What would it take to get ligatures working in emacs?

[ticviking]

I'm doing a lot of F# in emacs lately and find that I'd love to have this on my emacs like I do in Visual Studio.

I'm mostly looking for a starting point to work out what I would need to do to get the ball rolling myself.

[tonsky]

AFAIK, Emacs does not support ligatures. There’re plugins to do substitution on presentation level though, so you can replace some sequences to unicode symbols

[tonsky]

Check this out though https://github.com/tonsky/FiraCode/wiki/Setting-up-Emacs

[weavejester]

Not sure where the best place to report this is, but one of the lines in the Emacs workaround seems to cause Emacs to hang at 100% when connecting Cider, and produces the error:

error in process filter: Attempt to shape unibyte text

The offending line is:

(46 . ".\\(?:\\(?:\\.[.<]\\)\\|[.=]\\)")

Comment that out and everything works fine. The regexp looks pretty innocuous to me, but perhaps one of the buffers opened by Cider is causing an edge condition that makes it take a long time to match.

Should I open a new issue for this? This workaround isn't officially part of Fira Code, really, so I'm uncertain whether I should.

Edit: I believe this post addresses the bug directly.

[minimal]

I encountered the Attempt to shape unibyte text problem last week and found that the initial code from Yamamoto Mitsuharu on the mailing list was later fixed up into a nice elisp function and some changes to the C code to stop the error. The latest version of the mac port should be working and ligatures can be activated with mac-auto-operator-composition-mode. The commit is at https://github.com/railwaycat/mirror-emacs-mac/commit/e7a046987d66136da55ae10a9ef90728d1442cbb
Release email: https://lists.gnu.org/archive/html/emacs-devel/2015-08/msg00882.html

Since I'm running emacs 25 pre-release and my config doesn't work with 24.5, I patched emacs HEAD with the relevant code from the above commit and recompiled (I pointed homebrew emacs at my github). minimal/emacs@812dd51

I pasted the elisp into my config so i can enable and disable the ligatures easily and it's been working great ever since. https://github.com/railwaycat/mirror-emacs-mac/commit/e7a046987d66136da55ae10a9ef90728d1442cbb#diff-3b589fe753801617f11a90443057ef7eR483

This is all mac centric, don't know what the story is on other platforms.

[tonsky]

Ok, I’m not an emacs user, so I don’t really understand what’s going on. I put a link to this issue to the wiki page with Emacs setup instruction

[falood]

What should I do to ligature ~> and <~, please?

[RadicalZephyr]

The patch linked above doesn't apply cleanly to the emacs 24.5 distribution tarball. I've modified the patch slightly to accommodate the differences. I've built emacs with this patch on both linux and OS X and it seems to work fine and also fix the infinite loop issue.

unibyte.diff.txt

[glyph]

#158 is a more specific bug for the hang, I think

[emmanueltouzery]

While I can get fira code to work normally in my emacs on linux, I can't get ligatures to display (tried with firacode 1.200 OTF on emacs 25.0.95.1 and 24.5.1, using https://github.com/tonsky/FiraCode/wiki/Setting-up-Emacs). I read in this bugtracker that emacs on osx was patched to support ligatures so I wonder... Are the ligatures working only in emacs OSX, with no way to get it to work on linux short of patching and rebuilding emacs?
And if that is required, anybody knows where are the patches for emacs OSX, so I could apply them on linux too?

EDIT: I've built this emacs version from source: https://bitbucket.org/mituharu/emacs-mac (version 5.18) on linux, and even with that version and the "Setting up Emacs" setup, I still don't get ligatures.

[emmanueltouzery]

I've googled some more and stumbled on that email thread:
http://emacs.1067599.n5.nabble.com/otf-ligature-rendering-support-td345082.html

"Actually the mac-ct font backend driver, which is used in the NS port as well as the Mac port, already supports ligatures. So I tried to activate the use of ligatures with the setting"

So for now I think the ligatures only work in the OSX version of emacs, when running on mac. Please correct me if I'm wrong.

@emmanueltouzery I didn't do as deep research as you did. But it is not working for me on emacs on linux even with the settings in the "Setting up emacs" wiki page.

[emmanueltouzery]

@mordocai really? With ligatures? Which distribution is that? Or self-built emacs? No way i could get it to eork on linux. Glad if it's possible!

@emmanueltouzery

@mordocai said:

But it is not working for me

;(

[emmanueltouzery]

Ah yes sorry, misread you