@bun-win32/dwrite

Zero-dependency, zero-overhead Win32 DirectWrite bindings for Bun on Windows.

Overview

@bun-win32/dwrite exposes the dwrite.dll export using Bun's FFI. It provides a single class, Dwrite, which lazily binds the native symbol on first use. You can optionally preload it up-front via Preload().

dwrite.dll exports exactly one flat function — DWriteCreateFactory. It hands back an IDWriteFactory, and the entire DirectWrite surface (font enumeration, text layout, glyph metrics, ClearType/grayscale rasterization, typography, shaping) lives behind that object's COM vtable. This package binds the factory entry point; the included examples demonstrate the hand-driven COM vtable pattern (read.u64 + CFunction) for everything beyond it — the same proven approach used by @bun-win32/dxgi and @bun-win32/combase.

The bindings are strongly typed for a smooth DX in TypeScript.

Features

• Bun-first ergonomics on Windows 10/11.
• Direct FFI to dwrite.dll (DirectWrite font and text layout/typography engine).
• In-source docs in structs/Dwrite.ts with links to Microsoft Docs.
• Lazy binding on first call; optional eager preload (Dwrite.Preload()).
• No wrapper overhead; calls map 1:1 to native APIs.
• Strongly-typed Win32 aliases (see types/Dwrite.ts).

Requirements

• Bun runtime
• Windows 10 or later

Installation

bun add @bun-win32/dwrite

Quick Start

import Dwrite, { DWRITE_FACTORY_TYPE } from '@bun-win32/dwrite';

// __uuidof(IDWriteFactory) = b859ee5a-d838-4b5b-a2e8-1adc7d93db48
const iid = Buffer.from([0x5a, 0xee, 0x59, 0xb8, 0x38, 0xd8, 0x5b, 0x4b, 0xa2, 0xe8, 0x1a, 0xdc, 0x7d, 0x93, 0xdb, 0x48]);

const factory = Buffer.alloc(8);
const hr = Dwrite.DWriteCreateFactory(DWRITE_FACTORY_TYPE.DWRITE_FACTORY_TYPE_SHARED, iid.ptr!, factory.ptr!);
console.log(`DWriteCreateFactory → 0x${(hr >>> 0).toString(16)}`);

// factory.readBigUInt64LE(0) is now an IDWriteFactory*; walk its COM vtable
// with `read.u64` + `CFunction` (see example/font-observatory.ts).

[!NOTE] AI agents: see AI.md for the package binding contract and source-navigation guidance. It explains how to use the package without scanning the entire implementation.

Examples

Run the included examples:

bun run example/glyph-forge.ts
bun run example/font-observatory.ts

Notes

• Either rely on lazy binding or call Dwrite.Preload().
• iid is a caller-allocated 16-byte GUID buffer (Pointer); factory is a caller-allocated 8-byte slot (Pointer) that receives an IUnknown*/IDWriteFactory* interface pointer, read back as a bigint.
• All DirectWrite objects are COM interfaces — invoke their methods through the vtable and Release them when finished.
• Windows only. Bun runtime required.