[NTG-context] tlig feature sometimes does not work

Mohammad Hossein Bateni bateni at gmail.com
Sat Mar 13 02:01:16 CET 2021


Umm... the fallbacks are correct.  My conclusion is that tlig does not work
when the character is not in the font itself.  Is that the case?  Is this a
bug or a feature?

\starttext

 \definefontfallback[fall][dejavusansmono][0-0xfffff][check=yes,force=no]
     \definefontsynonym[Test][file:Mikhak-Medium.ttf][fallbacks=fall]
     \definefontfeature[tf][arabic][tlig=yes]
     \definedfont[Test*tf]
     foo--bar
     [\char"2013]
     [\char"2014]
\stoptext

On Fri, Mar 12, 2021 at 7:13 PM Mohammad Hossein Bateni <bateni at gmail.com>
wrote:

> Any idea why the ligature {U+647 and U+654 => U+6C0} does not kick in?
>
> On Fri, Mar 12, 2021 at 7:11 PM Mohammad Hossein Bateni <bateni at gmail.com>
> wrote:
>
>> That's bad.  It seems, I forgot to add the fallbacks properly.  I will
>> reach out to the designer to add those chars.
>>
>> On Fri, Mar 12, 2021 at 12:32 PM Hans Hagen <j.hagen at xs4all.nl> wrote:
>>
>>> On 3/11/2021 2:05 AM, Mohammad Hossein Bateni wrote:
>>> > Hi,
>>> >
>>> > Since most fonts do not have the standard tex ligatures built in, I
>>> tend
>>> > to add them when I load the fonts.  Once in a while, I run into fonts
>>> > where this does not work.
>>> >
>>> > See the attached tex/pdf files.  I basically load the font as follows:
>>> >
>>> > \definefontfeature[tf][arabic][tlig=yes]
>>> > \definedfont[dejavusansmono*tf]
>>> >
>>> > This works fine for DejaVuSansMono and for one Farsi font I use
>>> > (
>>> https://github.com/rastikerdar/vazir-font/blob/master/dist/Vazir-Regular.ttf
>>> > <
>>> https://github.com/rastikerdar/vazir-font/blob/master/dist/Vazir-Regular.ttf>)
>>>
>>> > but not for this other Farsi font
>>> > (
>>> https://github.com/aminabedi68/Mikhak/blob/master/Font/ttf/Mikhak-Medium.ttf
>>> > <
>>> https://github.com/aminabedi68/Mikhak/blob/master/Font/ttf/Mikhak-Medium.ttf>).
>>>
>>> > Perhaps this is because the last font is not standard, but
>>> > TrueType/OpenType standard is sometimes up for interpretation.
>>> >
>>> > I see two strange symptoms here:
>>> >
>>> > \showotfcomposition displays the tlig feature differently for the last
>>> > font.  It appears in the "extra" list, not in "basic".  Why is that?
>>> > What does this mean anyway?
>>>
>>> The font doesn't have endash and emdash so there is nothing to construct
>>> from the double -
>>>
>>> \starttext
>>>      \definedfont[file:Mikhak-Medium.ttf*default] foo--bar
>>>      [\char"2013]
>>>      [\char"2014]
>>> \stoptext
>>>
>>> Just ask the author to add these characters and you're fine.
>>>
>>> Hans
>>>
>>> -----------------------------------------------------------------
>>>                                            Hans Hagen | PRAGMA ADE
>>>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>>>         tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
>>> -----------------------------------------------------------------
>>>
>>
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