Fossil

**    in order to be able to construct /file URLs, the information provided by
**    the timeline-data-N blocks would have to be extended).
**  o kFRST, kLAST: check if the previous/next page should be opened if focus is
**    already at the top/bottom.
*/
(function(){
  window.addEventListener('load',function(){
// "Primary" (1) and "secondary" (2) selections swapped compared to CSS classes:
// (1)  .timelineSecondary →
//          /vdiff?to=, /timeline?sel2=
// (2)  .timelineSelected:not(.timelineSecondary) →
//          /vdiff?from=, /timeline?c=, /timeline?sel1=
    function focusDefaultId(){
      var tn = document.querySelector('.timelineSecondary .tl-nodemark')
                || document.querySelector(
                    '.timelineSelected:not(.timelineSecondary) .tl-nodemark')

                || document.querySelector('.timelineCurrent .tl-nodemark');
      return tn ? tn.id : 'm1';
    }
    function focusSelectedId(){
      var tn = document.querySelector('.timelineSecondary .tl-nodemark');

      return tn ? tn.id : null;
    }
    function focus2ndSelectedId(){
      var tn = document.querySelector(
                '.timelineSelected:not(.timelineSecondary) .tl-nodemark');
      return tn ? tn.id : null;
    }
    function focusCurrentId(){
      var tn = document.querySelector('.timelineCurrent .tl-nodemark');
      return tn ? tn.id : null;
    }
    function focusTickedId(){