# [NTG-context] tlig feature sometimes does not work

Hans Hagen j.hagen at xs4all.nl
Fri Mar 12 18:32:13 CET 2021

```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