[vector] Content-based dedup, remove font reference caching Replace glyph-ID-based dedup with content-based dedup for SVG path definitions and color glyph groups. Path/paint output is hashed and compared byte-for-byte against existing defs; identical content reuses the same def regardless of glyph ID. This eliminates the font reference held by draw/paint contexts (cached_font + hb_font_reference), which was keeping the font and its face alive longer than the caller expected. No font pointer is stored at all now. Also removes changed() — with content-based dedup, foreground and palette changes produce different content that naturally won't match cached entries. Assisted-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
HarfBuzz started as a text shaping engine but has grown into a full font platform — the ffmpeg of text shaping. It primarily supports OpenType, but also Apple Advanced Typography.
HarfBuzz shapes the majority of text on modern screens.
HarfBuzz is optimized for robustness, correctness, and performance — in that order. Achieve all.
Try it live at harfbuzz-world.cc — an interactive playground for shaping, subsetting, rasterization, vector output, and GPU rendering, all running in your browser.
Here is a quick map of its components:
| Library | Description |
|---|---|
| libharfbuzz | Text shaping, draw API, paint API. Highly configurable (see CONFIG.md). Optional integration backends compiled in: hb-ft (FreeType), hb-coretext (macOS), hb-uniscribe (Windows), hb-directwrite (Windows), hb-gdi (Windows), hb-glib, hb-graphite2. |
| libharfbuzz-subset | Font subsetting and variable-font instancing. |
| Library | Description |
|---|---|
| libharfbuzz-icu | ICU Unicode integration. |
| libharfbuzz-cairo | Cairo rendering integration. |
| libharfbuzz-gobject | GObject/GI bindings. |
| Library | Description |
|---|---|
| libharfbuzz-raster | Glyph rasterization to bitmaps, including color fonts. Uses hb-draw and hb-paint. |
| libharfbuzz-vector | Glyph output to vector formats (currently SVG), including color fonts. Uses hb-draw and hb-paint. |
| libharfbuzz-gpu | Encodes glyph outlines for GPU rasterization (Slug algorithm). Provides shader sources in GLSL, WGSL, MSL, and HLSL. Live demo. |
Notable missing feature: font hinting (including autohinting) is not implemented. For hinted rasterization, use FreeType or Skrifa.
For simplified builds, amalgamated sources are available: harfbuzz.cc (just libharfbuzz), harfbuzz-subset.cc (just libharfbuzz-subset), or harfbuzz-world.cc (everything, driven by a custom hb-features.h). For a live in-browser playground plus a worked example of the world.cc single-file build, see harfbuzz-world.cc.
| Tool | Description |
|---|---|
| hb-shape | Shape text and display glyph output. |
| hb-view | Render shaped text to an image. |
| hb-subset | Subset and optimize fonts. |
| hb-info | Display font metadata. |
| hb-raster | Render glyphs to bitmap images. |
| hb-vector | Render glyphs to vector formats (SVG). |
| hb-gpu | Interactive GPU text rendering. |
The canonical source tree and bug trackers are available on github. Both development and user support discussion around HarfBuzz happen on github as well.
For license information, see COPYING.
The API that comes with hb.h will not change incompatibly. Other, peripheral, headers are more likely to go through minor modifications, but again, we do our best to never change API in an incompatible way. We will never break the ABI.
The API and ABI are stable even across major version number jumps. In fact, current HarfBuzz is API/ABI compatible all the way back to the 0.9.x series. If one day we need to break the API/ABI, that would be called a new library.
As such, we bump the major version number only when we add major new features, the minor version when there is new API, and the micro version when there are bug fixes.
For user manual as well as API documentation, check: https://harfbuzz.github.io
Tarball releases and Win32/Win64 binary bundles are available on the github releases page.
For build information, see BUILD.md.
For custom configurations, see CONFIG.md.
For testing and profiling, see TESTING.md.
For using with Python, see README.python.md. There is also uharfbuzz.
For cross-compiling to Windows from Linux or macOS, see README.mingw.md.
To report bugs or submit patches please use github issues and pull-requests.
To get a better idea of where HarfBuzz stands in the text rendering stack you may want to read State of Text Rendering 2024. Here are a few presentation slides about HarfBuzz over the years:
More presentations and papers are available on behdad's website. In particular, the following studies are relevant to HarfBuzz development:
hb-decyclerhb-iterhb-ft >h_advance functionHarfBuzz /hærfˈbɒːz/
From Persian حرف (Harf: letter) and باز (Buzz: open). Transliteration of the Persian calque for OpenType.
As a noun: The Open Source text shaping engine.
As an adjective: Insincerely talkative; glib. A nod to the GNOME project where HarfBuzz originates from.
The logo shows حرفباز in the IranNastaliq font, on a Damascus steel background.
Background: Originally there was this font format called TrueType. People and companies started calling their type engines all things ending in Type: FreeType, CoolType, ClearType, etc. And then came OpenType, which is the successor of TrueType. So, for my OpenType implementation, I decided to stick with the concept but use the Persian translation. Which is fitting given that Persian is written in the Arabic script, and OpenType is an extension of TrueType that adds support for complex script rendering, and HarfBuzz is an implementation of OpenType text shaping.
HarfBuzz is used in Android, Chrome, ChromeOS, Firefox, GNOME, GTK+, KDE, Qt, LibreOffice, OpenJDK, XeTeX, Adobe Photoshop, Illustrator, InDesign, Microsoft Edge, Amazon Kindle, PlayStation, Godot Engine, Unreal Engine, Figma, Canva, QuarkXPress, Scribus, smart TVs, car displays, and many other places.
