Add /ringbelow, add anchors to base glyphs & accents. Then, add mark feature. (Request: IAST and ISO 15919 Glyphs)

[vizzmay]

Many of the glyphs used in IAST (International Alphabet of Sanskrit Transliteration) and ISO 15919 (Transliteration of Devanagari and related Indic scripts into Latin characters) are already covered under Latin Extended blocks. Some of them are not.

I am particularly interested in these glyphs:

• Ṝ = U+1E5C LATIN CAPITAL LETTER R WITH DOT BELOW AND MACRON
• ṝ = U+1E5D LATIN SMALL LETTER R WITH DOT BELOW AND MACRON
• Ḹ = U+1E38 LATIN CAPITAL LETTER L WITH DOT BELOW AND MACRON
• ḹ = U+1E39 LATIN SMALL LETTER L WITH DOT BELOW AND MACRON
• ̥ = U+0325 COMBINING RING BELOW (Used in R̥ r̥ L̥ l̥ R̥̅ r̥̅ L̥̅ l̥̅, which are ISO 15919 characters for vocalic Rs and Ls)
• Ṁ = U+1E40 LATIN CAPITAL LETTER M WITH DOT ABOVE
• ṁ = U+1E41 LATIN SMALL LETTER M WITH DOT ABOVE

[arrowtype]

We will probably fix this with combining accents. It won’t add the unicodes directly into the font, but these characters should be typable and render well with Recursive.

One question on Uppercase glyphs here, though:

The combining accents in Recursive are designed for lowercase glyphs, whereas glyphs like Ṝ or J́ would ideally get a case-specific combining accent.

Are such caps with accents required to be pre-composed in order to use case-specific accents, or is there some way in the mark feature to intelligently swap to .case variants of accents for uppercase glyphs?

This is related to #368

[arrowtype]

As an update on this for @benkiel:

• I have added the ringbelowcomb to all sources, with anchor _top
• I have added the top & bottom anchors to all base latin alphabet characters that were missing them, including .italic, .mono, and .sans alternates

These were added to the updating-terminology branch: https://github.com/arrowtype/recursive/commits/updating-terminology

I still need to manually fix anchor x-positioning in several glyphs (these plus their italic alts):
- [ ] F (bottom)
- [ ] b, d, f (top, at ascenders)
- [ ] j, q (bottom)

However, I think that now that they are included in the fonts, you should hopefully be able to add the mark feature to the build when you have an opening to. I will correct those anchor placements ASAP.

[benkiel]

The mark feature can swap intelligently.

[arrowtype]

Awesome!

[arrowtype]

This isn’t quite closed just yet, but is under active work.

[arrowtype]

To fix the Ṝ ṝ Ḹ ḹ issue, I will

• add top anchors to R dot below etc. Done with a script.
• make a new issue to add anchors to other precomposed characters that may be useful to add marks to Add 'mark' feature to fully cover all alternates (e.g. ".italic" glyphs) in static fonts #448
• Add the R dot below and L dot below to the base_uc class in src/features/features/ccmp.fea
• Also need to update mastering/utils.py to properly classify uppercase precomposed chars

[arrowtype]

This is currently working well in the variable font, though not quite in static fonts, in this beta 1.076 test build. (The static fonts still have the issue with lost anchors in alt glyphs, #448).

[arrowtype]

Okay, it’s now working well in the variable and static fonts! Will be released as v1.077.

[benkiel]

This is done. Closing.