BunPad Native

A hyper-lightweight native Windows text editor built entirely in TypeScript with Bun runtime and raw Win32 API calls. No Electron. No web views. Pure native UI.

Architecture

src/
├── app/          # Window, editor, menu, document management
├── extensions/   # VS Code extension host + manifest parsing
├── io/           # Native file dialogs (GetOpenFileNameW / GetSaveFileNameW)
├── loop/         # Non-blocking Win32 message pump (PeekMessageW)
├── plugins/      # Plugin API (EditorContext + lifecycle hooks)
├── theme/        # JSON theme system with live switching
├── ui/           # Custom-drawn menu bar and status bar
├── vscode/       # VS Code extension compatibility shim
└── win32/        # Low-level FFI bindings (DWM, GDI32, layout, strings)

Tech Stack

Layer	Technology
Runtime	Bun >= 1.1
UI	Raw Win32 via @bun-win32/user32, kernel32, comdlg32
Editor	RICHEDIT50W (Msftedit.dll) with EDIT fallback
Language	TypeScript (strict, ESM)
Linting	ESLint + Prettier
Packaging	bun build --compile → single .exe

Quick Start

# Install dependencies
bun install

# Run in development (with --watch)
bun run dev

# Run production build
bun run start

Scripts

Command	Description
bun run dev	Development mode with hot reload
bun run start	Production run
bun run build	Compile to dist/bunpad.exe
bun run verify	Typecheck + lint + format + all tests
bun run typecheck	TypeScript type checking
bun run lint	ESLint check
bun run format	Prettier formatting
bun run test:smoke	Smoke tests
bun run test:plugins	Plugin system tests
bun run test:extensions	Extension host tests
bun run test:menu	Menu system tests

Themes

Themes are JSON files in themes/ with the structure:

{
  "id": "dark",
  "name": "Dark",
  "ui": {
    "background": "#1e1e1e",
    "foreground": "#d4d4d4",
    "accent": "#569cd6",
    "border": "#3c3c3c",
    "menuBar": {
      "background": "#252526",
      "foreground": "#cccccc",
      "hover": "#3c3c3c",
      "active": "#569cd6"
    },
    "statusBar": {
      "background": "#252526",
      "foreground": "#858585",
      "accent": "#569cd6"
    }
  },
  "editor": {
    "background": "#1e1e1e",
    "foreground": "#d4d4d4",
    "selectionBackground": "#264f78",
    "caret": "#aeafad",
    "fontFamily": "Cascadia Code",
    "fontSize": 14
  },
  "chrome": { "darkTitleBar": true }
}

Built-in themes: dark, light, dracula, monokai, nord, solarized-dark, high-contrast.

Plugins

Drop .ts files into plugins/. Each plugin exports a default BunPadPlugin:

import type { BunPadPlugin } from "../src/plugins/types";

const plugin: BunPadPlugin = {
  name: "my-plugin",
  onEditorReady(ctx) {
    /* ... */
  },
  onTextChange(ctx) {
    /* ... */
  },
  onBeforeSave(ctx) {
    /* ... */
  },
};

export default plugin;

Available Hooks

Hook	Fires when
onEditorReady	Editor control is initialized
onTextChange	Buffer content changes
onBeforeSave	File is about to be written
onAfterSave	File has been saved

EditorContext API

• ctx.getText() — returns full buffer text
• ctx.setText(text) — replaces buffer content
• ctx.getCursorPosition() — returns { line, column }
• ctx.showToast(message) — shows a native toast notification

VS Code Extensions

BunPad supports a subset of VS Code extensions (text manipulation, snippets). Drop extensions into extensions/<name>/ with a package.json manifest.

The compatibility shim maps:

VS Code API	BunPad Implementation
vscode.window.showInformationMessage	MessageBoxW
vscode.workspace.fs	Bun filesystem APIs
vscode.TextDocument	RICHEDIT50W buffer
vscode.TextEditor	Native editor commands

Build & Packaging

# Full verify + compile
bun run build

# Output: dist/bunpad.exe

The compiled binary resolves themes/, plugins/, extensions/, and vscode-shim/ relative to its own directory.

Key Design Decisions

• Non-blocking message loop: Uses PeekMessageW + Bun.sleep(1) instead of GetMessageW to avoid blocking Bun's async I/O.
• GC-safe FFI: Strong references held to JSCallback WndProc and wide-string buffers on window instances.
• Manual struct packing: FFI structs (WNDCLASSEXW, MSG, OPENFILENAMEW) are manually packed as Buffers since packages expose Pointer types only.
• No web UI: Zero HTML, CSS, DOM, Electron, or Tauri. All UI rendered through native Win32 controls.

Requirements

• Windows 11 Pro (or Windows 10 1809+)
• Bun >= 1.1.0

License

MIT © involvex