I believe it's a bug.

https://github.com/contextgarden/context/blob/d025bcdf995be6951f69fed6869048ab22491b9e/tex/context/base/mkxl/font-col.lmt#L278

the newchar[] table, which should contain all chars supported by the
fallback termes font if I'm not mistaken, turns out to have only 392 chars
within 0x20-0x30C, far away from 0x2329-0x232A.

On Sun, 23 Apr 2023 at 03:26, Thomas A. Schmitz via ntg-context <
ntg-context@ntg.nl> wrote:

> Thank you, Pablo, but that doesn't help. I know how to use fallback
> fonts. I was wondering if the check key is working as it should.
>
> Thomas
>
> On 4/22/23 20:33, Pablo Rodriguez via ntg-context wrote:
> > Hi Thomas,
> >
> > I don’t know what check does (maybe just check?), but the standard
> > behaviour with \definefallbackfamily is only to fall back when the
> > character is missing from the main font.
> >
> > To force all characters from the range in the fallback font, "force=yes"
> > is required.
> >
> > Here you have a minimal sample (which doesn‘t use "preset=range:greek"),
> > adding "force=yes" gets all Greek glyphs from GFS Heraklit:
> >
> >    \definefallbackfamily [presentation] [serif] [GFSHeraklit]
> >    [range={greekandcoptic, greekextended}]
> >    \definefontfamily [presentation] [serif] [TeXGyrePagella]
> >    \setupbodyfont [presentation,12pt]
> >
> >    \starttext
> >    Pπμᾷσδ
> >    \stoptext
> >
> > Just in case it might help,
>
> --
> Prof. Dr. Thomas A. Schmitz
> Institut für Klassische und Romanische Philologie
> Universität Bonn
> Am Hof 1e
> 53113 Bonn
> http://www.philologie.uni-bonn.de/de/personal/schmitz
>
>
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