var OAS_banner_layers_id=new Array();
var OAS_banner_layers_top=new Array();
var OAS_banner_layers_count=0;
var OAS_scroll_started=false;

function OAS_register_layer(layerID, topPx) {
	OAS_banner_layers_id[OAS_banner_layers_count]=layerID;
	OAS_banner_layers_top[OAS_banner_layers_count]=topPx;
	OAS_banner_layers_count++;
	if (!OAS_scroll_started) {
		OAS_scroll_started=true;
		OAS_timerID=setTimeout("OAS_move_layer()", OAS_scroll_default_time);
	}
}

function OAS_move_layer() {
	if (OAS_banner_layers_count>0) {
		for (t=0; t<OAS_banner_layers_count; t++) {
			if (OAS_banner_layers_top[t]=="middle") {
				layerMiddle=Math.round(document.getElementById(OAS_banner_layers_id[t]).offsetHeight/2);
				windowMiddle=Math.round(document.body.clientHeight/2);
				newTop=(windowMiddle-layerMiddle)+document.body.scrollTop;
			}
			else if (OAS_banner_layers_top[t]=="bottom") {
				layerHeight=document.getElementById(OAS_banner_layers_id[t]).offsetHeight;
				windowHeight=document.body.clientHeight;
				newTop=(windowHeight-layerHeight)+document.body.scrollTop;
			}
			else {
				newTop=OAS_banner_layers_top[t]+document.body.scrollTop;
			}
			
			currentTop=document.getElementById(OAS_banner_layers_id[t]).offsetTop;
			if (currentTop!=newTop) {
				if (currentTop<newTop) {
					scrollSpeed=Math.round((newTop-currentTop)/30);
					if (scrollSpeed>30) scrollSpeed=30;
					else if (scrollSpeed<1) scrollSpeed=1;
					currentTop=currentTop+scrollSpeed;
					if (currentTop>newTop) currentTop=newTop;
				}
				else if (currentTop>newTop) {
					scrollSpeed=Math.round((currentTop-newTop)/30);
					if (scrollSpeed>30) scrollSpeed=30;
					else if (scrollSpeed<1) scrollSpeed=1;
					currentTop=currentTop-scrollSpeed;
					if (currentTop<newTop) currentTop=newTop;
				}
				document.getElementById(OAS_banner_layers_id[t]).style.top=currentTop;
			}
		}
		if (currentTop!=newTop) OAS_timerID=setTimeout("OAS_move_layer()", OAS_scroll_time);
		else OAS_timerID=setTimeout("OAS_move_layer()", OAS_scroll_default_time);
	}
}