RE: Embedded fonts + generic font families

Re: It is not clear to me if we apply the same rule in TTML2. Incidentally this is one of the effects of our non-normative referencing of semantic basis, which the Director queried in 2018. As part of any refactoring of TTML we should think about whether we can strengthen the normative definitions of style attributes.

+1

J

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P Before printing, think about the environment
From: Nigel Megitt [mailto:nigel.megitt@bbc.co.uk]
Sent: 24 January 2019 10:26
To: Pierre-Anthony Lemieux <pal@sandflow.com>; TTWG <public-tt@w3.org>
Subject: RE: Embedded fonts + generic font families

Hi Pierre,

good question!

The text of <generic-family-name><https://www.w3.org/TR/ttml2/#style-value-generic-family-name> in TTML2 says:

> The resolution of a generic family name to a concrete font instance is considered to be implementation dependent, both in the case of content authoring and content interpretation.

and

> If the generic family name default is specified (or implied by an initial value), then its typographic characteristics are considered to be implementation dependent;

which I think any way you play that through means that it is not specified.

Looking at the semantic derivations, XSL refers to CSS, and CSS2<https://www.w3.org/TR/2011/REC-CSS2-20110607/fonts.html#font-family-prop> says:

> Font family names that happen to be the same as a keyword value ('inherit', 'serif', 'sans-serif', 'monospace', 'fantasy', and 'cursive') must be quoted to prevent confusion with the keywords with the same names. The keywords 'initial' and 'default' are reserved for future use and must also be quoted when used as font names. UAs must not consider these keywords as matching the '<family-name>' type.

So by that rule there would be a difference in your example between the handling of tts:fontFamily='default' (generic font family name) and tts:fontFamily='"default"'  (non-generic). I have not checked if later iterations of CSS have modified this rule; this is the version of CSS2 that is referenced by TTML2.

It is not clear to me if we apply the same rule in TTML2. Incidentally this is one of the effects of our non-normative referencing of semantic basis, which the Director queried in 2018. As part of any refactoring of TTML we should think about whether we can strengthen the normative definitions of style attributes.

kind regards,

Nigel


________________________________
From: Pierre-Anthony Lemieux [pal@sandflow.com]
Sent: 24 January 2019 09:07
To: TTWG
Subject: Embedded fonts + generic font families
Good morning/evening,

Say the following is present in a TTML2 document:

  <resources>
    <font family="default" range="u+20-7f,u+90-9f">
      <source src="http://example.com/fonts/default.otf" type="font/otf"/>
    </font>
  </resources>

In the following snippet, is a presentation processor expected to use the embedded font, or is the font selection sill left to the implementation?

<p tts:fontFamily="default">font above or application-selected?</p>

Best,

-- Pierre



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