function Viewer(divElement) {
	this.divElem = divElement;
	this.height = 254;	
	var scrollSpeed = 6;
	
	this.isScrollable = isScrollable;
	this.getContentOverflow = getContentOverflow;
	this.changePosition = changePosition;
	this.getId = getId;
	
	if(this.isScrollable()) {				
		this.maxPosition = this.divElem.offsetTop;
		this.minPosition = this.maxPosition - this.getContentOverflow();	
		this.currentPosition = this.maxPosition;				
		this.clipTop = 0;
		this.clipBottom = this.height;	
	}	
}
	
	
function getId() {
	if(this.id == null) {
		var id = this.divElem.getAttribute("id");
		this.id = id.substr("content".length);
	}
	return this.id;
}

function getContentOverflow() {
	if(this.contentOverflow == null) {
		this.contentOverflow = this.divElem.offsetHeight - this.height;
	}
	return this.contentOverflow;
}

function isScrollable() {
	return this.getContentOverflow() > 0;
}

function changePosition(amount) {
	this.currentPosition += amount;	
	this.divElem.style.top = this.currentPosition;	
}