[MPEG-OTSPEC] CSS WG liaison to SC29 on Open Font Format (from Feb. 2020)

[nwillis at glyphography.com]

The issue that always struck me about the JSTF table definition is that 
there is no accompanying justification engine against which you could 
measure whether or not it works, partly works, or does not work. So it's 
a bit "underanswerable." It would be like attempting to assess whether 
there is enough detail in the GSUB/GPOS spec alone that you could go 
implement HarfBuzz, Uniscribe, or any of the rest: to implement one you 
definitely have to know more about the behavior needed from a shaping 
engine than solely what's defined in GSUB/GPOS ... but, conversely, you 
have to know more about what the shaping engine is going to do in order 
to know whether or not the GSUB/GPOS spec is well-written.

An interesting question might be to ask whether a JSTF table could 
contain all of the info needed to work for some _known_ H&J engine — a 
particular TeX flavor, hz-program, or so on.

I never really found a detailed account of how JSTF made it into the 
specification originally, such as describing whether it seemed to be 
written to match some particular private justification-engine's needs, 
or to match a hypothetical one that may have never appeared on the 
market.

(If that info is out there, I'd certainly appreciate seeing it.)

Nate

---


On 2024-02-21 16:13, John Hudson via mpeg-otspec wrote:
> Simon Cozens attempted an implementation of JSTF table support a few
> years ago, in an effort to find out whether it was actually
> implementable. As I recall, he determined that much of it could be
> implemented, but that there were some holes or things that could be
> improved. As far as I know, there is no JSTF table support in any
> shipping software, which I guess at least means we wouldn’t break
> anything were we to revise the spec to produce something workable for
> CSS.
> 
> JH
> 
> 
> On 2024-02-20 12:39 pm, Vladimir Levantovsky via mpeg-otspec wrote:
>> The liaison statement I mentioned during today's call can be 
>> found here:
>> https://lists.w3.org/Archives/Public/www-archive/2020Feb/att-0005/CSS-SC29-20200113.pdf
>> 
>> One of the aspects mentioned in the CSS WG statement is related to 
>> using cursive elongation for text justification purposes, which may be 
>> desirable for cursive writing and could be essential e.g. for many 
>> Arabic scripts - I am wondering if this can already be accomplished 
>> using JSTF table, and whether the existing specification needs to be 
>> updated to support it.
>> 
>> Thanks,
>> Vladimir
>> 
>> 
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> --
> 
> John Hudson
> Tiro Typeworks Ltd    www.tiro.com
> 
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