/*************************************************************************
  This code is from Dynamic Web Coding at www.dyn-web.com
  Copyright 2003-4 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_glide.js - requires dw_lib.js
  version date July 2004 
*/

// acc is number between -1 and 1 ( -1 full decelerated, 1 full accelerated, 0 linear, i.e. no acceleration)
dynObj.prototype.slideTo = function(destX,destY,slideDur,acc,endFn) {
    if (!document.getElementById) 
        return;
    this.slideDur = slideDur || .0001; 
    var acc = -acc || 0;
    if (endFn) 
        this.onSlideEnd = endFn;
    // hold destination values (check for movement on 1 axis only)
    if (destX == null) 
        this.destX = this.x; else this.destX = destX;
    if (destY == null) 
        this.destY = this.y; else this.destY = destY;
    this.startX = this.x; 
    this.startY = this.y;
    this.st = new Date().getTime();
    // control points for bezier-controlled slide (see www.youngpup.net accelimation)
    this.xc1 = this.x + ( (1+acc) * (this.destX-this.x)/3 );
    this.xc2 = this.x + ( (2+acc) * (this.destX-this.x)/3 );
    this.yc1 = this.y + ( (1+acc) * (this.destY-this.y)/3 );
    this.yc2 = this.y + ( (2+acc) * (this.destY-this.y)/3 );
    this.sliding = true;
    this.onSlideStart();
    dw_Animation.add(this.animString + ".doSlide()");
}

dynObj.prototype.doSlide = function() {
    if (!this.sliding) 
        return;  
    var elapsed = new Date().getTime() - this.st;
    if (elapsed < this.slideDur) {
        var x = dw_Bezier.getValue(elapsed/this.slideDur, this.startX, this.destX, this.xc1, this.xc2);
        var y = dw_Bezier.getValue(elapsed/this.slideDur, this.startY, this.destY, this.yc1, this.yc2);
        this.shiftTo( Math.round(x) ,Math.round(y) );
        this.onSlide();
    } else {    // if time's up
        dw_Animation.remove(this.animString + ".doSlide()");
        this.shiftTo(this.destX,this.destY);
        this.onSlide();
        this.sliding = false;
        this.onSlideEnd();
    }
}

dynObj.prototype.slideBy = function(dx,dy,slideDur,acc,endFn) {
    var destX=this.x+dx; 
    var destY=this.y+dy;
    this.slideTo(destX,destY,slideDur,acc,endFn);
}

dynObj.prototype.onSlideStart = function() {}

dynObj.prototype.onSlide = function() {}

dynObj.prototype.onSlideEnd = function() { if (this.el) this.el = null; }