Anyway, what good would it do to write that gadget emulator without using it, so I've put together a very rough proof of concept for a shared graphics editor gadget using SVG. I didn't write all of it myself, mind you. Jayesh Salvi started a discussion about SVG in Wave, and during that discussion he pointed us to an existing open source browser based SVG editor by Narendra Sisodiya and Pavol Rusnak.
That made my job reasonably easy. I chopped their editor to pieces and stripped out a lot of stuff, partially to reduce the amount of work to make it work with Wave, partially to remove features that aren't quite finished yet.
The result is still buggy (clearing the canvas doesn't work; deletion is shaky), not as efficient as it could be (at the moment it re-sends all attributes of modified elements instead of just the changed ones, but that's easily fixed), lacks lots of features (like moving objects, saving, loading external SVG's etc.).
More importantly, since I don't have sandbox access it has not been tested with the actually Google Wave client (hint, hint; any Google people reading this?) It is possible or even likely that it won't work in the real client, but any issues should be reasonable simple to fix.
It's been tested - somewhat - on Firefox and Safari. It is highly unlikely to work on Internet Explorer (it's possible it could work if you have an SVG plugin installed, but I doubt it). It could be made to work on IE via a shim layer to use VML instead of SVG, but that's not very high on my priority list at the moment - especially as Google looks set to introduce a suitable shim layer.
You can test it now by going to my gadget emulator, and entering the filename "svg-edit.xml".
If you want to experiment with the code on your own, get the latest version of my gadget emulator from the Github repository and the SVG editor gadget also from Github.
Not that while I welcome patches / suggestions, this is a proof of concept and I'm not sure how far I'll take it - I also have not talked to Narendra or Pavol about whether it's possible or desirable to fold any of the (fairly extensive) changes I made back into the original editor. If you'd like to see this turn into something more, let me hear about it in the comments.
UPDATE: I will be working with the SVG Edit guys to combined the two projects. Also see this post at The Next Web
(And if you're with the Google Wave team and want to give me sandbox access, e-mail me at [email protected] or [email protected] - I promise I'll use it to make sure this gadget runs properly in the actual client ;) )