var gbook = {
	height : false,
	animObj : false,
	showform : function()
	{
		var oBtn=document.getElementById('gbook_showform');
		var oForm=document.getElementById('gbook_form');
		if (gbook.height==false)
			gbook.getheight(oForm);
		cls.add(oBtn,'hidden');
		oForm.style.height='0px';
		cls.remove(oForm,'hidden');
		gbook.animObj=oForm;
		gbook.animate(+1);
	},
	
	hideform : function ()
	{
		var oBtn=document.getElementById('gbook_showform');
		var oForm=document.getElementById('gbook_form');
		if (gbook.height==false)
		{
			gbook.getheight(oForm);
		oForm.style.height=gbook.height+'px';
		}
		gbook.animObj=oForm;
		gbook.animate(-1);
	},
	
	getheight : function (oEl)
	{
		if (cls.has(oEl,'hidden'))
		{
			var position=oEl.style.position;
			var top=oEl.style.top;
			var left=oEl.style.left;
			oEl.style.top='99999px';
			oEl.style.left='10px';
			oEl.style.position='absolute';
			cls.remove(oEl,'hidden');
			gbook.height=oEl.offsetHeight;
			cls.add(oEl,'hidden');
			oEl.style.top=top;
			oEl.style.left=left;
			oEl.style.position=position;
		}
		else
			gbook.height=oEl.offsetHeight;
	},
	animate : function (iKam)
	{
		if (typeof(gbook.animObj)=='object')
		{
			var iSirka=parseInt(gbook.animObj.style.height,10);
			if (iKam>0)//pricitam
			{
				var pricti=(gbook.height-iSirka)/2;
				if (pricti<1)
					pricti=1;
				else if (pricti>50)
					pricti=50;
				iSirka+=pricti;
				
				if (iSirka<gbook.height)
				{
					gbook.animObj.style.height=iSirka+'px';
					setTimeout("gbook.animate("+iKam+");",30);
				}
			}
			else
			{
				var odecti=iSirka/2;
				if (odecti<1)
					odecti=1;
				else if (odecti>50)
					odecti=50;
				iSirka-=odecti;

				if (iSirka>0)
				{
					gbook.animObj.style.height=iSirka+'px';
					setTimeout("gbook.animate("+iKam+");",30);
				}
				else
				{
					var oBtn=document.getElementById('gbook_showform');
					var oForm=document.getElementById('gbook_form');
					cls.add(oForm,'hidden');
					cls.remove(oBtn,'hidden');
				}
			}				
		}
	}
}