WGridLayout (JWt Javadoc API)

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eu.webtoolkit.jwt
Class WGridLayout

java.lang.Object
  eu.webtoolkit.jwt.WObject
      eu.webtoolkit.jwt.WLayout
          eu.webtoolkit.jwt.WGridLayout

All Implemented Interfaces:: WLayoutItem

public class WGridLayout
extends WLayout
extends WLayout

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#getDecorationStyle()), 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 WLayout#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:

 {
        @code
        WContainerWidget w = new WContainerWidget(this);
        w.resize(WLength.Auto, new WLength(600));
 
        WGridLayout layout = new WGridLayout();
        layout.addWidget(new WText("Item 0 0"), 0, 0);
        layout.addWidget(new WText("Item 0 1"), 0, 1);
        layout.addWidget(new WText("Item 1 0"), 1, 0);
        layout.addWidget(new WText("Item 1 1"), 1, 1);
 
        w.setLayout(layout);
 }

Note: 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 WLayout#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 Summary
`WGridLayout()` Create a new grid layout.
`WGridLayout(WWidget parent)` Create a new grid layout.

Method Summary
`void`	`addItem(WLayoutItem item)` Adds a layout item.
`void`	`addItem(WLayoutItem item, int row, int column)` Adds a layout item to the grid.
`void`	`addItem(WLayoutItem item, int row, int column, int rowSpan)` Adds a layout item to the grid.
`void`	`addItem(WLayoutItem item, int row, int column, int rowSpan, int columnSpan)` Adds a layout item to the grid.
`void`	`addItem(WLayoutItem item, int row, int column, int rowSpan, int columnSpan, AlignmentFlag alignmen, AlignmentFlag... alignment)` Adds a layout item to the grid.
`void`	`addItem(WLayoutItem item, int row, int column, int rowSpan, int columnSpan, java.util.EnumSet<AlignmentFlag> alignment)` Adds a layout item to the grid.
`void`	`addLayout(WLayout layout, int row, int column)` Adds a nested layout item to the grid.
`void`	`addLayout(WLayout layout, int row, int column, AlignmentFlag alignmen, AlignmentFlag... alignment)` Adds a nested layout item to the grid.
`void`	`addLayout(WLayout layout, int row, int column, java.util.EnumSet<AlignmentFlag> alignment)` Adds a nested layout item to the grid.
`void`	`addLayout(WLayout layout, int row, int column, int rowSpan, int columnSpan)` Adds a nested layout item to the grid.
`void`	`addLayout(WLayout layout, int row, int column, int rowSpan, int columnSpan, AlignmentFlag alignmen, AlignmentFlag... alignment)` Adds a nested layout item to the grid.
`void`	`addLayout(WLayout layout, int row, int column, int rowSpan, int columnSpan, java.util.EnumSet<AlignmentFlag> alignment)` Adds a nested layout item to the grid.
`void`	`addWidget(WWidget widget, int row, int column)` Adds a widget to the grid.
`void`	`addWidget(WWidget widget, int row, int column, AlignmentFlag alignmen, AlignmentFlag... alignment)` Adds a widget to the grid.
`void`	`addWidget(WWidget widget, int row, int column, java.util.EnumSet<AlignmentFlag> alignment)` Adds a widget to the grid.
`void`	`addWidget(WWidget widget, int row, int column, int rowSpan, int columnSpan)` Adds a widget to the grid.
`void`	`addWidget(WWidget widget, int row, int column, int rowSpan, int columnSpan, AlignmentFlag alignmen, AlignmentFlag... alignment)` Adds a widget to the grid.
`void`	`addWidget(WWidget widget, int row, int column, int rowSpan, int columnSpan, java.util.EnumSet<AlignmentFlag> alignment)` Adds a widget to the grid.
`void`	`clear()` Removes and deletes all child widgets and nested layouts.
`boolean`	`columnIsResizable(int column)` Returns whether the user may drag a particular column border.
`int`	`getColumnCount()` Returns the column count.
`int`	`getColumnStretch(int column)` Returns the column stretch.
`int`	`getCount()` Returns the number of items in this layout.
`int`	`getHorizontalSpacing()` Returns the horizontal spacing.
`WLayoutItem`	`getItemAt(int index)` Returns the layout item at a specific index.
`int`	`getRowCount()` Returns the row count.
`int`	`getRowStretch(int row)` Returns the column stretch.
`int`	`getVerticalSpacing()` Returns the vertical spacing.
`void`	`removeItem(WLayoutItem item)` Removes a layout item (widget or nested layout).
`boolean`	`rowIsResizable(int row)` Returns whether the user may drag a particular row border.
`void`	`setColumnResizable(int column)` Sets whether the user may drag a particular column border.
`void`	`setColumnResizable(int column, boolean enabled)` Sets whether the user may drag a particular column border.
`void`	`setColumnStretch(int column, int stretch)` Sets the column stretch.
`void`	`setHorizontalSpacing(int size)` Sets the horizontal spacing.
`void`	`setRowResizable(int row)` Sets whether the user may drag a particular row border.
`void`	`setRowResizable(int row, boolean enabled)` Sets whether the user may drag a particular row border.
`void`	`setRowStretch(int row, int stretch)` Sets the row stretch.
`void`	`setVerticalSpacing(int size)` Sets the vertical spacing.

Methods inherited from class eu.webtoolkit.jwt.WLayout
`addWidget, clearLayoutItem, findWidgetItem, getContentsMargin, getImpl, getLayout, getParentLayout, getWidget, indexOf, removeWidget, setContentsMargins, setLayoutHint, setLayoutInParent, setParentLayout, setParentWidget, update, update, updateAddItem, updateRemoveItem`

Methods inherited from class eu.webtoolkit.jwt.WObject
`addChild, getId, getObjectName, remove, setObjectName, tr`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

WGridLayout

public WGridLayout(WWidget parent)

Create a new grid layout.

The grid will grow dynamically as items are added.

Use parent = null 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.

WGridLayout

public WGridLayout()

Create a new grid layout.

Calls this((WWidget)null)

Method Detail

addItem

public void addItem(WLayoutItem item)

Description copied from class: WLayout

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.

Specified by:: addItem in class WLayout

See Also:: WLayout.removeItem(WLayoutItem item), WLayout.addWidget(WWidget w)

removeItem

public void removeItem(WLayoutItem item)

Description copied from class: WLayout

Removes a layout item (widget or nested layout).

Specified by:: removeItem in class WLayout

See Also:: WLayout.addItem(WLayoutItem item), WLayout.removeWidget(WWidget w)

getItemAt

public WLayoutItem getItemAt(int index)

Description copied from class: WLayout

Returns the layout item at a specific index.

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

Specified by:: getItemAt in class WLayout

See Also:: WLayout.indexOf(WLayoutItem item), WLayout.getCount()

getCount

public int getCount()

Description copied from class: WLayout

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 getItemAt().

Specified by:: getCount in class WLayout

clear

public void clear()

Description copied from class: WLayout

Removes and deletes all child widgets and nested layouts.

This is similar to WContainerWidget#clear(), with the exception that the layout itself is not deleted.

Specified by:: clear in class WLayout

addItem

public void addItem(WLayoutItem item,
                    int row,
                    int column,
                    int rowSpan,
                    int columnSpan,
                    java.util.EnumSet<AlignmentFlag> alignment)

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

See Also:: addLayout(WLayout layout, int row, int column, EnumSet alignment), addWidget(WWidget widget, int row, int column, EnumSet alignment)

addItem

public final void addItem(WLayoutItem item,
                          int row,
                          int column,
                          int rowSpan,
                          int columnSpan,
                          AlignmentFlag alignmen,
                          AlignmentFlag... alignment)

Adds a layout item to the grid.

Calls addItem(item, row, column, rowSpan, columnSpan, EnumSet.of(alignmen, alignment))

addItem

public final void addItem(WLayoutItem item,
                          int row,
                          int column)

Adds a layout item to the grid.

Calls addItem(item, row, column, 1, 1, EnumSet.noneOf(AlignmentFlag.class))

addItem

public final void addItem(WLayoutItem item,
                          int row,
                          int column,
                          int rowSpan)

Adds a layout item to the grid.

Calls addItem(item, row, column, rowSpan, 1, EnumSet.noneOf(AlignmentFlag.class))

addItem

public final void addItem(WLayoutItem item,
                          int row,
                          int column,
                          int rowSpan,
                          int columnSpan)

Adds a layout item to the grid.

Calls addItem(item, row, column, rowSpan, columnSpan, EnumSet.noneOf(AlignmentFlag.class))