Advanced Font Shaping Options

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:

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

return {
  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:

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

Since: 20220101-133340-7edc5b5a

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

local wezterm = require 'wezterm'
return {
  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:

local wezterm = require 'wezterm'

return {
  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',
  },
}