Re: Emacs 28: Specific TTF font gets loaded with font-backend x instead of ftcrhb

[Tassilo Horn]

Eli Zaretskii <eliz@gnu.org> writes:

Hi Eli,

>> Is "the new way" the thing with composition-function-table?
>
> Yes.  We should use the so-called "automatic composition", which works
> via composition-function-table (as opposed to "static composition"
> currently used by prettify-symbols-mode).

Ok, thanks for the confirmation.

>> Something like the Fira Code font emacs setup shown here?
>> 
>>   
>> https://github.com/tonsky/FiraCode/wiki/Emacs-instructions#using-composition-char-table
>
> Something like that, yes.
>
>> I've tried that code although with the PragmataPro font in the hope
>> it would work at least partly given that both fonts offer a quite
>> large common subset of ligatures but couldn't see any difference,
>> e.g., -> is not composed to an arrow.
>
> That probably means PragmataPro doesn't support ligatures, at least
> not the one for ->.

It does, at least I get an -> arrow glyph in gedit.

>> Is there any documentation I could read?
>
> This area is notoriously under-documented.  What we have (and it's
> abysmally insufficient) is this:
>
>  . the code in composite.el, including the basic composition rules for
>    accented characters
>  . the code which sets composition-function-table in the various files
>    under lisp/language/, where language-specific composition rules are
>    provided
>  . the doc string of composition-get-gstring (the only place where we
>    document the form of the vectors shown by "C-u C-x =" for composed
>    character sequences)

Ok, I'll tinker with it when I find some spare time.

Bye,
Tassilo