Draxul

API docs: chrismaughan.com/Draxul — or generate locally with python scripts/gen_api_docs.py.

What is Draxul?

An experimental Dark Factory Agentic project with deep visualization of generated code.

• GPU-accelerated terminal host — cross-platform (Vulkan on Windows, Metal on macOS) terminal for PowerShell, WSL, Bash, Zsh, Git, and more
• Neovim GUI frontend — a full-featured replacement for nvim-qt, with deep nvim --embed integration over msgpack-RPC
• Interactive city view of a codebase — a living 3D city where buildings represent code modules, with live performance and test coverage overlays, clickable links back to source. The city is a human metaphor for the code an agent is building: interactive, informative, and introspective. Richard Wettle tried this back in 2007; we are giving it another go! Here's his site: https://wettel.github.io/codecity.html
• High-end renderer — a cross-platform game engine-style rendering pipeline with ambient occlusion, shadow maps, anti-aliasing, HDR, and more

None of the code has been human-written. Draxul is 100% agentically coded using multiple agents on Claude, Codex, and Gemini. Code reviews, feature updates, and planning are managed by agents with a human arbiter. A part-time project, built in less than 3 weeks at time of writing — several person-years of equivalent effort.

macOS

Windows

Gallery

Click any image to view full size.

Terminal host — Neovim with file tree	Terminal host — multi-pane with htop
Split panes with city view	City view with debug overlays
Building inspection panel	App module connections
Renderer module connections	Coverage overlay connections
Tooltip with source link	Live coverage overlay (Windows)
Test coverage heatmap	Test coverage detail
Diagnostics panel	Visualizing Git's source code

Features

For the full user-facing feature reference — config options, keybindings, terminal behaviour, mouse support, scrollback, and more — see FEATURES.md.

• Terminal emulator — run zsh, bash, powershell, or any shell; cross-platform
• Neovim GUI — full ext_linegrid UI with deep Neovim integration
• FreeType + HarfBuzz text pipeline with a dynamic glyph atlas
• Font fallback for Nerd Font, emoji, and plugin glyph coverage
• Configurable GUI shortcuts for the diagnostics panel, clipboard copy/paste, and font zoom
• Mouse input support for click, drag, and wheel events
• HiDPI / Retina-aware rendering with correct DPI font scaling
• Shared logging with console/file fallback and category filtering
• Thin app layer with separate window, renderer, font, grid, and Neovim modules
• Built-in diagnostics panel (toggle with F12) with live renderer, layout, and startup timing

Requirements

Windows

• CMake 3.25+
• Visual Studio 2022
• Vulkan SDK with glslc
• nvim on PATH (optional — required only for Neovim mode)

macOS

• CMake 3.25+
• Xcode Command Line Tools
• nvim on PATH (optional — required only for Neovim mode)

All other dependencies are fetched automatically with CMake FetchContent.

Building

Windows

Debug:

cmake --preset default
cmake --build build --config Debug --parallel

Release:

cmake --preset release
cmake --build build --config Release --parallel

macOS

Debug:

cmake --preset mac-debug
cmake --build build --parallel

Release:

cmake --preset mac-release
cmake --build build --parallel

Running

With no arguments, Draxul starts an embedded Neovim child process (nvim must be on PATH). To run as a plain terminal instead, use --host:

Windows

.\build\Release\draxul.exe                     # Neovim (default)
.\build\Release\draxul.exe --host powershell   # PowerShell terminal
.\build\Release\draxul.exe --host bash         # Bash (WSL)
.\build\Release\draxul.exe --host megacity --source C:\dev\linux  # MegaCity scan root override
.\build\Release\draxul.exe --console           # allocate a debug console for log output

For a Debug build, replace Release with Debug.

macOS

./build/draxul.app/Contents/MacOS/draxul                # Neovim (default)
./build/draxul.app/Contents/MacOS/draxul --host zsh     # Zsh terminal
./build/draxul.app/Contents/MacOS/draxul --host bash    # Bash terminal
./build/draxul.app/Contents/MacOS/draxul --host megacity --source ~/dev/linux  # MegaCity scan root override

Or launch via Finder / open:

open ./build/draxul.app

Supported --host values: nvim, zsh, bash, powershell / pwsh (Windows), wsl (Windows), megacity.

--source <path> overrides the MegaCity Tree-sitter scan root when launching --host megacity.

Configuration

Draxul stores user settings in a config.toml file under the platform app-config directory.

Programming ligatures are enabled by default. Set enable_ligatures = false if you prefer raw per-character glyphs.

GUI-level shortcuts can be remapped under a [keybindings] table:

enable_ligatures = true

[keybindings]
toggle_diagnostics = "F12"
copy = "Ctrl+Shift+C"
paste = "Ctrl+Shift+V"
font_increase = "Ctrl+="
font_decrease = "Ctrl+-"
font_reset = "Ctrl+0"

These bindings affect only Draxul-handled GUI actions. Normal Neovim input and keymaps still go through Neovim.

Convenience Script: do.py

The root do.py script is the recommended entry point for common tasks:

./do.py run          # build (if needed) and launch Draxul
./do.py smoke        # build and run the startup smoke test
./do.py test         # full test suite (unit tests + smoke + render snapshots)

./do.py basic        # run basic-view render snapshot compare
./do.py cmdline      # run cmdline-view render snapshot compare
./do.py unicode      # run unicode-view render snapshot compare
./do.py panel        # run panel-view render snapshot compare
./do.py renderall    # run all four render snapshot compares

./do.py blessbasic   # bless basic-view reference image
./do.py blesscmdline # bless cmdline-view reference image
./do.py blessunicode # bless unicode-view reference image
./do.py blesspanel   # bless panel-view reference image
./do.py blessall     # bless all four reference images

./do.py api          # build local Doxygen API docs
./do.py docs         # build all documentation artifacts
./do.py shot         # regenerate the README hero screenshot
./do.py coverage     # macOS: export build/coverage.lcov and refresh db/coverage.lcov

On Windows, use do <command> (via do.bat) instead of ./do.py.

do build relwithdebinfo  # Windows: optimized build with PDB symbols
do run                   # Debug build + run (ninja on Windows, make on macOS)
do run release           # Release build + run
do run relwithdebinfo    # Windows: optimized build with PDB symbols
do run release --vs      # Release build with VS generator (Windows)
do run --console         # Attach a debug console (Windows)
do smoke                 # Smoke test
do test                  # Full test suite

Testing

The repository includes lightweight native tests for grid logic, redraw parsing, input translation, RPC behavior, renderer state, and Unicode width conformance against headless Neovim.

Windows

Default is Debug:

scripts\run_tests.bat

Other modes:

scripts\run_tests.bat release
scripts\run_tests.bat both
scripts\run_tests.bat --reconfigure

macOS

Default is Debug:

./scripts/run_tests.sh

Other modes:

./scripts/run_tests.sh release
./scripts/run_tests.sh both
./scripts/run_tests.sh --reconfigure

The test scripts reuse the existing CMake cache when possible and only reconfigure when needed.

The CTest suite also includes:

• an app startup smoke test when nvim is available on PATH
• a render snapshot regression test when the platform reference image exists under tests/render/reference/

Render Snapshots

Draxul can now run deterministic render-snapshot tests by capturing pixels directly from the renderer output instead of taking a desktop screenshot.

Example compare run:

.\build\Debug\draxul.exe --console --render-test D:\dev\draxul\tests\render\basic-view.toml

Bless a new reference image:

.\build\Debug\draxul.exe --console --render-test D:\dev\draxul\tests\render\basic-view.toml --bless-render-test

Update the documentation screenshot for the current platform:

python .\scripts\update_screenshot.py

Notes:

• update_screenshot.py uses the presentation-oriented tests/render/readme-hero.toml scenario by default, so it captures your normal Neovim theme and statusline instead of the clean -u NONE --noplugin regression setup.
• The deterministic render regression scenarios remain under tests/render/ and continue to use fixed startup settings for stable compare/bless behavior.

Behavior:

• the scenario fixes window size, font, and Neovim startup commands
• Draxul waits for redraw activity to settle
• the renderer reads back the presented frame
• output is compared against a platform-specific reference image
• actual, diff, and report artifacts are written under tests/render/out/

Reference images live under tests/render/reference/ with platform suffixes like basic-view.windows.bmp and basic-view.macos.bmp.

Current scenarios:

• basic-view: line numbers, signcolumn, cursorline, and baseline text layout
• cmdline-view: bottom-row command-line rendering
• unicode-view: graphemes, emoji, wide glyphs, and Nerd Font/plugin icons
• panel-view: visible diagnostics panel layout and content

Logging

Draxul now uses a shared repo-local logger across the app, RPC/process layer, windowing, font stack, and renderers.

Environment controls:

$env:DRAXUL_LOG = "debug"
$env:DRAXUL_LOG_CATEGORIES = "app,rpc,font"
$env:DRAXUL_LOG_FILE = "logs\\draxul.log"

Notes:

• Default level is info.
• Categories are comma-separated.
• GUI launches without a console will fall back to a log file automatically.
• The DPI diagnostics in the window layer are now debug-only instead of always-on.

Diagnostics Panel

Press F12 to toggle the built-in diagnostics panel. This can be remapped via config.toml under [keybindings].

The panel is a bottom-aligned dockable window rendered at native physical-pixel resolution using the same font as the terminal. It exposes live runtime state across three tabs:

Window — window and terminal region dimensions, display DPI, cell size, and grid dimensions

Renderer — last frame time, rolling average frame time, dirty-cell count, and glyph atlas occupancy, count, and reset statistics

Startup — per-phase initialisation timing (Config, Window + Renderer, Font, ImGui, Host) and total wall-clock time

The panel does not intercept any keyboard input — the terminal remains fully interactive while it is visible.

Project Layout

draxul/
├── app/                    # App startup and main orchestration
├── libs/
│   ├── draxul-types/      # Shared POD types and event structs
│   ├── draxul-window/     # Window abstraction and SDL implementation
│   ├── draxul-renderer/   # Public renderer API and platform backends
│   ├── draxul-font/       # Font loading, shaping, glyph cache
│   ├── draxul-grid/       # Cell grid and highlight state
│   └── draxul-nvim/       # Neovim process, RPC, redraw handling, input
├── shaders/                # Vulkan and Metal shader sources
├── fonts/                  # Bundled font assets copied next to the app
├── tests/                  # Native test executable and fixture helpers
└── scripts/                # Build/test convenience scripts

For a guided human-facing overview of the repo structure, generated diagrams, and validation entry points, see docs/module-map.md.

CI

GitHub Actions builds and tests the project on:

• Windows
• macOS

The workflow uses the same repo-local test scripts as local development, including the startup smoke test.

Notes

• Windows uses a multi-config Visual Studio generator through CMakePresets.json.
• The renderer boundary is owned by draxul-renderer; app code should not include backend-private headers.
• Grapheme handling is much better than the original single-codepoint path, but broad Unicode width conformance against Neovim is still future hardening work.
• Visual regression testing now prefers direct swapchain/drawable readback over desktop screenshots so comparisons stay deterministic across window-manager state.

Architecture Diagrams

Architecture Overview

Regenerate with the prompt in plans/prompts/architecture_diagram.md.

CMake Target Dependencies

Regenerate with python scripts/build_docs.py.

Class Diagram

API Docs

The live API reference is published automatically to chrismaughan.com/draxul on every push to main.

To generate locally:

python scripts/gen_api_docs.py

This writes a local Doxygen site to docs/api/index.html.

Unicode Snapshot Example

Reference image:

What the render smoke does:

• launches a deterministic Neovim UI scenario at a fixed size with fixed fonts and commands
• waits for redraw activity to settle instead of capturing a half-initialized frame
• reads pixels back from the renderer output directly, not from the desktop compositor
• compares the captured image against a blessed platform reference
• writes actual, diff, and report artifacts under tests/render/out/

Why this is useful:

• it catches visual regressions that ordinary unit tests miss, such as tofu, broken fallback fonts, missing line numbers, layout shifts, or highlight mistakes
• the diff artifact makes it obvious what changed and roughly how much changed
• the report gives a mechanical pass/fail threshold instead of relying on guesswork
• --bless-render-test gives a controlled way to accept intentional visual changes