Some ligatures are incorrect

[Kethku]

https://github.com/be5invis/Iosevka

The demo shows:

Looks like something about the way iosevka renders ligatures doesn't play well with swash

[Kethku]

https://github.com/tonsky/FiraCode

The demo shows:

Looks like there are issues with fira code's ligatures as well

[zoomlogo]

This is only with length > 2 ligatures for Fira Code

[dfrg]

Thanks for the heads up. I'll trace the code and see what's going on.

[dfrg]

I pushed a fix for Iosevka and published 0.1.3 to crates.io. I'm hoping this will fix the Fira Code issues as well, but I'll test it in a bit.

[zoomlogo]

I'm hoping this will fix the Fira Code issues

Iosevka works now!

Just above length 2 ligatures in Fira Code dont.

[dfrg]

One out of two ain’t bad! Glad to hear that it’s working. I’ll have to look at Fira Code later this evening.

[dustinroepsch]

https://fsd.it/shop/fonts/pragmatapro/ The ligatures in PragmataPro don't render at all,

The text was:

    db.enter_span(&[S::family_list("PragmataProMonoLiga Nerd Font"), S::LineSpacing(1.)]);
    db.add_text("This test is PragmataProMonoLiga Nerd Font -> != <= == ==>");

In this example I'm using a version of PragmataPro that was patched with nerd fonts, but using a non patched version has the same issue.

PragmataPro isn't a free font, but if there is any info I can give you to help debug this, let me know! Thanks for the awesome project

[dfrg]

This bug seems like it has to do with rendering rather than shaping. Do you know if Pragmata has embedded bitmaps? The renderer in the demo only has support for the color variety to accommodate emojis.

I added a hotkey to the demo that will dump the glyph clusters. You can reduce the text in the build_document() function to just the desired ligatures, run the demo, and press F7 to print the layout info to the console. That might at least give some indication as to whether or not the shaper is assigning reasonable glyph indices.

You can also try disabling the calt feature to see if the non-ligated versions work. You can do that with this code:

db.enter_span(&[
    S::family_list("PragmataProMonoLiga Nerd Font"), 
    S::LineSpacing(1.),
    S::features(&[("calt", 0).into()][..])
]);

[dustinroepsch]

Thanks, I'll find time tomorrow to do that and post back here :)

[dfrg]

Fira Code should be fixed now (-> 0.1.4). These fonts really abuse the OpenType layout mechanisms, so thanks for the stress test :)

I should note that these are technically not ligatures from the OpenType perspective which explains why kitty uses a weird set of glyph name hacks to identify them.

[dustinroepsch]

I got that debug info for you, heres my build document function

fn build_document() -> doc::Document {
    use layout::*;
    let mut db = doc::Document::builder();

    use SpanStyle as S;

    db.enter_span(&[
        S::family_list("PragmataProLiga Nerd Font")
    ]);
    db.add_text("-> <= >= ==");
    db.leave_span();
    db.build()
}

A screenshot of the window:

And the output after hitting F7:

Pixel format of the window's GL context: PixelFormat { hardware_accelerated: true, color_bits: 24, alpha_bits: 8, depth_bits: 24, stencil_bits: 8, stereoscopy: false, double_buffer: true, multisampling: None, srgb: true }
OpenGL version 4.1 ATI-4.6.20
Evicted 0
| 0 | 0 | - | 5696 | 0.00, 29.00 |
| 1 | 1 | > | 5696 | 16.00, 29.00 |
| 2 | 2 |   | 4 | 32.00, 29.00 |
| 3 | 3 | < | 5696 | 48.00, 29.00 |
| 4 | 4 | = | 5696 | 64.00, 29.00 |
| 5 | 5 |   | 4 | 80.00, 29.00 |
| 6 | 6 | > | 5696 | 96.00, 29.00 |
| 7 | 7 | = | 5696 | 112.00, 29.00 |
| 8 | 8 |   | 4 | 128.00, 29.00 |
| 9 | 9 | = | 5696 | 144.00, 29.00 |
| 10 | 10 | = | 5696 | 160.00, 29.00 |

Thanks for taking the time to look into this!

[dustinroepsch]

Also tested disabling ligatures using S::features(&[("calt", 0).into()][..], with that setting everything renders just fine:

[dustinroepsch]

I don't know if pragmata uses bitmaps for ligatures, is there a tool I could use to check that? Thanks again and sorry about the spam!

[dustinroepsch]

UPDATE: I totally forgot to run cargo update to update swash before posting those results. After a cargo update, ligatures are working!! :)

Thanks for the help!

[Kethku]

This is fixed! @dfrg thanks for taking a look at this!

[msiglreith]

Hi! Found one additional issue with Fira Code I think (rev 437578f31c42d511e119392dcd1868091db53433):

Output: Expected: (Google Fonts)

The last 3 characters are interpreted as : :< instead of :: <.

[dfrg]

Thanks for catching this! I'll look into it and report back here when I figure out what's going on.

[dfrg]

This was a bit of a head scratcher as HarfBuzz, Uniscribe and swash were all producing identical results. It turns out that the version of Fira Code vended by Google Fonts is simply different from the one available on GitHub. If you grab the Google Fonts copy, swash will produce the expected output:

[msiglreith]

oh no - thanks a lot for tracking this down! It looks indeed much better with the Google Fonts version (also locally).

[dfrg]

I'd be lying if I said I hadn't made the same mistake a few times while working on this :) I'm going to go ahead and close, but feel free to reopen if you encounter any further inconsistencies!