subs — Subscript

subs (Subscript) presents subscript forms.

The specification’s Function field says only “The ‘subs’ feature is used to present subscript forms,” without naming which kind of glyph is affected. The Recommended implementation has two steps. First, a GSUB Single Substitution (or a contextual substitution) replaces the glyph with its subscript form; then, if that form isn’t correctly positioned yet, a GPOS Single Adjustment, Pair Adjustment, or contextual adjustment moves it further.

sinf (Scientific Inferiors) handles subscript forms specialized for chemical and mathematical notation; the sinf page explains how the two differ. sups (Superscript) is its counterpart.

Example

Without subs

H2O

With subs

H2O

.fea source

Preview textfeature subs { sub two by uni2082; sub four by uni2084; } subs;

Compiling…

Writing it in a feature file

The rules are written with Lookup Type 1.

.fea sourcefeature subs { sub two by uni2082; sub four by uni2084; } subs;

Preview textWithout rules

H2O

With rules

H2O

Compiling…

Specifications

• Microsoft OpenType Specification, Registered features — Tag: ‘subs’