Need a callback for "on just before position discontinuity frame"?

### Searched documentation and issues
https://exoplayer.dev/playlists.html

### Question
`onPositionDiscontinuity` is dispatched apparently after the first frame of the "next video" is already rendered. I am making a "playlist" of videos whose position on screen and size can change per video. The problem with waiting for the first frame of the next video is that I see the "next video" with the wrong size and potentially wrong position for a moment before I can correct it. I cannot seem to get to an event _just before_ the first frame of the "next video" is rendered so that it will look right. (I'm using OpenGL with a surface view used by the ExoPlayer).

Is this currently possible?

Or, would I need to dig into the source code and add an event for "on just before position discontinuity frame"?

If so, can you provide some easy tips for where I would do that in the code (which functions, code branches, etc.)?

Thanks!