@bun-win32/combase

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

Overview

@bun-win32/combase exposes the combase.dll exports using Bun's FFI. It provides a single class, Combase, which lazily binds native symbols on first use. You can optionally preload a subset or all symbols up-front via Preload().

This is the Windows Runtime (WinRT) activation core: the Ro* activation functions (RoInitialize, RoActivateInstance, RoGetActivationFactory), the full HSTRING string API (WindowsCreateString, WindowsGetStringRawBuffer, …), and the WinRT error-info surface (RoOriginateError, GetRestrictedErrorInfo, …). Combined with COM vtable invocation, this is the pure-FFI path to native toast notifications, System Media Transport Controls, sensors, and the rest of the WinRT projection — with no native build step.

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

Features

• Bun-first ergonomics on Windows 10/11.
• Direct FFI to combase.dll (WinRT activation, HSTRING strings, and Windows Runtime error APIs).
• In-source docs in structs/Combase.ts with links to Microsoft Docs.
• Lazy binding on first call; optional eager preload (Combase.Preload()).
• No wrapper overhead; calls map 1:1 to native APIs.
• Strongly-typed Win32 aliases (see types/Combase.ts).

Requirements

• Bun runtime
• Windows 10 or later

Installation

bun add @bun-win32/combase

Quick Start

import Combase, { RO_INIT_TYPE } from '@bun-win32/combase';

// Initialize the Windows Runtime on this thread.
Combase.RoInitialize(RO_INIT_TYPE.RO_INIT_MULTITHREADED);

// Create an HSTRING from a JS string.
const text = 'Windows.Globalization.Calendar';
const source = Buffer.from(text, 'utf16le');
const out = Buffer.alloc(8);
Combase.WindowsCreateString(source.ptr!, text.length, out.ptr!);
const hClassId = out.readBigUInt64LE(0);

// Activate the WinRT runtime class.
const instance = Buffer.alloc(8);
const hr = Combase.RoActivateInstance(hClassId, instance.ptr!);
console.log(`RoActivateInstance → 0x${(hr >>> 0).toString(16)}`);

Combase.WindowsDeleteString(hClassId);
Combase.RoUninitialize();

[!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/toast-notification.ts
bun run example/winrt-diagnostic.ts

Notes

• Either rely on lazy binding or call Combase.Preload().
• HSTRING, HSTRING_BUFFER, and the registration cookies are opaque handle tokens (bigint); HSTRING* out-parameters are caller-allocated buffers (Pointer).
• Windows only. Bun runtime required.