Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Thomas Savary via ntg-context]

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Hello, dear list !

In order to fix a few bugs in some OpenType features included in EB Garamond font provided by 
Google Fonts, I am trying to remove some ligatures (erroneous in some contexts) with 
fonts.handlers.otf.addfeature.

I must be missing something, because I can't get it to work.

Here is a minimal —non working—example :-)
(The attempted removal (“f_i” → “fi” only before “o”) is of course irrelevant. I chose it just for the 
sole purpose of this test, to provide a simple example. What I am trying to achieve is more complex, 
with other ligatures.) 

fonts.handlers.otf.addfeature{
        name = "unfio",
        type = "chainsubstitution",
        lookups = {
            { type = "multiple",
            data = { [ "f_i" ] = { "f", "i" } }
            }
        }
        rules = {
            { after = { { "o" } },
            current = { { "f_i" } },
            lookups = { 1 } }
        }
    }
}

Could someone please explain to me what I did wrong ?

Thomas Savary
1 le Grand-Plessis
F-85340 L’Île-d’Olonne
Tél. 06 22 82 61 34
https://compo85.fr/

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Re: Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Bruce Horrocks via ntg-context]

> On 24 Dec 2021, at 18:34, Thomas Savary via ntg-context <ntg-context@ntg.nl> wrote:
> 
> Hello, dear list !
> 
> In order to fix a few bugs in some OpenType features included in EB Garamond font provided by Google Fonts, I am trying to remove some ligatures (erroneous in some contexts) with fonts.handlers.otf.addfeature.
> 
> I must be missing something, because I can't get it to work.
> 
> Here is a minimal —non working—example :-)
> (The attempted removal (“f_i” → “fi” only before “o”) is of course irrelevant. I chose it just for the sole purpose of this test, to provide a simple example. What I am trying to achieve is more complex, with other ligatures.)
> 
> fonts.handlers.otf.addfeature{
>         name = "unfio",
>         type = "chainsubstitution",
>         lookups = {
>             { type = "multiple",
>             data = { [ "f_i" ] = { "f", "i" } }
>             }
>         }
>         rules = {
>             { after = { { "o" } },
>             current = { { "f_i" } },
>             lookups = { 1 } }
>         }
>     }
> }
> 
> Could someone please explain to me what I did wrong ?

Firstly, you have an extra } in the example above.

Secondly, rules need to come inside a data section. Thus (untested):

fonts.handlers.otf.addfeature{
    name = "unfio",
    type = "chainsubstitution",
    lookups = {
        {
            type = "substitution",
            data = {
                [ "f_i" ] = { "f", "i" }
            }
        }
    },
    data = {
        rules = {
            {
                after = { { "o" } },
                current = { { "f_i" } },
                lookups = { 1 }
            }
        }
    }
}

Regards,
—
Bruce Horrocks
Hampshire, UK

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Re: Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Hans Hagen via ntg-context]

On 12/25/2021 12:04 AM, Bruce Horrocks via ntg-context wrote:
> 
> 
>> On 24 Dec 2021, at 18:34, Thomas Savary via ntg-context <ntg-context@ntg.nl> wrote:
>>
>> Hello, dear list !
>>
>> In order to fix a few bugs in some OpenType features included in EB Garamond font provided by Google Fonts, I am trying to remove some ligatures (erroneous in some contexts) with fonts.handlers.otf.addfeature.
>>
>> I must be missing something, because I can't get it to work.
>>
>> Here is a minimal —non working—example :-)
>> (The attempted removal (“f_i” → “fi” only before “o”) is of course irrelevant. I chose it just for the sole purpose of this test, to provide a simple example. What I am trying to achieve is more complex, with other ligatures.)
>>
>> fonts.handlers.otf.addfeature{
>>          name = "unfio",
>>          type = "chainsubstitution",
>>          lookups = {
>>              { type = "multiple",
>>              data = { [ "f_i" ] = { "f", "i" } }
>>              }
>>          }
>>          rules = {
>>              { after = { { "o" } },
>>              current = { { "f_i" } },
>>              lookups = { 1 } }
>>          }
>>      }
>> }
>>
>> Could someone please explain to me what I did wrong ?
> 
> Firstly, you have an extra } in the example above.
> 
> Secondly, rules need to come inside a data section. Thus (untested):
> 
> fonts.handlers.otf.addfeature{
>      name = "unfio",
>      type = "chainsubstitution",
>      lookups = {
>          {
>              type = "substitution",
>              data = {
>                  [ "f_i" ] = { "f", "i" }
>              }
>          }
>      },
>      data = {
>          rules = {
>              {
>                  after = { { "o" } },
>                  current = { { "f_i" } },
>                  lookups = { 1 }
>              }
>          }
>      }
> }
the problem with this approach is that in a feature rich font like eb 
you never know where to kick this into the sequence and you even don't 
know how many variants of fi ligatures are there

Hans

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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Re: Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Hans Hagen via ntg-context]

On 12/25/2021 12:04 AM, Bruce Horrocks via ntg-context wrote:
> 
> 
>> On 24 Dec 2021, at 18:34, Thomas Savary via ntg-context <ntg-context@ntg.nl> wrote:
>>
>> Hello, dear list !
>>
>> In order to fix a few bugs in some OpenType features included in EB Garamond font provided by Google Fonts, I am trying to remove some ligatures (erroneous in some contexts) with fonts.handlers.otf.addfeature.
>>
>> I must be missing something, because I can't get it to work.
>>
>> Here is a minimal —non working—example :-)
>> (The attempted removal (“f_i” → “fi” only before “o”) is of course irrelevant. I chose it just for the sole purpose of this test, to provide a simple example. What I am trying to achieve is more complex, with other ligatures.)
>>
>> fonts.handlers.otf.addfeature{
>>          name = "unfio",
>>          type = "chainsubstitution",
>>          lookups = {
>>              { type = "multiple",
>>              data = { [ "f_i" ] = { "f", "i" } }
>>              }
>>          }
>>          rules = {
>>              { after = { { "o" } },
>>              current = { { "f_i" } },
>>              lookups = { 1 } }
>>          }
>>      }
>> }
>>
>> Could someone please explain to me what I did wrong ?
> 
> Firstly, you have an extra } in the example above.
> 
> Secondly, rules need to come inside a data section. Thus (untested):
> 
> fonts.handlers.otf.addfeature{
>      name = "unfio",
>      type = "chainsubstitution",
>      lookups = {
>          {
>              type = "substitution",
>              data = {
>                  [ "f_i" ] = { "f", "i" }
>              }
>          }
>      },
>      data = {
>          rules = {
>              {
>                  after = { { "o" } },
>                  current = { { "f_i" } },
>                  lookups = { 1 }
>              }
>          }
>      }
> }
A better an dmore reliable approach is this:

\startluacode
     local demo = {
         name    = "demo",
         options = {
             {
                 patterns = {
                     fio  = "f|io",
                 },
                 words = [[ fioot fiots ]],
             },
         },
     }
     table.save("oeps-fixes.llg",demo)
\stopluacode

\setuplanguage[en][goodies={oeps-fixes.llg}]

\setupbodyfont[ebgaramond]

\starttext
     fiets fiots fiats fioot
\stoptext

because you want to block certain ligatures but keep kerning etc (see 
older posts for more extensive examples)

Hans


-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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Re: Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Thomas Savary via ntg-context]

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Hi Bruce and Hans !

Thank you very much for your answers, that helped me a lot.

In fact, though I would love to switch to ConTeXt one day, I am still using LuaLaTeX — I am a slow 
learner and I know it will take me months to be able to achieve what I need for my job with 
ConTeXt and can do with LuaLaTeX and the Memoir class for the time being (despite sometimes 
being irritated by LaTeX limitations or oddities).

I need the EB Garamond variable font for future jobs, but this font, provided by Google Fonts, is 
such a mess : kerning problems, unusable OpenType features that have to be rewritten from 
scratch, shifts in glyphs table… For sure, the original font by Georg Duffner was much better, but I 
need the variable version. Lots of fixing necessary, but thanks to fonts.handlers.otf.addfeature I 
have almost succeeded to make it a usable Garamond.

Of course, it would be best to help Google improving this font, but I don’t have time yet.

The actual problem was with the italic ligatures "a_s", "e_s", "é_s", "i_s" and "u_s", that should occur 
only at the end of words and not everywhere. Instead of removing the unwanted ligatures, I chose 
another way as soon as I understood how to fully use “current” to describe not only a single glyph, 
but a string if necessary — for instance, current={ { "a", "e", "eacute", "i", "u"}, {"s"} }

Thanks for this wonderful tool !

Thomas Savary
1 le Grand-Plessis
F-85340 L’Île-d’Olonne
Tél. 06 22 82 61 34
https://compo85.fr/
Le samedi 25 décembre 2021, 00:04:51 CET Bruce Horrocks a écrit :
> > On 24 Dec 2021, at 18:34, Thomas Savary via ntg-context
> > <ntg-context@ntg.nl> wrote:
> > 
> > Hello, dear list !
> > 
> > In order to fix a few bugs in some OpenType features included in EB
> > Garamond font provided by Google Fonts, I am trying to remove some
> > ligatures (erroneous in some contexts) with
> > fonts.handlers.otf.addfeature.
> > 
> > I must be missing something, because I can't get it to work.
> > 
> > Here is a minimal —non working—example :-)
> > (The attempted removal (“f_i” → “fi” only before “o”) is of course
> > irrelevant. I chose it just for the sole purpose of this test, to
> > provide a simple example. What I am trying to achieve is more
> > complex, with other ligatures.)
> > 
> > fonts.handlers.otf.addfeature{
> > 
> >         name = "unfio",
> >         type = "chainsubstitution",
> >         lookups = {
> >         
> >             { type = "multiple",
> >             data = { [ "f_i" ] = { "f", "i" } }
> >             }
> >         
> >         }
> >         rules = {
> >         
> >             { after = { { "o" } },
> >             current = { { "f_i" } },
> >             lookups = { 1 } }
> >         
> >         }
> >     
> >     }
> > 
> > }
> > 
> > Could someone please explain to me what I did wrong ?
> 
> Firstly, you have an extra } in the example above.
> 
> Secondly, rules need to come inside a data section. Thus (untested):
> 
> fonts.handlers.otf.addfeature{
>     name = "unfio",
>     type = "chainsubstitution",
>     lookups = {
>         {
>             type = "substitution",
>             data = {
>                 [ "f_i" ] = { "f", "i" }
>             }
>         }
>     },
>     data = {
>         rules = {
>             {
>                 after = { { "o" } },

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Re: Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Hans Hagen via ntg-context]

On 12/25/2021 11:52 PM, Thomas Savary via ntg-context wrote:
> Hi Bruce and Hans !
> 
> 
> Thank you very much for your answers, that helped me a lot.
> 
> 
> In fact, though I would love to switch to ConTeXt one day, I am still 
> using LuaLaTeX — I am a slow learner and I know it will take me months 
> to be able to achieve what I need for my job with ConTeXt and can do 
> with LuaLaTeX and the Memoir class for the time being (despite sometimes 
> being irritated by LaTeX limitations or oddities).

keep in mind that context font handling and latex font handling can 
differ (and not all that is possible in context is in the generic font 
loader code); also, in (esp in lmtx) some solutions are not bound to fonts

> I need the EB Garamond variable font for future jobs, but this font, 
> provided by Google Fonts, is such a mess : kerning problems, unusable 
> OpenType features that have to be rewritten from scratch, shifts in 
> glyphs table… For sure, the original font by Georg Duffner was much 
> better, but I need the variable version. Lots of fixing necessary, but 
> thanks to fonts.handlers.otf.addfeature I have almost succeeded to make 
> it a usable Garamond.

a probably more reliable solution is to 'remove bad stuff' from the 
loaded font by running over the features and removing bad matches (which 
is less sensitive for order)

> Of course, it would be best to help Google improving this font, but I 
> don’t have time yet.

is that really a google font? afaik it doesn't originate there (unless 
it among those things that google grabs - and at some point possible 
discards)

> The actual problem was with the italic ligatures "a_s", "e_s", "é_s", 
> "i_s" and "u_s", that should occur only at the end of words and not 
> everywhere. Instead of removing the unwanted ligatures, I chose another 
> way as soon as I understood how to fully use “current” to describe not 
> only a single glyph, but a string if necessary — for instance, current={ 
> { "a", "e", "eacute", "i", "u"}, {"s"} }

ok, good that you got it working
  Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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Re: Contextual removal of some ligatures using fonts.handlers.otf.addfeature (LuaTeX 1.13.2)

[Thomas Savary via ntg-context]

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Thanks, Hans, for your advice.

> a probably more reliable solution is to 'remove bad stuff' from the
> loaded font by running over the features and removing bad matches
> (which is less sensitive for order)

I could edit the font features, indeed, but I run a GNU/Linux OS, and Fontforge cannot edit nor 
generate variable fonts. There seems to be a solution (https://www.youtube.com/watch?
v=xoQuWARCUWI[1] ), but so far beyond my technical capabilities that I cannot consider it.

> is that really a google font? afaik it doesn't originate there (unless
> it among those things that google grabs - and at some point possible
> discards)\0

Yes, it is, but not from the beginning. A great Garamond, the original font was designed by Georg 
Duffner. A few years ago, Google decided to make it a more complete font family : Octavio Pardo has 
done an excellent job with the bolder versions of EB Garamond and its conversion to a variable 
font. However, for whatever reasons, he did quite a rush job with the OpenType features ! Many 
essential features are lacking (despite the needed glyphs still being there), and most present 
features are poorly implemented, with a lot of typographic nonsense (concerning long s and long Q 
or the mentioned italic ligatures, for instance).
https://fonts.google.com/specimen/EB+Garamond[2]

I will contact Google Fonts shortly to report on the dozens of problems I have encountered that 
make the unfixed new version of EB Garamond unusable for anything but the most basic uses.
Fortunately, my significantly more demanding needs for a client were met with the invaluable help 
from LuaTeX, but that won't be enough for my own projects, much more complex (facsimile of 
ancient editions), until Google improves this font.

Thomas Savary
1 le Grand-Plessis
F-85340 L’Île-d’Olonne
Tél. 06 22 82 61 34
https://compo85.fr/




--------
[1] https://www.youtube.com/watch?v=xoQuWARCUWI
[2] https://fonts.google.com/specimen/EB+Garamond

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Re: (No subject header)

[Hans Hagen via ntg-context]

On 12/27/2021 9:27 PM, Thomas Savary via ntg-context wrote:
> Thanks, Hans, for your advice.
> 
>  > a probably more reliable solution is to 'remove bad stuff' from the
>  > loaded font by running over the features and removing bad matches
>  > (which is less sensitive for order)
> 
> I could edit the font features, indeed, but I run a GNU/Linux OS, and 
> Fontforge cannot edit nor generate variable fonts. There seems to be a 
> solution (https://www.youtube.com/watch?v=xoQuWARCUWI 
> <https://www.youtube.com/watch?v=xoQuWARCUWI> ), but so far beyond my 
> technical capabilities that I cannot consider it.
> 
>  > is that really a google font? afaik it doesn't originate there (unless
>  > it among those things that google grabs - and at some point possible
>  > discards)
> 
> Yes, it is, but not from the beginning. A great Garamond, the original 
> font was designed by Georg Duffner. A few years ago, Google decided to 
> make it a more complete font family : Octavio Pardo has done an 
> excellent job with the bolder versions of EB Garamond and its conversion 
> to a variable font. However, for whatever reasons, he did quite a rush 
> job with the OpenType features ! Many essential features are lacking 
> (despite the needed glyphs still being there), and most present features 
> are poorly implemented, with a lot of typographic nonsense (concerning 
> long s and long Q or the mentioned italic ligatures, for instance).

Strange, so basically only the shapes were taken an not the (in this 
case closely related features)?
> https://fonts.google.com/specimen/EB+Garamond 
> <https://fonts.google.com/specimen/EB+Garamond>
> 
> I will contact Google Fonts shortly to report on the dozens of problems 
> I have encountered that make the unfixed new version of EB Garamond 
> unusable for anything but the most basic uses.
> 
> Fortunately, my significantly more demanding needs for a client were met 
> with the invaluable help from LuaTeX, but that won't be enough for my 
> own projects, much more complex (facsimile of ancient editions), until 
> Google improves this font.
So actually the old pre-google fonts from GD are better? Hopefully they 
then stay available someplace.

Hans



-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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