A widget that implements this interface can receive keyboard focus.

abstract class Focusable {

 /**
  * Gets the widget's position in the tab index.
  * 
  * @return the widget's tab index
  */
 int get tabIndex;

 /**
  * Sets the widget's 'access key'. This key is used (in conjunction with a
  * browser-specific modifier key) to automatically focus the widget.
  * 
  * @param key the widget's access key
  */
 void set accessKey(int key);

 /**
  * Explicitly focus/unfocus this widget. Only one widget can have focus at a
  * time, and the widget that does will receive all keyboard events.
  * 
  * @param focused whether this widget should take focus or release it
  */
 void set focus(bool focused);

 /**
  * Sets the widget's position in the tab index. If more than one widget has
  * the same tab index, each such widget will receive focus in an arbitrary
  * order. Setting the tab index to <code>-1</code> will cause this widget to
  * be removed from the tab order.
  * 
  * @param index the widget's tab index
  */
 void set tabIndex(int index);
}