var xmlHttp
var basePath = "http://www.artgalleryaustralia.com.au/";
var url=basePath+"slides.php";
var pid = 0;
var slideHistory = new Array();

function startSlideShow() {
	nextSlide();
	pid = setInterval("nextSlide()", 7000);	
}
function stopSlideShow() {
	clearInterval(pid);
}
function nextSlide() {	
	arr = slideHistory.push(document.getElementById("slideId").value);
	xmlHttp=GetXmlHttpObject();
	if (xmlHttp==null) {
	  	return;
	} 

	document.getElementById("slides").innerHTML = document.getElementById("slideCache").innerHTML;
	xmlHttp.onreadystatechange=stateChanged;
	xmlHttp.open("GET",url,true);    
	xmlHttp.send(null);

} 
function prevSlide() {
    xmlHttp=GetXmlHttpObject();
    if (xmlHttp==null) {
	    return;
    } 
    slideId = slideHistory.pop();
    if (slideId == null) {
      alert("Already at first artwork.");
      return;
    }
    prevUrl = url+"?slideid="+slideId;
    xmlHttp.onreadystatechange=stateChangedPrev;
    xmlHttp.open("GET",prevUrl,true);    
    xmlHttp.send(null);
}
function stateChanged() { 
	if (xmlHttp.readyState==4) { 
	    document.getElementById("slideCache").innerHTML= xmlHttp.responseText;
	}
}
function stateChangedPrev() { 
	if (xmlHttp.readyState==4) { 
	    document.getElementById("slides").innerHTML= xmlHttp.responseText;
	}
}

function GetXmlHttpObject() {
	var xmlHttp=null;
	try {
	  // Firefox, Opera 8.0+, Safari
	  xmlHttp=new XMLHttpRequest();
	}
	catch (e) {
		// Internet Explorer
  		try {
  		  	xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  		}
  		catch (e) {
    		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  		}
	}
	return xmlHttp;
}