/*
Add to Map div
 onmouseover="dowheel();" onmouseout="stopwheel();
*/

function wheel(event){
  var delta = 0;
  // ie event handler
  if (!event) {  event = window.event;}
  // ie Opera  
  if (event.wheelDelta) {    
                        delta = event.wheelDelta/120;
                        // opera korrektur
                       if (window.opera){ delta = -delta;}
                       // mozilla
                       } else if (event.detail) {
                                                delta = -event.detail/3;
                                                }
  // wenn gescrollt wird tue dies
  if (delta){ setZoom(delta); }
  // mozilla scrolling verhindern
  if (event.preventDefault){  event.preventDefault();}
  // ie opera scrolling verhindern
  event.returnValue = false;
}

function dowheel(){

  // scroll listener hinzufügen
  if (window.addEventListener){
    // mozilla
    window.addEventListener('DOMMouseScroll', wheel, false);
  }

  // ie opera
  window.onmousewheel = document.onmousewheel = wheel;
}

function stopwheel(){
  // scroll listener hinzufügen
  if (window.removeEventListener){
    // mozilla
    window.removeEventListener('DOMMouseScroll', wheel, false);
  }

  // ie opera
  window.onmousewheel = document.onmousewheel = '';
}
function setZoom(delta) {
    if(delta<0){
      map.zoomIn();
    }else{
      map.zoomOut();
    }
}