luaharfbuzz

• Index

Contents

• Functions
• Class SubsetInput

Modules

• harfbuzz
• harfbuzzsubset

Examples

• core_types.lua

Module harfbuzzsubset

Lua bindings to the Harfbuzz subset API.

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• API Coverage Status

This module provides bindings to the HarfBuzz hb-subset API. It is designed to be used together with the main harfbuzz module.

Typical usage:

local hb = require('harfbuzz')
local hb_subset  = require("harfbuzzsubset")

local input = hb_subset.SubsetInput.new()

local wght = hb.Tag.new("wght")
local wdth = hb.Tag.new("wdth")
local face = hb.Face.new("myfont.ttf")

input:pin_axis_location(face, wght, 100)
input:pin_axis_location(face, wdth, 100)

input:keep_everything()

local new_face = hb_subset.subset(face, input)

local blob = new_face:blob()
local fh, err = io.open("out.ttf", "wb")
if not fh then error(err) end
fh:write(blob:get_data())
fh:close()

Info:

• Copyright: 2025
• License: MIT
• Author: Patrick Gundlach <gundlach@speedata.de>

Functions

subset (face, input)	Wraps hb_subset_or_fail.
version ()	Wraps hb_version.

Class SubsetInput

SubsetInput.new ()	Wraps hb_subset_input_create_or_fail.
SubsetInput:unicode_set ()	Wraps hb_subset_input_unicode_set.
SubsetInput:pin_axis_location (face, tag, value)	Wraps hb_subset_input_pin_axis_location.
SubsetInput:keep_everything ()	Wraps hb_subset_input_keep_everything.
SubsetInput:__gc ()	Wraps hb_subset_input_destroy.

Functions

subset (face, input)

Wraps hb_subset_or_fail.

Performs the actual subset operation, producing a new Face that only contains the glyphs and data configured on this input.

Parameters:

• face source Face object to subset.
• input SubsetInput object to subset based on.

Returns:

new Face object representing the subset, or nil on failure.

version ()

Wraps hb_version.

Class SubsetInput

SubsetInput.new ()

Wraps hb_subset_input_create_or_fail.

Initializes a new hb_subset_input_t. The returned object can be used to configure which glyphs and features are kept when subsetting a face.

Returns:

SubsetInput object, or nil on failure.

SubsetInput:unicode_set ()

Wraps hb_subset_input_unicode_set.

Returns the Unicode set associated with this subset input. The returned harfbuzz.Set can be modified (e.g. via add) to control which Unicode codepoints are included in the subset.

Returns:

Set object representing the Unicode set, or nil on failure.

SubsetInput:pin_axis_location (face, tag, value)

Wraps hb_subset_input_pin_axis_location.

Pins a variation axis at a specific value for subsetting.

Parameters:

• face Face object whose design space is being subset.
• tag Tag object representing the axis tag (e.g. "wght", "wdth").
• value numeric axis value to pin.

Returns:

true on success, false on failure.

SubsetInput:keep_everything ()

Wraps hb_subset_input_keep_everything.

Configures the input so that everything in the original face is kept. This is useful as a starting point before applying more specific filters.

SubsetInput:__gc ()

Wraps hb_subset_input_destroy.

Destructor for subset inputs. Normally this is invoked automatically by the garbage collector; applications rarely need to call it directly.