Re: [css-fonts] font-weight-adjust

Florian Rivoal wrote:

> Also, I am not particularly familiar with font file formats and font
> container file formats, so maybe this is a silly question, but but is
> that sufficient? is this fragment identified always sufficient to
> identify an individual font face down to 1 specific weight?

Yes, an individual font has a single weight/width/slant.

> I wonder if there could be for example cases where using this fragment
> identifier you could pick between italic or normal, or between
> proportional and monospace, or between serif and sans serif, but that
> would still leave you with a font file containing a few font faces of
> different weights.

The TrueType collection format is is basically a packaging format for
fonts, it's extremely simple. There's a header with a tag/version along
with an array of offsets to individual fonts within the package. There is
no other identifying information.

  https://www.microsoft.com/typography/otspec/otff.htm

Picking from fonts within the package would require parsing the relevant
style info for each of the fonts within the package. And platform vendors
in practice don't completely agree on the "correct" attribute used for
defining things like font weight (!!!).

Ideally, some form of unique id or attributes would be included in the
package header but it's not in the current version of the format.

Just to reiterate, no user agent currently supports the loading of webfonts
contained in TrueType collections.

Regards,

John Daggett
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