Secondary Terminal

A full-featured terminal extension that runs in the VSCode sidebar. With complete PTY emulation, interactive applications such as vim and less work correctly.

Features

• Sidebar Terminal: Terminal integrated into the VSCode sidebar
• Full PTY Emulation: Genuine pseudo-terminal implementation using Python
• Interactive App Support: Full support for vim, less, nano, etc.
• Dynamic Resizing: Automatically adjusts terminal size according to sidebar dimensions
• UTF-8 Support: Correctly displays multibyte characters including Japanese
• Custom Font: RobotoMono Nerd Font support
• Multi-Tab Support: Multiple independent terminal tabs, each with its own shell process and editor
• ACE Editor Integration: Built-in code editor (ACE) per tab for composing commands and text
• Clipboard Image Paste: Paste images from clipboard and insert file path reference (macOS only)
• Drop Zone: Drag & drop files from the explorer to insert file path references into the editor

Requirements

• Visual Studio Code 1.101.0 or later
• Python 3.x (for PTY emulation)
• macOS / Linux (currently only Unix-based OS supported)

Installation

Development Installation

1. Clone this repository:

   git clone <repository-url>
   cd secondary-terminal
   

2. Install dependencies:

   npm install
   

3. Compile TypeScript:

   npm run compile
   

4. Run in development mode with VSCode:

   • Open the project in VSCode
   • Press F5 to launch the extension in debug mode
   • A new VSCode window will open with the extension available

Local Installation

To install the extension to your local VSCode, copy the project directory path, then open the Command Palette (Cmd+Shift+P) and run:

Developer: Install Extension from Location...

Specify the project directory path (e.g., /path/to/secondary-terminal).

Installation via Symlink

As a simpler alternative, you can create a symbolic link in the extensions directory:

# For standard VSCode
ln -s /path/to/secondary-terminal ~/.vscode/extensions/secondary-terminal

# For VSCode Insiders
ln -s /path/to/secondary-terminal ~/.vscode-insiders/extensions/secondary-terminal

Then restart VSCode.

Updating After Code Changes

Steps to update after modifying the extension code:

1. Compile TypeScript:

   npm run compile
   # Or watch for changes and auto-compile
   npm run dev
   

2. Reload the extension in VSCode:

   • Open the Command Palette (Cmd+Shift+P)
   • Run Developer: Reload Window
   • Or fully restart VSCode

3. Test in development mode:

   • Open the project in VSCode
   • Press F5 to launch in debug mode
   • Test your changes in the new window

Development Commands

# Auto-compile (file watcher)
npm run dev

# Clean output directory
npm run clean

# Clean and recompile
npm run rebuild

# Lint code
npm run lint

Usage

1. After installing the extension, restart VSCode
2. A "Secondary Terminal" icon will appear in the sidebar
3. Click the icon to open the terminal panel
4. Use it like a regular terminal:
   • Execute commands
   • Edit files with vim (hjkl cursor movement supported)
   • Browse files with less
   • Other interactive applications
5. Use the built-in ACE editor to compose multi-line commands and send them to the terminal with Cmd+Enter
6. Paste images from clipboard using the 📷 button (macOS) — the image is saved to a temp file and inserted as [@<filepath>]
7. Drag & drop files onto the Drop Zone to insert file path references into the editor

Technical Specifications

• Frontend: High-performance terminal emulator using xterm.js
• Backend: Full pseudo-terminal implementation using Python's pty module
• Communication: Node.js child_process for communication between VSCode and Python
• Character Encoding: Full UTF-8 support
• Shell: zsh (default), with bash fallback

Known Issues

• Currently only Unix-based OS (macOS, Linux) supported
• Some advanced terminal features (multiple panes, etc.) are not yet supported
• Does not work on Windows

Performance Degradation with Large Scroll History

Terminal scrolling and UI responsiveness slow down as scroll history grows. This is a frontend-side issue unrelated to PTY. Rewriting PTY in Rust was attempted but showed no improvement (see feature/rust-pty branch), so the change was reverted.

Developer Information

File Structure

• src/extension.ts: Extension entry point
• src/terminalProvider.ts: Terminal provider implementation (tabs, ACE editor, PTY management)
• src/clipboardImageHandler.ts: macOS clipboard image extraction
• src/dropZoneProvider.ts: File drag & drop zone
• src/terminalSessionManager.ts: Terminal session persistence
• src/shellProcessManager.ts: Shell process lifecycle management
• resources/terminal.html: Main UI (xterm.js, ACE editor, tab bar)
• resources/xterm.css, resources/xterm.js: xterm.js library

Key Features

1. PTY Emulation: Full pseudo-terminal implementation via Python script
2. Dynamic Resizing: Automatic resize based on HTML element dimensions
3. Non-blocking I/O: High-performance I/O processing using select

Rust PTY Migration Attempt

A Rust-based PTY implementation was attempted to eliminate environment dependencies, but was abandoned due to macOS security restrictions. When spawning a binary located under /Users/ from Node.js, PTY creation is blocked and the process immediately becomes a zombie. See resources/pty-rs/README.md in the feature/rust-pty-migration branch for details.

License

MIT License

Author

ytyng