// declarations
var baseUrl 	= "";
var filenames 	= null;
var counter 	= 0;

function previous() {
	go(-1);
}
function next() {
	go(1);
}
function go(step) {
   // declarations
   var filename = "";
   
   // modify step
   counter += step;
   if (counter < 0) {
      counter = filenames.length-1;
   } else if (counter > filenames.length-1) {
      counter = 0;
   }
   
   // compose url
   filename = baseUrl + filenames[counter];
   
   // get image division
   var d = document.getElementById("slideshow_image");
   d.innerHTML = "<center><img src=\"" + filename + "\" /></center>";
}
function startSlideshow(base_url, picture_filenames) {
	// store base url
	baseUrl = base_url;
	if (base_url.substr(base_url.length) != "/") {
		baseUrl += "/";
	}
	
	// make baseUrl absolute
	if (baseUrl.match(/^(http|https|file):\/\/.*/)) {
		// url is absolute
		baseUrl = baseUrl;
	} else {
		// add hostname to url
		baseUrl = "http://" + document.location.host + baseUrl;
	}
	
	// convert filenames to array
	filenames = picture_filenames.split("$");
	
	// go to first picture
	go(0);
}
function showSlideshow(doc_url, picture_filenames, headline, summary) {
	// show popup
	window.open("../Slideshow?ReadForm&url=" + doc_url + "&filenames=" + picture_filenames + "&headline=" + headline + "&summary=" + summary, "hg_slideshow", "width=425,height=575");
	
	// return
	return false;
}