function increaseFontSize() {
  if (fontSize < 4) fontSize++;
  var activeSheets = Array('schriftgroesse'+fontSize, 'kontrast'+kontrastVersion);
  setActiveStyleSheet(activeSheets);
}

function decreaseFontSize() {
  if (fontSize > -2) fontSize--;
  var activeSheets = Array('schriftgroesse'+fontSize, 'kontrast'+kontrastVersion);
  setActiveStyleSheet(activeSheets);
}

function switchContrastVersion() {
  if (kontrastVersion==0) kontrastVersion=1;
  else kontrastVersion=0;
  var activeSheets = Array('schriftgroesse'+fontSize, 'kontrast'+kontrastVersion);
  setActiveStyleSheet(activeSheets);
}

function setActiveStyleSheet(titles) {
  var i, a, main;
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title")) {
      a.disabled = true;
      if(a.getAttribute("title") == titles[0] || a.getAttribute("title") == titles[1]) a.disabled = false;
    }
  }
}

function getActiveStyleSheet() {
  var i, a, j;
  j=0;
  var titles = Array();
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title") && !a.disabled)
    {
      titles[j]=a.getAttribute("title");
      j++;
    }
  }
  if (titles.length) return titles;
  else return null;
}

function getPreferredStyleSheet() {
  var i, a, j;
  j=0;
  var titles = Array();
  for(i=0; (a = document.getElementsByTagName("link")[i]); i++) {
    if(a.getAttribute("rel").indexOf("style") != -1
       && a.getAttribute("rel").indexOf("alt") == -1
       && a.getAttribute("title")
       )
    {
      titles[j]=a.getAttribute("title");
      j++;
    }
  }
  if (titles.length) return titles;
  else return null;
}

function createCookie(name,value,days) {
  if (days) {
    var date = new Date();
    date.setTime(date.getTime()+(days*24*60*60*1000));
    var expires = "; expires="+date.toGMTString();
  }
  else expires = "";
  document.cookie = name+"="+value+expires+"; path=/";
}

function readCookie(name) {
  var nameEQ = name + "=";
  var ca = document.cookie.split(';');
  for(var i=0;i < ca.length;i++) {
    var c = ca[i];
    while (c.charAt(0)==' ') c = c.substring(1,c.length);
    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
  }
  return null;
}

window.onload = function(e) {
  fontSizeCookie = readCookie("fontSizeCookie");
  fontSize = fontSizeCookie ? fontSizeCookie : 0;
  kontrastVersionCookie = readCookie("kontrastVersionCookie");
  kontrastVersion = kontrastVersionCookie ? kontrastVersionCookie : 0;

  var activeSheets = Array('schriftgroesse'+fontSize, 'kontrast'+kontrastVersion);
  setActiveStyleSheet(activeSheets);
}

window.onunload = function(e) {
  createCookie("fontSizeCookie", fontSize, 365);
  createCookie("kontrastVersionCookie", kontrastVersion, 365);
}

var fontSizeCookie = readCookie("fontSizeCookie");
var fontSize = fontSizeCookie ? fontSizeCookie : 0;
var kontrastVersionCookie = readCookie("kontrastVersionCookie");
var kontrastVersion = kontrastVersionCookie ? kontrastVersionCookie : 0;

var activeSheets = Array('schriftgroesse'+fontSize, 'kontrast'+kontrastVersion);
setActiveStyleSheet(activeSheets);