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StefanPeev / Common-Serif

The Common Serif project is based on Libertinus Serif.
SIL Open Font License 1.1
52 stars 2 forks source link

`st` not set as historical ligature? #61

Open dwhieb opened 4 weeks ago

dwhieb commented 4 weeks ago

I'm using Common Serif as a web font, and by default it displays st with the historical ligature, like so:

image

(That image was captured from the Common Serif demo at LocalFonts.eu.)

Common Serif seems to be treating st as a common ligature rather than a historical ligature. Because of this, the only way I can turn off the st ligature is by turning off all ligatures, which is undesirable.

Note that the similar ct ligature does seem to be treated as a historical ligature. It is only activated when I opt into historical ligatures for the font, which is the expected behavior.

StefanPeev commented 4 weeks ago

@dwhieb Please, give me a link to your website.

dwhieb commented 3 weeks ago

https://nisinoon.net/grammar

I've currently disabled common ligatures, so the st ligature isn't showing. But if you inspect the <body> tag in your browser and disable the font-variant-ligatures rule, you'll see the st ligature appear.

Alternatively, you can see the problem by taking the following steps:

  1. Go to the Common Serif page on LocalFonts.eu.
  2. Scroll down to the area where you can input sample text and type st ct in the box.
  3. You should see the ligature on st but not ct. If you then change the OpenType settings so that Standard Ligatures are not included, the st ligature disappears. Alternatively, if you choose Historical Ligatures, the ligatures appear on both st and ct.
StefanPeev commented 3 weeks ago

@dwhieb Thank you, Daniel. What will you say if I place /s /t in DLIG feature. I think that LIGA feature must look like this.

`feature liga { sub f f i by f_f_i; sub f f l by f_f_l; sub f f by f_f; sub f i by fi; sub f l by fl;

} liga;`

In HLIG ligature I'll place only the long s ligatures, everything else will be in DLIG ligatures.

dwhieb commented 3 weeks ago

I think that makes sense. It seems like the st ligature should be in the same category as the ct ligature, wherever that is.

It might be worth noting that the Libertinus font placed both ct and st in the HLIG category though:

https://github.com/alerque/libertinus/blob/master/sources/features/dhlig.fea

StefanPeev commented 3 weeks ago

@dwhieb I do not see reason st and ct ligatures to be placed in HLIG - it is better if they are part of DLIG.

dwhieb commented 3 weeks ago

That's fine by me! I defer to your expertise.