[HarfBuzz] HB coretext_aat shaper?

[Behdad Esfahbod]

On 15-03-17 05:48 PM, Adam Twardoch (List) wrote:
> 
>> On 18 Mar 2015, at 01:36, Behdad Esfahbod <behdad.esfahbod at gmail.com> wrote:
>>
>> On 15-03-17 05:27 PM, Adam Twardoch (List) wrote:
>>> Behdad, 
>>>
>>> What functionality does the coretext_aat shaper currently support?
>>
>> What the coretext_aat does is: if the font has 'mort' or 'morx' table, then
>> call the coretext shaper, otherwise fail (and let ot shaper handle).  It's
>> just a mechanism to choose which shaper to use.
> 
> I see. In this case, I'd recommend adding a check for the "kerx" table. One can think of an AAT font that has "kerx" but no "morx" or "mort". 

Is there any in the wild?


>>> I can see that it does something with "mort" and "morx", but possibly not "kerx" or the extended "kern" table? Or does it? With something like hb-view, which options (if any) are passed on? Direction, script, language, features? 
>>
>> Everything is supported.
> 
> I see. So you specify the features using OpenType Layout "lingo", then the feature tags get converted to AAT feature types using the the feature_mappings table in hb-coretext.cc, and then those AAT feature types are passed on to CoreText? 
> 
> And that means that the feature tags which are listed in 
> https://developer.apple.com/fonts/TrueType-Reference-Manual/RM09/AppendixF.html
> but are not in hb-coretext.cc feature_mappings (i.e. they don't translate to OT feature tags) cannot be accessed, correct? 

Right.

> (I'm not saying this is particularly troubling :) ). 
> 
> Best,
> A.
> 
>>
>>
>>> Thanks,
>>> A.
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> 
>