/* smooth scrolling
   changes links that link to other parts of this page to scroll
   smoothly to those links rather than jump to them directly, which
   can be a little disorienting.
   
   sil, http://www.kryogenix.org/
   
   v1.0 2003-11-11
   v1.1 2005-06-16 wrap it up in an object
*/

var ss = {
  fixalllinks: function() {
    // get a list of all links in the page
    var alllinks = document.getelementsbytagname('a');
    // walk through the list
    for (var i=0;i<alllinks.length;i++) {
      var lnk = alllinks[i];
      if ((lnk.href && lnk.href.indexof('#') != -1) && 
          ( (lnk.pathname == location.pathname) ||
	    ('/'+lnk.pathname == location.pathname) ) && 
          (lnk.search == location.search)) {
        // if the link is internal to the page (begins in #)
        // then attach the smoothscroll function as an onclick
        // event handler
        ss.addevent(lnk,'click',ss.smoothscroll);
      }
    }
  },

  smoothscroll: function(e) {
    // this is an event handler; get the clicked on element,
    // in a cross-browser fashion
    if (window.event) {
      target = window.event.srcelement;
    } else if (e) {
      target = e.target;
    } else return;

    // make sure that the target is an element, not a text node
    // within an element
    if (target.nodename.tolowercase() != 'a') {
      target = target.parentnode;
    }
  
    // paranoia; check this is an a tag
    if (target.nodename.tolowercase() != 'a') return;
  
    // find the <a name> tag corresponding to this href
    // first strip off the hash (first character)
    anchor = target.hash.substr(1);
    // now loop all a tags until we find one with that name
    var alllinks = document.getelementsbytagname('a');
    var destinationlink = null;
    for (var i=0;i<alllinks.length;i++) {
      var lnk = alllinks[i];
      if (lnk.name && (lnk.name == anchor)) {
        destinationlink = lnk;
        break;
      }
    }
  
    // if we didn't find a destination, give up and let the browser do
    // its thing
    if (!destinationlink) return true;
  
    // find the destination's position
    var destx = destinationlink.offsetleft; 
    var desty = destinationlink.offsettop;
    var thisnode = destinationlink;
    while (thisnode.offsetparent && 
          (thisnode.offsetparent != document.body)) {
      thisnode = thisnode.offsetparent;
      destx += thisnode.offsetleft;
      desty += thisnode.offsettop;
    }
  
    // stop any current scrolling
    clearinterval(ss.interval);
  
    cypos = ss.getcurrentypos();
  
    ss_stepsize = parseint((desty-cypos)/ss.steps);
    ss.interval =
setinterval('ss.scrollwindow('+ss_stepsize+','+desty+',"'+anchor+'")',10);
  
    // and stop the actual click happening
    if (window.event) {
      window.event.cancelbubble = true;
      window.event.returnvalue = false;
    }
    if (e && e.preventdefault && e.stoppropagation) {
      e.preventdefault();
      e.stoppropagation();
    }
  },

  scrollwindow: function(scramount,dest,anchor) {
    wascypos = ss.getcurrentypos();
    isabove = (wascypos < dest);
    window.scrollto(0,wascypos + scramount);
    iscypos = ss.getcurrentypos();
    isabovenow = (iscypos < dest);
    if ((isabove != isabovenow) || (wascypos == iscypos)) {
      // if we've just scrolled past the destination, or
      // we haven't moved from the last scroll (i.e., we're at the
      // bottom of the page) then scroll exactly to the link
      window.scrollto(0,dest);
      // cancel the repeating timer
      clearinterval(ss.interval);
      // and jump to the link directly so the url's right
      location.hash = anchor;
    }
  },

  getcurrentypos: function() {
    if (document.body && document.body.scrolltop)
      return document.body.scrolltop;
    if (document.documentelement && document.documentelement.scrolltop)
      return document.documentelement.scrolltop;
    if (window.pageyoffset)
      return window.pageyoffset;
    return 0;
  },

  addevent: function(elm, evtype, fn, usecapture) {
    // addevent and removeevent
    // cross-browser event handling for ie5+,  ns6 and mozilla
    // by scott andrew
    if (elm.addeventlistener){
      elm.addeventlistener(evtype, fn, usecapture);
      return true;
    } else if (elm.attachevent){
      var r = elm.attachevent("on"+evtype, fn);
      return r;
    } else {
      alert("handler could not be removed");
    }
  } 
}

ss.steps = 50;

ss.addevent(window,"load",ss.fixalllinks);