[mpeg-OTspec] GSUB lookup of type 5 (contextual) referring to another lookup of type 5

[Behdad Esfahbod]

On 13-05-22 06:57 PM, Bob Hallissy wrote:
>  
> 
> On 2013-05-22 at 13:29 Behdad Esfahbod wrote:
>> On 13-05-22 02:25 PM, Adam Twardoch (List) wrote:
>>> > is it valid
>>> > and "unproblematic" that a contextual lookup refers to a contextual lookup?
>> In HarfBuzz we support that up to 8 levels deep.
> 
> Wow -- who would have guessed that?

The 8 is just a constant, there to avoid infinite recursion.


> Can a contextual lookup refer to Contextual Chaining lookups as well?

Yes.

> Reverse Contextual Chaining lookups?

Partially.  The first sublookup will work, but not multiple ones.


> Presumably the phrase in the contextual lookup description:
>> Because multiple substitutions may occur per context, the SequenceIndex and
>> LookupListIndex refer to the glyph sequence after the text-processing client
>> has applied any previous lookups.
> still holds, so the referred-to contextual lookup may "see" a context quite
> different than original lookup.
> 
> I'm curious how people utilize this?

I have no idea.  I just implement this stuff :).

behdad


> Bob
> 
> 

-- 
behdad
http://behdad.org/