Hone Editor

High-performance, cross-platform code editor surface. Designed to be embedded by other applications — markdown editors, config editors, query consoles, or full IDEs.

All editor logic is written in TypeScript and shared across every platform. Native text rendering is handled by per-platform Rust FFI crates using each OS's native text stack.

Features

• Piece table text buffer with B-tree rope indexing — O(log n) for all operations
• Multi-cursor editing with selections, word boundaries, and cursor merging
• Syntax highlighting via two engines:
  • Tree-sitter on macOS/iOS/web (via web-tree-sitter on web) for TypeScript, JavaScript, Python, Rust, JSON, CSS
  • Keyword tokenizer fallback for 20+ languages — no grammar needed
• Bracket-pair colorization — three-color VS Code-style cycle
• Search and replace — literal, regex, case-sensitive, whole-word, incremental
• Code folding — indent-based and syntax-based
• Undo/redo with time-based coalescing
• Virtual scrolling — only visible lines are rendered
• Word wrap — none, word-boundary, or bounded column modes
• Diff engine — Myers algorithm with inline character-level diffs and hunk operations
• LSP client — completion, hover, go-to-definition, references, diagnostics, formatting
• DAP client — breakpoints, stepping, stack inspection, variable evaluation
• Ghost text — inline AI completion rendering
• Overlay layers — find highlights, Error Lens diagnostics, breakpoint gutter, fold chevrons, decorations
• Minimap, find/replace widget, autocomplete overlays

Platform Support

Platform	Renderer	Renderer language	Status
macOS	Core Text + Core Animation	Rust	Working (interactive demo)
iOS	Core Text + UIKit	Rust	Working (interactive demo)
Windows	DirectWrite + Direct2D	Rust	Working (interactive demo)
Linux	Pango + Cairo	Rust	Scaffolded
Android	Canvas + Skia (JNI)	Rust	Working (interactive demo)
Web	DOM	TypeScript	Working — mount() API, tree-sitter, full overlays

On every platform the editor is a single TypeScript codebase compiled by Perry; each platform provides a "dumb renderer" that implements the same hone_editor_* FFI contract against its native rendering primitive. On the web the rendering primitive is the DOM, so that renderer is also TypeScript (see native/web/dom-ffi.ts).

Architecture

core/               Platform-independent TypeScript (shared across all targets)
  buffer/           Piece table + B-tree rope text buffer
  document/         EditorDocument, EditBuilder, encoding detection
  cursor/           Multi-cursor management, selections, word boundaries
  commands/         Command registry + editing/navigation/selection/clipboard
  history/          Undo/redo with time-based coalescing
  viewport/         Virtual scrolling, line height cache
  tokenizer/        Lezer syntax highlighting
  search/           Search/replace engine
  folding/          Code folding
  diff/             Myers diff, inline char diff, hunk operations
  lsp-client/       LSP client (JSON-RPC transport, protocol types)
  dap-client/       DAP client (debug sessions, breakpoints, stepping)

view-model/         Reactive state bridging core -> rendering
  editor-view-model.ts    Central orchestrator
  theme.ts                Dark + light themes
  gutter.ts               Line numbers, fold indicators, breakpoints
  find-widget.ts          Find/replace controller
  ghost-text.ts           AI inline completions
  minimap.ts              Minimap data
  overlays.ts             Autocomplete, hover, parameter hints
  decorations.ts          Search highlights, selections, diagnostics

native/             Platform-specific renderers — implement hone_editor_* against the platform's rendering primitive
  macos/            Rust:       Core Text + NSView + Metal
  ios/              Rust:       Core Text + UIKit
  windows/          Rust:       DirectWrite + Direct2D + DirectComposition
  linux/            Rust:       Pango + Cairo
  android/          Rust:       Canvas + Skia via JNI
  web/              TypeScript: DOM (no Rust crate — Perry's web target compiles
                                the editor itself to WASM and imports JS FFI)

Quick Start

Prerequisites

• Bun (package manager and test runner)
• Rust (for native crates)

Install and Test

bun install
bun test

Run the macOS Demo

cd native/macos
cargo run --example demo_editor

Opens a window with a fully interactive editor — type, navigate with arrow keys, select with Shift+arrows, copy/paste with Cmd+C/V, scroll, right-click context menu.

Run the Windows Demo

cd native/windows
cargo run --example demo_editor

Opens a window with a fully interactive editor — type, navigate with arrow keys, select with Shift+arrows, copy/paste with Ctrl+C/V, scroll, right-click context menu.

Run the Web Demo

bun run examples/web/build.ts
python3 -m http.server -d examples/web/dist 8765
open http://localhost:8765/index.html

Produces in examples/web/dist/:

• hone-editor.wasm (~1.4 MB) — editor TypeScript compiled to WebAssembly via Perry
• hone-editor.js (~340 KB) — Perry runtime bridge + DOM FFI + tree-sitter bridge + mount() API
• index.html — minimal consumer page
• tree-sitter.wasm + per-language grammar wasms (TypeScript, JavaScript, Python, Rust, JSON, CSS)

Use from a web project

import { mount } from './hone-editor.js';

const ed = await mount(document.getElementById('editor'), {
  content: '// your code here',
  language: 'typescript',     // typescript, javascript, python, rust, json, css, markdown, …
  theme: 'dark',              // 'dark' | 'light'
  fontSize: 14,
  fontFamily: 'JetBrains Mono, Menlo, Monaco, monospace',
  readOnly: false,
  treeSitter: true,           // tree-sitter parsing (default: keyword tokenizer only)
});

// The returned controller drives the overlay layers:
ed.setFindHighlights('[{"line":2,"col":13,"len":6,"current":1}]');
ed.setLineDiagnostics('5:1:#f87171:type error message\n');     // line:severity:color:message
ed.setBreakpoints('3\n7');                                       // newline-separated 1-based lines
ed.setFoldRanges('5:0\n10:1');                                   // line:collapsed pairs
ed.clearFindHighlights();
ed.clearDiagnostics();

The TypeScript editor runs in WebAssembly; mount() wires the Perry-emitted bridge to the DOM renderer in native/web/dom-ffi.ts and to the web-tree-sitter bridge in native/web/tree-sitter-bridge.ts. The renderer is the exact analog of the per-platform Rust crates everywhere else — same hone_editor_* FFI contract, DOM as the platform's rendering primitive.

See examples/web/ for the full build pipeline and examples/web/entry.ts for the Perry-side entry point.

Run the Android Demo

cd native/android
bash run-demo.sh

Builds the Rust JNI library, installs the Kotlin demo app on an Android emulator, and launches a fully interactive editor.

Run the iOS Demo

cd native/ios
cargo run --example demo_editor_ios

Launches a fully interactive editor in the iOS Simulator with touch input, soft keyboard, and syntax highlighting.

Consuming the native crates from npm

The npm tarball ships every native rendering crate's Rust source so consumers can build them as part of their Perry-AOT pipeline. Two prerequisites apply until upstream Perry work lands — see native/NATIVE_CRATES.md for the full story:

1. perry-ffi is currently an unpublished workspace crate inside Perry's monorepo. Either keep a Perry checkout next to your project, or add a [patch.crates-io] in your workspace root pointing at it. Tracking issue: PerryTS/perry#1112.
2. Each crate's Cargo.toml declares [[example]] blocks; the examples/ directory is shipped as of 0.3.1.

The web target doesn't need any of this — it compiles TypeScript → WASM via Perry and the renderer is TypeScript, so there's no Rust crate to build.

Design Decisions

• No external editor dependencies — no CodeMirror, Monaco, or ProseMirror. Fully self-contained.
• Edits are atomic — EditBuilder collects changes and applies them in reverse offset order.
• Line endings normalized to \n internally; original style preserved for saving.
• Virtual scrolling — only visible lines plus a 10-line buffer zone are rendered.
• Identical FFI contract across all platforms — same function signatures, platform crates are interchangeable.

License

MIT