Hi Julian,
I've just started using this component and have come across a few problems/bugs. I've resolved these myself by maintaining my own structure for storing the xml (I use the component now only for the intitial parse of XML). I thought it would be useful to point out the problems for you or for any wpTools users (it took me quite some time to work out what was going wrong).
1. If you load an xml file into the component and then immediately save it, all you are left with is the xml declaration. This seems to be due to the fact that the first thing wpxmlInterface's savetostream function does is clear FData, which seems to be the storage mechanism for the xml.
I removed this and managed to save the XML.
2. The XML that is saved is not then well-formed. At its very end it has a repeat of the XML declaration. This seems to be caused by the SaveToStream function, which calls DoWriteStart, which writes the XML declaration at the end of the file.
3. Even if you comment out the call to doWriteStart, the saved XML is still not well-formed because of some extraneous characters at the very end of the file.
4. I tried to write a tag at a specific spot in the XML file using onStartTag. I assumed that the new tag would be written within the currenttag, but it was just added to the end of the file.
I hope this helps.
Cheers
Mark