CLAUDE.md - Lem Editor

Lem is a text editor written in Common Lisp with multiple frontend support (terminal, GUI, browser).

Quick Reference

# Build and run
make sdl2          # GUI version
make ncurses       # Terminal version

# Development
qlot install       # Install dependencies
make test          # Run tests

Project Structure

src/                    # Core editor
├── lem.lisp            # Entry point
├── buffer/             # Text buffer system
├── window/             # Window management
├── mode.lisp           # Mode system
├── keymap.lisp         # Key bindings
├── defcommand.lisp     # Command definition
└── interface.lisp      # Frontend abstraction

frontends/              # UI implementations
├── sdl2/               # Desktop GUI
├── ncurses/            # Terminal
└── webview/            # Browser-based

extensions/             # Language modes (50+)
├── lisp-mode/          # Common Lisp with REPL
├── lsp-mode/           # LSP client
└── vi-mode/            # Vim emulation

Architecture

Four-layer design: Frontends → Interface (lem-if:*) → Core → Extensions

Key abstractions:

• Buffer: Text storage with points, marks, undo history
• Window: Buffer display, organized in tree (splits) or floating
• Mode: Major (one per buffer) + Minor (multiple, toggleable)
• Command: Interactive operation via define-command

Coding Standards

This project uses code-contractor for automated PR review. code-contractor is a GitHub App that validates pull requests against rules defined in contract.yml.

All coding standards are defined in contract.yml at the repository root. Refer to it for:

• Package and file structure rules
• Documentation requirements
• Style conventions (loop syntax, error handling, etc.)
• Functional programming guidelines

Key Files for Common Tasks

Development Notes

• Use lem-core package symbols, avoid lem:: internal access
• Frontends implement lem-if:* generic functions
• Modes register via define-major-mode / define-minor-mode
• Commands register via define-command with argument descriptors

Configuration

User config locations (in order):

1. $LEM_HOME/init.lisp
2. ~/.config/lem/init.lisp
3. ~/.lem/init.lisp
4. ~/.lemrc

Documentation

• Architecture details: docs/ARCHITECTURE.md
• Extension development: docs/extension-development.md
• Online docs: https://lem-project.github.io/

Recent Changes

• 001-multi-language-canvas: Added Common Lisp (SBCL), tree-sitter-cl FFI bindings + lem/core, tree-sitter-cl, lem-call-graph (existing), lem-tree-sitter
• 001-multi-language-canvas: Added [if applicable, e.g., PostgreSQL, CoreData, files or N/A]

Active Technologies

• Common Lisp (SBCL), tree-sitter-cl FFI bindings + lem/core, tree-sitter-cl, lem-call-graph (existing), lem-tree-sitter (001-multi-language-canvas)
• N/A (in-memory graph structures, optional position caching) (001-multi-language-canvas)