Hi Steven,
This all looks correct to me. I agree with Jorg that it
would be nice to add this summary to the Wiki.
Steven Huey wrote:
Hello,
I'm trying to better understand how Batik works, and have spent some
time reading through the source code. I've included a summary below of
what I've learned so far figuring that it might help other newcomers to
Batik, and so that if I've missed anything perhaps some more experienced
developers can make any necessary corrections.
= A Summary of Using the JSVGCanvas Class to Display a SVG Document =
First of all it's important to note the class inheritance hierarchy
being used here since several methods called from the JSVGCanvas class
are actually implemented by some of the classes it inherits from.
JSVGCanvas : JSVGComponent : JGVTComponent : JComponent
After creating a JSVGCanvas instance the setURI() method is called with
a URI of the SVG document to load. If the URI is valid the
loadSVGDocument() method of the JSVGComponent class is called with the URI.
In the loadSVGDocument() method all document processing for the current
document is stopped, and then a org.apache.batik.bridge.DocumentLoader
and org.apache.batik.swing.svg.SVGDocumentLoader are created. The
SVGDocumentLoader handles the firing of document loading events and the
DocumentLoader uses a org.apache.batik.dom.svg.SAXSVGDocumentFactory to
create a org.w3c.dom.svg.SVGDocument instance. The SAXSVGDocumentFactory
in turn relies on a org.apache.batik.dom.util.SAXDocumentFactory to
parse the SVG data referenced by the given URI.
The JSVGCanvas relies on the SVGDocumentLoaderListener,
GVTTreeBuilderListener, and SVGLoadEventDispatcherListener listeners
that are added in the JSVGComponent constructor in order to know what is
going on with the loading, building, and rendering of the SVGDocument.
The listeners are implemented in the JGVT.Listener and
JSVGComponent.SVGListener classes.
When the document has finished being loaded and parsed the
setSVGDocument() method of the JSVGComponent classs is called, which
then calls the installSVGDocument() method in the same class.
The installSVGDocument() method:
1. Gets rid of any resources from the previous document (if any)
2. Create a new org.apache.batik.bridge.BridgeContext to associate the
SVG DOM and the GVT tree
3. Configures the component and BridgeContext instance based on the
document state (ALWAYS_STATIC, ALWAYS_DYNAMIC, ALWAYS_INTERACTIVE,
AUTODETECT)
4. Creates a org.apache.batik.swing.svg.GVTTreeBuilder with the
SVGDocument and BridgeContext
5. Initializes event handling for mouse and keyboard events
When the GVTTreeBuilder is done building the GVT tree the JSVGComponent
performs some additional configuration so that dynamic documents work
correctly, and then calls the scheduleGVTRendering() method of the
JGVTComponent class.
The scheduleGVTRendering() method calls the renderGVTTree() method of
the same class and:
1. Sets the size of the visible rect to be the size of the component
2. Creates either a static or dynamic image rendered based on the
document state (org.apache.batik.gvt.renderer.StaticRenderer or
org.apache.batik.gvt.renderer.DynamicRenderer)
3. Finds the inverse of the rendering transform, which is set to the
identity matrix
4. Creates a shape by transforming the rectangle found in step 1 with
the matrix from step 3
5. Creates a GVTTreeRenderer and starts the rendering thread
The GVTTreeRenderer fires GVT tree rendering events and calls the
repaint() method of the renderer. Once repainting is complete, the
JGVTComponent is notified of the fact by a GVT tree rendering event, and
in response repaints the component using the updated image that was
rendered offscreen by the renderer.
- Steven Huey
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