I'll create an account for the wiki, clean things up a bit, and add it
either over the weekend or early next week.
- Steve
On Feb 25, 2005, at 4:01 PM, Thomas DeWeese wrote:
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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