Public Member Functions

Wt::WGridLayout Class Reference

A layout manager which arranges widgets in a grid. More...

#include <Wt/WGridLayout>

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

List of all members.

Public Member Functions

 WGridLayout (WWidget *parent=0)
 Create a new grid 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 addItem (WLayoutItem *item, int row, int column, int rowSpan=1, int columnSpan=1, WFlags< AlignmentFlag > alignment=0)
 Adds a layout item to the grid.
void addLayout (WLayout *layout, int row, int column, WFlags< AlignmentFlag > alignment=0)
 Adds a nested layout item to the grid.
void addLayout (WLayout *layout, int row, int column, int rowSpan, int columnSpan, WFlags< AlignmentFlag > alignment=0)
 Adds a nested layout item to the grid.
void addWidget (WWidget *widget, int row, int column, WFlags< AlignmentFlag > alignment=0)
 Adds a widget to the grid.
void addWidget (WWidget *widget, int row, int column, int rowSpan, int columnSpan, WFlags< AlignmentFlag > alignment=0)
 Adds a widget to the grid.
void setHorizontalSpacing (int size)
 Sets the horizontal spacing.
int horizontalSpacing () const
 Returns the horizontal spacing.
void setVerticalSpacing (int size)
 Sets the vertical spacing.
int verticalSpacing () const
 Returns the vertical spacing.
int columnCount () const
 Returns the column count.
int rowCount () const
 Returns the row count.
void setColumnStretch (int column, int stretch)
 Sets the column stretch.
int columnStretch (int column) const
 Returns the column stretch.
void setRowStretch (int row, int stretch)
 Sets the row stretch.
int rowStretch (int row) const
 Returns the column stretch.
void setColumnResizable (int column, bool enabled=true)
 Sets whether the user may drag a particular column border.
bool columnIsResizable (int column) const
 Returns whether the user may drag a particular column border.
void setRowResizable (int row, bool enabled=true)
 Sets whether the user may drag a particular row border.
bool rowIsResizable (int row) const
 Returns whether the user may drag a particular row border.

Detailed Description

A layout manager which arranges widgets in a grid.

This is a layout class that arranges widgets in a grid, to span the entire area of the parent container. Each grid location (row, column) may contain one widget or nested layout. Horizontal and vertical space are divided so that each column/row is given its minimum size and the remaining space is dived according to stretch factors among the columns/rows. The minimum width of a column/row is based on the minimum dimensions of contained widgets or nested layouts. The default minimum height and width 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 columns or rows which allow the user to change the automatic layout provided by the layout manager (see setRowResizable() and setColumnResizable()). Resize handles between rows only work when the layout fills the parent vertical space (i.e. is not aligned to the top). Likewise, resize handles between columns only work when the layout fills the parent horiziontal space (i.e. is not aligned left, right or centered).

Columns and rows are separated using a constant spacing, which defaults to 6 pixels by default, and can be changed using setHorizontalSpacing() and setVerticalSpacing(). 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. It is not allowed to define padding for the container widget using its CSS 'padding' property or the WContainerWidget::setPadding(). This margin also defaults to 9 pixels, and can be changed using setContentsMargins().

For each column or row, a stretch factor may be defined, which controls how remaining horizontal or vertical space is used. Each column and row is stretched using the stretch factor to fill the remaining space. When the stretch factor is 0, the height of the row and its contents is not actively managed. As a consequence, the contents of each cell will not fill the cell. You may use a special stretch factor of -1 to indicate that the height of the row should not stretch but the contents height should be actively managed. This has as draw-back that the height of the row will no longer reduce in size when any of the cell contents reduces in size.

Usage example:

 Wt::WContainerWidget *w = new Wt::WContainerWidget(this);
 w->resize(WLength::Auto, 600);

 Wt::WGridLayout *layout = new Wt::WGridLayout();
 layout->addWidget(new Wt::WText("Item 0 0"), 0, 0);
 layout->addWidget(new Wt::WText("Item 0 1"), 0, 1);
 layout->addWidget(new Wt::WText("Item 1 0"), 1, 0);
 layout->addWidget(new Wt::WText("Item 1 1"), 1, 1);

 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 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.

Constructor & Destructor Documentation

Wt::WGridLayout::WGridLayout ( WWidget parent = 0 )

Create a new grid layout.

The grid will grow dynamically as items are added.

Use parent = 0 to create a layout manager that can be nested inside other layout managers or to specify a specific alignment when setting the layout to a WContainerWidget.


Member Function Documentation

void Wt::WGridLayout::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::WGridLayout::addItem ( WLayoutItem item,
int  row,
int  column,
int  rowSpan = 1,
int  columnSpan = 1,
WFlags< AlignmentFlag alignment = 0 
)

Adds a layout item to the grid.

Adds the item at (row, column). If an item was already added to that location, it is replaced (but not deleted).

An item may span several more rows or columns, which is controlled by rowSpan and columnSpan.

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 grid cell. 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(), addWidget()
void Wt::WGridLayout::addLayout ( WLayout layout,
int  row,
int  column,
WFlags< AlignmentFlag alignment = 0 
)

Adds a nested layout item to the grid.

Adds the layout at (row, column). If an item was already added to that location, it is replaced (but not deleted).

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 grid cell. 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(WLayout *, int, int, int, int, WFlags<AlignmentFlag>)
void Wt::WGridLayout::addLayout ( WLayout layout,
int  row,
int  column,
int  rowSpan,
int  columnSpan,
WFlags< AlignmentFlag alignment = 0 
)

Adds a nested layout item to the grid.

Adds the layout at (row, column). If an item was already added to that location, it is replaced (but not deleted).

An item may span several more rows or columns, which is controlled by rowSpan and columnSpan.

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 grid cell. 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(WLayout *, int, int, WFlags<AlignmentFlag>)
void Wt::WGridLayout::addWidget ( WWidget widget,
int  row,
int  column,
WFlags< AlignmentFlag alignment = 0 
)

Adds a widget to the grid.

Adds the widget at (row, column). If an item was already added to that location, it is replaced (but not deleted).

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 grid cell. 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:
addWidget(WWidget *, int, int, int, int, WFlags<AlignmentFlag>)
void Wt::WGridLayout::addWidget ( WWidget widget,
int  row,
int  column,
int  rowSpan,
int  columnSpan,
WFlags< AlignmentFlag alignment = 0 
)

Adds a widget to the grid.

Adds the widget at (row, column). If an item was already added to that location, it is replaced (but not deleted).

The widget may span several more rows or columns, which is controlled by rowSpan and columnSpan.

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 grid cell. 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:
addWidget(WWidget *, int, int, WFlags<AlignmentFlag>)
int Wt::WGridLayout::columnCount (  ) const

Returns the column count.

The grid dimensions change dynamically when adding contents to the grid.

See also:
rowCount()
bool Wt::WGridLayout::columnIsResizable ( int  column ) const

Returns whether the user may drag a particular column border.

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

See also:
setColumnResizable()
int Wt::WGridLayout::columnStretch ( int  column ) const

Returns the column stretch.

See also:
setColumnStretch(int, int)
int Wt::WGridLayout::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.

int Wt::WGridLayout::horizontalSpacing (  ) const

Returns the horizontal spacing.

See also:
setHorizontalSpacing(int)
WLayoutItem * Wt::WGridLayout::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::WGridLayout::removeItem ( WLayoutItem item ) [virtual]

Removes a layout item (widget or nested layout).

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

Implements Wt::WLayout.

int Wt::WGridLayout::rowCount (  ) const

Returns the row count.

The grid dimensions change dynamically when adding contents to the grid.

See also:
columnCount()
bool Wt::WGridLayout::rowIsResizable ( int  row ) const

Returns whether the user may drag a particular row border.

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

See also:
setRowResizable()
int Wt::WGridLayout::rowStretch ( int  row ) const

Returns the column stretch.

See also:
setRowStretch(int, int)
void Wt::WGridLayout::setColumnResizable ( int  column,
bool  enabled = true 
)

Sets whether the user may drag a particular column border.

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

The default value is false.

void Wt::WGridLayout::setColumnStretch ( int  column,
int  stretch 
)

Sets the column stretch.

Sets the stretch factor for column column.

See also:
columnStretch()
void Wt::WGridLayout::setHorizontalSpacing ( int  size )

Sets the horizontal spacing.

The default horizontal spacing is 9 pixels.

See also:
setVerticalSpacing(int)
void Wt::WGridLayout::setRowResizable ( int  row,
bool  enabled = true 
)

Sets whether the user may drag a particular row border.

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

The default value is false.

void Wt::WGridLayout::setRowStretch ( int  row,
int  stretch 
)

Sets the row stretch.

Sets the stretch factor for row row. See the description for the special value of -1.

See also:
rowStretch()
void Wt::WGridLayout::setVerticalSpacing ( int  size )

Sets the vertical spacing.

The default vertical spacing is 9 pixels.

See also:
setHorizontalSpacing(int)
int Wt::WGridLayout::verticalSpacing (  ) const

Returns the vertical spacing.

See also:
setVerticalSpacing(int)
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