TTML2 2nd > 2020-01-15

[himorin]

TTML2 2nd Edition
https://w3c.github.io/ttml2/index.html

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Dear i18n

As per the horizontal review requirements TTWG requests an internationalization review of TTML2 2nd Edition, based on the Editor's Draft at https://w3c.github.io/ttml2/index.html

The intended progress of this is CR -> PR -> Rec, since this is an amendment to an existing Rec that does not introduce any new features. Since no FPWD is expected, we are requesting review based on the ED.

The changes relative to the TTML2 (1st Edition) Rec at https://www.w3.org/TR/ttml2/ are listed at https://w3c.github.io/ttml2/ttml2-changes.html and are fixes to address issues discovered with the 1st Edition.

We suggest that you review based on the changes document, amongst which you may be especially interested in:

the changes to the font element,
the handling of text children of ruby container spans,
the font selection strategy used by the line height algorithm,

Kind regards,

Nigel Megitt

Chair, TTWG

[xfq]

I have just reviewed the document, for both the changes relative to the 1st Edition and for other parts of the document. Here are my observations:

Language

• ✓ xml:lang can be used to label natural languages of document, {paragraph,inline}-level text, and metadata.

Text direction

• ✓ It is possible to indicate base direction for paragraphs and indicate parts of the text where the base direction changes via styling using the tts:direction attribute.

• △ There doesn't seem to be a way to indicate the base direction using heuristics when tts:direction is not used.

• △ tts:direction only applies to p & span. Is it possible/useful to specify the base direction for the whole document (e.g. for the tt element)?

Characters

• △ Minor issue: there is a note in § 10.2.19 tts:fontSelectionStrategy. Terms like "code point" and "combining character sequence" might be more accurate than "character" and "contextual character sequence". On the other hand, the value of tts:fontSelectionStrategy is called character, so "character" may be easier to understand for the readers.

Encoding

• ✓ The default encoding is UTF-8, which is good.

Text decoration

• △ tts:textDecoration doesn't seem to support skipping ink. (See CSS for an example.)

• ✓ Emphasis marks are supported by using tts:textEmphasis.

Vertical text

• ✓ Rendering vertical text is possible.

• ✓ Text orientation can be specified or inferred using UTR50 Vertical_Orientation.

• ✓ Tate-chu-yoko is supported by using tts:textCombine.

  • There is an open issue about the ability to specify a preference for not fitting characters at all within an EM.

Line breaking

• △ There's reference to UAX14, but no way to control line breaking or hyphenation.

Ruby

• ✓ Ruby is supported for both horizontal and vertical writing modes.

• ✓ Double-sided ruby is supported.

• △ Bopomofo is not supported.

  • Related issue: Support for bopomofo ruby needed ttml2#253

Others

• ✓ tts:textAlign supports text-flow–relative values.

[r12a]

Since this is a 2nd edition the boat has already sailed, so i think most of the comments we would make based on @xfq points above would be relevant for a TTML-next, rather than for this version of the spec (ie. if we raise them now we should close them with a deferred label).

△ Bopomofo is not supported.

There is already an issue for this (#333), but we may want to add a deferred flag to that.

I have raised separate internal issues for the other items i consider need discussion.

[xfq]

Thanks @r12a!