A layout manager which arranges widgets horizontally or vertically. More...

#include <Wt/WBoxLayout.h>

Inheritance diagram for Wt::WBoxLayout:

Public Member Functions
	WBoxLayout (LayoutDirection dir)
	Creates a new box layout. More...

virtual void	addItem (std::unique_ptr< WLayoutItem > item) override
	Adds a layout item. More...

virtual std::unique_ptr< WLayoutItem >	removeItem (WLayoutItem *item) override
	Removes a layout item (widget or nested layout). More...

virtual WLayoutItem *	itemAt (int index) const override
	Returns the layout item at a specific index. More...

virtual int	count () const override
	Returns the number of items in this layout. More...

void	setDirection (LayoutDirection direction)
	Sets the layout direction. More...

LayoutDirection	direction () const
	Returns the layout direction. More...

void	setSpacing (int size)
	Sets spacing between each item. More...

int	spacing () const
	Returns the spacing between each item. More...

void	addWidget (std::unique_ptr< WWidget > widget, int stretch, WFlags< AlignmentFlag > alignment)
	Adds a widget to the layout. More...

template<typename Widget >
Widget *	addWidget (std::unique_ptr< Widget > widget, int stretch=0, WFlags< AlignmentFlag > alignment=None)
	Adds a widget to the layout, returning a raw pointer. More...

void	addLayout (std::unique_ptr< WLayout > layout, int stretch, WFlags< AlignmentFlag > alignment)
	Adds a nested layout to the layout. More...

template<typename Layout >
Layout *	addLayout (std::unique_ptr< Layout > layout, int stretch=0, WFlags< AlignmentFlag > alignment=None)

void	addSpacing (const WLength &size)
	Adds extra spacing. More...

void	addStretch (int stretch=0)
	Adds a stretch element. More...

void	insertWidget (int index, std::unique_ptr< WWidget > widget, int stretch=0, WFlags< AlignmentFlag > alignment=None)
	Inserts a widget in the layout. More...

template<typename Widget >
Widget *	insertWidget (int index, std::unique_ptr< Widget > widget, int stretch=0, WFlags< AlignmentFlag > alignment=None)
	Inserts a widget in the layout, returning a raw pointer. More...

void	insertLayout (int index, std::unique_ptr< WLayout > layout, int stretch=0, WFlags< AlignmentFlag > alignment=None)
	Inserts a nested layout in the layout. More...

template<typename Layout >
Layout *	insertLayout (int index, std::unique_ptr< Layout > layout, int stretch=0, WFlags< AlignmentFlag > alignment=None)

void	insertSpacing (int index, const WLength &size)
	Inserts extra spacing in the layout. More...

void	insertStretch (int index, int stretch=0)
	Inserts a stretch element in the layout. More...

bool	setStretchFactor (WLayout *layout, int stretch)
	Sets the stretch factor for a nested layout. More...

bool	setStretchFactor (WWidget *widget, int stretch)
	Sets the stretch factor for a widget. More...

void	setResizable (int index, bool enabled=true, const WLength &initialSize=WLength::Auto)
	Sets whether the use may drag a particular border. More...

bool	isResizable (int index) const
	Returns whether the user may drag a particular border. More...

Public Member Functions inherited from Wt::WLayout
virtual	~WLayout ()
	Destructor. More...

void	setPreferredImplementation (LayoutImplementation implementation)
	Set the preferred layout implementation. More...

void	addWidget (std::unique_ptr< WWidget > widget)
	Adds the given widget to the layout. More...

std::unique_ptr< WWidget >	removeWidget (WWidget *widget)
	Removes the given widget from the layout. More...

virtual int	indexOf (WLayoutItem *item) const
	Returns the index of a given item. More...

virtual WWidgetItem *	findWidgetItem (WWidget *widget) override
	Finds the widget item associated with the given widget.

virtual WWidget *	widget () override
	Returns the widget that is held by this WLayoutItem. More...

virtual WLayout *	layout () override
	Returns the layout that implements this WLayoutItem. More...

virtual WLayout *	parentLayout () const override
	Returns the layout in which this item is contained.

void	setContentsMargins (int left, int top, int right, int bottom)
	Set contents margins (in pixels). More...

void	getContentsMargins (int left, int top, int right, int bottom) const
	Returns the contents margins. More...

Public Member Functions inherited from Wt::WLayoutItem
virtual	~WLayoutItem ()
	Destructor.

Public Member Functions inherited from Wt::WObject
void	addChild (std::unique_ptr< WObject > child)
	Add a child WObject whose lifetime is determined by this WObject.

template<typename Child >
Child *	addChild (std::unique_ptr< Child > child)
	Add a child WObject, returning a raw pointer. More...

std::unique_ptr< WObject >	removeChild (WObject *child)
	Remove a child WObject, so its lifetime is no longer determined by this WObject.

template<typename Child >
std::unique_ptr< Child >	removeChild (Child *child)
	Remove a child WObject, so its lifetime is no longer determined by this WObject. More...

virtual const std::string	id () const
	Returns the (unique) identifier for this object. More...

virtual void	setObjectName (const std::string &name)
	Sets an object name. More...

virtual std::string	objectName () const
	Returns the object name. More...

void	resetLearnedSlots ()
	Resets learned stateless slot implementations. More...

template<class T >
void	resetLearnedSlot (void(T::*method)())
	Resets a learned stateless slot implementation. More...

template<class T >
WStatelessSlot *	implementStateless (void(T::*method)())
	Declares a slot to be stateless and learn client-side behaviour on first invocation. More...

template<class T >
WStatelessSlot *	implementStateless (void(T::method)(), void(T::undoMethod)())
	Declares a slot to be stateless and learn client-side behaviour in advance. More...

void	isNotStateless ()
	Marks the current function as not stateless. More...

template<class T >
WStatelessSlot *	implementJavaScript (void(T::*method)(), const std::string &jsCode)
	Provides a JavaScript implementation for a method. More...

Public Member Functions inherited from Wt::Core::observable
	observable () noexcept
	Default constructor.

virtual	~observable ()
	Destructor. More...

template<typename... Args, typename C >
auto	bindSafe (void(C::*method)(Args...)) noexcept
	Protects a method call against object destruction. More...

template<typename... Args, typename C >
auto	bindSafe (void(C::*method)(Args...) const) const noexcept
	Protects a const method call against object destruction. More...

template<typename Function >
auto	bindSafe (const Function &function) noexcept
	Protects a function against object destruction. More...

Private Member Functions
virtual void	setParentWidget (WWidget *parent) override
	Internal method.

Additional Inherited Members
Public Types inherited from Wt::WObject
typedef void(WObject::*	Method) ()
	Typedef for a WObject method without arguments.

Static Public Member Functions inherited from Wt::WLayout
static void	setDefaultImplementation (LayoutImplementation implementation)
	Sets the preferred layout implementation globally. More...

Protected Member Functions inherited from Wt::WLayout
	WLayout ()
	Create a layout.

void	update (WLayoutItem *item=nullptr)
	Update the layout. More...

Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot *	getStateless (Method method)
	On-demand stateless slot implementation. More...

Detailed Description

A layout manager which arranges widgets horizontally or vertically.

This layout manager arranges widgets horizontally or vertically inside the parent container.

The space is divided so that each widget is given its preferred size, and remaining space is divided according to stretch factors among widgets. If not all widgets can be given their preferred size (there is not enough room), then widgets are given a smaller size (down to their minimum size). If necessary, the container (or parent layout) of this layout is resized to meet minimum size requirements.

The preferred width or height of a widget is based on its natural size, where it presents its contents without overflowing. WWidget::resize() or (CSS width, height properties) can be used to adjust the preferred size of a widget.

The minimum width or height of a widget is based on the minimum dimensions of the widget or the nested layout. The default minimum height or width for a widget is 0. It can be specified using WWidget::setMinimumSize() or using CSS min-width or min-height properties.

You should use WContainerWidget::setOverflow(OverflowAuto) to automatically show scrollbars for widgets inserted in the layout to cope with a size set by the layout manager that is smaller than the preferred size.

When the container of a layout manager does not have a defined size (by having an explicit size, or by being inside a layout manager), or has has only a maximum size set using WWidget::setMaximumSize(), then the size of the container will be based on the preferred size of the contents, up to this maximum size, instead of the default behaviour of constraining the size of the children based on the size of the container. Note that because of the CSS defaults, a WContainer has by default no height, but inherits the width of its parent widget. The width is thus by default defined.

A layout manager may provide resize handles between items which allow the user to change the automatic layout provided by the layout manager (see setResizable()).

Each item is separated using a constant spacing, which defaults to 6 pixels, and can be changed using setSpacing(). In addition, when this layout is a top-level layout (i.e. is not nested inside another layout), a margin is set around the contents. This margin defaults to 9 pixels, and can be changed using setContentsMargins(). You can add more space between two widgets using addSpacing().

For each item a stretch factor may be defined, which controls how remaining space is used. Each item is stretched using the stretch factor to fill the remaining space.

Usage example:

Wt::WContainerWidget *w = addWidget(std::make_unique<Wt::WContainerWidget>());
w->resize(Wt::WLength(), 600);
 
auto layout = std::make_unique<Wt::WBoxLayout>(Wt::LayoutDirection::TopToBottom);
layout->addWidget(std::make_unique<Wt::WText>("One"));
layout->addWidget(std::make_unique<Wt::WText>("Two"));
layout->addWidget(std::make_unique<Wt::WText>("Three"));
layout->addWidget(std::make_unique<Wt::WText>("Four"));
 
w->setLayout(std::move(layout));

Note: When JavaScript support is not available, not all functionality of the layout is available. In particular, vertical size management is not available.; When a layout is used on a first page with progressive bootstrap, then the layout will progress only in a limited way to a full JavaScript-based layout. You can thus not rely on it to behave properly for example when dynamically adding or removing widgets.

Constructor & Destructor Documentation

◆ WBoxLayout()

Wt::WBoxLayout::WBoxLayout ( LayoutDirection dir )

Creates a new box layout.

This constructor is rarely used. Instead, use the convenient constructors of the specialized WHBoxLayout or WVBoxLayout classes.

Use parent = 0 to created a layout manager that can be nested inside other layout managers.

Member Function Documentation

◆ addItem()

void Wt::WBoxLayout::addItem ( std::unique_ptr< WLayoutItem > item )

overridevirtual

Adds a layout item.

The item may be a widget or nested layout.

How the item is layed out with respect to siblings is implementation specific to the layout manager. In some cases, a layout manager will overload this method with extra arguments that specify layout options.

See also: removeItem(WLayoutItem *), addWidget(WWidget *)

Implements Wt::WLayout.

◆ addLayout() [1/2]

template<typename Layout >

Layout* Wt::WBoxLayout::addLayout	(	std::unique_ptr< Layout >	layout,
		int	stretch = `0`,
		WFlags< AlignmentFlag >	alignment = `None`
	)

\briefs Adds a nested layout to the layout, returning a raw pointer.

This is implemented as:

Layout *result = layout.get();
addLayout(std::unique_ptr<WLayout>(std::move(layout)), stretch, alignment);
return result;

◆ addLayout() [2/2]

void Wt::WBoxLayout::addLayout	(	std::unique_ptr< WLayout >	layout,
		int	stretch,
		WFlags< AlignmentFlag >	alignment
	)

Adds a nested layout to the layout.

Adds a nested layout, with given stretch factor.

See also: addWidget(WWidget *, int, WFlags<AlignmentFlag>), insertLayout()

◆ addSpacing()

void Wt::WBoxLayout::addSpacing ( const WLength & size )

Adds extra spacing.

Adds extra spacing to the layout.

See also: addStretch(), insertStretch()

◆ addStretch()

void Wt::WBoxLayout::addStretch ( int stretch = 0 )

Adds a stretch element.

Adds a stretch element to the layout. This adds an empty space that stretches as needed.

See also: addSpacing(), insertStretch()

◆ addWidget() [1/2]

template<typename Widget >

Widget* Wt::WBoxLayout::addWidget	(	std::unique_ptr< Widget >	widget,
		int	stretch = `0`,
		WFlags< AlignmentFlag >	alignment = `None`
	)

Adds a widget to the layout, returning a raw pointer.

This is implemented as:

Widget *result = widget.get();
addWidget(std::unique_ptr<WWidget>(std::move(widget)), stretch, alignment);
return result;

◆ addWidget() [2/2]

void Wt::WBoxLayout::addWidget	(	std::unique_ptr< WWidget >	widget,
		int	stretch,
		WFlags< AlignmentFlag >	alignment
	)

Adds a widget to the layout.

Adds a widget to the layout, with given stretch factor. When the stretch factor is 0, the widget will not be resized by the layout manager (stretched to take excess space).

The alignment parameter is a combination of a horizontal and/or a vertical AlignmentFlag OR'ed together.

The alignment specifies the vertical and horizontal alignment of the item. The default value 0 indicates that the item is stretched to fill the entire column or row. The alignment can be specified as a logical combination of a horizontal alignment (Wt::AlignmentFlag::Left, Wt::AlignmentFlag::Center, or Wt::AlignmentFlag::Right) and a vertical alignment (Wt::AlignmentFlag::Top, Wt::AlignmentFlag::Middle, or Wt::AlignmentFlag::Bottom).

See also: addLayout(), insertWidget()

◆ count()

int Wt::WBoxLayout::count ( ) const

overridevirtual

Returns the number of items in this layout.

This may be a theoretical number, which is greater than the actual number of items. It can be used to iterate over the items in the layout, in conjunction with itemAt().

Implements Wt::WLayout.

◆ direction()

LayoutDirection Wt::WBoxLayout::direction ( ) const

Returns the layout direction.

See also: setDirection()

◆ insertLayout() [1/2]

template<typename Layout >

Layout* Wt::WBoxLayout::insertLayout	(	int	index,
		std::unique_ptr< Layout >	layout,
		int	stretch = `0`,
		WFlags< AlignmentFlag >	alignment = `None`
	)

\briefs Inserts a nested layout in the layout, returning a raw pointer.

This is implemented as:

Layout *result = layout.get();
addLayout(index, std::unique_ptr<WLayout>(std::move(layout)), stretch, alignment);
return result;

◆ insertLayout() [2/2]

void Wt::WBoxLayout::insertLayout	(	int	index,
		std::unique_ptr< WLayout >	layout,
		int	stretch = `0`,
		WFlags< AlignmentFlag >	alignment = `None`
	)

Inserts a nested layout in the layout.

Inserts a nested layout in the layout at positionindex, with given stretch factor.

See also: insertWidget(), addLayout()

◆ insertSpacing()

void Wt::WBoxLayout::insertSpacing	(	int	index,
		const WLength &	size
	)

Inserts extra spacing in the layout.

Inserts extra spacing in the layout at position index.

See also: insertStretch(), addSpacing()

◆ insertStretch()

void Wt::WBoxLayout::insertStretch	(	int	index,
		int	stretch = `0`
	)

Inserts a stretch element in the layout.

Inserts a stretch element in the layout at position index. This adds an empty space that stretches as needed.

See also: insertSpacing(), addStretch()

◆ insertWidget() [1/2]

template<typename Widget >

Widget* Wt::WBoxLayout::insertWidget	(	int	index,
		std::unique_ptr< Widget >	widget,
		int	stretch = `0`,
		WFlags< AlignmentFlag >	alignment = `None`
	)

Inserts a widget in the layout, returning a raw pointer.

This is implemented as:

Widget *result = widget.get();
insertWidget(index, std::unique_ptr<WWidget>(std::move(widget)), stretch, alignment);
return result;

◆ insertWidget() [2/2]

void Wt::WBoxLayout::insertWidget	(	int	index,
		std::unique_ptr< WWidget >	widget,
		int	stretch = `0`,
		WFlags< AlignmentFlag >	alignment = `None`
	)

Inserts a widget in the layout.

Inserts a widget in the layout at position index, with given stretch factor. When the stretch factor is 0, the widget will not be resized by the layout manager (stretched to take excess space).

The alignment specifies the vertical and horizontal alignment of the item. The default value None indicates that the item is stretched to fill the entire column or row. The alignment can be specified as a logical combination of a horizontal alignment (Wt::AlignmentFlag::Left, Wt::AlignmentFlag::Center, or Wt::AlignmentFlag::Right) and a vertical alignment (Wt::AlignmentFlag::Top, Wt::AlignmentFlag::Middle, or Wt::AlignmentFlag::AlignBottom).

See also: insertLayout(), addWidget(WWidget *, int, WFlags<AlignmentFlag>)

◆ isResizable()

bool Wt::WBoxLayout::isResizable ( int index ) const

Returns whether the user may drag a particular border.

This method returns whether the border that separates item index from the next item may be resized by the user.

See also: setResizable()

◆ itemAt()

WLayoutItem * Wt::WBoxLayout::itemAt ( int index ) const

overridevirtual

Returns the layout item at a specific index.

If there is no item at the index, 0 is returned.

See also: indexOf(WLayoutItem *) const, count()

Implements Wt::WLayout.

◆ removeItem()

std::unique_ptr< WLayoutItem > Wt::WBoxLayout::removeItem ( WLayoutItem * item )

overridevirtual

Removes a layout item (widget or nested layout).

See also: addItem(WLayoutItem *), removeWidget(WWidget *)

Implements Wt::WLayout.

◆ setDirection()

void Wt::WBoxLayout::setDirection ( LayoutDirection direction )

Sets the layout direction.

Note: Changing the layout direction after something (a widget or nested layout) has been added is not supported.

See also: direction()

◆ setResizable()

void Wt::WBoxLayout::setResizable	(	int	index,
		bool	enabled = `true`,
		const WLength &	initialSize = `WLength::Auto`
	)

Sets whether the use may drag a particular border.

This method sets whether the border that separates item index from the next item may be resized by the user, depending on the value of enabled.

The default value is false.

If an initialSize is given (that is not WLength::Auto), then this size is used for the size of the item, overriding the size it would be given by the layout manager.

◆ setSpacing()

void Wt::WBoxLayout::setSpacing ( int size )

Sets spacing between each item.

The default spacing is 6 pixels.

◆ setStretchFactor() [1/2]

bool Wt::WBoxLayout::setStretchFactor	(	WLayout *	layout,
		int	stretch
	)

Sets the stretch factor for a nested layout.

The layout must have previously been added to this layout using insertLayout() or addLayout().

Returns whether the stretch could be set.

◆ setStretchFactor() [2/2]

bool Wt::WBoxLayout::setStretchFactor	(	WWidget *	widget,
		int	stretch
	)

Sets the stretch factor for a widget.

The widget must have previously been added to this layout using insertWidget() or addWidget().

Returns whether the stretch could be set.

◆ spacing()

int Wt::WBoxLayout::spacing ( ) const

Returns the spacing between each item.

See also: setSpacing()

Public Member Functions

Private Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ WBoxLayout()

Member Function Documentation

◆ addItem()

◆ addLayout() [1/2]

◆ addLayout() [2/2]

◆ addSpacing()

◆ addStretch()

◆ addWidget() [1/2]

◆ addWidget() [2/2]

◆ count()

◆ direction()

◆ insertLayout() [1/2]

◆ insertLayout() [2/2]

◆ insertSpacing()

◆ insertStretch()

◆ insertWidget() [1/2]

◆ insertWidget() [2/2]

◆ isResizable()

◆ itemAt()

◆ removeItem()

◆ setDirection()

◆ setResizable()

◆ setSpacing()

◆ setStretchFactor() [1/2]

◆ setStretchFactor() [2/2]

◆ spacing()