/*
	These functions enable you (as a developer) to create a way for the user
	to increase and decrease the overall fontsize of the website.
	The CSS must contain "em" on the BODY tag font-size declaration.

	This worked ok for me:
	======================
	font-family:	arial, helvetica, sans-serif;
	font-size:		.75em;
	line-height:	1.20em;
	font-weight:	normal;
	white-space:	normal;

	For returning visitors of your website:
	=======================================
	You can use the function "checkVisitorFontSizePreference()" in body onload.
*/


var fontsize_default=	0.75; // em
var fontsize_min	=	0.75; // em
var fontsize_max	=	2.00; // em
var fontsize_steps	=	0.03; // em
var cookie_name		=	'current_fontsize';

function increaseFontSize() {
   var p = document.getElementsByTagName('body');
   for(i=0;i < p.length;i++) {
      if(p[i].style.fontSize) {
         var s = parseFloat(p[i].style.fontSize.replace("em",""));
      } else {
         var s = fontsize_default;
      }
      if(s < fontsize_max) {
         s += fontsize_steps;
      }
      p[i].style.fontSize = s+"em";
      var cfs = parseFloat(p[i].style.fontSize.replace("em",""));
   }
   createCookie('current_fontsize',cfs,365);
	return true;
}

function decreaseFontSize() {
   var p = document.getElementsByTagName('body');
   for(i=0;i < p.length;i++) {
      if(p[i].style.fontSize) {
         var s = parseFloat(p[i].style.fontSize.replace("em",""));
      } else {
         var s = fontsize_default;
      }
      if(s > fontsize_min) {
         s -= fontsize_steps;
      }
      p[i].style.fontSize = s+"em";
      var cfs = parseFloat(p[i].style.fontSize.replace("em",""));
   }
   createCookie('current_fontsize',cfs,365);
	return true;
}

function resetFontSize() {
	setFontSize(fontsize_default);
	createCookie('current_fontsize',fontsize_default,365);
	return true;
}

function setFontSize(desired_size) {
   var p = document.getElementsByTagName('body');
   for(i=0;i<p.length;i++) {
      p[i].style.fontSize = desired_size+"em";
      var cfs = parseFloat(p[i].style.fontSize.replace("em",""));
   }
	return true;
}

function checkVisitorFontSizePreference() {
	var cfs = readCookie('current_fontsize');
	if (cfs!=null) {
		setFontSize(cfs);
	} else {
		resetFontSize();
	}
	return true;
}