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From Thomas E Deweese <thomas.dewe...@kodak.com>
Subject BridgeExtension and the DOM
Date Wed, 09 May 2001 12:11:33 GMT

Hi Thierry,

   I'm working on the regular polygon extension example, and I have it
working... more or less :).

   As you might guess from the title there is still a sticking point
with the DOM.

My new tag looks like:

 <batikExt:regularPoly fill="blue" cx="225" cy="250" r="150" sides="6"/>

   First I wrote my BatikRegularPolyElementBridge and the
BatikBridgeExtension class, after a few tries I had my polygon coming
up 'black', (it was ignoring the 'fill' attribute).  

   I soon discovered that for the Bridge's fill/stroke stuff to work
the element had to be a subclass of SVGElement.  This led me to
construct a BatikRegularPolyElement class, and I stuck a call into
SVGOMDocument.registerCustomElementFactory so it would use my subclass
of SVGGraphicsElement for regularPoly nodes.

   The problem is that the Bridge Context stuff is done multiple times
(so each time I re-register my factory with the DOM, which is ugly),
and worse the Bridge Context stuff is done _after_ the DOM stuff (so
the first time the poly comes up black the second time blue :).

   In looking at SVGOMDocument, it appears that it has a very similar
structure to the Bridge (people register small factory objects for
each tag they want to handle).  So my question is should I build a
similar structure for the SVGOMDocument to allow for the dynamic
registration of custom DOM extensions?

   The other alternative I see would be to rewrite a lot of code that
assumes that the elements the bridge works on are SVGElements and have
all that code work on GenericElementNS (I already fixed one class cast
exception around this).

   Personally I think it makes some sense for people to have to extend
the DOM if they are interested in extending the Bridge.  In this case
the DOM extension would commonly register the corresponding
BridgeExtension as part of it's work.

   What do people think?

    I'm currently working on the example extension stuff in
    batik.ext.svg do we want to create an examples directory?

    Should it be a separate source tree, or a directory under batik?



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