WIP fifo and commit timing

[ids1024]

This needs testing, and still need to signal the commit timing.

I'd like to de-duplicate the different places that iterate over all different types of surface (instead of adding more code for this for fifo and commit timing, along with the existing send_frames, update_primary_output, send_dmabuf_feedback, visisible_output_for_surface, as well as the similar but slightly different code already shared in render_input_order()). But these seem to all be slightly different, so I'm not sure how best to unify them...

[Drakulix]

But these seem to all be slightly different, so I'm not sure how best to unify them...

That is the reason they are separate... I didn't want to sacrifice readability for some complex code-deduplication that can handle all the little differences.

[ids1024]

Yeah. If it were just as simple as needing an iterator over all types of windows (and other top level surfaces that may have their own popups and subsurfaces), that wouldn't be too bad. And all the uses could exhaustively match against any surface types. But then something like visisible_output_for_surface isn't just iterating over ever surface on an output, but trying to do the reverse.

There may be some way to structure all of this better, without a lot of duplication, of fairly opaque use of some very complicated surface iteration API, but I'm not sure the best way to do it.