/*
dw_glider.js - requires dw_lib.js
glide to maintain window location on scroll
version date: September 2003 

This code is from Dynamic Web Coding at www.dyn-web.com
See Terms of Use at http://www.dyn-web.com/bus/terms.html
Permission granted to use this code 
as long as this entire notice is included.	

Resources: ypChaser by Aaron Boodman (www.youngpup.net)
DHTML chaser tutorial at DHTML Lab - www.webreference.com/dhtml		
*/

Glider.holder = [];
function Glider(id, x, y, w, h, d, ac, limit) 
{
	this.glideDur = d || 1000; 
	this.origX = x; 
	this.origY = y; 
	this.ac = -ac || 0;
	this.baseObj = dynObj;
	this.baseObj(id, x, y, w, h, limit);
	this.limit = limit;
//	alert(limit)
	Glider.holder[Glider.holder.length] = this;
	if (!Glider.winHt) 
		Glider.winHt = getWinHeight();
}
Glider.prototype = new dynObj;
Glider.prototype.onGlideInit = function () {}
Glider.prototype.checkGlider = function() 
{
	var destY = getScrollY() + this.origY;
		if (destY != this.y) 
		{
			if (destY != this.dy) 
			{
				this.dy = destY;
				this.glideInit();
				this.onGlideInit();
			} 
			this.glide();
		}
}

Glider.prototype.glideInit = function() 
{
	this.gt = new Date().getTime();
	var distY = this.dy - this.y;
	if ( Math.abs(distY) > Glider.winHt ) 
	{	// distance greater than window height?
		this.gsy = (distY > 0)? this.dy - Glider.winHt: this.dy + Glider.winHt;
	} 
	else 
		this.gsy = this.y;
		
	this.g_yc1 = this.gsy + ( (1+this.ac) * (this.dy - this.gsy)/3 );
	this.g_yc2 = this.gsy + ( (2+this.ac) * (this.dy - this.gsy)/3 );
}

Glider.prototype.glide = function() 
{
	var elapsed = new Date().getTime() - this.gt;
	if (elapsed < this.glideDur) 
	{
		var y = dw_Bezier.getValue( elapsed/this.glideDur, this.gsy, this.dy, this.g_yc1, this.g_yc2 );
		this.shiftTo(null,y);
	} 
	else this.shiftTo(null,this.dy);
}

Glider.control = function() 
{
	for (var i=0; Glider.holder[i]; i++) 
	{
		var curObj = Glider.holder[i];
		if (curObj) curObj.checkGlider();
	}
}
//Glider.timer = setInterval("Glider.control()",20);
dw_Animation.add(Glider.control);

// returns height of window
function getWinHeight() 
{
	var winHt = 0;
	if (window.innerHeight) winHt = window.innerHeight-18;
	else 
		if (document.documentElement && document.documentElement.clientHeight) 
			winHt = document.documentElement.clientHeight;
		else 
			if (document.body && document.body.clientHeight) 
				winHt = document.body.clientHeight;	
	return winHt;
}	

// returns amount of vertical scroll
function getScrollY() 
{
	var sy = 0;
	if (document.documentElement && document.documentElement.scrollTop)
		sy = document.documentElement.scrollTop;
	else 
		if (document.body && document.body.scrollTop) 
			sy = document.body.scrollTop; 
		else 
			if (window.pageYOffset)
				sy = window.pageYOffset;
			else 
				if (window.scrollY)
					sy = window.scrollY;
	return sy;
}

// onresize, get window height
if (window.addEventListener)
	window.addEventListener("resize", function()
		{ 
			Glider.winHt = getWinHeight(); 
		}, 
	"false");
else if (window.attachEvent)
	window.attachEvent("onresize", function()
		{ 
			Glider.winHt = getWinHeight(); 
		} 
	);