoutBottomMargin).

For sublayouts the default margins are 0.

Changing the contents margins automatically invalidates the layout.

See also: invalidate()

Definition at line 181 of file qgraphicslayout.cpp.

References d, and invalidate().

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◆ setInstantInvalidatePropagation()

void QGraphicsLayout::setInstantInvalidatePropagation ( bool enable )

static

Since: 4.8

See also: instantInvalidatePropagation()

Calling this function with enable set to true will enable a feature that makes propagation of invalidation up to ancestor layout items to be done in one go. It will propagate up the parentLayoutItem() hierarchy until it has reached the root. If the root item is a QGraphicsWidget, it will post a layout request to it. When the layout request is consumed it will traverse down the hierarchy of layouts and widgets and activate all layouts that is invalid (not activated). This is the recommended behaviour.

If not set it will also propagate up the parentLayoutItem() hierarchy, but it will stop at the {first widget} it encounters, and post a layout request to the widget. When the layout request is consumed, this might cause it to continue propagation up to the parentLayoutItem() of the widget. It will continue in this fashion until it has reached a widget with no parentLayoutItem(). This strategy might cause drawing artifacts, since it is not done in one go, and the consumption of layout requests might be interleaved by consumption of paint events, which might cause significant flicker. Note, this is not the recommended behavior, but for compatibility reasons this is the default behaviour.

Definition at line 469 of file qgraphicslayout.cpp.

References g_instantInvalidatePropagation.

◆ updateGeometry()

void QGraphicsLayout::updateGeometry ( )

overridevirtual

\reimp

Reimplemented from QGraphicsLayoutItem.

Definition at line 314 of file qgraphicslayout.cpp.

References d, instantInvalidatePropagation(), invalidate(), QGraphicsLayoutItem::isLayout(), QGraphicsLayoutItem::parentLayoutItem(), and QGraphicsLayoutItem::updateGeometry().

Referenced by invalidate().

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◆ widgetEvent()

void QGraphicsLayout::widgetEvent ( QEvent * e )

virtual

This virtual event handler receives all events for the managed widget.

QGraphicsLayout uses this event handler to listen for layout related events such as geometry changes, layout changes or layout direction changes.

e is a pointer to the event.

You can reimplement this event handler to track similar events for your own custom layout.

See also: QGraphicsWidget::event(), QGraphicsItem::sceneEvent()

Definition at line 354 of file qgraphicslayout.cpp.

References activate(), QGraphicsLayoutItem::contentsRect(), e, QEvent::GraphicsSceneResize, invalidate(), isActivated(), QEvent::LayoutDirectionChange, QEvent::LayoutRequest, QGraphicsLayoutItem::parentLayoutItem(), and QGraphicsLayoutItem::setGeometry().

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Friends And Related Symbol Documentation

◆ QGraphicsWidget

friend class QGraphicsWidget

friend

Definition at line 47 of file qgraphicslayout.h.

The documentation for this class was generated from the following files:

qtbase/src/widgets/graphicsview/qgraphicslayout.h
qtbase/src/widgets/graphicsview/qgraphicslayout.cpp

Public Member Functions

Static Public Member Functions

Protected Member Functions

Friends

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QGraphicsLayout() [1/2]

◆ ~QGraphicsLayout()

◆ QGraphicsLayout() [2/2]

Member Function Documentation

◆ activate()

◆ addChildLayoutItem()

◆ count()

◆ getContentsMargins()

◆ instantInvalidatePropagation()

◆ invalidate()

◆ isActivated()

◆ itemAt()

◆ removeAt()

◆ setContentsMargins()

◆ setInstantInvalidatePropagation()

◆ updateGeometry()

◆ widgetEvent()

Friends And Related Symbol Documentation

◆ QGraphicsWidget