Implemented by panels that impose an explicit ordering on their children.

@see InsertPanel

abstract class IndexedPanel {

 /**
  * Gets the child widget at the specified index.
  *
  * @param index the child widget's index
  * @return the child widget
  */
 Widget getWidgetAt(int index);

 /**
  * Gets the number of child widgets in this panel.
  *
  * @return the number of children
  */
 int getWidgetCount();

 /**
  * Gets the index of the specified child widget.
  *
  * @param child the widget to be found
  * @return the widget's index, or <code>-1</code> if it is not a child of this
  *         panel
  */
 int getWidgetIndex(Widget child);

 /**
  * Removes the widget at the specified index.
  *
  * @param index the index of the widget to be removed
  * @return <code>false</code> if the widget is not present
  */
 bool removeAt(int index);
}