Font Forum

I've created a font for the new Old Uyghur unicode block. Like the Arabic script, letters in the Old Uyghur script usually have initial, medial, final, and isolated forms:



In addition to the standard initial, medial, final, and isolated forms for each letter, I have implemented a number of ligatures as Contextual Alternates. These also have initial, medial, isolated, and final forms:



As you can see above, these work just fine in Font Creator. The issue arises when I try to use the font in other places. Here, positional variants of base glyphs work fine, but only the medial forms of ligatures work. Here is an example generated in XeLaTeX:



... and another as a website with the font added in CSS:



Curiously, I get the same issue whether I use OTF, TTF, WOFF or WOFF2 formatting.

Does anyone have a clue how to get the positional variants of ligatures working?

Thanks in advance, and forgive me if I haven't used the lingo quite right -- this is my first time interacting with other human beings about font creation

The applications which use your font will use a rendering engine to render the text, something like Uniscribe or HarfBuzz. These rendering engines have a file of information on how to render the Initial, Medial and Final forms in Arabic. That is why the Initial, Medial and Final forms work in Arabic but don't work in Latin or Cyrillic.

Without a corresponding file for the language you are trying to reproduce the Initial, Medial and Final forms won't work.

Thanks very much for your reply!

Perhaps I didn't communicate my issue properly. The initial, medial, final, and isolated forms actually work fine for the base glyphs; it's the positional variants of the ligatures that don't work.

(The positional variants of the base glyphs don't work in Word for the reason you mention, but that's not a big deal for me.)

Niko Kontovas wrote: ↑Fri Sep 16, 2022 3:08 pm As you can see above, these work just fine in Font Creator.

For FontCreator to behave like a regular shaping engine, only enable the "_shaper". How does that turn out?

Bedankt voor je reactie

Turning on the _shaper does indeed produce the same result as the XeLaTeX & web examples! That is, all the base glyphs work fine in all positions, but the ligatures only work medially.

I am working on alternative form of the font where the positional variants are handled by calt, which fixes this specific issue, but I will need to modify all the other transformations that currently target medial forms (which are the default forms the way I've designed it). Having the fina, init, and isol features work out of the box on ligatures as well would still save a bunch of hassle.