# QML SceneGraph MCP Bridge

A [MCP](https://modelcontextprotocol.io/) server that bridges [GammaRay](https://github.com/KDAB/GammaRay) probe introspection data into MCP tools, enabling LLMs to inspect and debug Qt Quick / QML scene graphs, items, geometry, and materials.

## Architecture

```
Target Qt/QML App  ──TCP──►  GammaRay MCP Bridge  ──stdio──►  LLM / AI Agent
  (GammaRay probe                (GammaRay client +               (opencode,
   injected)                      qtmcp MCP server)                Claude Desktop, etc.)
```

The bridge is a GammaRay **client**: it connects to a probe injected into a target Qt/QML app, reads the same models the GammaRay GUI uses, and translates them into MCP JSON-RPC tool calls over stdio.

## Prerequisites

- Qt 6.8+ (system)
- C++20 compiler (GCC 12+, Clang 16+)
- GammaRay 3.4.0+ built from source (see [build instructions](#building-gammaray))
- [qtmcp](https://github.com/signal-slot/qtmcp) (consumed via FetchContent — no manual install)
- Python 3.10+ with `pytest` (for running the test suite)

## Building

### 1. Build and install GammaRay

```bash
cmake -S /path/to/GammaRay -B /path/to/GammaRay/build \
  -DCMAKE_INSTALL_PREFIX=$(pwd)/install-prefix
cmake --build /path/to/GammaRay/build
cmake --install /path/to/GammaRay/build --prefix $(pwd)/install-prefix
```

### 2. Build the bridge

```bash
cd bridge
cmake -S . -B build -G Ninja -DCMAKE_PREFIX_PATH=$(pwd)/../install-prefix
cmake --build build
```

### 3. Run

```bash
# Start a probe (inject into a QML app)
install-prefix/bin/gammaray --inject-only --listen tcp://127.0.0.1:11732 \
  --injector preload /usr/lib/qt6/bin/qml /path/to/app.qml -platform offscreen

# Start the bridge (stdio MCP server)
./run.sh
```

The bridge starts in lazy-connect mode. Call `connectProbe("127.0.0.1", 11732)` from your MCP client once the probe is up.

## MCP Tools

### Connection management
| Tool | Description |
|---|---|
| `connectProbe(host, port)` | Connect to a GammaRay probe (defaults: 127.0.0.1:11732) |
| `connectProbeDefault()` | Convenience: connect to 127.0.0.1:11732 |
| `disconnectProbe()` | Drop connection and forget URL |
| `probeStatus()` | Report connection state |

### Navigation
| Tool | Description |
|---|---|
| `listQuickWindows()` | List QQuickWindows in the target app |
| `selectQuickWindow(index)` | Select a window for scene graph introspection |
| `listQuickItems()` | Recursive QQuickItem tree with types and flags |
| `listScenegraphNodes()` | Recursive QSGNode tree (all node types) |

### QML Item inspection
| Tool | Description |
|---|---|
| `selectQuickItem(address)` | Select a QML item by address, populating its properties model |
| `getItemProperties(address)` | Get all Q_PROPERTY values (x, y, width, height, opacity, visible, z, anchors, text, font, etc.) |

### SG Node inspection
| Tool | Description |
|---|---|
| `selectScenegraphNode(address)` | Select a SG node, populating geometry/material sub-models |
| `getNodeVertices(address)` | Read vertex data of a GeometryNode |
| `getNodeAdjacency(address)` | Read adjacency/drawing mode of a GeometryNode |
| `getMaterialShaders(address)` | List shader stages for a node's material |
| `getShaderSource(row)` | Get shader source code (async via MaterialExtensionInterface) |
| `getMaterialProperties(address)` | Get material property name/value pairs |

### Rendering visualization
| Tool | Description |
|---|---|
| `setRenderMode(mode)` | Set render mode (NormalRendering, VisualizeOverdraw, etc.) |
| `setSlowMode(enabled)` | Toggle continuous rendering |

## Testing

```bash
# Unit tests only (no probe needed):
./tests/run_tests.sh --no-probe

# Full integration test suite (probe required):
./tests/run_tests.sh --no-probe  # skips probe-dependent tests
./tests/run_tests.sh -v          # verbose
```

See `tests/README.md` for details.

## License

GPL-2.0-or-later. The bridge links GammaRay libraries (GPL-2.0-or-later) and uses qtmcp (available under GPL-2.0-only).