Wt 3.1.10
Public Types | Public Member Functions
Wt::WBoxLayout Class Reference

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

#include <Wt/WBoxLayout>

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

List of all members.

Public Types

enum  Direction { LeftToRight, RightToLeft, TopToBottom, BottomToTop }
 Enumeration of the direction in which widgets are layed out. More...

Public Member Functions

 WBoxLayout (Direction dir, WWidget *parent=0)
 Creates a new box layout.
virtual void addItem (WLayoutItem *item)
 Adds a layout item.
virtual void removeItem (WLayoutItem *item)
 Removes a layout item (widget or nested layout).
virtual WLayoutItemitemAt (int index) const
 Returns the layout item at a specific index.
virtual int count () const
 Returns the number of items in this layout.
void setDirection (Direction direction)
 Sets the layout direction.
Direction direction () const
 Returns the layout direction.
void setSpacing (int size)
 Sets spacing between each item.
int spacing () const
 Returns the spacing between each item.
void addWidget (WWidget *widget, int stretch=0, WFlags< AlignmentFlag > alignment=0)
 Adds a widget to the layout.
void addLayout (WLayout *layout, int stretch=0, WFlags< AlignmentFlag > alignment=0)
 Adds a nested layout to the layout.
void addSpacing (const WLength &size)
 Adds extra spacing.
void addStretch (int stretch=0)
 Adds a stretch element.
void insertWidget (int index, WWidget *widget, int stretch=0, WFlags< AlignmentFlag > alignment=0)
 Inserts a widget in the layout.
void insertLayout (int index, WLayout *layout, int stretch=0, WFlags< AlignmentFlag > alignment=0)
 Inserts a nested layout in the layout.
void insertSpacing (int index, const WLength &size)
 Inserts extra spacing in the layout.
void insertStretch (int index, int stretch=0)
 Inserts a stretch element in the layout.
bool setStretchFactor (WLayout *layout, int stretch)
 Sets the stretch factor for a nested layout.
bool setStretchFactor (WWidget *widget, int stretch)
 Sets the stretch factor for a widget.
void setResizable (int index, bool enabled=true)
 Sets whether the use may drag a particular border.
bool isResizable (int index) const
 Returns whether the user may drag a particular border.

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 widgets is given its minimum size, and remaining space is divided according to stretch factors among the widgets. The widget minimum height or width is used for sizing each widget, whose default values may be overridden using WWidget::setMinimumSize().

If you want to use the layout manager for a container which does not have a height that is constrained somehow, you need to specify AlignTop in the alignment flags of WContainerWidget::setLayout(). Otherwise the behavior is undefined (the parent container will continue to increase in size as it tries to satisfy the constraints assuming a contrained height).

You can use WContainerWidget::setOverflow(OverflowAuto) or use a WScrollArea to automatically show scrollbars on a widget inserted in the layout.

A caveat with layout managers is that you cannot reliably use a stylesheet to add borders (or margin) to a widget inserted in a layout: this is broken on Internet Explorer. To provide the layout, the layout manager needs to set sizes on the contained widget but these sizes also need to take into account the border/margin width. Since on IE, this value will be 0 if the border or margin is provided by a stylesheet (as opposed to by inline CSS by using WWidget::decorationStyle()), the result will be wrong behaviour like widgets that keep growing in size.

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()). Resize handles between rows for a vertically oriented box layout only work when the layout fills the parent vertical space (i.e. is not aligned to the top). Likewise, resize handles between columns for a horizontally oriented box layout only work when the layout fills the parent horiziontal space (i.e. is not aligned left, right or centered).

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, which thus replaces padding defined for the container. This margin defaults to 9 pixels, and can be changed using setContentsMargins(). It is not allowed to define padding for the container widget using its CSS 'padding' property or the WContainerWidget::setPadding(). 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 = new Wt::WContainerWidget(this);
 w->resize(WLength(), 600);

 Wt::WBoxLayout *layout = new Wt::WBoxLayout(Wt::WBoxLayout::TopToBottom);
 layout->addWidget(new Wt::WText("One"));
 layout->addWidget(new Wt::WText("Two"));
 layout->addWidget(new Wt::WText("Three"));
 layout->addWidget(new Wt::WText("Four"));

 w->setLayout(layout);
Note:
This layout manager is applicable only to WContainerWidget container widgets. You may use it within an Ext::Container indirectly by first setting a WContainerWidget using a WFitLayout.
When JavaScript support is not available, only Safari and Firefox properly implement this box layout. For other browsers, only the horizontal layout is properly implemented, while vertically all widgets use their minimum size.
When set on a WContainerWidget, this layout manager accepts the following hints (see setLayoutHint()):
  • "table-layout" with possible values "auto" (default) or "fixed".
    Use "fixed" to prevent nested tables from overflowing the layout. In that case, you will need to specify a width (in CSS or otherwise) for at least one item in every column that has no stretch factor.

Member Enumeration Documentation

Enumeration of the direction in which widgets are layed out.

Enumerator:
LeftToRight 

Horizontal layout, widgets are arranged from left to right.

RightToLeft 

Horizontal layout, widgets are arranged from right to left.

TopToBottom 

Vertical layout, widgets are arranged from top to bottom.

BottomToTop 

Vertical layout, widgets are arranged from bottom to top.


Constructor & Destructor Documentation

Wt::WBoxLayout::WBoxLayout ( Direction  dir,
WWidget parent = 0 
)

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 ( WLayoutItem item) [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 *)

Implements Wt::WLayout.

void Wt::WBoxLayout::addLayout ( WLayout layout,
int  stretch = 0,
WFlags< AlignmentFlag alignment = 0 
)

Adds a nested layout to the layout.

Adds a nested layout, with given stretch factor.

See also:
addWidget(WWidget *, int, WFlags<AlignmentFlag>), insertLayout()
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 ( WWidget widget,
int  stretch = 0,
WFlags< AlignmentFlag alignment = 0 
)

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). You may use a special stretch factor of -1 to indicate that the widget should not take excess space but the contents height should still be actively managed. This may make sense for example if the widget is layout size aware).

The alignemnt 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::AlignLeft, Wt::AlignCenter, or Wt::AlignRight) and a vertical alignment (Wt::AlignTop, Wt::AlignMiddle, or Wt::AlignBottom).

See also:
addLayout(), insertWidget()
int Wt::WBoxLayout::count ( ) const [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().

Implements Wt::WLayout.

Direction Wt::WBoxLayout::direction ( ) const

Returns the layout direction.

See also:
setDirection()
void Wt::WBoxLayout::insertLayout ( int  index,
WLayout layout,
int  stretch = 0,
WFlags< AlignmentFlag alignment = 0 
)

Inserts a nested layout in the layout.

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

See also:
insertWidget(), addLayout()
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,
WWidget widget,
int  stretch = 0,
WFlags< AlignmentFlag alignment = 0 
)

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). You may use a special stretch factor of -1 to indicate that the widget should not take excess space but the contents height should still be actively managed. This may make sense for example if the widget is layout size aware).

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::AlignLeft, Wt::AlignCenter, or Wt::AlignRight) and a vertical alignment (Wt::AlignTop, Wt::AlignMiddle, or Wt::AlignBottom).

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

Implements Wt::WLayout.

void Wt::WBoxLayout::removeItem ( WLayoutItem item) [virtual]

Removes a layout item (widget or nested layout).

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

Implements Wt::WLayout.

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

Sets the layout direction.

See also:
direction()
void Wt::WBoxLayout::setResizable ( int  index,
bool  enabled = true 
)

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.

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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