bun-user32

Zero-dependency, zero-overhead Win32 User32 bindings for Bun on Windows.

Overview

bun-user32 exposes the User32 entry points exported by user32.dll using Bun's FFI. It provides a single class, User32, which lazily binds native symbols once via Init() and then calls directly into the DLL.

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

𝐢 · Symbol definitions were generated with AI assistance and reviewed for correctness against User32/Win32 signatures.

Features

• Bun-first ergonomics on Windows 10/11.
• Direct FFI to user32.dll (windows, input, clipboard, monitors, and more).
• In-source docs – each method includes a Microsoft Docs link above its declaration in structs/User32.ts.
• Lazy, one-time initialization (User32.Init()).
• No wrapper overhead; calls map 1:1 to native APIs.
• Strongly-typed Win32 aliases (see types/User32.ts).

Requirements

• Bun runtime
• Windows 10 or later

Installation

bun add bun-user32

Quick Start

import User32 from 'bun-user32';

// Bind all symbols from user32.dll once
User32.Init();

// Helper to create a null-terminated UTF-16LE buffer
const toWide = (s: string) => Buffer.from(s + '\0', 'utf16le');

// Call MessageBoxW(NULL, L"Hello", L"bun-user32", MB_OK)
User32.MessageBoxW(0, toWide('Hello from bun-user32').ptr, toWide('bun-user32').ptr, 0);

API Highlights

• Exact names and signatures that mirror the native API surface.
• Init() – Loads and binds all exported User32 symbols.
• MessageBoxW, FindWindowW, GetCursorPos, SetForegroundWindow, RegisterClassW, CreateWindowExW, and many more.
• Pointer-friendly – this package adds a .ptr property to ArrayBuffer/Buffer/DataView/TypedArray via a tiny runtime extension for Bun FFI convenience.

Notes

• Always call User32.Init() before invoking any User32.* function.
• User32 wide-string (*W) functions expect UTF-16LE + null terminator. Use a helper like toWide() and pass .ptr.
• Windows only. Bun runtime required.

TODO

• Additional helpers for string/struct marshalling.
• Small utilities for common patterns (window class registration, message loops).