[MPEG-OTSPEC] Minor ballot comment - change a field from 16 to 24 bits

[Liam R. E. Quin]

On Wed, 2025-04-02 at 22:45 +0900, mpsuzuki wrote:
> Dear Liam,
> 
> I apologize to ask a few questions to your post in 2 months ago...

Not at all, i am glad you spotted the mistake in the comment.

The change should have been to 7.3.9.1.3, which is in the new GVAR
table, not the gvar table.


> please
> let me ask a few questions.
> 
> 1) Adding a new version of "gvar" table whose DataOffset is 24-bit is
> bad option?

This option is what was agreed in a face to face meeting of the ad hoc
group in Portland, oregon, USA; we introduced a new table GVAR. This
comment was intended to refer to GVAR< not to the already-existing
gvar, as that would not be a compatible change - you are right!

> 
> 2) Some fonts with 24-bit DataOffset are already shipped to the
> market?

I don’t know the answer to that. I believe avar2 is already in use but
i don't know about 24-bit glyph IDs. For dataOffset, i think at the
moment the fonts are not being shipped yet.

> 
> 3) Some existing implementations are already capable to handle 24-bit
> DataOffset?

harfbuzz with a flag right not. If the comment is accepted, probably
there will be wider support very quickly.

What happened was that some people were building a font (i think a
colour icon or emoji font) and found that the dataoffset field
overflowed. But they can't really ship the font yet.

liam

-- 
Liam Quin, https://www.delightfulcomputing.com/
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