(In reply to comment #0)
> Sometimes we have a cue on an active track that starts within the video's
> timeline, but ends beyond the end of the video (maybe just ms beyond, because
> different browsers calculate a video's duration differently or you get rounding
> errors). We would like to see the onexit event being fired for such cues.

When should the exit event be fired, and why? Wouldn't this require also hiding the cue at playback end? That seems undesirable. 

> This opens door to a larger question: what to do with cues that start before
> the video starts, but end within it? These should also have onenter events. It
> would be nice to be able to deal with such cues, too, since in this way you can
> create an explicit order of cues that should be displayed as the video starts,
> e.g. if you want to display an ad from one track before you display a caption
> and render it in the remaining space.

The enter event should be fired, just as when one seeks into the middle of the cue. I believe the spec already requires this, but it wouldn't hurt to double check.

Please file just one issue per bug.

I don't think it makes sense to fire onexit for cues you haven't exit yet, as Philip says.