var imageCache = [];
var imageIndex = 0;

$observe(window, 'load', function(){

	imageCache.push($('screenshot1'));
	
	// first screenshot already loaded.
	
	for(var i = 2; i < 6; ++i)
	{
		loadImage('screenshots/screenshot' + i + '.png');
	}
});

function loadImage(url)
{
	var img = new Image();
	
	img.onload = function(){
		imageCache.push(this);
		this.onload = $empty;
	};

	// load it...
	img.src = url;
}

function nextImage(){
	if (++imageIndex >= imageCache.length) imageIndex = 0;
	setImage(imageIndex);
};


function prevImage(){
	if (--imageIndex < 0) imageIndex = imageCache.length - 1;
	setImage(imageIndex);
};

function setImage(index)
{
	var parent = $('screenshot');
	var img = imageCache[imageIndex];
	if (!img) return;
	
	if (img.className == '')
	{
		// naturalHeight not valid in IE.
		img.className = 'image' + img.height;
	}
		
	$Element.removeChildren(parent);
	parent.appendChild(img);
}