[libvirt] [RFC] making (newly public) EventImpl interface more consistent

Hi Folks - Since virEventRegisterImpl is now public (in libvirt.h), a nagging concern of mine has become more urgent. Essentially this callback gives clients a way of registering their own "handle (fd) watcher" and "timer" functionality for use by libvirt. What bugs me is the inconsistency between the handle-watcher and timer interfaces: the timer "add" function returns a timer id, which is then used to identify the timer to the "update" and "remove" functions. But the handle-watcher add / update / remove functions identify the watcher by the handle (fd). The semantics of registering the same handle twice aren't specified (what happens when we pass that same fd in a subsequent "update" or "remove"?). Even worse, this doesn't allow one to manage multiple watches on the same handle reasonably. So why not make the handle "add" function return a "watch id" (analogous to the "timer id" returned by the timer "add" fn)? And then use this watch id to specify the handle-watcher in the "update" and "remove" functions. This conveniently handles multiple watches on the same handle, and also makes the "handle-watching" interface more consistent with the "timer" interface (which is registered at the same time). We'd pass both the watch id and the handle (fd) into the watch-handler callback. I'd like to implement and submit this (along with fixups to the event test code) if there are no objections. Thanks, Dave P.S. I'm currently working on Java bindings to the new event code ...