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

[John Hudson]

On 2024-02-22 6:59 am, Simon Cozens via mpeg-otspec wrote:
> When Behdad, I and others did some thinking about the JSTF table last 
> year (with a view to potentially making a 2.0 version which interacted 
> better with variable fonts), we came to the realisation that 
> everything you can do with the JSTF table, you can actually now do 
> with a "JSTF" axis. So at this point it's entirely redundant.
>
> In fact, I think Behdad implemented JSTF-axis-based justification in 
> harfbuzz. (hb_shape_justify) 

How does the axis handle prioritisation of justification techniques?


In answer to Nate’s query about how the JSTF table made it into the 
spec, I discussed this, quite a few years ago, with Eliyezer Kohen. The 
table had been spec’d to provide mechanisms to address Arabic 
justification as the problem space had been described to Eliyezer by Tom 
Milo. This involved being able to define multiple mechanisms to affect 
justification—alternate forms, elongation, spacing adjustments—and then 
/prioritise/ these mechanisms. I think Nate is quite right that the 
table is not useful or really understandable without a corresponding 
justification engine specification, and my impression has long been that 
the JSTF table spec was something that would need to be revised in 
implementation (as various other parts of OpenType have been).

JH


-- 

John Hudson
Tiro Typeworks Ltdwww.tiro.com

Tiro Typeworks is physically located on islands
in the Salish Sea, on the traditional territory
of the Snuneymuxw and Penelakut First Nations.

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