Re: Ligature support

[Lars Ingebrigtsen <larsi@gnus.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> For example, the mode line can show stuff like "=-", and the font
> could have a ligature for that -- do we really want that ligature on
> the mode line?

That's a good point.  On the other hand, perhaps we want to use a
different font on the mode line when using one of these special fonts.

> Or the font could have a ligature for "ffi" -- do we want a variable
> named "efficient" be displayed with that ligature?  I'd be surprised.

Possibly, but probably not.  But I don't think people will choose to use
fonts for programming that have fonts like that.  (Are there even any
monospace fonts that have such ligatures?)  But when rendering document
using a variable-pitch font, then yes.

>> But it's certainly possible -- having a switch to tweak which ligatures
>> should be active on a per-mode/buffer basis is something we'd need to
>> look at.  I think we can look at that after we actually have ligatures
>> displayed at all, though.  😀
>
> Displaying them is easy, just set up composition-function-table
> accordingly (I can show you the code if you cannot figure that out).

Yes, please -- I've been poking at that, but didn't find the right
incantation.

> That's the least of our problems.

Well, it's one problem, and I think it's the one that has to be solved
first.  (I've now sent a message to the harfbuzz list to see whether
they have any input in how to get harfbuff to cough up this list of
strings based on the font.)

For instance, see bug#51385 where they have a weirdo font that maps
"[TRACE]" (and 260 other strings) to different glyphs.  We need that
list, because we certainly don't want to be passing "[TRACE]" to
harfbuzz when not using that font.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no