GitHub - leebase/lfznotepad

A faithful, native Windows Notepad clone built in Zig using raw Win32 APIs — no .NET runtime, no GUI framework, no installer. Single .exe, zero dependencies.

Why Zig? To demonstrate that agentic AI absorbs implementation complexity. The binary is ~1.1 MB vs 154 MB for the C# WinForms sibling project (LFNotepad). The human effort to direct both was identical.

Features

Matches classic Windows Notepad (pre-AI era) feature-for-feature:

• File: New · Open · Save · Save As (with encoding selection) · Page Setup · Print · Exit
• Edit: Undo · Cut · Copy · Paste · Delete · Find · Find Next · Replace · Go To · Select All · Time/Date
• Format: Word Wrap · Font
• View: Zoom In / Out / Restore · Status Bar toggle
• Status Bar: Ln/Col · Zoom % · Encoding · Line Endings
• Behavior: Dirty tracking (title asterisk) · Save-changes dialog · Drag-and-drop file open · Command-line file argument · Right-click context menu

Requirements

Quick Start

# Clone
git clone <repo-url> lfznotepad
cd lfznotepad

# Fetch zigwin32 dependency (already recorded in build.zig.zon)
zig fetch

# Build
zig build

# Run
zig build run
# or directly:
.\zig-out\bin\LFZNotepad.exe

The output binary is at zig-out\bin\LFZNotepad.exe (~1.1 MB, no installer needed).

Build Reference

zig build            # Compile only
zig build run        # Compile + launch
zig build test       # Run unit tests

Capturing build errors (recommended — PowerShell terminal can truncate stderr):

zig build 2>&1 | Set-Content -Encoding UTF8 build_errors.txt
# then open build_errors.txt

Project Structure

lfznotepad/
├── build.zig              # Zig 0.15 build script
├── build.zig.zon          # Package manifest (zigwin32 dependency + hash)
├── src/
│   ├── main.zig           # Entry point — GetModuleHandle, load riched20.dll, init comctl32
│   ├── window.zig         # Main window class, WndProc, AppState, layout
│   ├── menu.zig           # Full Win32 menu bar (CreateMenu/AppendMenuW)
│   ├── menu_ids.zig       # All WM_COMMAND IDs as a Zig enum (no magic numbers)
│   ├── statusbar.zig      # comctl32 status bar — 4 parts: Ln/Col, Zoom%, Encoding, CRLF
│   ├── helpers/
│   │   ├── file.zig       # File I/O, BOM-based encoding detection, UTF-8/16 conversion
│   │   ├── edit.zig       # Edit menu helpers (clipboard, select-all, time/date insert)
│   │   ├── format.zig     # Word wrap toggle, font dialog (ChooseFontW), zoom (EM_SETZOOM)
│   │   └── print.zig      # Win32 printing (PrintDlgExW, GDI pagination)
│   └── dialogs/
│       ├── find.zig       # Modeless Find dialog (CreateDialogParamW)
│       ├── replace.zig    # Modeless Replace dialog
│       ├── goto.zig       # Modal Go To Line dialog (DialogBoxParamW)
│       ├── opensave.zig   # Open/Save As file dialogs (GetOpenFileNameW / GetSaveFileNameW)
│       └── about.zig      # About dialog
└── tests/
    └── file_tests.zig     # Encoding detection and file round-trip tests

Key Win32 / Zig Conventions

These are critical to know before modifying the code:

AgentFlow Documentation

This project uses the AgentFlow methodology for human-AI collaboration. These files support autonomous AI execution and cross-session/cross-agent continuity:

AgentFlow Development Loop

CODE → BUILD (zig build) → TEST → TEST AS LEE (verify .exe runs) → FIX → LOOP → DOCUMENT → COMMIT

Sprint end-gate (required before moving to next sprint):

1. zig build test passes
2. Manual verify: launch .exe, exercise all new features
3. Update context.md and WHERE_AM_I.md
4. git commit

Continuing Work in Another Agent Harness

Orientation (do this first)

1. Read AGENTS.md          — rules and conventions
2. Read context.md         — current state, what's done, what's next
3. Read WHERE_AM_I.md      — milestone view
4. Read sprint-plan.md     — sprint tasks and definitions of done

Getting the build working

zig build 2>&1 | Set-Content -Encoding UTF8 build_errors.txt
# Read build_errors.txt for full error output (do NOT rely on terminal — it truncates)

Autonomy level

Mode 3 — Autonomous. Build, test, commit without asking for approval.
Only interrupt the human for: breaking design decisions, ambiguous requirements, blocked on user input.

Known gotchas for new agents

1. Terminal truncation: PowerShell stderr output is cut off. Always redirect to file.
2. zigwin32 packed structs: All flag types are packed struct(u32). Use struct literal syntax, never cast raw integers. Check field names in the zigwin32 source at %LOCALAPPDATA%\zig\p\zigwin32-*\win32\.
3. EM_SETEVENTMASK: Must be sent to the RichEdit control after creation to receive EN_SELCHANGE via WM_NOTIFY.
4. Modeless dialogs (Find/Replace): Must be given the RichEdit HWND, not the main window HWND, for text operations.
5. Word Wrap: Implemented via EM_SETTARGETDEVICE on the RichEdit, not by changing window styles directly.

Current Status

Session History

This project was built across multiple AI agent sessions on different platforms. All features were verified and tested by the human (Lee).

Raw session notes: antigravity_session_raw.md · kimi_session_raw.md · opencode_session_raw.md

Relationship to LFNotepad (C# version)

Both projects are part of the same case study demonstrating supervisor-mode agentic AI development.