Consider adding support for "before" and "after" annotation position

[palemieux]

Only "outside" is currently required for #rubyPosition and the position component of #textEmphasis.

Since "outside" is optimized for two-line blocks, it is not clear that this is sufficient to support 2+ lines (and even 1 line).

Recommend consider supporting "before" and "after" as well.

[nigelmegitt]

Will this issue still be valid after w3c/ttml2#798 has been merged?

[palemieux]

@nigelmegitt I think so, since 'outside` is only intended to be used with 1- or 2-line blocks.

[css-meeting-bot]

The Working Group just discussed Consider adding support for "before" and "after" annotation position imsc-vnext-reqs#23, and agreed to the following:

• RESOLUTION: Support `"before"` and `"after"` values for `tts:rubyPosition`.

The full IRC log of that discussion

<nigel> Topic: Consider adding support for "before" and "after" annotation position imsc-vnext-reqs#23
<nigel> github: https://github.com//issues/23
<nigel> Pierre: Note that #25 may need to change depending on what we decide for #23 here.
<nigel> .. Today IMSC 1.1 has requirement only for rubyPosition="outside".
<nigel> .. After some digging, I think that's optimised for 2 line presentations.
<nigel> .. My understanding is sometimes there are 3 lines, depending on the authorial style.
<nigel> .. If they are anything other than 2 lines the author will need more control than outside,
<nigel> .. and will need to position rubys before or after, so my suggestion is simply to support
<nigel> .. before and after as well as outside for rubyPosition.
<nigel> .. From an implementation perspective there's more syntax but in terms of layout it's
<nigel> .. kind of a no-op because before and after need to be supported for outside anyway.
<nigel> .. This reflects feedback I have received.
<nigel> Cyril: I have no objection. We were proponents for outside but we don't have a problem
<nigel> .. with people using before and after if they want to. It's not exactly a no-op for implementation
<nigel> .. but the cost is minimal.
<nigel> Pierre: The risk is too great to not include.
<nigel> Nigel: I think that's right, and also would note that whatever syntax we accept for
<nigel> .. rubyPosition we also permit in rubyReserve.
<nigel> Pierre: Yes.
<nigel> RESOLUTION: Support `"before"` and `"after"` values for `tts:rubyPosition`.