window.onload = function(){
  textChanger.init(); 	
}

var textChanger = {
	cpanel : 'textchanger',  //set here the id of the element (div, p) within you want to insert the control panel
	element : 'content',   	 //set here the id of the element (div, p) within you want to change the text
	defaultFS : 1.1,         //set here the default font size in 'em'
	init: function(){
	  var cpel = document.getElementById(textChanger.cpanel);
	  var el = document.getElementById(textChanger.element);
	  if (cpel == null || el == null) {
	    alert('The elements with the \"'+textChanger.cpanel+'\" and/or \"'+textChanger.element+'\" ID do not exist in HTML source.');
      } else {
		cpel.innerHTML = 
		'Dimensioni carattere <a id="decrease" href="#" title="Diminuisci la grandezza del carattere"> - A</a>'+
		'<a id="increase" href="#" title="Aumenta la grandezza del carattere"> + A</a>'
		var sz = textChanger.getCookie();
		el.style.fontSize = sz ? sz + 'em' : textChanger.defaultFS + 'em';
		var incr = document.getElementById('increase');
		incr.onclick = function(){
	      textChanger.changeSize(1);
	      return false;
	    };
		var decr = document.getElementById('decrease');
		decr.onclick = function(){
	      textChanger.changeSize(0);
	      return false;
	    };
	  }
	},

	changeSize: function(val){
	  var el = document.getElementById(textChanger.element);
	  var size = el.style.fontSize.substring(0,3);
	  var fSize = parseFloat(size,10);
	  if (val == 1) {
		fSize += 0.11;
		if (fSize > 2.0) fSize = 2.0;
      } else {
		fSize -= 0.11;
		if (fSize < 0.5) fSize = 0.5;
	  }		
	  el.style.fontSize = fSize + 'em';
	  textChanger.updateCookie(fSize);
    },
		
	updateCookie: function(vl){
	  var today = new Date();
	  var exp = new Date(today.getTime() + (365*24*60*60*1000)); //the cookie will expire in one year  
	  document.cookie = 'textChangerL=size=' + vl + ';' +'expires=' + exp.toGMTString() + ';' +'path=/';
	},

	getCookie: function(){ 
	  var cname = 'textChangerL=size=';	
	  var start = document.cookie.indexOf(cname);
	  var len = start + cname.length;
	  if ((!start) && (cname != document.cookie.substring(0,cname.length))) {
        return null;
      }
	  if (start == -1) return null;
	  var end = document.cookie.indexOf(";",len);
	  if (end == -1) end = document.cookie.length;
	  return unescape(document.cookie.substring(len, end));
	}
}