@interslavic/slovosbor-serif

Slovosbor Serif is an extensively revised, typographically enriched variable serif typeface commissioned and funded by Yaroslav Serhieiev, designed and expanded by S.-V. Sofienczuk-Wojczyszyn (derived from IBM Plex Serif v5 by Bold Monday). It is specifically tailored for Interslavic, modern Slavic languages (Russian, Ukrainian, Belarusian, Bulgarian, Serbian, Macedonian, Polish, Czech, Slovak, Croatian, Slovenian), and historical Cyrillic texts.

Packaged in the @fontsource/* standard structure with split WOFF2 subsets and OpenType layout features preserved.

Quick Start

Installation

npm install @interslavic/slovosbor-serif
# or
yarn add @interslavic/slovosbor-serif

Usage in CSS / JS

Import the variable font across all subsets:

// In your JS/TS entry point
import '@interslavic/slovosbor-serif';
// or
import '@interslavic/slovosbor-serif/variable.css';

Or in CSS:

@import '@interslavic/slovosbor-serif';

body {
  font-family: 'Slovosbor Serif', Georgia, serif;
  font-weight: 400; /* Any weight between 100 and 700 */
  font-style: normal;
}

If you only need specific subsets:

@import '@interslavic/slovosbor-serif/cyrillic.css';
@import '@interslavic/slovosbor-serif/latin.css';
@import '@interslavic/slovosbor-serif/greek.css';
@import '@interslavic/slovosbor-serif/pi.css';

Direct HTML / CDN usage

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@interslavic/slovosbor-serif/index.css">

Typography & OpenType Features

Slovosbor Serif features deep linguistic engineering across GPOS mark attachments and GSUB substitutions:

1. Combining Diacritics & GPOS Mark-to-Base

Combining accents (U+0300–0304, U+0306–030C, U+0312, U+0315, U+031B, U+0323, U+0326–0328, U+032D–032E, U+0331) and modifier spacing marks (U+02BB–02BC, U+02C7, U+02D8–02D9, U+02DB, U+02DD) are duplicated across all script subsets.

• Ensures mark-attachment never splits across @font-face boundaries.
• Stacking accents on Cyrillic vowels and historical letters (ѣ́, ѫ́, ѧ́, є́, и́, у́, ю́, э́, я́) sit precisely over the letter stem rather than drifting as loose ticks.

2. The Yat Letter (ѣ / Ѣ, U+0462, U+0463)

• Automatic Uppercase Ascender Shift (calt): When an uppercase Yat appears in all-caps text (e.g. СѢЮ), the crossbar aligns with the cap-height while the vertical stem extends into the ascender zone (Yatcyrl.alt01).
• Italic Default: By default, Italic uses form 2 (yatcyrl.alt01). The historical standard form is accessible via ss09 and aalt.
• Bulgarian Locl / Salt: In Bulgarian localization (:lang(bg) / loclBGR), Yat automatically renders in its authentic Bulgarian form (yatcyrl.alt01 in upright, yatcyrl.alt02 in italic); engaging salt inside Bulgarian further selects the alternative triangular/calligraphic shape (yatcyrl.alt02).

<!-- Bulgarian Yat in Bulgarian context -->
<p lang="bg" style="font-feature-settings: 'salt' 1;">
  Българскиятъ езикъ ... буквитѣ
</p>

3. Yus Letters (ѫ ѭ ѧ ѩ, U+0467, U+0469, U+046B, U+046D)

• Default: Standard typographic historical Yus forms.
• Handwritten Yus (ss10): Switches all Big and Little Yus forms (including iotated and accented forms) to calligraphic handwritten variants (yusbigcyrl.alt01, yusiotifiedbigcyrl.alt01, etc.).
• Round Yus (salt): Activates round Yus variant.

/* Activate calligraphic handwritten Yus forms */
.ancient-text {
  font-feature-settings: 'ss10' 1;
}

4. Cyrillic Localization (locl)

• Bulgarian (:lang(bg) / cyrl/BGR): Authentic Bulgarian lowercase Cyrillic letterforms (13+ characters: в, г, д, ж, з, и, й, к, л, п, т, ц, ш, щ, ю).
• Serbian & Macedonian (:lang(sr), :lang(mk) / cyrl/SRB, cyrl/MKD):
  • Upright (Roman): Matches standard pan-Slavic / Interslavic Cyrillic (without Bulgarian distortions).
  • Italic: Automatically engages Serbian italic glyphs for г, д, п, т.

<!-- Automatically uses Serbian italic glyphs for г д п т -->
<p lang="sr" style="font-style: italic;">
  г д п т
</p>

5. Stylistic Sets Summary

| Feature | Name | Description | |---|---|---| | calt | Contextual Alternates | Automatically raises uppercase Ѣ stem in all-caps text | | locl | Localized Forms | BGR (Bulgarian Cyrillic), SRB/MKD (Serbian italic г,д,п,т), CSL (Church Slavonic) | | ss07 | Alternate У | Alternate У with matching accented forms (Ў, Ӯ, Ӱ, Ӳ) | | ss09 | Alternate Cyrillic | Alternative forms for б, д, ы, ш with underline, etc. | | ss10 | Handwritten Yus | Calligraphic handwritten forms for ѫ, ѭ, ѧ, ѩ and their accented variants | | salt | Stylistic Alternates | Round Yus, Bulgarian Yat, alternate т, ш | | aalt | Access All Alternates | Full index of all 60+ letter alternate variants for glyph palettes |

File Structure

• index.css, variable.css — imports all 6 subsets in normal and italic.
• cyrillic.css — Cyrillic-only subset.
• latin.css — Latin-1, Latin-2, Latin-3 subsets.
• files/*.woff2 — optimized, pyftsubset-compiled WOFF2 webfonts.
• raw/*.ttf — full unsubsetted Variable TTFs (100–700 weight).

License

• Font Software: SIL Open Font License 1.1
• Original work: Copyright © 2017 IBM Corp. with Reserved Font Name "Plex" (by Mike Abbink & Bold Monday).
• Modifications: Copyright © 2026 S.-V. Sofienczuk-Wojczyszyn.