[MPEG-OTSPEC] Removal of the CFF and CF2 from OFF standard

John Hudson john at tiro.ca
Thu Oct 8 22:07:58 CEST 2020

On 08102020 11:50 am, Behdad Esfahbod wrote:
>     Accepting that rasterisation and layout implementation specs
>     should exist, whether they should exist as /part/ of OFF is less
>     obvious to me.
> How so? OFF files include bytes (CFF/CFF2 hinting data as well as 
> GSUB/GPOS lookups) without specification of how to be used to display 
> text using that font. This is akin to an image format specification 
> without a decoding algorithm specified.
> What is the use of such a file format standard then?

I've been publicly lamenting the absence of an implementation 
specification for OTL for a very long time, as you know. And can make 
the case that this should be a standard, not simply a recommendation, 
and that as a standard it /might/ belong as part of OFF. In that case, 
the issue for me is whether I want to subject the work of creating that 
standard to the ISO process with its annoyances and limitations. So in 
that case, I can also make the argument for the OTL implementation spec 
being independent of the font file format spec — so we can have a 
public, editable draft, for exampe —, and have the two standards 
reference each other rather than being rolled into one. But that is just 
an argument from process.

In the case of rasterisation, I think there is actually a stronger 
argument to be made for keeping the implementation spec independent of 
the font file format spec because, for the reasons I suggested in my 
previous message, we don't need to standardise a single implementation, 
and might actually benefit from multiple implementation specs, rather 
than shoe-horning one of them into the OFF standard.

My understanding is that Adobe themselves have multiple hint interpreter 
implementations—the whole philosophy of the PS/CFF hinting model is that 
there /can/ be multiple rasterisers and these can change over time 
independently of the font data—, so even if ‘acceptable to Adobe’ were 
the criterion for including one rasterisation spec in OFF, /which one?/



John Hudson
Tiro Typeworks Ltd    www.tiro.com
Salish Sea, BC        tiro at tiro.com

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