[ttml2] Derivation of `tts:fontVariant` points to a non-existent section (#1277)

nigelmegitt has just created a new issue for https://github.com/w3c/ttml2:

== Derivation of `tts:fontVariant` points to a non-existent section ==
The [derivation of `tts:fontVariant`](https://www.w3.org/TR/2021/CR-ttml2-20210309/#derivation-fontVariant) points to [CSS Fonts Level 3](https://www.w3.org/TR/2018/REC-css-fonts-3-20180920/) §6.11 for a definition of the `font-variant-position` property. That section does not exist, and appears to have moved to CSS Fonts Level 4 - §6.5 in both the [WD](https://www.w3.org/TR/css-fonts-4/#font-variant-position-prop) and the [ED](https://drafts.csswg.org/css-fonts/#font-variant-position-prop) and is marked as an at-risk feature.

We should update the reference. It is non-normative, so there's no normative impact. However, the TTML2 specification for [`tts:fontVariant`](https://www.w3.org/TR/2021/CR-ttml2-20210309/#style-attribute-fontVariant) is very light and omits important details that are in the CSS specification, especially the recommendation to synthesise simulated glyphs if the desired ones are not available in the font.

We should consider duplicating the CSS approach to require or recommend or even just permit synthesis of simulated glyphs so that this feature is usable more generally, or if we do not do that, then mention that the feature is dependent on the glyph variants being present in the used font.

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/1277 using your GitHub account


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Received on Wednesday, 8 January 2025 11:38:40 UTC