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Thanks so much for your reply.
I have been looking into things today and in short I'm moving back towards
what you're saying... that is, to use standard SVG instead of extending the
SVG syntax for our purposes.
I can see that I'm obviously suffering from lack of experience and things such
as this are something that I don't even think of :o(. Good thing that I can
turn to this list for ideas (thanks again).
I have implemented a little application that reads a very basic floor plan and
I was able to dynamically update the image using a VotingSimulator thread
(yay).
(Oh, btw... it would be a good idea to make it more clear in the documentation
for Batik that JSVGCanvas's setDocumentState( JSVGCanvas.ALWAYS_DYNAMIC )
_must_ be called _before_ setting the document with the setDocument( Document
) if you want to be able to retrieve an UpdateManager from that JSVGCanvas
instance! It took me forever to figure out that getUpdateManager() always
returned null because I called the setDocumentState method after I had called
the setDocument method).
I've pretty much decided on using standard SVG and I think your suggestion
about using internal stylesheets looks really good so I think I'll use that
too.
There is, however, one little thing that I'm not quite shure on how to solve.
That thing is my "layer" concept. In my application, I'd want to be able to
turn on and off various information layers. For example, I'd like to be able
to turn off the voting "layer" so that all chairs are displayed normally. I
am able to imagine how that would be done (simply defining a class called
"off" in the stylesheet and setting all chairs to that) but I'm having a more
difficult time imagining how I could solve other types of layers such as the
name of the person sitting in that chair. I'd like to be able to somehow
"overlay" this information in the same location as the chair is put on the
basic floor plan (my goal is to keep the basic floor plan as simple as
possible so it is easy to update it, rearrange chairs and so on). This
information is pulled from a database so your suggestion of using the persons
name as the ID instead of an integer would not work for us, people can switch
chairs and so on and information about which person is sitting in which chair
is registered into a database. I'd like to be able to easily add such
information layers (where information is pulled from a database and rendered
on top of the chair location). Unfortunately I'm not quite getting how it
would be best to do that. Here are some questions that are related to this
problem:
1) Is it possible in SVG to define anything within the <use> tag? What I mean
is that the chairs are rendered on the floor plan by referencing the "chair
definition". Is it possible to do something like:
<use xlink:href="#chair" x="20" y="20">
<circle x="5" y="5" .../>
</use>
The way I see it is that the circle would then be rendered within its own
coordinate system and the area of the referenced element would be used as its
viewport (I hope I'm making myself clear).
If this would be possible, adding information "layers" would be a piece of
cake by utilizing regular DOM manipulation like I've already done with the
fill element in my little test application.
2) If #1 is impossible, how would you suggest to achieve something similar?
Kind regards and thanks for your answers,
Stefan Freyr
On Thursday 07 August 2003 13:29, G. Wade Johnson wrote:
> Apologies in advance for a fairly long post.
>
> If I'm not misunderstanding, the basic design of what you want is
> relatively easy with just SVG and Batik. (Even without adding new
> attributes or elements.<grin/>) I'll have to defer to Thomas on the
> extending approach, I've not used that as yet.
>
> Modifying your example slightly,
>
> <svg xmlns:xlink="http://www.w3.org/1999/xlink";
> xmlns="http://www.w3.org/2000/svg";>
> <defs>
> <g id="chair"/>
> <style type="text/css"><![CDATA[
> .yes { fill:green; }
> .no { fill:red; }
> ]]></style>
> </defs>
>
> <use id="chair1" xlink:href="#chair" x="10" y="10"/>
> <use id="chair2" xlink:href="#chair" x="20" y="20"/>
> ...
> </svg>
>
> For a simple change in state like the vote, you could have the data
> stream that you read for updates contain the id and vote. For example,
> a CSV data stream with one change per line:
>
> chair1,yes
> chair2,no
> ...
>
> (For more complex changes, a more complex data stream might be
> necessary. But, to start, simpler might be better.)
>
> As each vote comes in you do the following,
>
> doc.getElementById( idstr ).setAttributeNS( null, "class", vote );
>
> Of course, you will need the document in the 'doc' variable, and the
> 'idstr' and 'vote' need to be set up correctly. (Not to mention error
> checking.) But this is the basic idea.
>
> I could also see using a person's name for the chair id instead of
> a number, which could lead to other interesting features.
>
> If you want to keep up with more than a single state, associating
> a Java object with each "chair" would allow you to manipulate the
> the object in arbitrary ways.
>
> Also the "class" attribute can contain a space-separated list of
> classes. As long as the properties don't conflict, this allows
> you to make fairly complex visual effects.
>
> This approach would require you to develop less code and the SVG
> files could be created using standard tools. (That may not be an
> issue yet, but you can bet that someone is going to ask to make
> the picture more complex over time. Good tools would make that
> less of a hardship.)
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