Recently I found myself questioning a fairly basic premise. One of those you've always "known" the answer to, but never gone as far as proving to yourself.

If you use hide-whens to hide a computed-text area does it still compute its value? If it does, this could be a needless drain on resources.

Well, the answer is no, they don't compute. To find this out I did some fairly crude testing. I added a Computed Text area with this formula:

html:="";
@For(n := 1; n <= 1000; n := n + 1;
html:=html+@Text(n)
);
html

The result is one really long string printed to the browser that looks like this:

1 2 3 4 5 6… …998 999 1000

Directly below it I added an image. The browser would wait until all the numbers had been printed before it triggered a separate request to the server to fetch the image. Using an HTTP sniffer it's easy to see the time difference between the request for the page and the request for the image. This difference is roughly the time taken to compute the formula.

Without any hide-whens the page took an average of 0.3s to load. With the computed area hidden it took 0.1s to load. Not very scientific, I know, but it was consistent and enough to convince me there's no need to worry.

You know, sometimes I think the more I use Domino the less I actually know. Last Thursday's post is another example of this.