Re: rendering directly to java.awt.Graphics2D

On Wed, Aug 3, 2011 at 1:03 PM, Mike Jarmy <[email protected]> wrote:
> I'm working with a custom widget toolkit that is built directly on top
> of java.awt -- in other words I'm not using Swing, or SWT, or anything
> other than a framework built on plain old AWT.
>
> I'd like to be able to render (and animate) SVG drawings directly onto
> a java.awt.Graphics2D instance.  However, I'm having a bit of trouble
> figuring out how exactly to do that with batik.  I *think* that I need
> to decode my SVG drawing into a GVT tree, and then render the tree.
> However I can't figure out which part of batik I need in order to do
> the rendering.  Transcoder and SVGGraphics2D do not seem to be quite
> what I want. Actually, I haven't yet figured out the
> decoding-to-GVT-step either, but I'm assuming that's pretty
> straightforward.
>
> So can anyone give me a pointer on how to do this?  Perhaps just point
> me to an existing example?  My first goal is to just get static images
> rendering.
>
> After that, I'll need to get animation working.  I'm assuming that
> supporting animation will entail updating the drawing's current time
> every so oftern on a separate thread, via the AnimationEngine, and
> then re-rendering the updated GVT?
>
> I *could* do all this by rendering into a static java.awt.Image, and
> then bliting the Image (i.e. roll my own double-buffering), but I'd
> prefer to figure out how to just draw directly onto a Graphics2D
> instance first.  That's because the framework I'm using already has
> some double-buffering, so I most likely wont need to do that with the
> SVG rendering.
>
> Thanks,
> Mike Jarmy
>
> P.S. FYI, I'll probably never need to support handling interactive user input.
>

OK, I have discovered the GraphicsNode.paint(Graphics2D g2d)  method,
which may be all I need to call once I actually get a valid GVT build.
 However, I'm having trouble building a GVT from a
java.io.InputStream.  Here is the code I'm using:

            String parser = XMLResourceDescriptor.getXMLParserClassName();
            SAXSVGDocumentFactory f = new SAXSVGDocumentFactory(parser);
//            String uri = "http://www.example.org/document.svg";
            Document document = f.createDocument(null, inputStream);

            UserAgent userAgent = new UserAgentAdapter();
            DocumentLoader loader = new DocumentLoader(userAgent);
            BridgeContext bctx = new BridgeContext(userAgent, loader);
            bctx.setDynamicState( BridgeContext.DYNAMIC );
            GVTBuilder builder = new GVTBuilder();
            this.gvtRoot = builder.build(bctx, document);

This code fails at the call to GVTBuilder.build(), with the following error:

Invalid CSS document.
Unable to make sense of URL for connection
        at org.apache.batik.css.engine.CSSEngine.parseStyleSheet(CSSEngine.java:1149)
        at org.apache.batik.dom.svg.SVGDOMImplementation.createCSSEngine(SVGDOMImplementation.java:117)
        at org.apache.batik.dom.ExtensibleDOMImplementation.createCSSEngine(ExtensibleDOMImplementation.java:212)
        at org.apache.batik.bridge.BridgeContext.initializeDocument(BridgeContext.java:378)
        at org.apache.batik.bridge.GVTBuilder.build(GVTBuilder.java:55)
        at com.tridium.svg.ui.BSvgDrawing.loadDrawing(BSvgDrawing.java:305)

Could that be because I'm passing a null value in for the URI when I
create the document from the InputStream?  I have noticed that I get
the same error no matter what I pass in for the URI.  Is there perhaps
a better way to construct a Document from an InputStream?

Thanks,
Mike Jarmy