Subj : recommendation for XML Events
To   : netscape.public.mozilla.jseng
From : Aaron Reed
Date : Fri May 14 2004 05:33 pm

Hey,

In the course of trying to implement XML Events (bug 164482) we're 
trying to make <script> tags basically execute like JavaScript 
functions.  So that you could have something like:

.....
<script id="popper" type="application/x-javascript" declare="declare">
    alert("popper action hit");
</script>

<a href="doc.html" ev:event="activate" ev:handler="#popper"> The 
Document </a>
.....

So if you click on the link "The Document", you would get a javascript 
alert saying, "popper action hit".

So what we have done so far is pretty much just add a method to 
nsHTMLScriptElement that gets called when the script needs to execute. 
This method gets the JS code from the contents of the <script> tag, call 
scriptContext->CompileFunction to get a function object, then call 
scriptContext->CallEventHandler passing in the functionObject and the 
arguments.

This code works just fine.  No problems.  However, we recognize that 
this could be really inefficient, especially if the handler is some kind 
of mousemove handler or a handler attached to a bunch of different 
elements.  Compiling and executing the script on every invocation must 
be expensive.  So I'm guessing that we need some way to cache the 
resulting compiled code (I assume compiling the code is the most 
inefficient part) and/or keeping around the functionObject.  Is this 
kind of thing already done somewhere in Mozilla that we can use as an 
example?  Any "gotchas" to look out for?

Any advice appreciated.

Thanks,
--Aaron

.