sS hjs_sendWindowVisibilityToWebSocket() {
  ret hjs([[
    // version 1
    
    var isTabActive;
    
    function wsSendTabActive() {
      wsOnOpen(function() {
        console.log("isTabActive=" + isTabActive);
        console.log("Sending");
        ws.send(JSON.stringify({"isTabActive": isTabActive}));
      });
    }
    
    wsSendTabActive();
  
    window.onfocus = function () { 
      isTabActive = true; 
      wsSendTabActive();
    }; 
  
    window.onblur = function () { 
      isTabActive = false; 
      wsSendTabActive();
    };
    
    // version 2
    
    function wsSendVisibility() {
      wsOnOpen(function() {
        var vis = document.visibilityState;
        console.log("visibility=" + vis);
        ws.send(JSON.stringify({"visibility": vis}));
      });
    }
    
    wsSendVisibility();
    document.addEventListener("visibilityChange", wsSendVisibility);
  ]]);
}