====== behavior: history  ======

Implementation of navigational history. 

behavior:history is navigation history manager. All ''<frame>'' elements 


===== Elements =====
that have this behavior applied by default:

    *  ''<frameset history>'' - horizontal slider, inline block;
    *  ''<frame history>'' - horizontal slider, block;

===== Attributes =====
 n/a    

===== Events =====
    *  ''HISTORY_PRIOR'' - the behavior posts this message to itself while handling ALT+LEFT key. If it was not handled by anyone then it restores previous navigational state if any;
    *  ''HISTORY_NEXT'' - the behavior posts this message to itself while handling ALT+RIGHT key. If it was not handled by anyone then it goes to next navigational state if any;
    *  ''HISTORY_STATE_CHANGED'' - notification broadcasted by the behavior when state of history stack has changed.

===== Methods =====

Richtext supports following so called ''xcall()'' methods, see dom::element::xcall() function.

  * ''xcall("goBack"): bool'' - navigates back;
  * ''xcall("goForward"): bool'' - navigates forward;
  * ''xcall("canGoBack"): bool'' - true if there are states to navigate back;
  * ''xcall("canGoForward"): bool'' - true if there are states to navigate forward;