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"
  }),
}