code: function(ev){
      var _self = this,
        canvas = _self.get('canvas'),
        tipGroup = _self.get('tipGroup'),
        point,
        tipInfo;
  
      if(!tipGroup){
        return;
      }
      point = canvas.getPoint(ev.clientX,ev.clientY);
      if(_self._isInAxis(point)){
        _self._processTracking(point,tipGroup);
      }else{
        _self.onMouseOut();
      }
    }
docs: 处理鼠标在画板上移动