Interface for creating and manipulating focusable elements that aren't naturally focusable in all browsers, such as DIVs.

abstract class FocusImpl {

 /**
  * Remove focus from [Element].
  */
 void blur(dart_html.Element elem);

 /**
  * Create focusable element.
  */
 dart_html.Element createFocusable();

 /**
  * Set focus on [Element].
  */
 void focus(dart_html.Element elem);

 /**
  * Return [Element] tab index.
  */
 int getTabIndex(dart_html.Element elem);

 /**
  * Set [Element] tab [index].
  */
 void setTabIndex(dart_html.Element elem, int index);

 /**
  * Set Access Key for keyboard navigation.
  */
 void setAccessKey(dart_html.Element elem, int key);

 /**
  * Static instance of FocusImpl.
  */
 static FocusImpl implPanel;

 /**
  * This instance may not be a {@link FocusImplStandard}, because that special
  * case is only needed for things that aren't naturally focusable on some
  * browsers, such as DIVs. This exact class works for truly focusable widgets
  * on those browsers.
  *
  * The compiler will optimize out the conditional.
  */
 static FocusImpl implWidget;

 /**
  * Return instance of [FocusImpl] depends on broswer.
  */
 static FocusImpl getFocusImplForPanel() {
   if (implPanel == null) {
     implPanel = new FocusImplDefault();
   }
   return implPanel;
 }

 /**
  * Returns the focus implementation class for manipulating focusable elements
  * that are naturally focusable in all browsers, such as text boxes.
  */
 static FocusImpl getFocusImplForWidget() {
   if (implWidget == null) {
     implWidget = new FocusImplDefault(); //(implPanel is FocusImplStandard) ? new FocusImpl() : implPanel;
   }
   return implWidget;
 }
}