Base class for objects that can get the focus.
The focus is used to designate an element that will receive keyboard events.
|canGrabFocus||Return true if the element can be focused.|
|delegatesFocus||Whether the element should delegate the focus to its children.|
|focusable||True if the element can be focused.|
|focusController||Return the focus controller for this element.|
|tabIndex||An integer used to sort focusables in the focus ring. Must be greater than or equal to zero.|
|Blur||Tell the element to release the focus.|
|Focus||Attempt to give the focus to this element.|
|HandleEvent||Handle an event, most often by executing the callbacks associated with the event.|
|HasBubbleUpHandlers||Return true if event handlers for the event propagation BubbleUp phase have been attached on this object.|
|HasTrickleDownHandlers||Returns true if event handlers, for the event propagation TrickleDown phase, are attached to this object.|
|RegisterCallback||Adds an event handler to the instance. If the event handler has already been registered for the same phase (either TrickleDown or BubbleUp) then this method has no effect.|
|SendEvent||Sends an event to the event handler.|
|UnregisterCallback||Remove callback from the instance.|