# mendo - Fast and simple Markdown viewer

A native Windows Markdown viewer that renders directly using Direct2D/DirectWrite, achieving fast performance and low memory usage.

**[Japanese / 日本語](README.md)**

![mendo screenshot](./example/image/mendo_light.png)

## Installation

Install via [winget](https://learn.microsoft.com/windows/package-manager/winget/):

```
winget install tanaton.mendo
```

## Features

- **Zero-HTML rendering** — Markdown is drawn directly with Direct2D + DirectWrite, never converted to HTML
- **Mermaid diagrams** — Render `mermaid` code blocks as diagrams (via offscreen WebView2)
- **LaTeX math** — Render `$$...$$` block equations with KaTeX. Only paragraphs consisting solely of a `$$...$$` block are rendered; paragraphs mixing math with other text are shown as plain text.
- **Fully offline** — Mermaid.js and other resources are embedded in the executable; no network connection required
- **File watching** — Auto-reload on external file changes
- **Syntax highlighting** — C++, Python, JavaScript, Go, Rust, PowerShell, Bash, cmd
- **Navigation history** — `Alt+Left/Right`, mouse side buttons, mouse gestures, touchpad swipe with scroll position restoration
- **Image display** — PNG, JPEG, BMP and more
- **Zoom** — `Ctrl++` / `Ctrl+-` / `Ctrl+Mouse wheel` (0.25x to 5.00x, 17 levels)
- **Drag & Drop** — Drop `.md` files onto the window to open
- **3-pane layout** — File explorer / Table of contents / Markdown content
- **Dark mode** — Toggle between light and dark themes
- **Persistent settings** — Dark mode, zoom level, last opened file saved to `%LOCALAPPDATA%\mendo\`

## Supported Markdown Elements

| Element | Status |
|---|---|
| Headings (H1-H6) | Supported |
| Paragraphs | Supported |
| Bold / Italic / Strikethrough | Supported |
| Inline code | Supported |
| Fenced code blocks | Supported (with syntax highlighting) |
| Images (PNG / JPEG / BMP) | Supported (async loading) |
| Mermaid diagrams | Supported (WebView2 rendering) |
| LaTeX math (`$$...$$`) | Supported for block equations only. Rendered when the paragraph consists solely of a `$$...$$` block; mixed paragraphs fall back to plain text. |
| GitHub Alerts | Supported (Note / Tip / Important / Warning / Caution) |
| Links (external / page anchors) | Supported |
| Ordered / Unordered lists | Supported (nested) |
| Task lists | Supported |
| Blockquotes | Supported |
| Tables | Supported (with alignment) |
| Horizontal rules | Supported |

## Keyboard Shortcuts

| Key | Action |
|---|---|
| `Ctrl+O` | Open file |
| `Ctrl+C` | Copy selected text |
| `Ctrl+Shift+C` | Copy selected text as formatted (HTML) |
| `Ctrl+A` | Select all |
| `Ctrl+F` | Find |
| `Ctrl+1` | Toggle file explorer |
| `Ctrl+2` | Toggle table of contents |
| `Ctrl++` / `Ctrl+-` | Zoom in / Zoom out |
| `Ctrl+0` | Reset zoom (100%) |
| `Ctrl+Mouse wheel` | Zoom in / Zoom out |
| `Alt+Left` | Go back |
| `Alt+Right` | Go forward |
| `F1` | Show help |
| `F5` | Reload |
| `Up` `Down` | Scroll |
| `Page Up` `Page Down` | Page scroll |
| `Home` `End` | Jump to top / bottom |
| `Esc` | Deselect |

## Mouse Operations

| Operation | Action |
|---|---|
| Drag | Text selection |
| Double-click | Word selection |
| Right-click + horizontal drag | Mouse gesture (back / forward) |
| Touchpad horizontal swipe | Back / Forward |
| Side buttons | Back / Forward |
| Splitter drag | Resize pane width |
| Click link | Open external link in browser / Jump to anchor |
| Code block copy button | Copy code block to clipboard |

## Context Menu

| Item | Action |
|---|---|
| Left / Right buttons | Back / Forward |
| Open in editor | Open current file in default editor |
| Copy | Copy selected text (when text is selected) |
| Copy as HTML | Copy selected text as HTML rich text. Preserves formatting when pasted into Word, Outlook, etc. (when text is selected) |
| Dark mode | Toggle light/dark theme |

## Screenshots

![mendo with mermaid](./example/image/mendo_light_mermaid.png)

![mendo dark mode](./example/image/mendo_dark_test.png)

## Build

### Requirements

- Windows 10 or later
- Visual Studio 2022 (MSVC, C++23)
- CMake 3.20+

### Build Steps

```
cmake -B build
cmake --build build --config Release
```

Output: `build/Release/mendo.exe`

Build without tests:

```
cmake -B build -DMENDO_BUILD_TESTS=OFF
cmake --build build --config Release
```

### Run Tests

```
cmake --build build --config Release
build/tests/Release/mendo_tests.exe
```

### Build with Tracy Profiler (developers)

Embeds [Tracy](https://github.com/wolfpld/tracy) v0.13.1 for frame timing, zone tracing, and counter time-series plots. Tracy is built in `TRACY_ON_DEMAND` mode, so instrumentation is a no-op until a Tracy GUI client connects.

```
cmake -B build_tracy -DMENDO_USE_TRACY=ON
cmake --build build_tracy --config Release
```

Launch the Tracy GUI (download from [Releases](https://github.com/wolfpld/tracy/releases)) and then run `build_tracy/Release/mendo.exe` to connect. Tracy is only linked and instrumented when `MENDO_USE_TRACY=ON`; the default build (OFF) is completely unaffected.

## Usage

```
mendo.exe [filepath]
```

If launched without arguments, open a file with `Ctrl+O` or drag & drop.

## Tech Stack

| Layer | Technology |
|---|---|
| Language | C++23 (MSVC) |
| GUI | Win32 API |
| 2D rendering | Direct2D (`ID2D1HwndRenderTarget`) |
| Text rendering | DirectWrite (`IDWriteTextLayout`) |
| Diagrams | WebView2 + [Mermaid.js](https://mermaid.js.org/) |
| Markdown parser | [md4c](https://github.com/mity/md4c) (SAX-style callbacks) |
| Tests | Google Test v1.17.0 |
| Build | CMake 3.20+ |

## License

[MIT](LICENSE)

See [THIRD_PARTY_LICENSES.md](THIRD_PARTY_LICENSES.md) for third-party library licenses.