[MPEG-OTSPEC] Note on VARC conditions and condition set negation

[Behdad Esfahbod]

On Thu, Apr 11, 2024 at 2:40 PM Skef Iterum <skef at skef.org> wrote:

> This proposal is a particular way of supporting arbitrary boolean
> expressions in OFF. That does have the benefit of "just doing it" -- it's
> certainly preferable to adding significantly more complexity while falling
> short of total generality.
>
> However, there were presumably reasons this route wasn't taken to begin
> with, probably having to do with complexity, and those would have to be
> discussed. I.e.: Is this too much rope?
>

As someone who was part of the initial varfont initiative, it wasn't done
this way because we didn't deem the need. Note that feature variations are
a big "if else if else if else..." already. So the need for this kind of
negated logic is much less.


> This direction would be fine with me if it's fine with the group, but I
> feel that would a discussion for the upcoming, more onerous phase of work,
> not to squeeze in before the up coming deadline.
>
Honestly, the new addition is pretty small compared to the whole work. So
I'd rather earmark it in than wait. What I want to avoid is VARC going in
and implemented, then five years later Condition updated and implemented...

> I suppose if we go this way I would favor changing the
LookupVariationRecord and leaving the FeatureVariationRecord as is (so,
supporting the new formats but still going though a condition set).

I agree.

b
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