// gives up and down scroll buttons to images, spans, ... named left_name, right_name, respectively.
// will keep the default scroll_box's style overflow if it encounters errors (so make overflow: auto;)

// usage: put this after the scrollbox div:  var div_scroll1 = new TextScroll('div_scroll1', 'scroll_box');

function TextScroll(scrollname, div_name, left_name, right_name) {
    this.div_name = div_name;
    this.name = scrollname;
    this.scrollCursor = 0;
    this.speed = 5;
    this.timeoutID = null;
    this.div_obj = null;
    this.left_name = left_name;
    this.dn_name = right_name;
	
	var left_limit=0;
	var right_limit=170;
	
	document.getElementById("scroll_left").style.visibility = 'hidden';
	document.getElementById("scroll_right").style.visibility = 'visible';
	
	eval("window.getInstance = function() { return window."+this.name+"; }");

	this.stopScroll = function() {
			obj = getInstance();
			if(obj.timeoutID) {
        		clearTimeout(obj.timeoutID);
				obj.timeoutID = null;
			}
    	}

	this.scrollLeft = function() {
			obj = getInstance();
			if (obj.div_obj) {
				obj.scrollCursor = (obj.scrollCursor - obj.speed) < 0 ? 0 : obj.scrollCursor - obj.speed;
				obj.div_obj.scrollLeft = obj.scrollCursor;
				obj.timeoutID = setTimeout(obj.name + ".scrollLeft()", 5);
			}
			
			if (this.scrollCursor < right_limit) {
				document.getElementById("scroll_right").style.visibility = 'visible';
			} 
			if (this.scrollCursor <= left_limit) {
				document.getElementById("scroll_left").style.visibility = 'hidden';
			} 
			
			
    	}

	this.scrollRight = function() {
			obj = getInstance();
			if (obj.div_obj) {
				obj.scrollCursor += obj.speed;
				obj.div_obj.scrollLeft = obj.scrollCursor;
				obj.timeoutID = setTimeout(obj.name + ".scrollRight()", 5);
			}
		
			if (this.scrollCursor > left_limit){
				document.getElementById("scroll_left").style.visibility = 'visible';
			}
			if (this.scrollCursor > right_limit){
				document.getElementById("scroll_right").style.visibility = 'hidden';
			}
	    }
		
	this.scrollUp = function() {
			if (this.div_obj) {
				this.scrollCursor = (this.scrollCursor - this.speed) < 0 ? 0 : this.scrollCursor - this.speed;
				this.div_obj.scrollTop = this.scrollCursor;
				this.timeoutID = setTimeout(this.name + ".scrollUp()", 5);
			}
		}
	
	this.scrollDown = function() {
			if (this.div_obj) {
				this.scrollCursor += this.speed;
				this.div_obj.scrollTop = this.scrollCursor;
				this.timeoutID = setTimeout(this.name + ".scrollDown()", 5);
			}
		}


	this.resetScroll = function() {
			if (this.div_obj) {
				this.div_obj.scrollTop = 0;
				this.scrollCursor = 0;
			}
		}

	if (document.getElementById) {
		div_obj = document.getElementById(this.div_name);
		if (div_obj) {
			this.div_obj = div_obj;
			this.div_obj.style.overflow = 'hidden';
		}
		div_up_obj = document.getElementById(this.left_name);
		div_dn_obj = document.getElementById(this.dn_name);
		if (div_up_obj && div_dn_obj) {

		//div_up_obj.setAttribute("onmouseover", scrollname + ".scrollUp();")
		//div_up_obj.setAttribute("onmouseout", scrollname + ".stopScroll();")
		
		//div_dn_obj.setAttribute("onmouseover", scrollname + ".scrollDown();")
		//div_dn_obj.setAttribute("onmouseout", scrollname + ".stopScroll();")
			
		div_up_obj.onmouseover = this.scrollLeft;
		div_up_obj.onmouseout = this.stopScroll;

		div_dn_obj.onmouseover = this.scrollRight;
		div_dn_obj.onmouseout = this.stopScroll;

		}
	}
}