var scrollButtonCache = {
_count:		0,
_idPrefix:	"-scroll-button-cache-",

getId:	function () {
return this._idPrefix + this._count++;
},

remove:	function ( o ) {
delete this[ o.id ];
}
};

function ScrollButton( oEl, oScrollContainer, nDir ) {
this.htmlElement = oEl;
this.scrollContainer = oScrollContainer;
this.dir = nDir;

this.id = scrollButtonCache.getId();
scrollButtonCache[ this.id ] = this;

this.makeEventListeners();
this.attachEvents();
}

ScrollButton.scrollIntervalPause = 100;
ScrollButton.scrollAmount = 18;

ScrollButton.prototype.startScroll = function () {
this._interval = window.setInterval(
"ScrollButton.eventListeners.oninterval(\"" + this.id + "\")",
ScrollButton.scrollIntervalPause );
};

ScrollButton.prototype.endScroll = function () {
if ( this._interval != null ) {
window.clearInterval( this._interval );
delete this._interval;
}
};

ScrollButton.prototype.makeEventListeners = function () {
if ( this.eventListeners != null )
return;

this.eventListeners = {
onmouseover:	new Function( "ScrollButton.eventListeners.onmouseover(\"" + this.id + "\")" ),
onmouseout:		new Function( "ScrollButton.eventListeners.onmouseout(\"" + this.id + "\")" ),
onbeforeunload:	new Function( "ScrollButton.eventListeners.onbeforeunload(\"" + this.id + "\")" )		
};
};

ScrollButton.prototype.attachEvents = function () {
if ( this.eventListeners == null )
return;

this.htmlElement.attachEvent( "onmouseover", this.eventListeners.onmouseover );
this.htmlElement.attachEvent( "onmouseout", this.eventListeners.onmouseout );
window.attachEvent( "onbeforeunload", this.eventListeners.onbeforeunload );
};

ScrollButton.prototype.detachEvents = function () {
if ( this.eventListeners == null )
return;

this.htmlElement.detachEvent( "onmouseover", this.eventListeners.onmouseover );
this.htmlElement.detachEvent( "onmouseout", this.eventListeners.onmouseout );
window.detachEvent( "onbeforeunload", this.eventListeners.onbeforeunload );
};

ScrollButton.prototype.destroy = function () {
this.endScroll();
this.detachEvents();

this.htmlElement = null;
this.scrollContainer = null;
this.eventListeners = null;

scrollButtonCache.remove( this );
};

ScrollButton.eventListeners = {
onmouseover:	function ( id ) {
scrollButtonCache[id].startScroll();
},

onmouseout:		function ( id ) {
scrollButtonCache[id].endScroll();
},

oninterval:		function ( id ) {
var oThis = scrollButtonCache[id];
switch ( oThis.dir ) {
case 8:
oThis.scrollContainer.scrollTop -= ScrollButton.scrollAmount;
break;

case 2:
oThis.scrollContainer.scrollTop += ScrollButton.scrollAmount;
break;

case 4:
oThis.scrollContainer.scrollLeft -= ScrollButton.scrollAmount;
break;

case 6:
oThis.scrollContainer.scrollLeft += ScrollButton.scrollAmount;
break;
}
},

onbeforeunload:	function ( id ) {
scrollButtonCache[id].destroy();
}
};