tooltip只在甘特图上显示，鼠标移动到表格上不显示

参考链接：

forum.dhtmlx.com/t/tooltips/…

gantt.plugins({
  tooltip: true
});

var mouse_on_grid = false;

gantt.templates.tooltip_text = function(start,end,task){
  if(mouse_on_grid) return "<b>Task:</b> "+task.text+"<br/><b>Start date:</b> " + 
    gantt.templates.tooltip_date_format(start)+ 
    "<br/><b>End date:</b> "+gantt.templates.tooltip_date_format(end);
  return ""

};

gantt.attachEvent("onMouseMove", function (id, e){
  if (e.clientX <= gantt.config.grid_width) mouse_on_grid = true;
  else mouse_on_grid = false;
}); 


gantt.init("gantt_here");

gantt.parse(<data>);