if (document.getElementById) {
	window.onload = initialize
}
function initialize() {
	var divs = document.getElementsByTagName("div")
	for (var i = 0; i < divs.length; i++) {
		if (divs[i].className == "screen") {
			setScreenHeight(divs[i])
		}
		else if (divs[i].className == "body") {
			divs[i].style.top = ((getSlideHeight() - divs[i].offsetHeight)/2 - 45) + "px"
		}
		else if (divs[i].className == "footer") {
			insertFooterControls(divs[i])
		}
	}
	document.onkeydown = captureKeystroke
}

function setScreenHeight(screen) {
	screen.style.height = getScreenHeight() + "px"
	screen.style.paddingTop = getScreenPaddingTop() + "px"
}

function getScreenHeight() {
	if (typeof(screenHeight) == "undefined") {
		if (window.innerHeight) { // Standards-compliant Browsers
			screenHeight = window.innerHeight;
		}
		else if (document.documentElement.clientHeight) { // IE 6 in standards mode
			screenHeight = document.documentElement.clientHeight;
		}
		else if (document.body.clientHeight ) { // IE 5
			screenHeight = document.body.clientHeight;
		}
		else {
			screenHeight = 0;
		}
		if (screenHeight < getSlideHeight()) { screenHeight = getSlideHeight() }
	}
	return screenHeight
}

function getScreenPaddingTop() {
	if (typeof(screenPaddingTop) == "undefined") {
		screenPaddingTop = Math.round((getScreenHeight() - getSlideHeight())/2)
		if (screenPaddingTop < 0) { screenPaddingTop = 0 }
	}
	return screenPaddingTop
}

function getSlideHeight() {
	if (typeof(slideHeight) == "undefined") {
		var divs = document.getElementsByTagName("div")
		for (var i = 0; i < divs.length; i++) {
			if (divs[i].className == "slide") {
				if (window.innerHeight) { // Standards-compliant Browsers
					slideHeight = divs[i].offsetHeight;
				}
				else if (document.documentElement.clientHeight) { // IE 6 in standards mode
					slideHeight = divs[i].offsetHeight;
				}
				else if (document.body.clientHeight ) { // IE 5
					slideHeight = divs[i].offsetHeight + 4;
				}
				else {
					slideHeight = 0;
				}
				break;
			}
		}
	}
	return slideHeight
}

function insertFooterControls(footer) {
	var footerID = "" + footer.id
	if (footerID != "first") {
		backImg = document.createElement("img")
		backImg.src = "images/back.gif"
		backImg.alt = "Back"
		backImg.title = ""
		backImg.className = "control"
		backImg.onclick = back
		footer.appendChild(backImg)
	}
	if (footerID == "") {
		barImg = document.createElement("img")
		barImg.src = "images/bar.gif"
		barImg.alt = "|"
		barImg.title=""
		footer.appendChild(barImg)
	}
	if (footerID != "last") {
		nextImg = document.createElement("img")
		nextImg.src = "images/next.gif"
		nextImg.alt = "Next"
		nextImg.title = ""
		nextImg.className = "control"
		nextImg.onclick = next
		footer.appendChild(nextImg)
	}
}

function back() {
	currentNode = this
	while (currentNode.className != "screen") { currentNode = currentNode.parentNode; }
	do { currentNode = currentNode.previousSibling; } while (currentNode.className != "screen")
	document.location = "#" + currentNode.id;
}

function next() {
	currentNode = this
	while (currentNode.className != "screen") { currentNode = currentNode.parentNode; }
	do { currentNode = currentNode.nextSibling; } while (currentNode.className != "screen")
	document.location = "#" + currentNode.id;
}

function captureKeystroke(event) {
	if (document.all) { // Internet Explorer
		event = window.event;
		switch (event.keyCode) {
		case 33 : // PageUp
			event.returnValue = false;
			window.scrollBy(0, -getScrollByHeight());
			break;
		case 34 : // PageDown
			event.returnValue = false;
			window.scrollBy(0, getScrollByHeight());
			break;
		default :
			// alert(window.event.keyCode);
		}
	}
}

function getScrollByHeight() {
	if (typeof(scrollByHeight) == "undefined") {
		if (window.innerHeight) { // Standards-compliant Browsers
			// not working here yet...
		}
		else if (document.documentElement.clientHeight) { // IE 6 in standards mode
			scrollByHeight = getScreenHeight() + getScreenPaddingTop()

		}
		else if (document.body.clientHeight ) { // IE 5
			scrollByHeight = getScreenHeight()
		}
		else {
			scrollByHeight = 0;
		}
	}
	return scrollByHeight
}