A Rust 🦀️ font loading, positioning and rendering toolkit

Alibaba

Last update: Dec 27, 2022

Related tags

Command-line font-toolkit

Overview

Toolkit used to load, match, measure and render texts.

NOTE: This project is a work in progress. Text measuring and positioning is a complex topic. A more mature library is a sensible choice.

Compile the module:

npm run build
npm run build:wasi
node examples/node.mjs

Font querying

This module uses a special font matching logic. A font's identity contains the font family (name), weight, italic, and stretch (font width). When querying, any subset of the memtioned information is allowed except that the font family is required.

The query is then splitted into 4 filters, in the order of family -> weight -> italic -> stretch. Each filter could strim the result set, and:

If after any filter the result contains only one font, it is immediately returned.
If after all filters, 0 or more than 1 font are left, the query fails

General API (WASM API)

`new FontKit()`

Create a new font registry

`fontkit.add_font_from_buffer(buffer: Uint8Array) -> FontKey`

Add a font from a buffer, return the standard key of this font

`fontkit.query(key: FontKey) -> Font | undefined`

Query a font

`font.has_glyph(c: char) -> boolean`

Check if the font contains glyph for a given char

`font.ascender() -> number`

The ascender metric of the font

`font.descender() -> number`

The descender metric of the font

`font.units_per_em() -> number`

The units of metrics of this font

`font.glyph_path(c: char) -> GlyphPath | undefined`

Get the glyph path of a char, if any

`glyphPath.scale(scaleFactor: number)`

The glyph of font is very large (by the unit of units_per_em), the method could scale the path for convenience

`glyphPath.translate(x: number, y: number)`

Translate the path

`glyphPath.to_string() -> string`

Export the glyph path as an SVG path string

Node.js Support

Currently this module supports Node.js via WASI API. This requires the --experimental-wasi-unstable-preview1 flag and only limited APIs are provided.

Example

import { dirname } from 'path';
import { fileURLToPath } from 'url';

// Import the Node.js specific entry module
import { FontKitIndex } from '../node.mjs';

// Get current path, or you could use any path containing font files
const __dirname = dirname(fileURLToPath(import.meta.url));

// Create an instance of `FontKitIndex`, which is generally a font registry.
// By doing this, an object is created in Rust. So be sure to call `.free()`
// later
const fontkit = new FontKitIndex();

// Await here is needed as it initiate the WASM module
await fontkit.initiate();

// Add a search path, fonts are recursively indexed. This method could
// be called multiple times
fontkit.addSearchPath(__dirname);

// Query a font, additional params including weight, stretch, italic are supported
const font = fontkit.font('Open Sans');

// Get the actual path of the font
console.log(font.path());

// Free the memory of the registry
fontkit.free();

Being a minimal API, after getting the actual path of the font, you could load the file into a Uint8Array buffer, and use the normal WASM APIs to load / use the font. So basically the Node.js API here is only for indexing and querying fonts.

API

`new FontKitIndex()`

Create a new font registry only for indexing. Holding the info (not the actual buffers) of the fonts it found.

`fontkitIndex.addSearchPath(path: string)`

Search recursively in a path for new fonts. Supports ttf/otf/woff/woff2 fonts. The fonts are loaded to grab their info, and then immediately released.

`fontkitIndex.query(family: string, weight?=400, italic?=false, strech?=5) -> Font | undefined`

Query a font. Check querying for details

`fontkitIndex.free()`

Free the registry. Further calls will panic the program

`font.path() -> string`

Get the path of the font

Comments

fix(ras): fix text angle render

当glyph path中存在角度较小的尖角，并且设置较大的stroke-width的时候会出现尖角突出过长，违背了本身的拓扑关系，这种情况和stroke-linejoin及stroke-miterlimit相关。pathfinder默认miterlimit为10，缩小这个值可以改善尖角渲染的问题，现保持与SVG spec一致。

opened by KylinLee 2
feat(lib): js new class syntax support
js new class syntax support for FontKey and Width classes

BREAKING CHNAGE: new method of FontKey and Width class not be used.

difference:

Before:

FontKey.new(...params) Width.new(str)

After:

new FontKey(...params) new Width(str)

use new keyword is more intuitive.
opened by KylinLee 1
feat(ras): expose stroke style param

expose two stroke style param (line-cap, line-join) may be sometimes need custom the stroke style like SVG stroke-linecap and stroke-linejoin. I added two parameters for Font::bitmap, set None to use fontkit default.

opened by KylinLee 0
feat(ras): add stroke offset correction

when render glyph path with stroke, we'll get two bitmaps, these layers has different width and height, so we need to align this two layers, but simply calculate the width and height can not work well, we need a offset correction to set the new position of stroke bitmap pixel. the x, y correction mostly be a positive number, because stroke always larger than the fill bitmap.

opened by KylinLee 0
fix(ras): fix stroke broken

fix stroke broken

to fix this, remove obtuse angle in quadratic bezier curve. if path's last end point is equal to the first move segment(M) point, stroke width will loss at the last end point.

this pr only remove line-to segment(L) which end point is equal to move segment(M)

I'm not sure if it will affect the correct path, so is't a experimental function.

opened by KylinLee 0
Support TextMetrics API
https://developer.mozilla.org/en-US/docs/Web/API/TextMetrics

[ ] actualBoundingBoxAscent

[ ] actualBoundingBoxDescent

[ ] actualBoundingBoxLeft

[ ] actualBoundingBoxRight

[ ] alphabeticBaseline

[ ] emHeightAscent

[ ] emHeightDescent

[ ] fontBoundingBoxAscent

[ ] fontBoundingBoxDescent

[ ] hangingBaseline

[ ] ideographicBaseline

[ ] width
opened by yisibl 0

Owner

Alibaba

Alibaba Open Source

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