General Clipboard Listener

A Cross-Platform clipboard listener that listens for both text and image (screenshots).

npm package: https://www.npmjs.com/package/general-clipboard-listener

Installation

npm i @crosscopy/clipboard

Usage

It has a very easy to use event-based system.

See demo.ts for a demo.

Run ts-node demo.ts.

import clipboardEventListener from "./@crosscopy/clipboard";

console.log(clipboard.readTextSync());
  console.log(await clipboard.readText());
  const imgBuf = clipboard.readImageSync();
  // console.log(imgBuf.toString("base64"));
  // console.log(clipboard.readImageBase64Sync());
  // await clipboard.writeImage(base64img); // add fake image to clipboard
  clipboard.writeImageSync(base64img); // add fake image to clipboard
  console.log(""); // give some time
  console.assert(clipboard.readImageBase64Sync() === base64img);

  // * test readimage
  clipboard.writeImageSync(base64img);
  console.log();
  console.assert(
    (await clipboard.readImage()).toString("base64") === base64img
  );

  await clipboard.writeImage(base64img);
  console.log();
  console.assert((await clipboard.readImageBase64()) === base64img);
  clipboard.on("text", (text) => {
    console.log(text);
  });
  clipboard.on("image", (data) => {
    fs.writeFileSync("test.png", data);
  });
  clipboard.listen();
  setTimeout(() => {
    clipboard.close();
  }, 10000);

Note

This is an important note. If you write some data and read it immediately using the sync APIs, you may not be able to get the data. It needs a tiny bit of time to process. any code between the two lines should work, such as console.log().

Here I use await sleep(1) to make it work.

const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));

cb.writeTextSync("abc");
await sleep(1);
const text = cb.readTextSync();

If this package becomes popular some day and people requires a fix, I will fix it. For now, this implementation is good enough for CrossCopy.

I never need to write and read immediately after unless during testing.

Explanation

It's achieved using child process + stdout.

I took a golang version of the listener from golang-design/clipboard.

When a change is detected, IMAGE_CHANGED or TEXT_CHANGED is printed to stdout.

This library runs compiled go-version clipboard listener using child process and listen to the stdout.

If it sees the keywords in child process's stdout, an event will be emitted.

Run npm run demo to see a demo for 10 sec. Once started, copy some text and screenshot and check the terminal.

Supported Platforms

Format: process.platform/process.arch

The process here is from nodejs.

Supported platforms can be found in go-clipboard-monitor.

If your nodejs gives different platform or arch, it may not work.

Release

Cross Compile doesn't work due to some CGO problem. Have to build on different platforms manually.

go build -o binaries/go-clipboard-darwin-arm64
go build -o binaries/go-clipboard-darwin-x64
go build -o binaries/go-clipboard-win32-x64.exe
go build -o binaries/go-clipboard-linux-x64
go build -o binaries/go-clipboard-linux-arm
go build -o binaries/go-clipboard-linux-arm64