selection-hook/README.md

Text selection monitoring of native Node.js module with N-API across applications

# Text Selection Hook for Node.js and Electron

[![npm version](https://img.shields.io/npm/v/selection-hook?style=flat)](https://www.npmjs.org/package/selection-hook)

A native Node.js module with Node-API that allows monitoring text selections across applications using multiple methods.

## Features

Maybe the first-ever open-source, fully functional text selection tool.

- **Cross-application text selection monitoring**
  - Capture selected text content and its screen coordinates
  - Auto-triggers on user selection, or manual API triggers
  - Rich API to control the selection behaviors
- **Input event listeners**
  - Mouse events: `down/up/wheel/move`
  - Keyboard events: `keydown/keyup`
  - _No additional hooks required_ – works natively.
- **Multi-method text extraction** (automatic fallback):
  - _UI Automation_ (modern apps)
  - _Accessibility APIs_ (legacy apps)
  - _Focused control_ (active input fields)
  - _Clipboard fallback_ (simulated `Ctrl+C` with optimizations)
- **Clipboard**
  - Read/write clipboard
- **Compatibility**
  - Node.js `v10+` | Electron `v3+`
  - TypeScript support included.

## Platform

Currently only supports Windows. macOS/Linux support is coming soon.

## Installation

```bash
npm install selection-hook
```

### Notes

#### Avoid rebuilding

The npm package ships with a pre-built `.node` file — no rebuilding needed. For Electron rebuild issues, add these values to your `electron-forge` config to avoid rebuilding:

```javascript
rebuildConfig: {
    onlyModules: [],
},
```

#### Python setuptools

When building, if the `ModuleNotFoundError: No module named 'distutils'` error prompt appears, please install the necessary Python library via `pip install setuptools`.

## Demo

```bash
npm run demo
```

## Usage

```javascript
const SelectionHook = require("selection-hook");

// Create a new instance
// You can design it as a singleton pattern to avoid resource consumption from multiple instantiations
const selectionHook = new SelectionHook();

// Listen for text selection events
selectionHook.on("text-selection", (data) => {
  console.log("Selected text:", data.text);
  // For mouse start/end position and text range coornidates
  // see API Reference below.
});

// Start monitoring (with default configuration)
selectionHook.start();

// When you want to get the current selection directly
const currentSelection = selectionHook.getCurrentSelection();
if (currentSelection) {
  console.log("Current selection:", currentSelection.text);
}

// Stop, you can start it again
selectionHook.stop();
// Clean up when done
selectionHook.cleanup();
```

See [`examples/node-demo.js`](https://github.com/0xfullex/selection-hook/blob/main/examples/node-demo.js) for detailed usage.

## API Reference

### Constructor

```javascript
const hook = new SelectionHook();
```

### Methods

#### **`start(config?: SelectionConfig): boolean`**

Start monitoring text selections.

Config options (with default values):

```javascript
{
  debug?: false,                 // Enable debug logging
  enableMouseMoveEvent?: false,  // Enable mouse move tracking, can be set in runtime
  enableClipboard?: true,        // Enable clipboard fallback, can be set in runtime
  selectionPassiveMode?: false,  // Enable passive mode, can be set in runtime
  clipboardMode?: SelectionHook.FilterMode.DEFAULT,    // Clipboard mode, can be set in runtime
  clipboardFilterList?: string[]                       // Program list for clipboard mode, can be set in runtime
  globalFilterMode?: SelectionHook.FilterMode.DEFAULT, // Global filter mode, can be set in runtime
  globalFilterList?: string[]                          // Global program list for global filter mode, can be set in runtime
}
```

see [`SelectionHook.FilterMode`](#selectionhookfiltermode) for details

#### **`stop(): boolean`**

Stop monitoring text selections.

#### **`getCurrentSelection(): TextSelectionData | null`**

Get the current text selection if any exists.

#### **`enableMouseMoveEvent(): boolean`**

Enable mouse move events (high CPU usage). Disabled by default.

#### **`disableMouseMoveEvent(): boolean`**

Disable mouse move events. Disabled by default.

#### **`enableClipboard(): boolean`**

Enable clipboard fallback for text selection. Enabled by default.

#### **`disableClipboard(): boolean`**

Disable clipboard fallback for text selection. Enabled by default.

#### **`setClipboardMode(mode: ClipboardMode, programList?: string[]): boolean`**

Configure how clipboard fallback works with different programs. See `SelectionHook.FilterMode` constants for details.

#### **`setGlobalFilterMode(mode: FilterMode, programList?: string[]): boolean`**

Configure which applications should trigger text selection events. You can include or exclude specific applications from the selection monitoring. See `SelectionHook.FilterMode` constants for details.

#### **`setFineTunedList(listType: FineTunedListType, programList?: string[]): boolean`**

Configure fine-tuned lists for specific application behaviors. This allows you to customize how the selection hook behaves with certain applications that may have unique characteristics.

For example, you can add `acrobat.exe` to those lists to enable text seleted in Acrobat.

List types:
- `EXCLUDE_CLIPBOARD_CURSOR_DETECT`: Exclude cursor detection for clipboard operations
- `INCLUDE_CLIPBOARD_DELAY_READ`: Include delay when reading clipboard content 

See `SelectionHook.FineTunedListType` constants for details.

#### **`setSelectionPassiveMode(passive: boolean): boolean`**

Set passive mode for selection (only triggered by getCurrentSelection, `text-selection` event will not be emitted).

#### **`writeToClipboard(text: string): boolean`**

Write text to the system clipboard. This is useful for implementing custom copy functions.

#### **`readFromClipboard(): string | null`**

Read text from the system clipboard. Returns clipboard text content as string, or null if clipboard is empty or contains non-text data.

#### **`isRunning(): boolean`**

Check if selection-hook is currently running.

#### **`cleanup()`**

Release resources and stop monitoring.

### Events

#### **`text-selection`**

Emitted when text is selected, see [`TextSelectionData`](#textselectiondata) for `data` structure

```javascript
hook.on("text-selection", (data: TextSelectionData) => {
  // data contains selection information
});
```

#### **`mouse-move`**, **`mouse-up`**, **`mouse-down`**

Mouse events, see [`MouseEventData`](#mouseeventdata) for `data` structure

```javascript
hook.on("mouse-XXX", (data: MouseEventData) => {
  // data contains mouse coordinates and button info
});
```

#### **`mouse-wheel`**

Mouse wheel events, see [`MouseWheelEventData`](#mousewheeleventdata) for `data` structure

```javascript
hook.on("mouse-wheel", (data: MouseWheelEventData) => {
  // data contains wheel direction info
});
```

#### **`key-down`**, **`key-up`**

Keyboard events, see [`KeyboardEventData`](#keyboardeventdata) for `data` structure

```javascript
hook.on("key-XXX", (data: KeyboardEventData) => {
  // data contains key code and modifier info
});
```

#### **`status`**

Hook status changes

```javascript
hook.on("status", (status: string) => {
  // status is a string, e.g. "started", "stopped"
});
```

#### **`error`**

Error events
Only display errors when `debug` set to `true` when `start()`

```javascript
hook.on("error", (error: Error) => {
  // error is an Error object
});
```

### Data Structure

**Note**: All coordinates are in physical coordinates (virtual screen coordinates) in Windows. You can use `screen.screenToDipPoint(point)` in Electron to convert the point to logical coordinates.

#### `TextSelectionData`

Represents text selection information including content, source application, and coordinates.

| Property        | Type              | Description                                                   |
| --------------- | ----------------- | ------------------------------------------------------------- |
| `text`          | `string`          | The selected text content                                     |
| `programName`   | `string`          | Name of the application where selection occurred              |
| `startTop`      | `Point`           | First paragraph's top-left coordinates (px)                   |
| `startBottom`   | `Point`           | First paragraph's bottom-left coordinates (px)                |
| `endTop`        | `Point`           | Last paragraph's top-right coordinates (px)                   |
| `endBottom`     | `Point`           | Last paragraph's bottom-right coordinates (px)                |
| `mousePosStart` | `Point`           | Mouse position when selection started (px)                    |
| `mousePosEnd`   | `Point`           | Mouse position when selection ended (px)                      |
| `method`        | `SelectionMethod` | Indicates which method was used to detect the text selection. |
| `posLevel`      | `PositionLevel`   | Indicates which positional data is provided.                  |

Type `Point` is `{ x: number; y: number }`

When `PositionLevel` is:

- `MOUSE_SINGLE`：only `mousePosStart` and `mousePosEnd` is provided, and `mousePosStart` equals `mousePosEnd`
- `MOUSE_DUAL`: only `mousePosStart` and `mousePosEnd` is provided
- `SEL_FULL`: all the mouse position and paragraph's coordinates are provided

#### `MouseEventData`

Contains mouse click/movement information in screen coordinates.

| Property | Type     | Description                                                                                      |
| -------- | -------- | ------------------------------------------------------------------------------------------------ |
| `x`      | `number` | Horizontal pointer position (px)                                                                 |
| `y`      | `number` | Vertical pointer position (px)                                                                   |
| `button` | `number` | Same as WebAPIs' MouseEvent.button <br /> `0`=Left, `1`=Middle, `2`=Right, `3`=Back, `4`=Forward |

#### `MouseWheelEventData`

Describes mouse wheel scrolling events.

| Property | Type     | Description                         |
| -------- | -------- | ----------------------------------- |
| `button` | `number` | `0`=Vertical, `1`=Horizontal scroll |
| `flag`   | `number` | `1`=Up/Right, `-1`=Down/Left        |

#### `KeyboardEventData`

Represents keyboard key presses/releases.

| Property   | Type      | Description                       |
| ---------- | --------- | --------------------------------- |
| `sys`      | `boolean` | System key pressed (Alt/Ctrl/Win) |
| `vkCode`   | `number`  | Windows virtual key code          |
| `scanCode` | `number`  | Hardware scan code                |
| `flags`    | `number`  | Additional state flags            |
| `type`     | `string?` | Internal event type               |
| `action`   | `string?` | `"key-down"` or `"key-up"`        |

### Constants

#### **`SelectionHook.SelectionMethod`**

Indicates which method was used to detect the text selection:

- `NONE`: No selection detected
- `UIA`: UI Automation
- `FOCUSCTL`: Focused control
- `ACCESSIBLE`: Accessibility interface
- `CLIPBOARD`: Clipboard fallback

#### **`SelectionHook.PositionLevel`**

Indicates which positional data is provided:

- `NONE`: No position information
- `MOUSE_SINGLE`: Only single mouse position
- `MOUSE_DUAL`: Mouse start and end positions (when dragging to select)
- `SEL_FULL`: Full selection coordinates (see [`TextSelectionData`](#textselectiondata) structure for details)
- `SEL_DETAILED`: Detailed selection coordinates (reserved for future use)

#### **`SelectionHook.FilterMode`**

Before version `v0.9.16`, this variable was named `ClipboardMode`

- `DEFAULT`: The filter mode is disabled
- `INCLUDE_LIST`: Only the programs in list will pass the filter
- `EXCLUDE_LIST`: Only the progrmas NOT in in list will pass the filter

#### **`SelectionHook.FineTunedListType`**

Defines types for fine-tuned application behavior lists:

- `EXCLUDE_CLIPBOARD_CURSOR_DETECT`: Exclude cursor detection for clipboard operations. Useful for applications with custom cursors (e.g., Adobe Acrobat) where cursor shape detection may not work reliably.
- `INCLUDE_CLIPBOARD_DELAY_READ`: Include delay when reading clipboard content. Useful for applications that modify clipboard content multiple times in quick succession (e.g., Adobe Acrobat).

### TypeScript Support

This module includes TypeScript definitions. Import the module in TypeScript as:

```typescript
import {
  SelectionHookConstructor,
  SelectionHookInstance,
  SelectionConfig,
  TextSelectionData,
  MouseEventData,
  MouseWheelEventData,
  KeyboardEventData,
} from "selection-hook";

// use `SelectionHookConstructor` for SelectionHook Class
const SelectionHook: SelectionHookConstructor = require("selection-hook");
// use `SelectionHookInstance` for SelectionHook instance
const hook: SelectionHookInstance = new SelectionHook();
```

See [`index.d.ts`](https://github.com/0xfullex/selection-hook/blob/main/index.d.ts) for details.

## Used By

This project is used by:

- **[Cherry Studio](https://github.com/CherryHQ/cherry-studio)**: A full-featured AI client, with Selection Assistant that conveniently enables AI-powered translation, explanation, summarization, and more for selected text.