The QLayout class is the base class of geometry managers. More...

Inheritance diagram for QLayout:

Public Types
enum	SizeConstraint

Public Methods
	QLayout ()

	QLayout (QWidget *parent)

bool	activate ()

virtual void	addItem (QLayoutItem *item) = 0

void	addWidget (QWidget *w)

QMargins	contentsMargins () const

QRect	contentsRect () const

QSizePolicy::ControlTypes	controlTypes () const override

virtual int	count () const = 0

Qt::Orientations	expandingDirections () const override

QRect	geometry () const override

void	getContentsMargins (int left, int top, int right, int bottom) const

virtual int	indexOf (QWidget *widget) const

void	invalidate () override

bool	isEmpty () const override

bool	isEnabled () const

virtual QLayoutItem *	itemAt (int index) const = 0

QLayout *	layout () override

int	margin () const

QSize	maximumSize () const override

QWidget *	menuBar () const

QSize	minimumSize () const override

QWidget *	parentWidget () const

void	removeItem (QLayoutItem *item)

void	removeWidget (QWidget *widget)

virtual QLayoutItem *	replaceWidget (QWidget from, QWidget to, Qt::FindChildOptions options=Qt::FindChildrenRecursively)

bool	setAlignment (QLayout *layout, Qt::Alignment alignment)

void	setAlignment (Qt::Alignment alignment)

bool	setAlignment (QWidget *widget, Qt::Alignment alignment)

void	setContentsMargins (const QMargins &margins)

void	setContentsMargins (int left, int top, int right, int bottom)

void	setEnabled (bool enable)

void	setGeometry (const QRect &rect) override

void	setMargin (int margin)

void	setMenuBar (QWidget *widget)

void	setSizeConstraint (SizeConstraint constraint)

void	setSpacing (int spacing)

SizeConstraint	sizeConstraint () const

int	spacing () const

virtual QLayoutItem *	takeAt (int index) = 0

void	update ()

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	event (QEvent *event)

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Public Methods inherited from QLayoutItem
	QLayoutItem (Qt::Alignment alignment=Qt::Alignment ())

virtual	~QLayoutItem ()

Qt::Alignment	alignment () const

virtual bool	hasHeightForWidth () const

virtual int	heightForWidth (int width) const

virtual int	minimumHeightForWidth (int width) const

void	setAlignment (Qt::Alignment alignment)

virtual QSize	sizeHint () const = 0

virtual QSpacerItem *	spacerItem ()

virtual QWidget *	widget ()

Static Public Methods
static QSize	closestAcceptableSize (const QWidget *widget, const QSize &size)

Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Protected Methods
void	addChildLayout (QLayout *layout)

void	addChildWidget (QWidget *widget)

QRect	alignmentRect (const QRect &rect) const

void	childEvent (QChildEvent *event) override

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Properties
	margin

	sizeConstraint

	spacing

Properties inherited from QObject
	objectName

Friends
class	QWidget

Additional Inherited Members
Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Public Slots inherited from QObject
void	deleteLater ()

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

The QLayout class is the base class of geometry managers. This is an abstract base class which is inherited by QBoxLayout, QGridLayout, QFormLayout, and QStackedLayout.

To create a custom layout manager inherit from this class and then implement the methods addItem(), sizeHint(), setGeometry(), itemAt() and takeAt(). You should also implement minimumSize() to ensure your layout is not resized to zero size if there is too little space. To support children whose heights depend on their widths, implement hasHeightForWidth() and heightForWidth().

Geometry management stops when the layout manager is deleted.

See also: QLayoutItem, Layout Management

Member Enumeration Documentation

enum QLayout::SizeConstraint

The possible values are shown in the following table.

Constant	Value	Description
`QLayout::SetDefaultConstraint`	`0`	The main widget's minimum size is set to minimumSize(), unless the widget already has a minimum size.
`QLayout::SetFixedSize`	`3`	The main widget's size is set to sizeHint(); it can not be resized at all.
`QLayout::SetMinimumSize`	`2`	The main widget's minimum size is set to minimumSize(); it can not be smaller.
`QLayout::SetMaximumSize`	`4`	The main widget's maximum size is set to maximumSize(); it can not be larger.
`QLayout::SetMinAndMaxSize`	`5`	The main widget's minimum size is set to minimumSize() and its maximum size is set to maximumSize().
`QLayout::SetNoConstraint`	`1`	The widget is not constrained.

See also: setSizeConstraint()

Constructor & Destructor Documentation

QLayout::QLayout ( QWidget * parent )

Constructs a new top-level QLayout, with the given parent which can not be a nullptr. There can be only one top-level layout for a widget. It is returned by QWidget::layout().

QLayout::QLayout ( )

Constructs a new child QLayout. This layout has to be inserted into another layout before geometry management will work.

Method Documentation

bool QLayout::activate ( )

Redoes the layout for parentWidget() if necessary. You should generally not need to call this because it is automatically called at the most appropriate times. It returns true if the layout was redone.

See also: update(), QWidget::updateGeometry()

void QLayout::addChildLayout ( QLayout * layout )

protected

This method is called from addLayout() and insertLayout() to add layout as a sub-layout.

See also: QBoxLayout::addLayout(), QBoxLayout::insertLayout(), QGridLayout::addLayout()

void QLayout::addChildWidget ( QWidget * widget )

protected

This method is called from addWidget() to add widget as a managed widget of a layout.

If widget is already managed by a layout, this method will give a warning and remove the widget from that layout. This method must be called before adding widgets to the layout's data structure.

void QLayout::addItem ( QLayoutItem * item )

pure virtual

Implemented in a subclasses to add a new item. This method is not usually called in application code. To add a widget to a layout use addWidget(). To add a child layout use addLayout() provided by the relevant QLayout subclass.

Note: The ownership of item is transferred to the layout and it is the layout's responsibility to delete it.

See also: addWidget(), QBoxLayout::addLayout(), QGridLayout::addLayout()

Implemented in QFormLayout::addItem(), QGridLayout::addItem(), QStackedLayout::addItem(), QBoxLayout::addItem()

void QLayout::addWidget ( QWidget * w )

Adds widget w to the current layout in a manner specific to the layout.

QRect QLayout::alignmentRect ( const QRect & rect ) const

protected

Returns the rectangle that should be covered when the geometry of this layout is set to rect, provided that this layout supports setAlignment(). The result is derived from sizeHint() and expanding(). It is never larger than rect.

void QLayout::childEvent ( QChildEvent * event )

overrideprotected

Reimplemented from QObject::childEvent()

QSize QLayout::closestAcceptableSize	(	const QWidget *	widget,
		const QSize &	size
	)

static

Returns a size that satisfies all size constraints on widget, including heightForWidth() and that is as close as possible to size.

QMargins QLayout::contentsMargins ( ) const

Returns the margins used around the layout. By default QLayout uses the values provided by the style. On most platforms the margin is 11 pixels in all directions.

See also: setContentsMargins()

QRect QLayout::contentsRect ( ) const

Returns the layout's geometry() rectangle, but taking into account the contents margins.

See also: setContentsMargins(), getContentsMargins()

QSizePolicy::ControlTypes QLayout::controlTypes ( ) const

overridevirtual

Returns the control type(s) for the layout item. For a QWidgetItem, the control type comes from the widget's size policy; for a QLayoutItem, the control types is derived from the layout's contents.

See also: QSizePolicy::controlType()

Reimplemented from QLayoutItem::controlTypes()

int QLayout::count ( ) const

pure virtual

Must be implemented in subclasses to return the number of items in the layout.

See also: itemAt()

Implemented in QFormLayout::count(), QGridLayout::count(), QBoxLayout::count(), QStackedLayout::count()

Qt::Orientations QLayout::expandingDirections ( ) const

overridevirtual

Returns whether this layout can make use of more space than sizeHint(). A value of Qt::Vertical or Qt::Horizontal means that it wants to grow in only one dimension, whereas Qt::Vertical | Qt::Horizontal means that it wants to grow in both dimensions.

The default implementation returns Qt::Horizontal | Qt::Vertical. Subclasses reimplement it to return a meaningful value based on their child widget's size policies.

See also: sizeHint()

Implements QLayoutItem::expandingDirections()

QRect QLayout::geometry ( ) const

overridevirtual

See also: setGeometry()

Implements QLayoutItem::geometry()

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

Extracts the left, top, right, and bottom margins used around the layout and assigns them to left, top, right, and bottom unless they are null pointers. By default, QLayout uses the values provided by the style. On most platforms the margin is 11 pixels in all directions.

Default values are PM_LayoutLeftMargin, PM_LayoutTopMargin, PM_LayoutRightMargin, and PM_LayoutBottomMargin.

See also: contentsMargins(), setContentsMargins(), QStyle::pixelMetric(), QStyle::PixelMetric

int QLayout::indexOf ( QWidget * widget ) const

virtual

Searches for widget in this layout (not including child layouts). Returns the index of widget, or -1 if widget is not found. The default implementation iterates over all items using itemAt().

void QLayout::invalidate ( )

overridevirtual

Reimplemented from QLayoutItem::invalidate()

bool QLayout::isEmpty ( ) const

overridevirtual

Implements QLayoutItem::isEmpty()

bool QLayout::isEnabled ( ) const

Returns true if the layout is enabled, otherwise returns false.

See also: setEnabled()

QLayoutItem * QLayout::itemAt ( int index ) const

pure virtual

Must be implemented in subclasses to return the layout item at index. If there is no such item, the method must return a nullptr. Items are numbered consecutively starting from 0. If an item is deleted, other items will be renumbered.

This method can be used to iterate over a layout. The following code will draw a rectangle for each layout item in the layout structure of the widget.

static void paintLayout(QPainter *painter, QLayoutItem *item) {
    QLayout *layout = item->layout();
 
    if (layout) {
       for (int i = 0; i < layout->count(); ++i) {
          paintLayout(painter, layout->itemAt(i));
       }
    }
 
    painter->drawRect(item->geometry());
}
 
void MyWidget::paintEvent(QPaintEvent *) {
    QPainter painter(this);
 
    if (layout()) {
        paintLayout(&painter, layout());
    }
}

See also: count(), takeAt()

Implemented in QFormLayout::itemAt(), QGridLayout::itemAt(), QBoxLayout::itemAt(), QStackedLayout::itemAt()

QLayout * QLayout::layout ( )

overridevirtual

Reimplemented from QLayoutItem::layout()

int QLayout::margin ( ) const

Returns the value of the property.

QSize QLayout::maximumSize ( ) const

overridevirtual

Returns the maximum size of this layout. This is the largest size that the layout can have while still respecting the specifications. The returned value does not include the space required by QWidget::setContentsMargins() or menuBar(). The default implementation allows unlimited resizing.

Implements QLayoutItem::maximumSize()

QWidget * QLayout::menuBar ( ) const

Returns the menu bar set for this layout or a nullptr if no menu bar is set.

See also: setMenuBar()

QSize QLayout::minimumSize ( ) const

overridevirtual

Returns the minimum size of this layout. This is the smallest size that the layout can have while still respecting the specifications. The returned value does not include the space required by QWidget::setContentsMargins() or menuBar(). The default implementation allows unlimited resizing.

Implements QLayoutItem::minimumSize()

Reimplemented in QStackedLayout::minimumSize()

QWidget * QLayout::parentWidget ( ) const

Returns the parent widget of this layout or a nullptr if this layout is not installed on any widget. If the layout is a sub-layout, this function returns the parent widget of the parent layout.

See also: parent()

void QLayout::removeItem ( QLayoutItem * item )

Removes the given item from the layout. It is the caller's responsibility to delete the item. Notice that item can be a layout (since QLayout inherits QLayoutItem).

See also: removeWidget(), addItem()

void QLayout::removeWidget ( QWidget * widget )

Removes the widget from the layout. After this call, it is the caller's responsibility to give the widget a reasonable geometry or to put the widget back into a layout.

Note: The ownership of widget remains the same as when it was added.

See also: removeItem(), QWidget::setGeometry(), addWidget()

QLayoutItem * QLayout::replaceWidget	(	QWidget *	from,
		QWidget *	to,
		Qt::FindChildOptions	options = `Qt::FindChildrenRecursively`
	)

virtual

Searches for widget from and replaces it with widget to if found. Returns the layout item that contains the widget from on success. Otherwise 0 is returned. If options contains Qt::FindChildrenRecursively (the default), sub-layouts are searched for doing the replacement. Any other flag in options is ignored.

Notice that the returned item therefore might not belong to this layout, but to a sub-layout.

The returned layout item is no longer owned by the layout and should be either deleted or inserted to another layout. The widget from is no longer managed by the layout and may need to be deleted or hidden. The parent of widget from is left unchanged.

This method works for the built in layouts but might not work for custom layouts.

See also: indexOf()

bool QLayout::setAlignment	(	QLayout *	layout,
		Qt::Alignment	alignment
	)

Sets the alignment for the layout to alignment and returns true if layout is found in this QLayout (not including child layouts), otherwise returns false.

void QLayoutItem::setAlignment ( Qt::Alignment alignment )

using

Sets the alignment of this item to alignment. Item alignment is only supported by some child classes.

See also: alignment()

bool QLayout::setAlignment	(	QWidget *	widget,
		Qt::Alignment	alignment
	)

Sets the alignment for widget to alignment and returns true if widget is found in this layout (not including child layouts), otherwise returns false.

void QLayout::setContentsMargins ( const QMargins & margins )

Sets the margins to use around the layout. By default, QLayout uses the values provided by the style. On most platforms the margin is 11 pixels in all directions.

See also: contentsMargins()

void QLayout::setContentsMargins	(	int	left,
		int	top,
		int	right,
		int	bottom
	)

Sets the left, top, right, and bottom margins to use around the layout. By default, QLayout uses the values provided by the style. On most platforms the margin is 11 pixels in all directions.

Default values are PM_LayoutLeftMargin, PM_LayoutTopMargin, PM_LayoutRightMargin, and PM_LayoutBottomMargin.

See also: contentsMargins(), getContentsMargins(), QStyle::pixelMetric(), QStyle::PixelMetric

void QLayout::setEnabled ( bool enable )

Enables this layout if enable is true, otherwise disables it. An enabled layout adjusts dynamically to changes a disabled layout acts as if it did not exist. By default all layouts are enabled.

See also: isEnabled()

void QLayout::setGeometry ( const QRect & rect )

overridevirtual

See also: geometry()

Implements QLayoutItem::setGeometry()

Reimplemented in QStackedLayout::setGeometry()

void QLayout::setMargin ( int margin )

Sets the value of the property to margin.

void QLayout::setMenuBar ( QWidget * widget )

Tells the geometry manager to place the menu bar widget at the top of parentWidget(), outside QWidget::contentsMargins(). All child widgets are placed below the bottom edge of the menu bar.

See also: menuBar()

void QLayout::setSizeConstraint ( SizeConstraint constraint )

Sets the value of the property to constraint.

void QLayout::setSpacing ( int spacing )

Sets the value of the property to spacing.

SizeConstraint QLayout::sizeConstraint ( ) const

Returns the value of the property.

int QLayout::spacing ( ) const

Returns the value of the property.

QLayoutItem * QLayout::takeAt ( int index )

pure virtual

Must be implemented in subclasses to remove the layout item at index from the layout, and return the item. If there is no such item, the method must do nothing and return a nullptr. Items are numbered consecutively from 0. If an item is removed, other items will be renumbered.

The following code fragment shows a safe way to remove all items from a layout:

QLayoutItem *child;
 
while ((child = layout->takeAt(0)) != 0) {
   // do something
 
   delete child;
}

See also: itemAt(), count()

Implemented in QFormLayout::takeAt(), QGridLayout::takeAt(), QBoxLayout::takeAt(), QStackedLayout::takeAt()

void QLayout::update ( )

Updates the layout for parentWidget(). You should generally not need to call this because it is automatically called at the most appropriate times.

See also: activate(), invalidate()

Property Documentation

QLayout::margin

deprecated

Deprecated:: This property holds the width of the outside border of the layout.

Use setContentsMargins() and getContentsMargins() instead.

See also: contentsRect(), spacing

Properties	Class Methods
read	margin
write	setMargin

QLayout::sizeConstraint

This property holds the resize mode of the layout. The default mode is SetDefaultConstraint.

Properties	Class Methods
read	sizeConstraint
write	setSizeConstraint

QLayout::spacing

This property holds the spacing between widgets inside the layout. If no value is explicitly set the layout's spacing is inherited from the parent layout or from the style settings for the parent widget. For QGridLayout and QFormLayout, it is possible to set different horizontal and vertical spacings using setHorizontalSpacing() and setVerticalSpacing(). In this case spacing() returns -1.

See also: contentsRect(), getContentsMargins(), QStyle::layoutSpacing(), QStyle::pixelMetric()

Properties	Class Methods
read	spacing
write	setSpacing

Public Types

Public Methods

Static Public Methods

Protected Methods

Properties

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation

Property Documentation