/* 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
*/

function ss_fixAllLinks() {
  // 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',smoothScroll);
    }
  }
}

function smoothScroll(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.nodeType == 3) {
    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();
  }
}

function ss_scrollWindow(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;
  }
}

function ss_getCurrentYPos() {
  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;
}

function ss_addEvent(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");
  }
} 

var ss_INTERVAL;
var ss_STEPS = 25;

ss_addEvent(window,"load",ss_fixAllLinks);