NPP_HandleEvent not called for windows plugins?

Before I enter a bug, I want to make sure there hasn't been a change in the specification for which the document hasn't been updated.

I have a simple windows plug-in that's loaded within an HTML page, being embedded using <OBJECT> (it has height and width). It does not create any hwnds, it just is an empty shell that returns NPERR_NO_ERROR (or 'true' or whatever success indicates) for everything.

It's NPP_HandleEvent() function is never called (it is set in NP_GetEntryPoints()).

Is there something specific I need to do in order to get NPP_HandleEvents to be called?  On the mac, it is called repeatedly  for all sorts of events.  The code is almost the same; one difference is that on the mac, NPP_New negotiates (using NPN_SetValue) the Cocoa Event Model.

Is there some event model that needs negotiating on Windows?

Thanks,
Rudi