Subj : Re: String property & DOM synchro
To   : netscape.public.mozilla.jseng
From : Lorenzo Pastrana
Date : Mon Jun 28 2004 03:11 pm


Hi,
thanks for the reply :)

>
> What do you mean by 'flying' object?

Well, actually the problem takes place in my
 'native data to jsval conversion routine'

The conversion is used in a dom where only methods and handlers can be
implemented in js, the rest of the structure is native C++ and no js code
can be fired outside a method or handler.

It does the following :

when SpiderMonkey asks for a property value in the getter of an object, it
returns a proprely initialized jsval according to the following rule :

if the data asked for is a 'scalar' (integer, real, boolean, etc.) get the
value from the object and use appropriate conversion ok...

if the data asked for is an object, build the corresponding object if not
done yet (using JS_DefineObject or JS_NewObject depending on situations)
and return with OBJECT_TO_JSVAL ok, my objects behaves nice..

then if SM is waiting for a string, I do the folowing for now :

    return STRING_TO_JSVAL(JS_NewString(jscontext, str_data, str_length));

String that gets GC'ed later : a flying object _as done for doubles_
This might not be the correct thing to do (you just tell me), but
worked well for simple get/set operations until now :

The particularity of this arises when in js code one comes to do something
like :

this.some_string_prop.concat(some_other_string);

witch fails to update the right data (the dom's one) since it operates on
the 'flying' object, now I'd like to get to a solution where the above js
code works ok with methods on strings as it works with any method of my
other objects...

But the fact is that I can't reasonably tell (even if I actually kept a
track of the instanciated string) 'when' the data was changed by a method,
without doing ugly polling or whatever...

The thing is : would there be an interception / notification mechanism you
would think of in order to get my dom in sync with the strings data?

I've been thru the apidoc and found nothing related, thru jsstr.c nothing
that helps..
I thought of inserting a notification mechanism in jsstr.c but before I
branch :( I call for help :)

Thanks.

> You really have to show your code for me to help effectively.
>
> /be
>
> >I've been looking the API doc but there's nothing like a
> >'JS_NativeCallStub',
> >I'd be glad if someone hinted me about some way to intercept changes in
the
> >string or some way to 'overload' the String type in order to keep my DOM
in
> >sYnc ..
> >
> >Thanks.
> >
> >Lorenzo.

.