Last week I had a request that a popup window be opened each time a user logged in to a Domino website. They could browse Anonymously without the popup, but as soon as they log in it should appear. Only once per login though and not again until they next logged in.

Kind of like having an onLogin event in JavaScript. Which, we all know, there isn't. So I invented one using a little trickery with cookies. Here's how.

In the $$HTMLHead field I added this as the very first line:

@If(
 @UserName="Anonymous"; ""; 
 @SetHTTPHeader("Set-Cookie"; "POST_LOGIN_CODE_RAN=1")
);

In the Form's HTML Body Attributes I then added the following code:

@If(
   @UserName!="Anonymous"  &
     !@Contains(HTTP_Cookie; "POST_LOGIN_CODE_RAN");
 "onload=\"MyApp.onLogin()\"";
 ""
)

In a "global" Script Library I added:

var MyApp={};
MyApp.onLogin = function(){
 document.getElementById('message').innerText=
  "Welcome. You have just logged in.";
}

You can see a demo of it here.

It works by using a kind of loophole, if you will, in the cookie-setting method. That is that the HTTP_Cookie field doesn't contain any cookies you set until the next time you open a page on the site after you set it.

So, when you login, the server sends a cookie to the browser to say you're no longer anonymous. However, at this point, the HTTP_Cookie field does not contain this new cookie as it was merely received by the browser.

This overlap between setting the cookie and the server knowing the page contains the cookie only lasts for one page view. It's this page where you have the chance to run some post login code. Next time you open a page the browser tells the server it does now have the cookie as the HTTP_Cookie field contains the value and so the code doesn't run.

Note: I had thought you could do the same thing by testing for DomAuthSessId in the cookie, but you can't, as it gets set during the names.nsf?login request which results in the 302 redirect to the page being logged in to. So it's not the page you're logging in to which sets this cookie and it does exist by the time the page loads.

I suppose you could do the reverse and have an onLogout event too. If I get chance I'll add it in to the demo before I put in the Sandbox area for download. For now I just want to check this is of use to you all and worth making available? Does it even make sense? I get a bit worried my overly-verbose explanations do no favours for the matter at hand and just confuse what is quite a simple solution.