ypSimpleScroll.prototype.scrollNorth = function() 
{ 
	this.startScroll(90) 
}
ypSimpleScroll.prototype.scrollSouth = function() 
{ 
	this.startScroll(270)  
}
ypSimpleScroll.prototype.scrollWest  = function() 
{ 
	this.startScroll(180) 
}
ypSimpleScroll.prototype.scrollEast  = function() 
{ 
	this.startScroll(0)   
}

// start scrolling in an arbitrary direction, with an optional arbitrary speed.
// if no speed is provided, the default speed from the constructor parameter is used.

ypSimpleScroll.prototype.startScroll = function(deg, speed) 
{
  	if (this.loaded)
  	{
    		if (this.aniTimer) 
		window.clearTimeout(this.aniTimer)
    		this.overrideScrollAngle(deg)
    		this.speed    = speed ? speed : this.origSpeed
    		this.lastTime = (new Date()).getTime() - this.y.minRes
    		this.aniTimer = window.setTimeout(this.gRef + ".scroll()", this.y.minRes)
  	}
}

// kills pending calls to .scroll(), resets speed

ypSimpleScroll.prototype.endScroll = function() 
{
	if (this.loaded)
  	{
    		window.clearTimeout(this.aniTimer)
    		this.aniTimer = 0;
    		this.speed = this.origSpeed
  	}
}

// override the current angle from startScroll() with a new angle
// this method should not be used with scrollTo() because it will
// override the angle created by the first two params to scrollTo().

ypSimpleScroll.prototype.overrideScrollAngle = function(deg) 
{
	if (this.loaded)
  	{
    		deg = deg % 360
    		if (deg % 90 == 0) 
		{
      		var cos = deg == 0  ? 1 : deg == 180 ? -1 : 0
      		var sin = deg == 90 ? -1 : deg == 270 ? 1 : 0
    		} 
		else 
		{
      		var angle = deg * Math.PI / 180
      		var cos   = Math.cos(angle)
      		var sin   = Math.sin(angle)
      		sin = -sin
    		}
    		this.fx = cos / (Math.abs(cos) + Math.abs(sin))
    		this.fy = sin / (Math.abs(cos) + Math.abs(sin))
    		this.stopH = deg == 90 || deg == 270 ? this.scrollLeft : deg < 90 || deg > 270 ? this.scrollW : 0
    		this.stopV = deg == 0 || deg == 180 ? this.scrollTop : deg < 180 ? 0 : this.scrollH
  	}
}

// override the speed for the current scroll.
// should not be used with scrollTo, unless you want to 
// override the speed computed from the aniLen param of scrollTo()

ypSimpleScroll.prototype.overrideScrollSpeed = function(speed) 
{
	if (this.loaded) this.speed = speed
}

// scroll to an arbitrary position in two dimensions over in
// an arbitrary lenth of time.

ypSimpleScroll.prototype.scrollTo = function(stopH, stopV, aniLen) 
{
	if (this.loaded)
  	{
    		if (stopH != this.scrollLeft || stopV != this.scrollTop) 
		{
      		if (this.aniTimer) window.clearTimeout(this.aniTimer)
      		this.lastTime = (new Date()).getTime()
      		var dx = Math.abs(stopH - this.scrollLeft)
      		var dy = Math.abs(stopV - this.scrollTop)
      		var d = Math.sqrt(Math.pow(dx,2) + Math.pow(dy,2))
      		this.fx = (stopH - this.scrollLeft) / (dx + dy)
      		this.fy = (stopV - this.scrollTop) / (dx + dy)
      		this.stopH = stopH
      		this.stopV = stopV
      		this.speed = d / aniLen * 1000
      		window.setTimeout(this.gRef + ".scroll()", this.y.minRes)
    		}
  	}
}

// jump to an arbitrary position in two dimensions.

ypSimpleScroll.prototype.jumpTo = function(nx, ny) 
{ 
	if (this.loaded)
  	{
    		nx = Math.min(Math.max(nx, 0), this.scrollW)
   		ny = Math.min(Math.max(ny, 0), this.scrollH)
    		this.scrollLeft = nx
    		this.scrollTop = ny
    		if (this.y.ns4)
		this.content.moveTo(-nx, -ny)
    		else 
		{
      		this.content.style.left = -nx + "px"
      		this.content.style.top = -ny + "px"
    		}
  	}
}



// =========================================================================
// =============================== private =================================
// =========================================================================

ypSimpleScroll.minRes = 10
ypSimpleScroll.ie  = document.all ? 1 : 0
ypSimpleScroll.ns4 = document.layers ? 1 : 0
ypSimpleScroll.dom = document.getElementById ? 1 : 0
ypSimpleScroll.mac = navigator.platform == "MacPPC"
ypSimpleScroll.mo5 = document.getElementById && !document.all ? 1 : 0

// recursively calls itself to animate

ypSimpleScroll.prototype.scroll = function() 
{
	this.aniTimer = window.setTimeout(this.gRef + ".scroll()", this.y.minRes)
 	var nt = (new Date()).getTime()
  	var d = Math.round((nt - this.lastTime) / 1000 * this.speed)
  	if (d > 0)
  	{
    		var nx = d * this.fx + this.scrollLeft
    		var ny = d * this.fy + this.scrollTop
		var xOut = (nx >= this.scrollLeft && nx >= this.stopH) || (nx <= this.scrollLeft && nx <= this.stopH)
    		var yOut = (ny >= this.scrollTop && ny >= this.stopV)  || (ny <= this.scrollTop && ny <= this.stopV)
    		//window.status = nx + " " + this.fx + " " + this.scrollLeft + " " + this.stopH + " | " + ny + " " + this.fy + " " + this.scrollTop + " " + this.stopV + " : " + d
    		if (nt - this.lastTime != 0 && ((this.fx == 0 && this.fy == 0) || (this.fy == 0 && xOut) || (this.fx == 0 && yOut) || (this.fx != 0 && this.fy != 0 && xOut && yOut)))
    		{
      		this.jumpTo(this.stopH, this.stopV)
      		this.endScroll()
    		}
    		else 
		{
      		this.jumpTo(nx, ny)
      		this.lastTime = nt
    		}
  	}
}

// constructor

function ypSimpleScroll(id, left, top, width, height, speed, contentWidth, initLeft, initTop)
{
	var y = this.y = ypSimpleScroll
  	if (!initLeft)     initLeft     = 0
  	if (!initTop)      initTop      = 0
  	if (!contentWidth) contentWidth = width

// fix for netscape4 first-page bug.

  	if (document.layers && !y.ns4) 
	history.go(0)
	if (y.ie || y.ns4 || y.dom) 
	{
    		this.loaded    = false
    		this.id      = id
    		this.origSpeed  = speed
    		this.aniTimer  = false
    		this.op      = ""
    		this.lastTime  = 0
    		this.clipH    = height
    		this.clipW    = width
    		this.scrollTop  = initTop
    		this.scrollLeft  = initLeft

    // global reference to this object

    		this.gRef = "ypSimpleScroll_"+id
    		eval(this.gRef+"=this")
		var d = document
    		d.write('<style type="text/css">')
    		d.write('#' + this.id + 'Container { left:' + left + 'px; top:' + top + 'px; width:' + width + 'px; height:' + height + 'px; clip:rect(0 ' + width + ' ' + height + ' 0); overflow:hidden; }')
    		d.write('#' + this.id + 'Container, #' + this.id + 'Content { position:absolute; }')
    		d.write('#' + this.id + 'Content { left:' + (-initLeft) + 'px; top:' + (-initTop) + 'px; width:' + contentWidth + 'px; }')
    		d.write('</style>')
  	}
}

// once the nceesary objects are present in the DOM, this gathers some info about them.

ypSimpleScroll.prototype.load = function() 
{
	var d, lyrId1, lyrId2
	d = document
  	lyrId1 = this.id + "Container"
  	lyrId2 = this.id + "Content"
  	this.container  = this.y.dom ? d.getElementById(lyrId1) : this.y.ie ? d.all[lyrId1] : d.layers[lyrId1]
  	this.content  = obj2 = this.y.ns4 ? this.container.layers[lyrId2] : this.y.ie ? d.all[lyrId2] : d.getElementById(lyrId2)
  	this.docH    = Math.max(this.y.ns4 ? this.content.document.height : this.content.offsetHeight, this.clipH)
  	this.docW    = Math.max(this.y.ns4 ? this.content.document.width  : this.content.offsetWidth,  this.clipW)
  	this.scrollH  = this.docH - this.clipH
  	this.scrollW  = this.docW - this.clipW
  	this.loaded    = true
  	this.scrollLeft = Math.max(Math.min(this.scrollLeft, this.scrollW),0)
  	this.scrollTop  = Math.max(Math.min(this.scrollTop, this.scrollH),0)
  	this.jumpTo(this.scrollLeft, this.scrollTop)
}