code: function startHandler(evt) {
          startHandlerOriginal.call(this, evt);
          // must be a picture, only one picture!!
          var node = this.els[1].querySelector('img:first-child');
          var device = this.deviceEvents;
          if (device.hasTouch && node !== null) {
              IN_SCALE_MODE = true;
              var transform = getComputedTranslate(node);
              startTouches = getTouches(evt.targetTouches);
              startX = transform.translateX - 0;
              startY = transform.translateY - 0;
              currentScale = transform.scaleX;
              zoomNode = node;
              var pos = getPosition(node);
              if (evt.targetTouches.length == 2) {
                  lastTouchStart = null;
                  var touches = evt.touches;
                  var touchCenter = getCenter({
                      x: touches[0].pageX,
                      y: touches[0].pageY
                  }, {
                      x: touches[1].pageX,
                      y: touches[1].pageY
                  });
                  node.style.webkitTransformOrigin = generateTransformOrigin(touchCenter.x - pos.left, touchCenter.y - pos.top);
              } else if (evt.targetTouches.length === 1) {
                  var time = (new Date()).getTime();
                  gesture = 0;
                  if (time - lastTouchStart < 300) {
                      evt.preventDefault();
                      gesture = 3;
                  }
                  lastTouchStart = time;
              }
          }
      }
docs: Start event handle
  @param {object} evt