Font Shaping

Advanced Font Shaping Options

Font shaping is the process which expands font ligatures and applies other advanced font display features that are encoded in your chosen font, in order to correctly position and display the appropriate glyphs on your display.

The HarfBuzz library is used to perform font shaping.

The harfbuzz_features option allows specifying the features to enable when using harfbuzz for font shaping.

There is some light documentation here: https://harfbuzz.github.io/shaping-opentype-features.html but it boils down to allowing opentype feature names to be specified using syntax similar to the CSS font-feature-settings options: https://developer.mozilla.org/en-US/docs/Web/CSS/font-feature-settings. The OpenType spec lists a number of features here: https://docs.microsoft.com/en-us/typography/opentype/spec/featurelist

Options of likely interest will be:

• calt - https://docs.microsoft.com/en-us/typography/opentype/spec/features_ae#tag-calt
• clig - https://docs.microsoft.com/en-us/typography/opentype/spec/features_ae#tag-clig

If you want to disable ligatures in most fonts, then you may want to use a setting like this:

config.harfbuzz_features = { 'calt=0', 'clig=0', 'liga=0' }

Some fonts make available extended options via stylistic sets. If you use the Fira Code font, it lists available stylistic sets here: https://github.com/tonsky/FiraCode/wiki/How-to-enable-stylistic-sets

and you can set them in wezterm:

-- Use this for a zero with a line through it rather than a dot
-- when using the Fira Code font
config.harfbuzz_features = { 'zero' }

Since: Version 20220101-133340-7edc5b5a

The functionality described in this section requires version 20220101-133340-7edc5b5a of wezterm, or a more recent version.

You can specify harfbuzz_features on a per-font basis, rather than globally for all fonts:

config.font = wezterm.font {
  family = 'JetBrains Mono',
  harfbuzz_features = { 'calt=0', 'clig=0', 'liga=0' },
}

and this example disables ligatures for JetBrains Mono, but keeps the default for the other fonts in the fallback:

config.font = wezterm.font_with_fallback {
  {
    family = 'JetBrains Mono',
    weight = 'Medium',
    harfbuzz_features = { 'calt=0', 'clig=0', 'liga=0' },
  },
  { family = 'Terminus', weight = 'Bold' },
  'Noto Color Emoji',
}