Wt  4.0.2
Public Member Functions | Private Member Functions | List of all members
Wt::WBoxLayout Class Reference

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

#include <Wt/WBoxLayout.h>

Inheritance diagram for Wt::WBoxLayout:
Inheritance graph
[legend]

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< WLayoutItemremoveItem (WLayoutItem *item) override
 Removes a layout item (widget or nested layout). More...
 
virtual WLayoutItemitemAt (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< WWidgetremoveWidget (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 WWidgetItemfindWidgetItem (WWidget *widget) override
 Finds the widget item associated with the given widget.
 
virtual WWidgetwidget () override
 Returns the widget that is held by this WLayoutItem. More...
 
virtual WLayoutlayout () override
 Returns the layout that implements this WLayoutItem. More...
 
virtual WLayoutparentLayout () 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< WObjectremoveChild (WObject *child)
 Remove a child WObject, so its lifetime is no longer determined by this WObject.
 
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...
 

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) or use a WScrollArea 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

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

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.

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

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

Adds extra spacing.

Adds extra spacing to the layout.

See also
addStretch(), insertStretch()
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()
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()
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;
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.

LayoutDirection Wt::WBoxLayout::direction ( ) const

Returns the layout direction.

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

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;
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()
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()
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>)
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;
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()
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.

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.

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()
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.

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

Sets spacing between each item.

The default spacing is 6 pixels.

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.

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.

int Wt::WBoxLayout::spacing ( ) const

Returns the spacing between each item.

See also
setSpacing()

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