Remove tts:fontShear and add tts:shear and/or tts:lineShear

[palemieux]

In light of w3c/ttml2#784 , tts:shear should replace tts:fontShear .

[palemieux]

Add Editor's Note indicating that support for tts:shear and/or tts:lineShear is being considered, and feedback is welcome.

[css-meeting-bot]

The Working Group just discussed tts:fontShear should be tts:shear imsc-vnext-reqs#24, and agreed to the following:

• SUMMARY: @palemieux to raise an issue with CSS WG, and to add an ed note to the pull request to note ongoing query re lineShear.
• SUMMARY: Continue to investigate options for using shear and lineShear
• SUMMARY: Temporarily add shear and lineShear with editorial notes against both, pending a later resolution.

The full IRC log of that discussion

<nigel> Topic: tts:fontShear should be tts:shear imsc-vnext-reqs#24
<nigel> github: https://github.com//issues/24
<nigel> Cyril: I think it should be lineShear. I know it is not supported in CSS, because it requires
<nigel> .. breaking lines into separate paragraphs, but lineShear is what people expect in terms of
<nigel> .. rendering, in all the examples.
<nigel> Pierre: The author can do that by creating two `p`s.
<nigel> Cyril: The implementation can do it by breaking into `p`s.
<nigel> Pierre: It's not simple, and it means if you ever want block shear then you can't - you can't
<nigel> .. have the flexibility to shear each `p`.
<nigel> .. I did ask about line breaks in Japanese subtitles and my understanding is it is not acceptable
<nigel> .. to let line wrap wrap lines.
<nigel> Cyril: That's not the case, we use that all the time.
<nigel> Pierre: The feedback I received is that authors want to control line breaks and you cannot
<nigel> .. just break anywhere in Japanese.
<nigel> Cyril: My concern is that using multiple `p`s can mess up the timing. It makes the document
<nigel> .. much simpler if you have one `p` per region or per event.
<nigel> Nigel: How are we going to figure this out?
<nigel> Cyril: I think we need to gather more feedback.
<nigel> .. Would it be an option so support both shear and lineShear?
<nigel> Pierre: Supporting lineShear is going to be extremely difficult.
<nigel> Nigel: Because we're missing something in CSS?
<nigel> Pierre: Yes it only allows shearing of blocks.
<nigel> Nigel: Yes, I found that in my research too.
<nigel> Pierre: The overall challenge is turning a bunch of lines into a bunch of `p`s requires
<nigel> .. restructuring the entire span tree. With rubys on top of that it's going to be hard to
<nigel> .. implement and also I suspect brittle. I don't want us to understaimate the complexity
<nigel> .. of doing this correctly.
<nigel> s/staim/estim
<nigel> Nigel: I have a suggestion that we raise this requirement with the CSS WG.
<nigel> .. I think the requirement is to be able to apply shear to line areas.
<nigel> Pierre: Yes, like many of our requests, CSS does not deal with lines, but we need to.
<nigel> Nigel: Do we ever need to shear spans within a line?
<nigel> Pierre: I'm not aware of that requirement
<nigel> Cyril: Me neither - normally it is the entire line.
<nigel> Pierre: I'm fairly certain that tts:fontShear is not needed for subtitles and captions.
<nigel> .. Ideally both lineShear and shear would be supported, but lineShear is challenging to implement.
<nigel> .. Is IMSC 1.1 broken if lineShear is not supported?
<nigel> Nigel: My proposal is to support shear for now, raise an issue with CSS WG for lineshear
<nigel> .. with the intent of adding support for it to a future version of IMSC 1.1.
<nigel> Pierre: I like that approach for now.
<nigel> .. Also Glenn filed another issue recently with CSS recently too, which we should track.
<nigel> Nigel: I have a list in the agenda actually.
<nigel> Cyril: One concern about shear is what if the user changes the font size and suddenly you
<nigel> .. have line wrapping, then the alignment is not desired.
<nigel> Pierre: If you shear as the entire `p` is the result completely objectionable?
<nigel> .. For 2 lines there's a very subtle difference, but with 4 lines you see a pretty big difference.
<nigel> .. Not being Japanese, I don't know if the result is unacceptable or just a bit strange or
<nigel> .. annoying.
<nigel> Cyril: I'll come back to you on this one.
<nigel> Pierre: Thank you, I will continue to dig on this too.
<nigel> ACTION: Pierre to raise an issue with CSS WG requesting support for lineShear
<trackbot> Created ACTION-512 - Raise an issue with css wg requesting support for lineshear [on Pierre-Anthony Lemieux - due 2018-06-21].
<nigel> Pierre: I think it is clear that we will replace fontShear with shear, and deal with lineShear
<nigel> .. separately?
<nigel> Cyril: I'd rather make one pull request for the shear part.
<nigel> Pierre: We know fontShear is bad so we need to address that now.
<nigel> Cyril: Just add an editor's note to the pull request that we're considering adding lineShear
<nigel> Pierre: Sounds like a good solution.
<nigel> SUMMARY: @palemieux to raise an issue with CSS WG, and to add an ed note to the pull request to note ongoing query re lineShear.
<nigel> PROPOSAL: Drop fontShear support and add shear support, with continuing consideration for lineShear
<nigel> Cyril: We would prefer support for lineShear but not shear. We don't think we are going to
<nigel> .. use shear at all.
<nigel> Nigel: OK I won't record a resolution for that.
<nigel> SUMMARY: Continue to investigate options for using shear and lineShear
<nigel> Cyril: I would suggest adding both shear and lineShear and add a note to lineShear to say
<nigel> .. we are investigating implementation difficulties given CSS, and add a note to shear
<nigel> .. saying we are investigating line alignment issues. Then we can add both and remove one
<nigel> .. or the other [or neither] later.
<nigel> Pierre: That's fine with me
<nigel> SUMMARY: Temporarily add shear and lineShear with editorial notes against both, pending a later resolution.