Re: otf ligature rendering support?

[K. Handa]

In article <address@hidden>, Yuri D'Elia <address@hidden> writes:

> I'm not fully aware of how much otf is supported in emacs, but I found a
> good reason to want ligatures in a monospaced font:

> http://www.fsd.it/fonts/pragmatapro/PragmataPro_Haskell_liga.png

> PragmataPro supports ligatures for a good set of common operators. This
> makes it much less troublesome than "prettify-symbols-mode" since
> indentation/spacing is not changed.

> How would I enable the proper GSUB feature in emacs? Are ligatures
> supported at all?

Currently, Emacs can not control which OTF features to
apply.  Emacs leaves it to font drivers on eash platform.  I
actually tried to give Emacs such facility, and src/font.c
contains not-yet-finished code within "#if 0" and "#endif".

I want to finish the code, but I'm not sure I can work on it
soon.

> I can specify otf parameters in `font-spec', but the following:

> (set-fontset-font nil 'latin
>                 (font-spec :family "PragmataPro"
>                            :otf '(latn nil (liga))))

> Doesn't really show any ligatures (or any other otf feature).

The above just tells Emacs to select such an OTF font that
has `liga' GPOS feature for `latn' script.

By the way, if you are running Emacs on X with libm17n-flt
and libotf libraries, you can override the default behavior
of those libraries by putting the attached two files under
~/.m17n.d/.  It assumes that the family name of PragmataPro
font is "PragmataPro".  If that is not the case, please
replace "PragmataPro" in generic.fst with a proper family
name.

---
K. Handa
address@hidden

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