// JavaScript Document
function Visual() {
	this.fade = function(obj_id,to,step,delay,onFinish) {
		v_obj = document.getElementById(obj_id);
		if(v_obj == null) {
			alert('Não foi possível localizar o objeto!');
			return;
		}
		if(v_obj.style.opacity == 'undefined') {
			v_obj.style.opacity = 1;
		}
		v_opacity = Number(v_obj.style.opacity)*100;
		if(step == 0) {
			alert('O valor do parametro step deve ser diferente de zero!');
			return;
		} else if (step > 0) {
			v_opacity += step;
			if(v_opacity >= to) {
				this.setOpacity(v_obj,to);
				eval(onFinish);
				return;
			}
			this.setOpacity(v_obj,v_opacity);
			setTimeout("VisualObj.fade('"+obj_id+"',"+to+","+step+","+delay+",'"+onFinish+"')",delay);
			return;
		} else if (step < 0) {
			v_opacity += step;
			if(v_opacity <= to) {
				this.setOpacity(v_obj,to);
				eval(onFinish);
				return;
			}
			this.setOpacity(v_obj,v_opacity);
			setTimeout("VisualObj.fade('"+obj_id+"',"+to+","+step+","+delay+",'"+onFinish+"')",delay);
			return;
		}
	}
	this.setOpacity = function(obj,value) {
		value = Math.round(value);
		obj.style.filter = "alpha(opacity="+value+")"
		obj.style.opacity = value/100;
	}
}
VisualObj = new Visual();