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

#include <qlayout.h>

Inheritance diagram for QLayout:

Collaboration diagram for QLayout:

Public Types
enum	SizeConstraint { SetDefaultConstraint , SetNoConstraint , SetMinimumSize , SetFixedSize , SetMaximumSize , SetMinAndMaxSize }
	Describes how the layout constrains the size of the widget. More...

Public Member Functions
	QLayout (QWidget *parent=nullptr)
	Constructs a new top-level QLayout, with parent parent.
	~QLayout ()
virtual int	spacing () const
virtual void	setSpacing (int)
void	setContentsMargins (int left, int top, int right, int bottom)
void	setContentsMargins (const QMargins &margins)
void	unsetContentsMargins ()
void	getContentsMargins (int left, int top, int right, int bottom) const
QMargins	contentsMargins () const
QRect	contentsRect () const
bool	setAlignment (QWidget *w, Qt::Alignment alignment)
	Sets the alignment for widget w to alignment and returns true if w is found in this layout (not including child layouts); otherwise returns `false`.
bool	setAlignment (QLayout *l, Qt::Alignment alignment)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets the alignment for the layout l to alignment and returns `true` if l is found in this layout (not including child layouts); otherwise returns `false`.
void	setSizeConstraint (SizeConstraint constraint)
SizeConstraint	sizeConstraint () const
void	setSizeConstraints (SizeConstraint horizontal, SizeConstraint vertical)
void	setHorizontalSizeConstraint (SizeConstraint constraint)
SizeConstraint	horizontalSizeConstraint () const
void	setVerticalSizeConstraint (SizeConstraint constraint)
SizeConstraint	verticalSizeConstraint () const
void	setMenuBar (QWidget *w)
	Tells the geometry manager to place the menu bar widget at the top of parentWidget(), outside QWidget::contentsMargins().
QWidget *	menuBar () const
	Returns the menu bar set for this layout, or \nullptr if no menu bar is set.
QWidget *	parentWidget () const
	Returns the parent widget of this layout, or \nullptr if this layout is not installed on any widget.
void	invalidate () override
	\reimp
QRect	geometry () const override
	\reimp
bool	activate ()
	Redoes the layout for parentWidget() if necessary.
void	update ()
	Updates the layout for parentWidget().
void	addWidget (QWidget *w)
	Adds widget w to this layout in a manner specific to the layout.
virtual void	addItem (QLayoutItem *)=0
	Implemented in subclasses to add an item.
void	removeWidget (QWidget *w)
	Removes the widget widget from the layout.
void	removeItem (QLayoutItem *)
	Removes the layout item item from the layout.
Qt::Orientations	expandingDirections () const override
	Returns whether this layout can make use of more space than sizeHint().
QSize	minimumSize () const override
	Returns the minimum size of this layout.
QSize	maximumSize () const override
	Returns the maximum size of this layout.
virtual void	setGeometry (const QRect &) override
	\reimp
virtual QLayoutItem *	itemAt (int index) const =0
	Must be implemented in subclasses to return the layout item at index.
virtual QLayoutItem *	takeAt (int index)=0
	Must be implemented in subclasses to remove the layout item at index from the layout, and return the item.
virtual int	indexOf (const QWidget *) const
	Searches for widget widget in this layout (not including child layouts).
virtual int	indexOf (const QLayoutItem *) const
virtual int	count () const =0
	Must be implemented in subclasses to return the number of items in the layout.
bool	isEmpty () const override
	\reimp
QSizePolicy::ControlTypes	controlTypes () const override
	\reimp
virtual QLayoutItem *	replaceWidget (QWidget from, QWidget to, Qt::FindChildOptions options=Qt::FindChildrenRecursively)
int	totalMinimumHeightForWidth (int w) const
int	totalHeightForWidth (int w) const
QSize	totalMinimumSize () const
QSize	totalMaximumSize () const
QSize	totalSizeHint () const
QLayout *	layout () override
	\reimp
void	setEnabled (bool)
	Enables this layout if enable is true, otherwise disables it.
bool	isEnabled () const
	Returns `true` if the layout is enabled; otherwise returns `false`.
void	setAlignment (Qt::Alignment a)
	Sets the alignment of this item to alignment.
Public Member Functions inherited from QObject
Q_INVOKABLE	QObject (QObject *parent=nullptr)
	Constructs an object with parent object parent.
virtual	~QObject ()
	Destroys the object, deleting all its child objects.
virtual bool	event (QEvent *event)
	This virtual function receives events to an object and should return true if the event e was recognized and processed.
virtual bool	eventFilter (QObject watched, QEvent event)
	Filters events if this object has been installed as an event filter for the watched object.
QString	objectName () const
Q_WEAK_OVERLOAD void	setObjectName (const QString &name)
	Sets the object's name to name.
void	setObjectName (QAnyStringView name)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
QBindable< QString >	bindableObjectName ()
bool	isWidgetType () const
	Returns `true` if the object is a widget; otherwise returns `false`.
bool	isWindowType () const
	Returns `true` if the object is a window; otherwise returns `false`.
bool	isQuickItemType () const
	Returns `true` if the object is a QQuickItem; otherwise returns `false`.
bool	isQmlObjectType () const
	Returns whether the object has been created by the QML engine or ownership has been explicitly set via QJSEngine::setObjectOwnership().
bool	signalsBlocked () const noexcept
	Returns `true` if signals are blocked; otherwise returns `false`.
bool	blockSignals (bool b) noexcept
	If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it).
QThread *	thread () const
	Returns the thread in which the object lives.
bool	moveToThread (QThread *thread QT6_DECL_NEW_OVERLOAD_TAIL)
	Changes the thread affinity for this object and its children and returns `true` on success.
int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
	This is an overloaded function that will start a timer of type timerType and a timeout of interval milliseconds.
int	startTimer (std::chrono::nanoseconds time, Qt::TimerType timerType=Qt::CoarseTimer)
void	killTimer (int id)
	Kills the timer with timer identifier, id.
void	killTimer (Qt::TimerId id)
template<typename T>
T	findChild (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns the child of this object that can be cast into type T and that is called name, or \nullptr if there is no such object.
template<typename T>
QList< T >	findChildren (QAnyStringView aName, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	Returns all children of this object with the given name that can be cast to type T, or an empty list if there are no such objects.
template<typename T>
T	findChild (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
template<typename T>
QList< T >	findChildren (Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
const QObjectList &	children () const
	Returns a list of child objects.
void	setParent (QObject *parent)
	Makes the object a child of parent.
void	installEventFilter (QObject *filterObj)
	Installs an event filter filterObj on this object.
void	removeEventFilter (QObject *obj)
	Removes an event filter object obj from this object.
QMetaObject::Connection	connect (const QObject sender, const char signal, const char *member, Qt::ConnectionType type=Qt::AutoConnection) const
bool	disconnect (const char signal=nullptr, const QObject receiver=nullptr, const char *member=nullptr) const
bool	disconnect (const QObject receiver, const char member=nullptr) const
void	dumpObjectTree () const
	Dumps a tree of children to the debug output.
void	dumpObjectInfo () const
	Dumps information about signal connections, etc.
bool	setProperty (const char *name, const QVariant &value)
	Sets the value of the object's name property to value.
bool	setProperty (const char *name, QVariant &&value)
QVariant	property (const char *name) const
	Returns the value of the object's name property.
QList< QByteArray >	dynamicPropertyNames () const
QBindingStorage *	bindingStorage ()
const QBindingStorage *	bindingStorage () const
QObject *	parent () const
	Returns a pointer to the parent object.
bool	inherits (const char *classname) const
	Returns `true` if this object is an instance of a class that inherits className or a QObject subclass that inherits className; otherwise returns `false`.
Public Member Functions inherited from QLayoutItem
	QLayoutItem (Qt::Alignment alignment=Qt::Alignment())
	Constructs a layout item with an alignment.
virtual	~QLayoutItem ()
	Destroys the QLayoutItem.
virtual QSize	sizeHint () const =0
	Implemented in subclasses to return the preferred size of this item.
virtual bool	hasHeightForWidth () const
	Returns `true` if this layout's preferred height depends on its width; otherwise returns `false`.
virtual int	heightForWidth (int) const
	Returns the preferred height for this layout item, given the width, which is not used in this default implementation.
virtual int	minimumHeightForWidth (int) const
	Returns the minimum height this widget needs for the given width, w.
virtual QWidget *	widget () const
	If this item manages a QWidget, returns that widget.
virtual QSpacerItem *	spacerItem ()
	If this item is a QSpacerItem, it is returned as a QSpacerItem; otherwise \nullptr is returned.
Qt::Alignment	alignment () const
	Returns the alignment of this item.
void	setAlignment (Qt::Alignment a)
	Sets the alignment of this item to alignment.

Static Public Member Functions
static QSize	closestAcceptableSize (const QWidget *w, const QSize &s)
	Returns a size that satisfies all size constraints on widget, including heightForWidth() and that is as close as possible to size.
Static Public Member Functions inherited from QObject
static QMetaObject::Connection	connect (const QObject sender, const char signal, const QObject receiver, const char member, Qt::ConnectionType=Qt::AutoConnection)
	\threadsafe
static QMetaObject::Connection	connect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &method, Qt::ConnectionType type=Qt::AutoConnection)
template<typename Func1, typename Func2>
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::ContextTypeForFunctor< Func2 >::ContextType context, Func2 &&slot, Qt::ConnectionType type=Qt::AutoConnection)
template<typename Func1, typename Func2>
static QMetaObject::Connection	connect (const typename QtPrivate::FunctionPointer< Func1 >::Object *sender, Func1 signal, Func2 &&slot)
static bool	disconnect (const QObject sender, const char signal, const QObject receiver, const char member)
	\threadsafe
static bool	disconnect (const QObject sender, const QMetaMethod &signal, const QObject receiver, const QMetaMethod &member)
static bool	disconnect (const QMetaObject::Connection &)
	Disconnect a connection.
template<typename Func1, typename Func2>
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const typename QtPrivate::FunctionPointer< Func2 >::Object receiver, Func2 slot)
template<typename Func1>
static bool	disconnect (const typename QtPrivate::FunctionPointer< Func1 >::Object sender, Func1 signal, const QObject receiver, void **zero)

Protected Member Functions
void	widgetEvent (QEvent *)
void	childEvent (QChildEvent *e) override
	\reimp
void	addChildLayout (QLayout *l)
	This function is called from `addLayout()` or `insertLayout()` functions in subclasses to add layout childLayout as a sub-layout.
void	addChildWidget (QWidget *w)
	This function is called from `addWidget()` functions in subclasses to add w as a managed widget of a layout.
bool	adoptLayout (QLayout *layout)
QRect	alignmentRect (const QRect &) const
	Returns the rectangle that should be covered when the geometry of this layout is set to r, provided that this layout supports setAlignment().
	QLayout (QLayoutPrivate &d, QLayout , QWidget )
Protected Member Functions inherited from QObject
QObject *	sender () const
	Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns \nullptr.
int	senderSignalIndex () const
int	receivers (const char *signal) const
	Returns the number of receivers connected to the signal.
bool	isSignalConnected (const QMetaMethod &signal) const
virtual void	timerEvent (QTimerEvent *event)
	This event handler can be reimplemented in a subclass to receive timer events for the object.
virtual void	customEvent (QEvent *event)
	This event handler can be reimplemented in a subclass to receive custom events.
virtual void	connectNotify (const QMetaMethod &signal)
virtual void	disconnectNotify (const QMetaMethod &signal)
	QObject (QObjectPrivate &dd, QObject *parent=nullptr)

Properties
int	spacing
	the spacing between widgets inside the layout
QMargins	contentsMargins
	the margins used around the layout
SizeConstraint	sizeConstraint
	the resize mode of the layout.
SizeConstraint	horizontalSizeConstraint
	The horizontal size constraint.
SizeConstraint	verticalSizeConstraint
	The vertical size constraint.
Properties inherited from QObject
QString	objectName
	the name of this object

Friends
class	QApplicationPrivate
class	QWidget

Additional Inherited Members
Public Slots inherited from QObject
void	deleteLater ()
	\threadsafe
Signals inherited from QObject
void	destroyed (QObject *=nullptr)
	This signal is emitted immediately before the object obj is destroyed, after any instances of QPointer have been notified, and cannot be blocked.
void	objectNameChanged (const QString &objectName, QPrivateSignal)
	This signal is emitted after the object's name has been changed.
Protected Attributes inherited from QObject
QScopedPointer< QObjectData >	d_ptr
Protected Attributes inherited from QLayoutItem
Qt::Alignment	align
Related Symbols inherited from QObject
template< class T > T	qobject_cast (const QObject *object)
	Returns the given object cast to type T if the object is of type T (or of a subclass); otherwise returns \nullptr.
template< typename T > T	qFindChildqFindChildren (const QObject *obj, const QString &name)()
template< typename T > QList< T >	qFindChildrenqFindChildren (const QObject *obj, const QString &name)()
	QObjectList
	\macro Q_CLASSINFO(Name, Value)

Detailed Description

The QLayout class is the base class of geometry managers.

\inmodule QtWidgets

This is an abstract base class inherited by the concrete classes QBoxLayout, QGridLayout, QFormLayout, and QStackedLayout.

For users of QLayout subclasses or of QMainWindow there is seldom any need to use the basic functions provided by QLayout, such as setSizeConstraint() or setMenuBar(). See \l{Layout Management} for more information.

To make your own layout manager, implement the functions addItem(), sizeHint(), setGeometry(), itemAt() and takeAt(). You should also implement minimumSize() to ensure your layout isn't resized to zero size if there is too little space. To support children whose heights depend on their widths, implement hasHeightForWidth() and heightForWidth(). See the \l{layouts/flowlayout}{Flow Layout} example for more information about implementing custom layout managers.

Geometry management stops when the layout manager is deleted.

See also: QLayoutItem, {Layout Management}, {Basic Layouts Example}, {Flow Layout Example}

Definition at line 26 of file qlayout.h.

Member Enumeration Documentation

◆ SizeConstraint

enum QLayout::SizeConstraint

Describes how the layout constrains the size of the widget.

A vertical constraint affects the widget's height, while a horizontal constraint affects its width.

The possible values are:

\value SetDefaultConstraint In the constrained orientation(s), the widget’s minimum extent is set to \l minimumSize(), unless a minimum size has already been set.

\value SetFixedSize In the constrained orientation(s), the widget’s extent is set to \l sizeHint(), and it cannot be resized in that direction.

\value SetMinimumSize In the constrained orientation(s), the widget’s minimum extent is set to \l minimumSize().

\value SetMaximumSize In the constrained orientation(s), the widget’s maximum extent is set to \l maximumSize().

\value SetMinAndMaxSize In the constrained orientation(s), the widget’s minimum extent is set to \l minimumSize(), and the maximum extent is set to \l maximumSize().

\value SetNoConstraint No size constraints are applied to the widget.

See also: setSizeConstraint(), setSizeConstraints(), horizontalSizeConstraint(), setHorizontalSizeConstraint(), setVerticalSizeConstraint()

Enumerator
SetDefaultConstraint
SetNoConstraint
SetMinimumSize
SetFixedSize
SetMaximumSize
SetMinAndMaxSize

Definition at line 40 of file qlayout.h.

Constructor & Destructor Documentation

◆ QLayout() [1/2]

QLayout::QLayout ( QWidget * parent = nullptr )

explicit

Constructs a new top-level QLayout, with parent parent.

The layout is set directly as the top-level layout for parent. There can be only one top-level layout for a widget. It is returned by QWidget::layout().

If parent is \nullptr, then you must insert this layout into another layout, or set it as a widget's layout using QWidget::setLayout().

See also: QWidget::setLayout()

Definition at line 74 of file qlayout.cpp.

◆ ~QLayout()

QLayout::~QLayout ( )

Destroys the layout, deleting all child layouts. Geometry management stops when a top-level layout is deleted.

The layout classes will probably be fatally confused if you delete a sublayout.

Definition at line 688 of file qlayout.cpp.

◆ QLayout() [2/2]

QLayout::QLayout	(	QLayoutPrivate &	dd,
		QLayout *	lay,
		QWidget *	w )

protected

Definition at line 84 of file qlayout.cpp.

Member Function Documentation

◆ activate()

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()

Definition at line 974 of file qlayout.cpp.

◆ addChildLayout()

void QLayout::addChildLayout ( QLayout * childLayout )

protected

This function is called from addLayout() or insertLayout() functions in subclasses to add layout childLayout as a sub-layout.

The only scenario in which you need to call it directly is if you implement a custom layout that supports nested layouts.

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

Definition at line 707 of file qlayout.cpp.

◆ addChildWidget()

void QLayout::addChildWidget ( QWidget * w )

protected

This function is called from addWidget() functions in subclasses to add w as a managed widget of a layout.

If w is already managed by a layout, this function will produce a warning, and remove w from that layout. This function must therefore be called before adding w to the layout's data structure.

Definition at line 823 of file qlayout.cpp.

◆ addItem()

virtual void QLayout::addItem ( QLayoutItem * item )

pure virtual

Implemented in subclasses to add an item.

How it is added is specific to each subclass.

This function is not usually called in application code. To add a widget to a layout, use the addWidget() function; to add a child layout, use the addLayout() function provided by the relevant QLayout subclass.

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

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

Implemented in CardLayout, CardLayout, QBoxLayout, QDockWidgetLayout, QFormLayout, QGridLayout, QMainWindowLayout, QStackedLayout, and QToolBarLayout.

◆ addWidget()

void QLayout::addWidget ( QWidget * w )

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

This function uses addItem().

Definition at line 177 of file qlayout.cpp.

◆ adoptLayout()

bool QLayout::adoptLayout ( QLayout * layout )

protected

Definition at line 725 of file qlayout.cpp.

◆ alignmentRect()

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

protected

Returns the rectangle that should be covered when the geometry of this layout is set to r, provided that this layout supports setAlignment().

The result is derived from sizeHint() and expandingDirections(). It is never larger than r.

Definition at line 1404 of file qlayout.cpp.

◆ childEvent()

void QLayout::childEvent ( QChildEvent * e )

overrideprotectedvirtual

\reimp

Reimplemented from QObject.

Definition at line 558 of file qlayout.cpp.

◆ closestAcceptableSize()

QSize QLayout::closestAcceptableSize	(	const QWidget *	w,
		const QSize &	s )

static

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

Definition at line 1537 of file qlayout.cpp.

◆ contentsMargins()

QMargins QLayout::contentsMargins ( ) const

Since: 4.6

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()

Definition at line 368 of file qlayout.cpp.

◆ contentsRect()

QRect QLayout::contentsRect ( ) const

Since: 4.3

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

See also: setContentsMargins(), getContentsMargins()

Definition at line 383 of file qlayout.cpp.

◆ controlTypes()

QSizePolicy::ControlTypes QLayout::controlTypes ( ) const

overridevirtual

\reimp

Reimplemented from QLayoutItem.

Definition at line 440 of file qlayout.cpp.

◆ count()

virtual 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 CardLayout, CardLayout, QBoxLayout, QDockWidgetLayout, QFormLayout, QGridLayout, QMainWindowLayout, QStackedLayout, and QToolBarLayout.

◆ expandingDirections()

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 widgets's \l{QSizePolicy}{size policies}.

See also: sizeHint()

Implements QLayoutItem.

Reimplemented in QToolBarLayout.

Definition at line 923 of file qlayout.cpp.

◆ geometry()

QRect QLayout::geometry ( ) const

overridevirtual

\reimp

Implements QLayoutItem.

Definition at line 462 of file qlayout.cpp.

◆ getContentsMargins()

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

Since: 4.3

For each of left, top, right and bottom that is not \nullptr, stores the size of the margin named in the location the pointer refers to.

By default, QLayout uses the values provided by the style. On most platforms, the margin is 11 pixels in all directions.

See also: setContentsMargins(), QStyle::pixelMetric(), {QStyle::}{PM_LayoutLeftMargin}, {QStyle::}{PM_LayoutTopMargin}, {QStyle::}{PM_LayoutRightMargin}, {QStyle::}{PM_LayoutBottomMargin}

Definition at line 338 of file qlayout.cpp.

◆ horizontalSizeConstraint()

QLayout::SizeConstraint QLayout::horizontalSizeConstraint ( ) const

Definition at line 1365 of file qlayout.cpp.

◆ indexOf() [1/2]

int QLayout::indexOf ( const QLayoutItem * layoutItem ) const

virtual

Since: 5.12 Searches for layout item layoutItem in this layout (not including child layouts).

Returns the index of layoutItem, or -1 if layoutItem is not found.

Reimplemented in QToolBarLayout.

Definition at line 1259 of file qlayout.cpp.

◆ indexOf() [2/2]

int QLayout::indexOf ( const QWidget * widget ) const

virtual

Searches for widget 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().

Reimplemented in QToolBarLayout.

Definition at line 1240 of file qlayout.cpp.

◆ invalidate()

void QLayout::invalidate ( )

overridevirtual

\reimp

Reimplemented from QLayoutItem.

Reimplemented in QMainWindowLayout, and QToolBarLayout.

Definition at line 471 of file qlayout.cpp.

◆ isEmpty()

bool QLayout::isEmpty ( ) const

overridevirtual

\reimp

Implements QLayoutItem.

Reimplemented in QToolBarLayout.

Definition at line 424 of file qlayout.cpp.

◆ isEnabled()

bool QLayout::isEnabled ( ) const

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

See also: setEnabled()

Definition at line 1525 of file qlayout.cpp.

◆ itemAt()

virtual 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 function must return \nullptr. Items are numbered consecutively from 0. If an item is deleted, other items will be renumbered.

This function 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 CardLayout, CardLayout, QBoxLayout, QDockWidgetLayout, QFormLayout, QGridLayout, QMainWindowLayout, QStackedLayout, and QToolBarLayout.

◆ layout()

QLayout * QLayout::layout ( )

overridevirtual

\reimp

Reimplemented from QLayoutItem.

Definition at line 292 of file qlayoutitem.cpp.

◆ maximumSize()

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 doesn't include the space required by QWidget::setContentsMargins() or menuBar().

The default implementation allows unlimited resizing.

Implements QLayoutItem.

Definition at line 906 of file qlayout.cpp.

◆ menuBar()

QWidget * QLayout::menuBar ( ) const

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

Definition at line 874 of file qlayout.cpp.

◆ minimumSize()

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 doesn't include the space required by QWidget::setContentsMargins() or menuBar().

The default implementation allows unlimited resizing.

Implements QLayoutItem.

Reimplemented in QMainWindowLayout, QStackedLayout, and QToolBarLayout.

Definition at line 891 of file qlayout.cpp.

◆ parentWidget()

QWidget * QLayout::parentWidget ( ) const

Returns the parent widget of this layout, or \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()

Definition at line 401 of file qlayout.cpp.

◆ removeItem()

void QLayout::removeItem ( QLayoutItem * item )

Removes the layout item 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()

Definition at line 1490 of file qlayout.cpp.

◆ removeWidget()

void QLayout::removeWidget ( QWidget * widget )

Removes the widget 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 or to explicitly hide it if necessary.

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

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

Definition at line 1462 of file qlayout.cpp.

◆ replaceWidget()

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

virtual

Since: 5.2

Searches for widget from and replaces it with widget to if found. Returns the layout item that contains the widget from on success. Otherwise \nullptr 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 function works for the built-in Qt layouts, but might not work for custom layouts.

See also: indexOf()

Definition at line 1153 of file qlayout.cpp.

◆ setAlignment() [1/3]

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

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets the alignment for the layout l to alignment and returns true if l is found in this layout (not including child layouts); otherwise returns false.

Definition at line 213 of file qlayout.cpp.

◆ setAlignment() [2/3]

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

Sets the alignment of this item to alignment.

{Note:} Item alignment is only supported by QLayoutItem subclasses where it would have a visual effect. Except for QSpacerItem, which provides blank space for layouts, all public Qt classes that inherit QLayoutItem support item alignment.

Definition at line 47 of file qlayoutitem.cpp.

◆ setAlignment() [3/3]

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

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

Definition at line 190 of file qlayout.cpp.

◆ setContentsMargins() [1/2]

void QLayout::setContentsMargins ( const QMargins & margins )

Since: 4.6

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()

Definition at line 304 of file qlayout.cpp.

◆ setContentsMargins() [2/2]

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

Since: 4.3

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.

See also: getContentsMargins(), QStyle::pixelMetric(), {QStyle::}{PM_LayoutLeftMargin}, {QStyle::}{PM_LayoutTopMargin}, {QStyle::}{PM_LayoutRightMargin}, {QStyle::}{PM_LayoutBottomMargin}

Definition at line 279 of file qlayout.cpp.

◆ setEnabled()

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()

Definition at line 1514 of file qlayout.cpp.

◆ setGeometry()

void QLayout::setGeometry ( const QRect & r )

overridevirtual

\reimp

Implements QLayoutItem.

Reimplemented in CardLayout, CardLayout, QBoxLayout, QDockWidgetLayout, QFormLayout, QGridLayout, QMainWindowLayout, QStackedLayout, and QToolBarLayout.

Definition at line 453 of file qlayout.cpp.

◆ setHorizontalSizeConstraint()

void QLayout::setHorizontalSizeConstraint ( SizeConstraint constraint )

Definition at line 1355 of file qlayout.cpp.

◆ setMenuBar()

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.

Definition at line 861 of file qlayout.cpp.

◆ setSizeConstraint()

void QLayout::setSizeConstraint ( SizeConstraint constraint )

Definition at line 1317 of file qlayout.cpp.

◆ setSizeConstraints()

void QLayout::setSizeConstraints	(	SizeConstraint	horizontal,
		SizeConstraint	vertical )

Since: 6.10

Sets both the horizontal and vertical size constraints.

See also: sizeConstraint(), horizontalSizeConstraint(), verticalSizeConstraint()

Definition at line 1329 of file qlayout.cpp.

◆ setSpacing()

void QLayout::setSpacing ( int spacing )

virtual

Reimplemented in QBoxLayout, QFormLayout, and QGridLayout.

Definition at line 257 of file qlayout.cpp.

◆ setVerticalSizeConstraint()

void QLayout::setVerticalSizeConstraint ( SizeConstraint constraint )

Definition at line 1381 of file qlayout.cpp.

◆ sizeConstraint()

QLayout::SizeConstraint QLayout::sizeConstraint ( ) const

Definition at line 1339 of file qlayout.cpp.

◆ spacing()

int QLayout::spacing ( ) const

virtual

Reimplemented in QBoxLayout, QFormLayout, and QGridLayout.

Definition at line 246 of file qlayout.cpp.

◆ takeAt()

virtual 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 function must do nothing and return 0. 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)) != nullptr) {
    ...
    delete child->widget(); // delete the widget
    delete child;   // delete the layout item
}

See also: itemAt(), count()

Implemented in CardLayout, CardLayout, QBoxLayout, QDockWidgetLayout, QFormLayout, QGridLayout, QMainWindowLayout, QStackedLayout, and QToolBarLayout.

◆ totalHeightForWidth()

int QLayout::totalHeightForWidth ( int w ) const

Also takes contentsMargins and menu bar into account.

Definition at line 595 of file qlayout.cpp.

◆ totalMaximumSize()

QSize QLayout::totalMaximumSize ( ) const

Also takes contentsMargins and menu bar into account.

Definition at line 659 of file qlayout.cpp.

◆ totalMinimumHeightForWidth()

int QLayout::totalMinimumHeightForWidth ( int w ) const

Also takes contentsMargins and menu bar into account.

Definition at line 575 of file qlayout.cpp.

◆ totalMinimumSize()

QSize QLayout::totalMinimumSize ( ) const

Also takes contentsMargins and menu bar into account.

Definition at line 615 of file qlayout.cpp.

◆ totalSizeHint()

QSize QLayout::totalSizeHint ( ) const

Also takes contentsMargins and menu bar into account.

Definition at line 636 of file qlayout.cpp.

◆ unsetContentsMargins()

void QLayout::unsetContentsMargins ( )

Since: 6.1

Unsets any user-defined margins around the layout. The layout will use the default values provided by the style.

See also: setContentsMargins()

Definition at line 317 of file qlayout.cpp.

◆ update()

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()

Definition at line 950 of file qlayout.cpp.

◆ verticalSizeConstraint()

QLayout::SizeConstraint QLayout::verticalSizeConstraint ( ) const

Definition at line 1390 of file qlayout.cpp.

◆ widgetEvent()

void QLayout::widgetEvent ( QEvent * e )

protected

Performs child widget layout when the parent widget is resized. Also handles removal of widgets. e is the event

Definition at line 520 of file qlayout.cpp.

◆ QApplicationPrivate

friend class QApplicationPrivate

friend

Definition at line 138 of file qlayout.h.

◆ QWidget

friend class QWidget

friend

Definition at line 139 of file qlayout.h.

Property Documentation

◆ contentsMargins

QMargins QLayout::contentsMargins

readwrite

the margins used around the layout

Since: 4.6

By default, QLayout uses the values provided by the style. On most platforms, the margin is 11 pixels in all directions.

See also: setContentsMargins(), getContentsMargins()

Definition at line 32 of file qlayout.h.

◆ horizontalSizeConstraint

SizeConstraint QLayout::horizontalSizeConstraint

readwrite

The horizontal size constraint.

Since: 6.10

The default mode is \l {QLayout::SetDefaultConstraint}

See also: verticalSizeConstraint(), sizeConstraint()

Definition at line 36 of file qlayout.h.

◆ sizeConstraint

SizeConstraint QLayout::sizeConstraint

readwrite

the resize mode of the layout.

Setting the size constraint for the dialog. Setting a vertical or horizontal size constraint will override this.

The default mode is \l {QLayout::SetDefaultConstraint} {SetDefaultConstraint}.

See also: horizontalSizeConstraint(), verticalSizeConstraint()

Definition at line 35 of file qlayout.h.

◆ spacing

int QLayout::spacing

readwrite

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 \l{QGridLayout::}{setHorizontalSpacing()} and \l{QGridLayout::}{setVerticalSpacing()}. In that case, spacing() returns -1.

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

Definition at line 31 of file qlayout.h.

◆ verticalSizeConstraint

SizeConstraint QLayout::verticalSizeConstraint

readwrite

The vertical size constraint.

Since: 6.10

The default mode is \l {QLayout::SetDefaultConstraint}

See also: horizontalSizeConstraint(), sizeConstraint()

Definition at line 37 of file qlayout.h.

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

qtbase/src/widgets/kernel/qlayout.h (8825bcdbdab5f37b185261d7ba06260dc8e9930d)
qtbase/src/widgets/kernel/qlayout.cpp (aa1fedb3f21284ba0abe0b9868962fcbc641d351)
qtbase/src/widgets/kernel/qlayoutitem.cpp (8825bcdbdab5f37b185261d7ba06260dc8e9930d)

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Properties

Friends

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ SizeConstraint

Constructor & Destructor Documentation

◆ QLayout() [1/2]

◆ ~QLayout()

◆ QLayout() [2/2]

Member Function Documentation

◆ activate()

◆ addChildLayout()

◆ addChildWidget()

◆ addItem()

◆ addWidget()

◆ adoptLayout()

◆ alignmentRect()

◆ childEvent()

◆ closestAcceptableSize()

◆ contentsMargins()

◆ contentsRect()

◆ controlTypes()

◆ count()

◆ expandingDirections()

◆ geometry()

◆ getContentsMargins()

◆ horizontalSizeConstraint()

◆ indexOf() [1/2]

◆ indexOf() [2/2]

◆ invalidate()

◆ isEmpty()

◆ isEnabled()

◆ itemAt()

◆ layout()

◆ maximumSize()

◆ menuBar()

◆ minimumSize()

◆ parentWidget()

◆ removeItem()

◆ removeWidget()

◆ replaceWidget()

◆ setAlignment() [1/3]

◆ setAlignment() [2/3]

◆ setAlignment() [3/3]

◆ setContentsMargins() [1/2]

◆ setContentsMargins() [2/2]

◆ setEnabled()

◆ setGeometry()

◆ setHorizontalSizeConstraint()

◆ setMenuBar()

◆ setSizeConstraint()

◆ setSizeConstraints()

◆ setSpacing()

◆ setVerticalSizeConstraint()

◆ sizeConstraint()

◆ spacing()

◆ takeAt()

◆ totalHeightForWidth()

◆ totalMaximumSize()

◆ totalMinimumHeightForWidth()

◆ totalMinimumSize()

◆ totalSizeHint()

◆ unsetContentsMargins()

◆ update()

◆ verticalSizeConstraint()

◆ widgetEvent()

Friends And Related Symbol Documentation

◆ QApplicationPrivate

◆ QWidget

Property Documentation

◆ contentsMargins

◆ horizontalSizeConstraint

◆ sizeConstraint

◆ spacing

◆ verticalSizeConstraint