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From Ziru Zhu <z...@cc.gatech.edu>
Subject Re: Dynamic Document Update
Date Sat, 02 Aug 2003 18:07:43 GMT
Hi Thomas,

> Hi Ziru,
>
> Ziru Zhu wrote:
> > I am currently using Batik to develop in our visualization part of
> > project.
>
>    I hope you are finding it useful.

Sure.  It adds lots of flexibilities to our project.

> > Our SVG doc contains some scripts providing some interactive
> > functionalities such as rotation, zooming and so on.  Also the doc should
> > be dynamically updatable so that new data from the server side can be used
> > to update the DOC contents.
> >
> > Unfortunately, a NullPointer exception is thrown out when we activating
> > the scripts by clicking the displaying portion while the update manager is
> > substituing stale data.  The problem is how to disable the scripting
> > feature when UpdateMgr thread is changing the DOC.
>
>    It isn't 100% clear if by 'scripting' you mean ecma script or not.
> I would assume so, but since all ecma script is run in the UpdateMgr
> thread I don't see how your changes and the script could be running
> at the same time.  Put another way the scripting features is
> 'disabled' when the UpdateMgr is working - to be more accurate
> scripting is 'delayed' - to be even more accurate the delivery of
> events that trigger scripting are delayed.  The place I could see
> you getting into trouble would be if you have 'setTimeout' or getURL
> stuff going on in which case it is your responsability to ensure
> you notice when stuff leaves the DOM tree - you can always 'stop'
> the update manger thread if you are truely done but that will
> kill the document entirely.

Yes, I mean ECMA script.

I am a little vague on the "delay".  Will the events be triggered during
the update (but delayed processing after the update) or not?  In my codes,
the scripts are also changed in the UpdateMgr.  Is it possible that the
events are triggered before the update but be delivered to the changed
scripts after the UpdateMgr deal with all these.

>    You may need to provide more information about the exact
> circumstance of the NPE (perhaps provide the stack trace -
> with line numbers?), or a reproducable test case before I can
> help you any more.
>
> > Second, I find that the SVG display will not work if I change (or add /
> > remove) the svgRoot's attributes in the UpdateMgr.  Is there any work
> > around for this?
>
>    Once again can you be more specific?  Standalone test case?

Well, I changed the ViewBox attributes of the SVGRoot element, because in
our project, new data may need to readjust the whole view port of the
image.  I thought I did change the attributes, because when I dumped the
dynamic DOM to a disk file, it could be displayed correctly on the screen
by using JSVGCanvas.  However, I failed to do that without dumping all
these.

As to the standalone test case, I will try to pack the relevant part and
send you a copy.

Thanks.

Ziru

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