var currentslide = 0;
var slides = new Array();
var numslides = 14;
var popup = null;

function slidePopup() {
  var url = "./slideshow/index.html";
  var name = "_slideshow";
  var position = "";
  var width = null;
  var height = null;
  var x = null;
  var y = null;
  var w = window;

  width = w.innerWidth 
       || (w.document.documentElement.clientWidth || w.document.body.clientWidth);
  height = w.innerHeight 
       || (w.document.documentElement.clientHeight || w.document.body.clientHeight);

  x = w.screenLeft || w.screenX;
  y = w.screenTop || w.screenY;

  if (width!=null && height!=null) {
    var top = Math.floor((height - 525)/2) + y;
    var left = Math.floor((width - 640)/2) + x;
    position = ", top="+top+"px, left="+left+"px";
  }
  
  var features = "width=640px, height=525px" + position;
  if (popup==null || popup.closed) {
    popup = w.open(url, name, features);
  }
  popup.focus();
  return false;
}
function slideClose() {
  window.close();
}
function slidePreload() {
  for (i=0; i<numslides; i++) {
    slides[i] = new Image();
    slides[i].src = 'slide_'+i+'.jpg';
  }
}
function slidePrev() {
  currentslide--;
  if (currentslide<0) {
    currentslide = numslides-1;
  }
  currentslide = (currentslide % numslides);
  slideShow();
}
function slideNext() {
  currentslide++;
  currentslide = (currentslide % numslides);
  slideShow();
}
function slideShow() {
  var element = document.getElementById('slides');
  element.src = slides[currentslide].src;

  var prev = document.getElementById('prev');
  var next = document.getElementById('next');

  if (currentslide==0) {
    prev.style.display = 'none';
  } else if (currentslide==numslides-1) {
    next.style.display = 'none';
  } else {
    prev.style.display = 'block';
    next.style.display = 'block';
  }
}