Missing default ObjectCodec when decoding from XML #178

Version: release 0.1.0

I was trying to decode the following XML:

<GraphDataModel><root><Cell id="0"><Object as="style"/></Cell><Cell id="1" parent="0"><Object as="style"/></Cell><Cell id="B_#0" value="rootNode" vertex="1" parent="1"><Geometry _x="100" _y="100" _width="100" _height="80" as="geometry"/><Object as="style"/></Cell></root></GraphDataModel>

const doc = xmlUtils.parseXml(str);
const codec = new Codec(doc);
codec.decode(doc.documentElement, this.graph.getDataModel());

And got error like this:

Uncaught Error: Invalid x supplied.
    at set x [as x] (Point.js:44:19)
    at GraphView.updateCellState (GraphView.js:743:32)
    at GraphView.validateCellState (GraphView.js:676:26)
    at GraphView.validateCellState (GraphView.js:691:30)
    at GraphView.validateCellState (GraphView.js:691:30)
    at GraphView.validate (GraphView.js:444:58)
    at ModelEditorGraph.graphModelChanged (Graph.js:429:19)
    at Graph.graphModelChangeListener (Graph.js:348:18)
    at GraphDataModel.fireEvent (EventSource.js:132:41)
    at edit.notify (GraphDataModel.js:958:25)

After doing a lot of debugging, I found that CodecRegistry.getCodecByName(node.nodeName) does not return the default ObjectCodec for some elements (like Point, Geometry, etc... ). Therefore the decoding procedure returns the original xml element, and breaks later procedure.

I also found that if I do encoding before decoding, no error will occurs because encoding procedure uses CodecRegistry.getCodec(constructor_) which Registers a new default codec for the given constructor, if no codec has been previously defined.

My possible workaround: Manually register ObjectCodec for missing codecs:

CodecRegistry.register(new ObjectCodec(new Geometry()));
CodecRegistry.register(new ObjectCodec(new Point()));
CodecRegistry.register(new ObjectCodec(new Array()));

Perhaps CodecRegistry.getCodecByName(node.nodeName) should return a default codec like CodecRegistry.getCodec(constructor_) does?