/*************************************************************************
  This code is from Dynamic Web Coding at www.dyn-web.com
  Copyright 2001-5 by Sharon Paine 
  See Terms of Use at www.dyn-web.com/bus/terms.html
  regarding conditions under which you may use this code.
  This notice must be retained in the code as is!
*************************************************************************/

dw_scrollObjs = {};
dw_scrollObj.speed = 100; // default speed for mouseover scrolling

function dw_scrollObj(wnId, lyrId, cntId) {
  this.id = wnId; dw_scrollObjs[this.id] = this;
  this.animString = "dw_scrollObjs." + this.id;
  this.load(lyrId, cntId);
}

dw_scrollObj.loadLayer = function(wnId, id, cntId) {
  if ( dw_scrollObjs[wnId] ) dw_scrollObjs[wnId].load(id, cntId);
}

dw_scrollObj.prototype.load = function(lyrId, cntId) {
  if (!document.getElementById) return;
  var wndo, lyr;
  if (this.lyrId) {
    lyr = document.getElementById(this.lyrId);
    lyr.style.visibility = "hidden";
  }
  lyr = document.getElementById(lyrId);
  wndo = document.getElementById(this.id);
  lyr.style.top = this.y = 0; lyr.style.left = this.x = 0;
  this.maxY = (lyr.offsetHeight - wndo.offsetHeight > 0)? lyr.offsetHeight - wndo.offsetHeight: 0;
  this.wd = cntId? document.getElementById(cntId).offsetWidth: lyr.offsetWidth;
  this.maxX = (this.wd - wndo.offsetWidth > 0)? this.wd - wndo.offsetWidth: 0;
  this.lyrId = lyrId; // hold id of currently visible layer
  lyr.style.visibility = "visible";
  this.on_load(); this.ready = true;
}

dw_scrollObj.prototype.on_load = function() {}  

dw_scrollObj.prototype.shiftTo = function(lyr, x, y) {
  lyr.style.left = (this.x = x) + "px"; 
  lyr.style.top = (this.y = y) + "px";
}

/* dw_glidescroll.js  version date: June 2004 */

dw_scrollObj.slideDur = 500; // duration of glide

dw_scrollObj.scrollBy = function(wnId, x, y, dur) {
  if ( dw_scrollObjs[wnId] ) dw_scrollObjs[wnId].glideBy(x, y, dur);
}

dw_scrollObj.scrollTo = function(wnId, x, y, dur) {
  if ( dw_scrollObjs[wnId] ) dw_scrollObjs[wnId].glideTo(x, y, dur);
}

// Resources for time-based slide algorithm: 
//  DHTML chaser tutorial at DHTML Lab - www.webreference.com/dhtml	
//  and cbe_slide.js from	www.cross-browser.com by Mike Foster
dw_scrollObj.prototype.glideBy = function(dx, dy, dur) {
  if ( !document.getElementById || this.sliding ) return;
  this.slideDur = dur || dw_scrollObj.slideDur;
  this.destX = this.destY = this.distX = this.distY = 0;
  this.lyr = document.getElementById(this.lyrId);
  this.startX = this.x; this.startY = this.y;
  if (dy < 0) this.distY = (this.startY + dy >= -this.maxY)? dy: -(this.startY  + this.maxY);
  else if (dy > 0) this.distY = (this.startY + dy <= 0)? dy: -this.startY;
  if (dx < 0) this.distX = (this.startX + dx >= -this.maxX)? dx: -(this.startX + this.maxX);
  else if (dx > 0) this.distX = (this.startX + dx <= 0)? dx: -this.startX;
  this.destX = this.startX + this.distX; this.destY = this.startY + this.distY;
  this.slideTo(this.destX, this.destY);
}

dw_scrollObj.prototype.glideTo = function(destX, destY, dur) {
  if ( !document.getElementById || this.sliding) return;
  this.slideDur = dur || dw_scrollObj.slideDur;
  this.lyr = document.getElementById(this.lyrId); 
  this.startX = this.x; this.startY = this.y;
  this.destX = -Math.max( Math.min(destX, this.maxX), 0);
  this.destY = -Math.max( Math.min(destY, this.maxY), 0);
  this.distY = this.destY - this.startY;
  this.distX =  this.destX - this.startX;
  this.slideTo(this.destX, this.destY);
}

dw_scrollObj.prototype.slideTo = function(destX, destY) {
  this.per = Math.PI/(2 * this.slideDur); this.sliding = true;
	this.slideStart = (new Date()).getTime();
	this.aniTimer = setInterval(this.animString + ".doSlide()",10);
  this.on_slide_start(this.startX, this.startY);
}

dw_scrollObj.prototype.doSlide = function() {
	var elapsed = (new Date()).getTime() - this.slideStart;
	if (elapsed < this.slideDur) {
		var x = this.startX + this.distX * Math.sin(this.per*elapsed);
		var y = this.startY + this.distY * Math.sin(this.per*elapsed);
    this.shiftTo(this.lyr, x, y); this.on_slide(x, y);
	} else {	// if time's up
    clearInterval(this.aniTimer); this.sliding = false;
		this.shiftTo(this.lyr, this.destX, this.destY);
    this.lyr = null; this.on_slide_end(this.destX, this.destY);
	}
}

dw_scrollObj.prototype.on_slide_start = function() {}
dw_scrollObj.prototype.on_slide = function() {}
dw_scrollObj.prototype.on_slide_end = function() {}

// glide scrolling layer to specified element
// arguments: id of element to scroll to, scroll area id (same id as passed to constructor, i.e., 'wn')
// id of layer element is contained in (i.e., layer to load in scroll area)
// glide-scroll duration (optional)
dw_scrollObj.scrollToAnchor = function(id, wnId, lyrId, dur) {
  if ( dw_scrollObjs[wnId] && document.getElementById) { 
    var el = document.getElementById(id);
    // check if correct layer is loaded in scroll area
    // if not, load it
    if ( dw_scrollObjs[wnId].lyrId != lyrId ) dw_scrollObjs[wnId].load(lyrId);
    var lyr = document.getElementById( dw_scrollObjs[wnId].lyrId );
    var x = dw_getLayerOffset(el, lyr, 'left');
    var y = dw_getLayerOffset(el, lyr, 'top');
    dw_scrollObjs[wnId].glideTo(x, y, dur);
  } 
}

// Get position of el within layer (oCont)
function dw_getLayerOffset(el, oCont, sOff) {
    var off = "offset" + sOff.charAt(0).toUpperCase() + sOff.slice(1);
    var val = el[off];
    while ( (el = el.offsetParent) != oCont ) 
        val += el[off];
    var clientOff = off.replace("offset", "client");
    if ( el[clientOff] ) val += el[clientOff];
    return val;
}