Which is great, except … what URI scheme and path does one use?  Every example I could find always passed null for the image, so after giving up on the web I joined the Prism mailing list and posted a question.  The first response was to use the inline data scheme, with a base64-encoded image.  It was ugly, but it worked.

A later response, however, yielded the proper way:

resource://webapp/path/to/image.png

I’ve created a webapp bundle that does just that.  Unfortunately, such bundles at present only work with the stand-alone version of Prism.  The Firefox add-on is really a better way to run Prism, but if you’re using it you’ll need to do a little manual mucking in your webapp profile to use this bundle.

Stand-Alone Bundle

So, if you just want the bundle, here you go.  Note that I haven’t really tested it on the stand-alone version, so please let me know if something is broken.

Hack Your Webapp

As I said, if you’re using the add-on version, you’ll need to do a little manual hacking.  After you create the webapp, as described in my earlier post, open up Explorer and navigate to your Prism webapp bundle cache.  On Windows, this is in %APPDATA%\WebApps (something like C:\Users\Brian\AppData\Roaming\WebApps); on Linux, it is ~/.webapps.  You should see your Google Wave webapp in that directory.  Add the webapp.js script to that directory, and also add in images/google-wave-52×32.png.  Now you should get a toaster pop-up and task bar notification when there are new waves.

It would be nice if Google were to add a <link rel=”webapp”> to Wave, referencing an appropriate bundle.  If anybody there sees this and cares to use my code as a crude starting point, I am releasing this code under an MIT license.