function NavigBar(){}

NavigBar.navigator =
function /* navigator */( p, th, mh, wpsize )
{
  var navigBar;
  
  var total_pages = Math.ceil(th/mh);  
  if (total_pages > 1) {
    var pfirst = 0;
    var plast = total_pages - 1;

    var wpfirst;
    var wplast; 
    if ( total_pages > wpsize ) {
      var radio = Math.floor(wpsize/2);

      if ( (wpsize % 2) == 1 ) {
        wpfirst = p - radio;
        wplast = p + radio;
      } else {
        wpfirst = p - radio + 1;
        wplast = p + radio;    
      }

      if ( wpfirst < pfirst)  {
        wplast = wplast + (pfirst - wpfirst);
        wpfirst = pfirst;
      }
      if ( wplast > plast ) {
        wpfirst = wpfirst - (wplast - plast);
        wplast = plast;
      }

    } else {
      wpfirst = pfirst;
      wplast = plast;
    }

    var wprev = null;
    var wnext = null;  
    //if ( wpfirst > pfirst ) wprev = wpfirst-1;
    //if ( wplast < plast ) wnext = wplast+1;
    if ( p > pfirst ) wprev = p-1;
    if ( p < plast ) wnext = p+1;
    
    
    navigBar = {pagesTotal:total_pages, pageFirst:wpfirst, pageLast:wplast, windowPrev:wprev, windowNext:wnext};
    
  } else {
    navigBar = null;
  }
  
  return (navigBar); 
}