drawio

What this skill does

# Draw.io Diagram Skill

Generate draw.io diagrams as native `.drawio` files. Optionally export to PNG, SVG, or PDF with the diagram XML embedded (so the exported file remains editable in draw.io), or generate a browser URL that opens the diagram directly in the draw.io editor.

## How to create a diagram

1. **Generate draw.io XML** in mxGraphModel format for the requested diagram
2. **Write the XML** to a `.drawio` file in the current working directory using the Write tool
3. **Handle the requested output format**:
   - `png` / `svg` / `pdf` → locate the draw.io CLI (see [draw.io CLI](#drawio-cli)), export with `--embed-diagram`, then delete the source `.drawio` file. If the CLI is not found, keep the `.drawio` file and tell the user they can install the draw.io desktop app to enable export, or use `url` mode instead, or open the `.drawio` file directly
   - `url` → generate a browser URL from the XML and open it (see [Browser URL output](#browser-url-output)). Keep the `.drawio` file as a persistent local copy
   - *(no format)* → no extra step; the `.drawio` file is the output
4. **Open the result** — the exported file if exported, the browser URL if `url`, or the `.drawio` file otherwise. If the open command fails, print the file path (or URL) so the user can open it manually

## Choosing the output format

Check the user's request for a format preference. Examples:

- `/drawio create a flowchart` → `flowchart.drawio`
- `/drawio png flowchart for login` → `login-flow.drawio.png`
- `/drawio svg: ER diagram` → `er-diagram.drawio.svg`
- `/drawio pdf architecture overview` → `architecture-overview.drawio.pdf`
- `/drawio url flowchart for user login` → opens browser at `app.diagrams.net` with the diagram, keeps `login-flow.drawio` locally

If no format is mentioned, just write the `.drawio` file and open it in draw.io. The user can always ask to export later.

### Supported export formats

| Format | Embed XML | Notes |
|--------|-----------|-------|
| `png` | Yes (`-e`) | Viewable everywhere, editable in draw.io |
| `svg` | Yes (`-e`) | Scalable, editable in draw.io |
| `pdf` | Yes (`-e`) | Printable, editable in draw.io |
| `jpg` | No | Lossy, no embedded XML support |

PNG, SVG, and PDF all support `--embed-diagram` — the exported file contains the full diagram XML, so opening it in draw.io recovers the editable diagram.

## Browser URL output

When the user requests `url` format, generate a draw.io URL that opens the diagram directly in the browser editor at `app.diagrams.net` — no draw.io Desktop required.

### How it works

1. The `.drawio` file is written to disk as usual (gives the user a persistent local copy they can re-edit)
2. The XML is compressed with Node.js's built-in `zlib` and base64-encoded
3. The result is embedded in a `https://app.diagrams.net/#create=...` URL
4. The URL is opened in the default browser

This uses only Node.js built-in modules (`zlib`, `child_process`) — no external dependencies.

### URL generation

Run this `node -e` one-liner to read the `.drawio` file and print the URL (replace `DIAGRAM.drawio` with the actual filename):

```bash
URL=$(node -e '
const fs = require("fs");
const zlib = require("zlib");
const xml = fs.readFileSync(process.argv[1], "utf8");
const compressed = zlib.deflateRawSync(encodeURIComponent(xml)).toString("base64");
const payload = encodeURIComponent(JSON.stringify({ type: "xml", compressed: true, data: compressed }));
console.log("https://app.diagrams.net/?grid=0&pv=0&border=10&edit=_blank#create=" + payload);
' DIAGRAM.drawio)
```

The URL format matches the MCP Tool Server. Node.js's `zlib.deflateRawSync` and `pako.deflateRaw` both implement RFC 1951 and produce identical output, so URLs from either source are interchangeable.

### Opening the URL

| Environment | Command |
|-------------|---------|
| macOS | `open "$URL"` |
| Linux (native) | `xdg-open "$URL"` |
| WSL2 | Write a temp `.url` file, open via `cmd.exe` (see below) |
| Windows (native) | Write a temp `.url` file, open via `start` (see below) |

**Why the `.url` workaround on Windows/WSL2?** `cmd.exe`'s `start` command treats `&` as a command separator and strips everything after `#` in URLs. The diagram payload lives in the `#create=...` fragment, so passing the URL directly causes it to be silently lost. A `.url` shortcut file preserves the URL intact.

**macOS / Linux example:**

```bash
open "$URL"      # macOS
xdg-open "$URL"  # Linux
```

**WSL2 example:**

```bash
TMPFILE=$(mktemp --suffix=.url)
printf '[InternetShortcut]\r\nURL=%s\r\n' "$URL" > "$TMPFILE"
cmd.exe /c start "" "$(wslpath -w "$TMPFILE")"
```

**Windows (native) example:**

```cmd
echo [InternetShortcut] > %TEMP%\drawio.url
echo URL=%URL% >> %TEMP%\drawio.url
start "" "%TEMP%\drawio.url"
```

### After opening

Print the URL so the user can copy or share it, and confirm the local file path:

```
Opened in browser: <URL>
Local file: DIAGRAM.drawio
```

The `.drawio` file stays on disk so the user can re-edit it later, attach it elsewhere, or export it to an image format on demand.

### URL length

The URL embeds the full compressed diagram in its hash fragment. Very large diagrams may hit browser URL length limits (typically ~32K–2MB depending on the browser). For complex diagrams that exceed the limit, fall back to writing the `.drawio` file and opening it locally.

## draw.io CLI

The draw.io desktop app includes a command-line interface for exporting.

### Locating the CLI

First, detect the environment, then locate the CLI accordingly:

#### WSL2 (Windows Subsystem for Linux)

WSL2 is detected when `/proc/version` contains `microsoft` or `WSL`:

```bash
grep -qi microsoft /proc/version 2>/dev/null && echo "WSL2"
```

On WSL2, use the Windows draw.io Desktop executable via `/mnt/c/...`:

```bash
DRAWIO_CMD=`/mnt/c/Program Files/draw.io/draw.io.exe`
```

The backtick quoting is required to handle the space in `Program Files` in bash.

If draw.io is installed in a non-default location, check common alternatives:

```bash
# Default install path
`/mnt/c/Program Files/draw.io/draw.io.exe`

# Per-user install (if the above does not exist)
`/mnt/c/Users/$WIN_USER/AppData/Local/Programs/draw.io/draw.io.exe`
```

#### macOS

```bash
/Applications/draw.io.app/Contents/MacOS/draw.io
```

#### Linux (native)

```bash
drawio   # typically on PATH via snap/apt/flatpak
```

#### Windows (native, non-WSL2)

```
"C:\Program Files\draw.io\draw.io.exe"
```

Use `which drawio` (or `where draw.io` on Windows) to check if it's on PATH before falling back to the platform-specific path.

### Export command

```bash
drawio -x -f <format> -e -b 10 -o <output> <input.drawio>
```

**WSL2 example:**

```bash
`/mnt/c/Program Files/draw.io/draw.io.exe` -x -f png -e -b 10 -o diagram.drawio.png diagram.drawio
```

Key flags:
- `-x` / `--export`: export mode
- `-f` / `--format`: output format (png, svg, pdf, jpg)
- `-e` / `--embed-diagram`: embed diagram XML in the output (PNG, SVG, PDF only)
- `-o` / `--output`: output file path
- `-b` / `--border`: border width around diagram (default: 0)
- `-t` / `--transparent`: transparent background (PNG only)
- `-s` / `--scale`: scale the diagram size
- `--width` / `--height`: fit into specified dimensions (preserves aspect ratio)
- `-a` / `--all-pages`: export all pages (PDF only)
- `-p` / `--page-index`: select a specific page (1-based)

### Opening the result

| Environment | Command |
|-------------|---------|
| macOS | `open <file>` |
| Linux (native) | `xdg-open <file>` |
| WSL2 | `cmd.exe /c start "" "$(wslpath -w <file>)"` |
| Windows | `start <file>` |

**WSL2 notes:**
- `wslpath -w <file>` converts a WSL2 path (e.g. `/home/user/diagram.drawio`) to a Windows path (e.g. `C:\Users\...`). This is required because `cmd.exe` cannot resolve `/mnt/c/...` style paths.
- The empty string `""` after `start` is required to prevent `start` from interpreting the filename as a window title.

**WSL2 example:**

```bash
cmd.exe /c start "" "$(wslpa