/*

Constructor Ticker(name, id, shiftBy, interval)

Methods
=======
Ticker.start(): starts the animation of the ticker
Ticker.stop(): stops the animation of the ticker
Ticker.changeInterval(newinterval): changes the shifting interval to newinterval

Properties
==========
Ticker.name: name of global variable containing reference to the ticker object
Ticker.id: id of the DIV containing the Ticker data
Ticker.shiftBy: Number of pixels to shift the Ticker each time it fires.
Ticker.interval: Number of millisecond intervals between times Ticker fires
Ticker.runId: Value returned from setTimeout or null if the Ticker is not running
Ticker.div: Reference to DIV containing the Ticker data
  
*/

function Ticker(name, id, shiftBy, interval) {
	this.name	= name;
	this.id		= id;
	this.shiftBy	= shiftBy ? shiftBy : 1;
	this.interval	= interval ? interval : 100;
	this.runId	= null;

	this.div = document.getElementById(id);

	// remove extra textnodes that may separate the child nodes
	// of the ticker div

	var node = this.div.firstChild;
	var next;

	while (node) {
		next = node.nextSibling;
		if (node.nodeType == 3)
			this.div.removeChild(node);
		node = next;
	}

	//end of extra textnodes removal
	this.left = 0;
	this.shiftLeftAt = this.div.firstChild.offsetWidth;
	this.div.style.height	= this.div.firstChild.offsetHeight;
	this.div.style.width = 2 * screen.availWidth;
	this.div.style.visibility = 'visible';
}

function startTicker() {
	this.stop();
	this.left -= this.shiftBy;

	if (this.left <= -this.shiftLeftAt) {
		this.left = 0;
		this.div.appendChild(this.div.firstChild);
		this.shiftLeftAt = this.div.firstChild.offsetWidth;
	}

	this.div.style.left = (this.left + 'px');
	this.runId = setTimeout(this.name + '.start()', this.interval);
}

function stopTicker() {
	if (this.runId) clearTimeout(this.runId);
	this.runId = null;
}

function changeTickerInterval(newinterval) {
	if (typeof(newinterval) == 'string') newinterval =  parseInt('0' + newinterval, 10); 
	if (typeof(newinterval) == 'number' && newinterval > 0) this.interval = newinterval;
	this.stop();
	this.start();
}

/* Prototypes for Ticker */
Ticker.prototype.start = startTicker;
Ticker.prototype.stop = stopTicker;
Ticker.prototype.changeInterval = changeTickerInterval;