Windows FFI

NodeJS wrappers around Windows p-invoke/dll functions in user32, gdi32, etc. (based on node-ffi-napi)

Installation

• 1) Install ffi-napi in your project: npm i ffi-napi
  • 1.1) You may need to install the windows-build-tools first for ffi-napi to be able to build: npm install --global --production windows-build-tools
• 2) Install: npm i windows-ffi
  • 2.1) If you're using windows-ffi in symlinked mode, supply the parent project's copy of the node-ffi libraries using the init code below:

    // Make sure the code below runs before windows-ffi is imported! (example approach: https://stackoverflow.com/a/42817956)
    import ffi from "ffi-napi";
    import ref from "ref-napi";
    import refStructDI from "ref-struct-di";
    import {SupplyConfig} from "windows-ffi/Dist/@UserSupplied/PreImportConfig.js";
    
    SupplyConfig({ffi, ref, refStructDI});
    

Usage

While this library is meant to gradually expand to cover more of the Windows API, it will never be 100%, because it's a "develop as you need it" sort of endeavor.

Some of the most common and/or noteworthy functionalities are shown below.

Capture image-data from a region on-screen

import {VRect, CaptureScreenshot, GetForegroundWindowHandle} from "windows-ffi";

// First capture a screenshot of a section of the screen.
const screenshot = CaptureScreenshot({
    windowHandle: GetForegroundWindowHandle(), // comment to screenshot all windows
    rectToCapture: new VRect(0, 0, 800, 600),
});

// The image-data is now stored in the `screenshot.buffer` Buffer object.
// Access it directly (and cheaply) using the helper functions on `screenshot`.
for (let x = 0; x < 800; x++) {
    console.log(`Pixel color at [${x}, 0] is:`, screenshot.GetPixel(x, 0).ToHex_RGB());
}

Performance:

• Full-screen (2560x1440), all windows (ie. "desktop" window): ~80ms
• Full-screen (2560x1440), single window: ~20ms
• Region (700x200), all windows (ie. "desktop" window): ~50ms
• Region (700x200), single window: ~4ms

Tasks

General:

• Create an accompanying library for Windows-specific functionalities that do not require the ffi-napi dependency. (I've had pains with ffi-related building during NodeJS updates, so things that can be done without that dependency is beneficial to bundle separately)