Hi Jake,
"Jake B" <[EMAIL PROTECTED]> wrote on 08/18/2007 02:19:00 PM:
> Hello, I'm trying to determine if Batik is an appropriate library to
> use in order to fulfill my project's special requirements. I am
> trying to construct a web application in which the users would
> interact with an SVG document within their browser. Rather than
> construct this application as a rich or fat client ( i.e., deploying
> JSVGCanvas inside a Java applet), I need to construct the
> interactive SVG front-end as a thin client. The only thing that the
> users would need to download would be a basic SVG document, and a
> minimal AJAX engine to pass UI events to the server, fetch updates
> from the server, and update the page asyncronously.
Just up front I'm not sure that I buy that your clients will
be much thinner,
as it sounds like the clients will be making the same changes as the
server
does. However, I don't really know what your host on the server will look
like,
what other facilities it might tap into to generate the updates.
> Basically, I need to push all of the logic to the server, and
> update the client-side SVG document by evaluating server-generated
> javascript function calls asyncronously.
>
> I believe that Batik's implementation of the SVG DOM would be superb
> for modelling the state of the client-side SVG document. However,
> every time the server-side model is changed programmatically, it
> would also need to generate javascript to update the document on the
> client's side.
> For example, if the user were to click and drag a rectangle down to
> a new position, the client would use the AJAX engine to pass the
> user's mouse input event to the server. The server would switch this
> event, and update its model of the client's document, probably with
> a function call like ' rectangle.setAttributeNS(null, "y", "20");'.
> The server would then generate javascript code to pass back to the
> client, probably with a function call like 'rectangle.y = 20'.
Actually the Javascript to update the client's SVG Document will look
like 'rectangle.setAttributeNS(null, "y", "20")', exactly the same
as is used on the server...
> When the client's AJAX engine next pings the server, it GETs this code,
> runs eval on it, and updates the contents on the screen.
> My question is, does anyone know of a way to tell Batik to generate
> javascript that can be used to manipulate client-side SVG in the
> above fashion?
Probably the easiest thing would be to register a DOM Change Event
listener. This get's called whenever anything changes in the DOM.
The tricky thing tends to be figuring out how to tell the remote DOM
which element(s) you are manipulating. You can't send a 'pointer' and
normally you don't have id's on every element. You can try to identify
it by it's position in the DOM tree but SAX/DOM implementations may
split text elements in some cases which complicates things a bit.
> If this functionality does not exist yet, I'm willing to write it
> myself. If anyone has any advice as to what would be the best way to
> build this functionality onto the existing core modules, I would
> greatly appreciate it if you would let me know.
It doesn't already generate JavaScript but other than the caveat
above that is pretty simple.
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