@bun-win32/windowsaccessbridge-64

Zero-dependency, zero-overhead Java Access Bridge bindings for Bun on Windows.

Overview

@bun-win32/windowsaccessbridge-64 exposes the WindowsAccessBridge-64.dll exports using Bun's FFI. It provides a single class, WindowsAccessBridge, which lazily binds native symbols on first use. You can optionally preload a subset or all symbols up-front via Preload().

The Java Access Bridge is the bridge that lets Windows assistive technologies read and drive Swing/AWT applications. These bindings cover all 97 exports: window classification, AccessibleContext navigation, text/table/hypertext/value/selection accessors, and the event-callback registration functions.

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

Features

• Bun-first ergonomics on Windows 10/11.
• Direct FFI to WindowsAccessBridge-64.dll (window classification, accessible-context inspection, text/table/value queries, event callbacks).
• In-source docs in structs/WindowsAccessBridge.ts with links to the upstream OpenJDK headers.
• Lazy binding on first call; optional eager preload (WindowsAccessBridge.Preload()).
• No wrapper overhead; calls map 1:1 to native exports.
• Strongly-typed aliases (see types/WindowsAccessBridge.ts).

Requirements

• Bun runtime
• Windows 10 or later
• WindowsAccessBridge-64.dll (installed with any Java runtime; on PATH/System32)
• A running Java application with the Access Bridge enabled (jabswitch -enable) to inspect live UI

Installation

bun add @bun-win32/windowsaccessbridge-64

Quick Start

import WindowsAccessBridge from '@bun-win32/windowsaccessbridge-64';

// 1. Initialize the bridge once.
WindowsAccessBridge.Windows_run();

// 2. Each Java VM registers its windows with this process by posting messages after
//    Windows_run. Pump the message queue (e.g. via User32 PeekMessageW/DispatchMessageW)
//    for ~1s so registration lands before you classify any window.

// 3. Classify a window and read its root AccessibleContext.
if (WindowsAccessBridge.isJavaWindow(hWnd)) {
  const vmID = Buffer.alloc(4);
  const context = Buffer.alloc(8);
  WindowsAccessBridge.getAccessibleContextFromHWND(hWnd, vmID.ptr, context.ptr);

  const info = Buffer.alloc(6188); // sizeof(AccessibleContextInfo)
  WindowsAccessBridge.getAccessibleContextInfo(vmID.readInt32LE(0), context.readBigUInt64LE(0), info.ptr);

  const name = info.toString('utf16le', 0, 2048).replace(/\0.*$/s, ''); // name[MAX_STRING_SIZE]
  const role = info.toString('utf16le', 4096, 4096 + 512).replace(/\0.*$/s, ''); // role[SHORT_STRING_SIZE]
  console.log(role, name);

  WindowsAccessBridge.releaseJavaObject(vmID.readInt32LE(0), context.readBigUInt64LE(0));
}

[!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/jab-inspector.ts        # exhaustive Java accessibility-tree diagnostic
bun run example/accessibility-radar.ts  # animated radar that lights up Java windows live

Notes

• Either rely on lazy binding or call WindowsAccessBridge.Preload().
• The DLL exports use lower-camelCase internal names (getAccessibleContextInfo, setFocusGainedFP); signatures follow the OpenJDK AccessBridgeCalls.h / AccessBridgePackages.h headers.
• Most query functions round-trip to a live JVM over Windows messages — they need a running Java app and a pumped message loop in the calling process to return data.
• Windows only. Bun runtime required.
• SAL types & naming: nullability is in the type — Optional<T> (formally optional, SAL _*opt_) and Nullable<T> (plain [in]/[out] the docs say can be NULL), the null sentinel derived from T (null for pointers LP*/P*, 0n for handles/by-value addresses); direction is in the parameter name — _out (_Out_), _in_out (_Inout_), _In_ bare. See AI.md and the repo AGENTS.md.