function scrolltext(content, btnprevious, btnnext, autostart) {
  this.delay = 10;
  this.lineheight = 20;
  this.amount = 1; //ע��:lineheightһ��ҫ������amount.
  this.direction = "up";
  this.timeout = 1500;
  this.scrollcontent = this.$(content);
  this.scrollcontent.innerhtml += this.scrollcontent.innerhtml;
  //this.scrollcontent.scrolltop = 0;
  if (btnnext) {
    this.nextbutton = this.$(btnnext);
    this.nextbutton.onclick = this.getfunction(this, "next");
    this.nextbutton.onmouseover = this.getfunction(this, "stop");
    this.nextbutton.onmouseout = this.getfunction(this, "start");
  }
  if (btnprevious) {
    this.previousbutton = this.$(btnprevious);
    this.previousbutton.onclick = this.getfunction(this, "previous");
    this.previousbutton.onmouseover = this.getfunction(this, "stop");
    this.previousbutton.onmouseout = this.getfunction(this, "start");
  }
  this.scrollcontent.onmouseover = this.getfunction(this, "stop");
  this.scrollcontent.onmouseout = this.getfunction(this, "start");
  if (autostart) {
    this.start();
  }
}

scrolltext.prototype.$ = function(element) {
  return document.getelementbyid(element);
}

scrolltext.prototype.previous = function() {
  cleartimeout(this.autoscrolltimer);
  cleartimeout(this.scrolltimer);
  this.scroll("up");
}

scrolltext.prototype.next = function() {
  cleartimeout(this.autoscrolltimer);
  cleartimeout(this.scrolltimer);
  this.scroll("down");
}

scrolltext.prototype.start = function() {
  cleartimeout(this.autoscrolltimer);
  this.autoscrolltimer = settimeout(this.getfunction(this, "autoscroll"), this.timeout);
}

scrolltext.prototype.stop = function() {
  cleartimeout(this.scrolltimer);
  cleartimeout(this.autoscrolltimer);
}

scrolltext.prototype.autoscroll = function() {
  if (this.direction == "up") {
    if (parseint(this.scrollcontent.scrolltop) >= parseint(this.scrollcontent.scrollheight) / 2) {
      this.scrollcontent.scrolltop = 0;
    }
    this.scrollcontent.scrolltop += this.amount;
  } else {
    if (parseint(this.scrollcontent.scrolltop) <= 0) {
      this.scrollcontent.scrolltop = parseint(this.scrollcontent.scrollheight) / 2;
    }
    this.scrollcontent.scrolltop -= this.amount;
  }
  if (parseint(this.scrollcontent.scrolltop) % this.lineheight != 0) {
    this.scrolltimer = settimeout(this.getfunction(this, "autoscroll"), this.delay);
  } else {
    this.autoscrolltimer = settimeout(this.getfunction(this, "autoscroll"), this.timeout);
  }
}

scrolltext.prototype.scroll = function(direction) {
  if (direction == "up") {
    if (this.scrollcontent.scrolltop == 0) {
      this.scrollcontent.scrolltop = parseint(this.scrollcontent.scrollheight) / 2;
    }
    this.scrollcontent.scrolltop -= this.amount;
  } else {
    this.scrollcontent.scrolltop += this.amount;
  }
  if (parseint(this.scrollcontent.scrolltop) >= parseint(this.scrollcontent.scrollheight) / 2) {
    this.scrollcontent.scrolltop = 0;
  }
  if (parseint(this.scrollcontent.scrolltop) % this.lineheight != 0) {
    this.scrolltimer = settimeout(this.getfunction(this, "scroll", direction), this.delay);
  }
}

scrolltext.prototype.getfunction = function(variable, method, param) {
  return function() {
    variable[method](param);
  }
}