Thankfully, it looks like this was just a problem with my implementation of
the OpenType feature and not with ConTeXt's handling of it! (I worried that
it might be ConTeXt when I saw that XeLaTeX was handing the feature
correctly.) Hans graciously helped me identify the problem, and everything
looks good now!

Joey

On Tue, Aug 17, 2021 at 8:56 AM Joey McCollum <jmccollum20140511@gmail.com>
wrote:

> Shouldn't dlig automatically be enabled under the "hebrew" feature set? In
> font-pre.mkiv, hebrew inherits from semitic-complete, which sets dlig=yes.
>
> Still, if I explicitly add dlig, as in the following example, things
> change, but they still aren't right:
>
> ```
>
> \starttypescriptcollection[keteryg]
>
> \starttypescript[serif][keteryg]
>
> \definefontsynonym[Serif][file:../fonts/KeterYG/KeterYG-Medium.ttf][features=hebrew]
> % all the necessary Hebrew features, including dlig
>
> \stoptypescript
>
>
> \starttypescript[keteryg]
>
> \definetypeface[keteryg][rm][serif][keteryg][default]
>
> \stoptypescript
>
> \stoptypescriptcollection
>
>
> %Set up the main font:
>
> \setupbodyfont[keteryg]
>
> %Set up right-to-left alignment:
>
> \setupalign[r2l]
>
> %Explicitly add dlig (in case it wasn't there already):
>
> \definefontfeature[plus-dlig][dlig=yes]
>
>
> \starttext
>
> \addff{plus-dlig}
>
> שֹׂבַע
>
> עָשׂוֹר
>
> קֹשֶׁט
>
> שֹׁשַׁנִּים
>
> עָשׂוֹר
>
> מֹשֶׁה
>
> שַׁלֹשׁ
>
> \stoptext ``` In examples 1, 3, 4, and 6, the *holam *of the preceding
> letter (which should have been stripped in the contextual substitution)
> just seems to have been moved farther up. In fact, the output looks like it
> would look if I turned off the reordercombining feature. (And indeed, if I
> manually reorder the glyphs to the Hebrew Layout Intelligence order, then
> the results look like they did when I just used the "hebrew" feature.)
>
>
> I may have forgotten to attach the font file I was using for this test. If
> that is the case, it is available at
> https://github.com/jjmccollum/Keter-YG.
>
>
> Joey
>
> On Tue, Aug 17, 2021 at 5:19 AM Hans Hagen <j.hagen@xs4all.nl> wrote:
>
>> On 8/17/2021 2:07 AM, Joey McCollum wrote:
>>
>> > Sorry to bring this up after over a year, but I just noticed something
>> > that doesn't seem right. I implemented some contextual substitutions in
>> > my own fork of the Keter YG Hebrew font (.ttf file attached) under the
>> > "dlig" feature that should do the following two things:
>> but you don't enable dlig
>>
>> -----------------------------------------------------------------
>>                                            Hans Hagen | PRAGMA ADE
>>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>>         tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
>> -----------------------------------------------------------------
>>
>