dw_scrollObj.stopScroll = function(wnId) {

  if ( dw_scrollObjs[wnId] ) dw_scrollObjs[wnId].endScroll();

}



// increase speed onmousedown of scroll links

dw_scrollObj.doubleSpeed = function(wnId) {

  if ( dw_scrollObjs[wnId] ) dw_scrollObjs[wnId].speed *= 2;

}



dw_scrollObj.resetSpeed = function(wnId) {

  if ( dw_scrollObjs[wnId] ) dw_scrollObjs[wnId].speed /= 2;

}



// algorithms for time-based scrolling and scrolling onmouseover at any angle adapted from youngpup.net

dw_scrollObj.initScroll = function(wnId, deg, sp) {

  if ( dw_scrollObjs[wnId] ) {

    var cosine, sine;

    if (typeof deg == "string") {

      switch (deg) {

        case "up"    : deg = 90;  break;

        case "down"  : deg = 270; break;

        case "left"  : deg = 180; break;

        case "right" : deg = 0;   break;

        default: 

          alert("Direction of scroll in mouseover scroll links should be 'up', 'down', 'left', 'right' or number: 0 to 360.");

       }

    } 

    deg = deg % 360;

    if (deg % 90 == 0) {

      cosine = (deg == 0)? -1: (deg == 180)? 1: 0;

      sine = (deg == 90)? 1: (deg == 270)? -1: 0;

    } else {

      var angle = deg * Math.PI/180;

      cosine = -Math.cos(angle); sine = Math.sin(angle);

    }

    dw_scrollObjs[wnId].fx = cosine / ( Math.abs(cosine) + Math.abs(sine) );

    dw_scrollObjs[wnId].fy = sine / ( Math.abs(cosine) + Math.abs(sine) );

    dw_scrollObjs[wnId].endX = (deg == 90 || deg == 270)? dw_scrollObjs[wnId].x:

      (deg < 90 || deg > 270)? -dw_scrollObjs[wnId].maxX: 0; 

    dw_scrollObjs[wnId].endY = (deg == 0 || deg == 180)? dw_scrollObjs[wnId].y: 

      (deg < 180)? 0: -dw_scrollObjs[wnId].maxY;

    dw_scrollObjs[wnId].startScroll(sp);

  }

}



// speed (optional) to override default speed (set in dw_scrollObj.speed)

dw_scrollObj.prototype.startScroll = function(speed) {

  if (!this.ready) return; if (this.timerId) clearInterval(this.timerId);

  this.speed = speed || dw_scrollObj.speed;

  this.lyr = document.getElementById(this.lyrId);

  this.lastTime = ( new Date() ).getTime();

  this.on_scroll_start();  

  this.timerId = setInterval(this.animString + ".scroll()", 10); 

}



dw_scrollObj.prototype.scroll = function() {

  var now = ( new Date() ).getTime();

  var d = (now - this.lastTime)/1000 * this.speed;

  if (d > 0) {

    var x = this.x + this.fx * d; var y = this.y + this.fy * d;

    if (this.fx == 0 || this.fy == 0) { // for horizontal or vertical scrolling

      if ( ( this.fx == -1 && x > -this.maxX ) || ( this.fx == 1 && x < 0 ) || 

        ( this.fy == -1 && y > -this.maxY ) || ( this.fy == 1 && y < 0 ) ) {

        this.lastTime = now;

        this.shiftTo(this.lyr, x, y);

        this.on_scroll(x, y);

      } else {

        clearInterval(this.timerId); this.timerId = 0;

        this.shiftTo(this.lyr, this.endX, this.endY);

        this.on_scroll_end(this.endX, this.endY);

      }

    } else { // for scrolling at an angle (stop when reach end on one axis)

      if ( ( this.fx < 0 && x >= -this.maxX && this.fy < 0 && y >= -this.maxY ) ||

        ( this.fx > 0 && x <= 0 && this.fy > 0 && y <= 0 ) ||

        ( this.fx < 0 && x >= -this.maxX && this.fy > 0 && y <= 0 ) ||

        ( this.fx > 0 && x <= 0 && this.fy < 0 && y >= -this.maxY ) ) {

        this.lastTime = now;

        this.shiftTo(this.lyr, x, y);

        this.on_scroll(x, y);

      } else {

        clearInterval(this.timerId); this.timerId = 0;

        this.on_scroll_end(this.x, this.y);

      }

    }

  }

}



dw_scrollObj.prototype.endScroll = function() {

  if (!this.ready) return;

  if (this.timerId) clearInterval(this.timerId);

  this.timerId = 0;  this.lyr = null;

}



dw_scrollObj.prototype.on_scroll = function() {}

dw_scrollObj.prototype.on_scroll_start = function() {}

dw_scrollObj.prototype.on_scroll_end = function() {}