// JavaScript Document for rollover images on WebDuck University
//function to preload the images for rollover affects.
function preloadImage(url){
	var i = new Image();
	i.src = url;
	return i;
}
//assign variables to the preloaded images
if (document.images){
	var purchaseOn = preloadImage(siteRoot+"/images/buttons/purchase_btn_on.jpg");
	var purchaseOff = preloadImage(siteRoot+"/images/buttons/purchase_btn.jpg");
	var tabOn = preloadImage(siteRoot+"/images/tabs/orange_tab_on.png");
	var blueTab = preloadImage(siteRoot+"/images/tabs/blue_tab.png");
	var leftOver = preloadImage(siteRoot+"/images/left-nav/rollover-bg.jpg");
	var leftOff = preloadImage(siteRoot+"/images/left-nav/bg-repeat.jpg");
}
//mouse over image swap
function mouseOn(imgName){
	if(document.images)
		document[imgName].src=eval(imgName + "On.src");
}
//mouse off image restore
function mouseOff(imgName){
	if(document.images)
		document[imgName].src=eval(imgName + "Off.src");
}
//mouse over tab background change
function tabOver(tab){
	if(document.getElementById('tab_'+tab)){
		if(tab != chosenTab){
			document.getElementById('tab_'+tab).style.background = 'url("'+siteRoot+'/images/tabs/orange_tab_on.png") top left no-repeat';
		}
	}
}
//mouse out tab background change 
function tabOut(tab){
	if(document.getElementById('tab_'+tab)){
		if(tab != chosenTab){
			document.getElementById('tab_'+tab).style.background = 'url("'+siteRoot+'/images/tabs/orange_tab.png") top left no-repeat';
		}
	}
}
//click a tab background image change and zindex adjustment
function tabClick(tab){
	document.getElementById('tab_'+chosenTab).style.background = 'url("'+siteRoot+'/images/tabs/orange_tab.png") top left no-repeat';
		document.getElementById('tab_'+chosenTab).style.borderBottom = 'solid 1px #000000';
		document.getElementById('tab_'+chosenTab).style.zIndex = chosenTab;
	if(document.getElementById('tab_'+tab)){
		document.getElementById('tab_'+tab).style.background = 'url("'+siteRoot+'/images/tabs/blue_tab.png") top left no-repeat';
		document.getElementById('tab_'+tab).style.borderBottom = 'solid 1px #000066';
		document.getElementById('tab_'+tab).style.zIndex = tab+2;
		chosenTab = tab;
	}
}
//left navigation selection
function subjectClick(subject){
	if(document.getElementById('leftNav_'+subject)){
		if(document.getElementById('leftNavChoice_'+subject).style.display == 'block'){
			document.getElementById('leftNav_'+subject).style.background = 'url("'+siteRoot+'/images/left-nav/bg-repeat.jpg") repeat-y';
			document.getElementById('leftNavChoice_'+subject).style.display = 'none';
		}else{
			document.getElementById('leftNav_'+subject).style.background = 'url("'+siteRoot+'/images/left-nav/rollover-bg.jpg") repeat-y';
			document.getElementById('leftNavChoice_'+subject).style.display = 'block';
		}
	}
}