/OT_Features-Workshops

A centralized collection of all materials for my OpenType Features workshops

BSD 3-Clause "New" or "Revised" LicenseBSD-3-Clause

OpenType Features Workshops

Introduction

OpenType features empower fonts to behave more responsively for users. They enable on-the-fly glyph substitution and positioning, providing a typesetting experience that is both seamless and highly customizable.

To enhance your fonts with the added power of OpenType features, all you need to do is:

  1. Add extra glyphs for any desired substitutions.
  2. Write a bit of code (in a syntax specified by Adobe) to define the conditions under which these swaps or positional changes occur.

Common OpenType Features

** in Latin-based type-setting

These were listed in alphabetical order, but then reordered for grouping purposes.

Feature tag Friendly name Description
calt Contextual Alternates Glyph swaps depending on which glyphs are around them.
case Case-sensitive Forms Glyph swaps depending on whether they’re in an all-caps context.
cpsp Capital Spacing Glyph spacing changes depending on whether they’re in an all-caps context.
c2sc Small Capitals From Capitals Glyph swaps from uppercase to small capitals.
smcp Small Capitals Glyph swaps from lowercase to small capitals.
dlig Discretionary Ligatures Glyph swaps from multiple glyphs to one ligature glyph, usually ornamental / decorative.
liga Standard Ligatures Glyph swaps from multiple glyphs to one ligature glyph, usually functional / necessary.
frac Fractions Glyph swaps from multiple glyphs to one or more fraction-specific glyph(s).
subs Subscript Glyph swaps from default figures to subscript figures.
sups Superscript Glyph swaps from default figures to superscript figures.
init Initial Forms Glyph swaps at the beginning of a word.
medi Medial Forms Glyph swaps in the middle of a word.
fina Terminal Forms Glyph swaps at the end of a word.
lnum Lining Figures Glyph swaps from oldstyle (lowercase) figures to lining (uppercase) figures.
onum Oldstyle Figures Glyph swaps from lining (uppercase) figures to oldstyle (lowercase) figures.
tnum Tabular Figures Glyph swaps from proportional figures to tabular (monospaced) figures.
pnum Proportional Figures Glyph swaps from tabular (monospaced) figures to proportional figures.
locl Localized Forms Glyph swaps depending on geographic context.
salt Stylistic Alternates Glyph swaps for general stylistic effect.
ss01 – ss20 Stylistic Set 1 – Stylistic Set 20 Glyph swaps for stylistic effect, usually named sets with specific themes.
swsh Swash Glyph swaps from default glyphs to swash glyphs.
zero Slashed Zero Glyph swaps from default zeros to slashed zeros.

For a list of all supported OpenType features, refer to this link.

Examples

Below, you will see examples of OpenType Feature File code, ranging from simple to complex. Each of them is self-contained and hypothetically fully functional.

Minimalist Structure

This is the most bare-bones way you can write OpenType code. This works, though!

feature liga {       # Simply initialize the feature, in this case Standard Ligatures...
    sub f f by f_f;  # make a swap rule ...
} liga;              # and close the feature.

Basic Structure

Here, we're being explicit about the font being intended for Latin-based support / usage.

# Establish the geographic and script locale
languagesystem DFLT dflt;
languagesystem latn dflt;

# Write a feature, in this case, Stylistic Set 1
feature ss01 {
    sub A by A.ss01;
    sub B by B.ss01;
    sub C by C.ss01;
} ss01;

Complex Structure

As your desired features become more and more complex, it would be a good idea to use good organizational habits, as seen here. Below, you will see:

  • Script tags
  • Defined @ variables
  • Defined lookup
  • Feature declaration
  • A name for that feature
  • A referenced lookup
# Establish the geographic and script locale
languagesystem DFLT dflt;
languagesystem latn dflt;

# Optional: Set up some nice organized swappable sets of glyph names, stored in “variables”
@ss01_off = [A      B      C     ];
@ss01_on  = [A.ss01 B.ss01 C.ss01];

# Optional: Make a "lookup" that you can reference later as many times as you want.
lookup my_cool_lookup {
    sub @ss01_off by @ss01_on;
} my_cool_lookup;

# Write a feature, in this case, Stylistic Set 1
feature ss01 {
    # Optional: Define the feature name for Stylistic Set 1
    featureNames {
        name 1 0 0 "My Cool Set";  # Numbers are Unicode platform, Default script, Default language
    };
    # Reference the lookup you set up earlier
    lookup my_cool_lookup;
} ss01;

Resources