Wt::WLayout Class Reference

An abstract base class for layout managers. More...

#include <Wt/WLayout.h>

Inheritance diagram for Wt::WLayout:

Public Member Functions
virtual	~WLayout ()
	Destructor. More...
void	setPreferredImplementation (LayoutImplementation implementation)
	Set the preferred layout implementation. More...
virtual void	addItem (std::unique_ptr< WLayoutItem > item)=0
	Adds a layout item. More...
void	addWidget (std::unique_ptr< WWidget > widget)
	Adds the given widget to the layout. More...
virtual std::unique_ptr< WLayoutItem >	removeItem (WLayoutItem *item)=0
	Removes a layout item (widget or nested layout). More...
std::unique_ptr< WWidget >	removeWidget (WWidget *widget)
	Removes the given widget from the layout. More...
virtual int	count () const =0
	Returns the number of items in this layout. More...
virtual WLayoutItem *	itemAt (int index) const =0
	Returns the layout item at a specific index. 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...

Static Public Member Functions
static void	setDefaultImplementation (LayoutImplementation implementation)
	Sets the preferred layout implementation globally. More...

Protected Member Functions
	WLayout ()
	Create a layout.
void	update (WLayoutItem *item=nullptr)
	Update the layout. More...
virtual void	setParentWidget (WWidget *parent) override
	Internal method.
Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot *	getStateless (Method method)
	On-demand stateless slot implementation. More...

Private Member Functions
virtual void	setParentLayout (WLayout *parentLayout) override
	Internal method.

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

Detailed Description

An abstract base class for layout managers.

This class is the abstract base class for any layout manager. A layout manager is associated with a container widget, and manages the layout of children inside the whole space available to the container widget.

The implementation of the layout manager depends on the container widget to which it is set, and is therefore deferred to WLayoutImpl.

Note

When applying a layout manager to a WContainerWidget, you may not define any padding for the container widget. Instead, use setContentsMargins().

Constructor & Destructor Documentation

~WLayout()

Wt::WLayout::~WLayout ( )

virtual

Destructor.

This will delete the layout (and nested layouts), but not the contained widgets.

Member Function Documentation

addItem()

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

pure virtual

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 *)

Implemented in Wt::WGridLayout, Wt::WFitLayout, Wt::WBoxLayout, and Wt::WBorderLayout.

addWidget()

void Wt::WLayout::addWidget

(

std::unique_ptr< WWidget >

widget

)

Adds the given widget to the layout.

This method wraps the widget in a WWidgetItem and calls addItem(WLayoutItem *).

How the widget 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

removeWidget(WWidget *), addItem(WLayoutItem *)

count()

virtual int Wt::WLayout::count ( ) const

pure virtual

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().

Implemented in Wt::WGridLayout, Wt::WFitLayout, Wt::WBoxLayout, and Wt::WBorderLayout.

getContentsMargins()

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

Returns the contents margins.

See also

setContentsMargins()

indexOf()

int Wt::WLayout::indexOf ( WLayoutItem *  item ) const

virtual

Returns the index of a given item.

The default implementation loops over all items, and returns the index for which itemAt(index) equals item.

See also

itemAt(int) const

Reimplemented in Wt::WFitLayout.

itemAt()

virtual WLayoutItem* Wt::WLayout::itemAt ( int  index ) const

pure virtual

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()

Implemented in Wt::WGridLayout, Wt::WFitLayout, Wt::WBoxLayout, and Wt::WBorderLayout.

layout()

virtual WLayout* Wt::WLayout::layout ( )

overridevirtual

Returns the layout that implements this WLayoutItem.

This implements a type-safe upcasting mechanism to a WLayout.

Implements Wt::WLayoutItem.

removeItem()

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

pure virtual

Removes a layout item (widget or nested layout).

See also

addItem(WLayoutItem *), removeWidget(WWidget *)

Implemented in Wt::WGridLayout, Wt::WFitLayout, Wt::WBoxLayout, and Wt::WBorderLayout.

removeWidget()

std::unique_ptr< WWidget > Wt::WLayout::removeWidget

(

WWidget *

widget

)

Removes the given widget from the layout.

This method finds the corresponding WWidgetItem and calls removeItem(WLayoutItem *), and returns the widget.

See also

addWidget(WWidget *), removeItem(WLayoutItem *)

setContentsMargins()

void Wt::WLayout::setContentsMargins	(	int	left,
		int	top,
		int	right,
		int	bottom
	)

Set contents margins (in pixels).

The default contents margins are 9 pixels in all directions.

Note

Only used when the layout manager is applied to a WContainerWidget.

See also

setContentsMargins()

setDefaultImplementation()

void Wt::WLayout::setDefaultImplementation ( LayoutImplementation  implementation )

static

Sets the preferred layout implementation globally.

The default implementation for box layouts and fit layouts is Flex (if supported by the browser). Otherwise a fallback to JavaScript is used.

Because there are cases where Flex does not work properly, this method can be used to set the global preferred implementation to instead. Since this is a system-wide setting, and not a per-session setting, you should call this function before any session is created, e.g. in main() before calling WRun(). setPreferredImplementation()

setPreferredImplementation()

void Wt::WLayout::setPreferredImplementation

(

LayoutImplementation

implementation

)

Set the preferred layout implementation.

The default implementation for box layouts and fit layouts is Flex (if supported by the browser). Otherwise a fallback to JavaScript is used.

See also

setDefaultImplementation()

update()

void Wt::WLayout::update ( WLayoutItem *  item = nullptr )

protected

Update the layout.

Must be called whenever some properties of the layout have changed.

widget()

virtual WWidget* Wt::WLayout::widget ( )

overridevirtual

Returns the widget that is held by this WLayoutItem.

This implements a type-safe upcasting mechanism to a WWidgetItem.

Implements Wt::WLayoutItem.