search

w3c / ttml2

Timed Text Markup Language 2 (TTML2)
https://w3c.github.io/ttml2/
Other
40 stars 16 forks source link

Clarify "the first font obtained" in tts:lineHeight normal algorithm. #1241

Open skynavga opened 2 years ago

skynavga commented 2 years ago

Clarify the following ambiguity regarding the tts:lineHeight="normal" algorithm in §10.2.27:

If possible, the resolution of this ambiguity should favor the CSS Fonts Module definition of first available font, in which case the use of tts:fontSelectionStrategy as a mapping constrain becomes moot.

Note that this ambiguity is present regardless of whether tts:lineHeight is applied to p or span.

nigelmegitt commented 2 years ago

Note that this ambiguity is present regardless of whether tts:lineHeight is applied to p or span.

Presumably this is just an aside, not relevant to the issue, but just wanted to note that tts:lineHeight only applies to p.

skynavga commented 2 years ago

@nigelmegitt see the following spec text in §10.2.27:

Note:

In addition to explicitly applying to p elements, the value of this style property inherited by span element and anonymous span descendants of a p element is used to compute the half leading of their generated inline areas, about which see [XSL-FO 1.1], §4.5, and [CSS2], §10.8.1.

admittedly, this does not use the phrase applies to, but that's cutting it rather thin, as uses to compute is pretty close; note that in both CSS and XSL line-height is said to apply to our equivalent of both p and span for the reason we give in this Note;

nigelmegitt commented 1 year ago

(apologies for the delay)

Ah, I see what you mean @skynavga, you're referring to the used value of tts:lineHeight that is needed when laying out inline areas, thanks, that makes sense.