# Plugin System

## Summary

MatterControl supports extensibility through plugin hooks, registered callbacks, and editor extensions. While not a traditional assembly-loading plugin system, it provides extension points for OEM customization, cloud services integration, and custom design tools.

## Technical Description

### Extension Points

The application provides several extension mechanisms:

```
ApplicationController
├── Plugin Delegates (cloud features)
├── Library.MenuExtensions (context menus)
├── EditorExtensions (property editors)
└── SceneOperations (design tools)
```

### Delegate-Based Plugins

`ApplicationController` exposes `Func`/`Action` delegates for plugin integration:

| Delegate | Type | Purpose |
|----------|------|---------|
| `GetPrinterProfileAsync` | `Func<PrinterInfo, string, Task<PrinterSettings>>` | Cloud profile retrieval |
| `SyncCloudProfiles` | `Func<string, Action<double,string>, Task>` | Profile sync |
| `GetPublicProfileList` | `Func<Task<OemProfileDictionary>>` | Public profile listing |
| `DownloadPublicProfileAsync` | `Func<string, Task<PrinterSettings>>` | Profile download |
| `GuestUserActive` | `Func<bool>` | Auth check |
| `GetAuthPage` | `Func<AuthenticationContext, DialogPage>` | Auth dialog |
| `UserHasPermission` | `Func<IObject3D, bool>` | Permission check |
| `UserHasPro` | `Func<bool>` | License validation |
| `PushPrintTaskToServer` | `Func<PrintTask, Task<Dictionary<string,string>>>` | Cloud tracking |

### Editor Extensions

Custom property editors registered via `EditorExtensionsConfig`:

```csharp
EditorExtensions.RegisterFactory((theme, undoBuffer) => new SheetEditor());
EditorExtensions.RegisterFactory((theme, undoBuffer) => new PropertyEditor(theme, undoBuffer));
```

**IObject3DEditor Interface:**
```csharp
public interface IObject3DEditor
{
    string Name { get; }
    bool Unlocked { get; }
    GuiWidget Create(IObject3D item, UndoBuffer undoBuffer, ThemeConfig theme);
}
```

### Library Menu Extensions

Add custom actions to library context menus:

```csharp
Library.MenuExtensions.Add(new LibraryAction()
{
    Title = "Custom Action",
    Action = (items, library) => { /* implementation */ },
    IsEnabled = (items, library) => true
});
```

### Scene Operations

Register custom design tools via `SceneOperations`:

```csharp
SceneOperations.RegisterOperation(
    new SceneSelectionOperation()
    {
        Title = "Custom Operation",
        Icon = iconImage,
        Action = (sceneContext) => { /* implementation */ }
    });
```

### OEM Customization

OEMs can customize via static data:

```
StaticData/
├── OEMSettings/
│   ├── OEMProfile.json (branding)
│   └── toc.json (help content)
├── Printers/
│   └── {OEM}/ (printer profiles)
└── Themes/
    └── System/ (custom themes)
```

**OEMProfile.json:**
```json
{
  "ShowHelpOption": true,
  "ShowAuthenticationDialog": true,
  "ShowGettingStarted": true,
  "WindowTitleExtra": "OEM Edition"
}
```

### Content Providers

Register custom file format handlers:

```csharp
Library.ContentProviders.Add("custom", new CustomContentProvider());
```

**IContentProvider Interface:**
```csharp
public interface IContentProvider
{
    Task<IObject3D> LoadAsync(Stream stream, CancellationToken cancellationToken);
    Task SaveAsync(IObject3D object3D, Stream stream);
}
```

### Experimental Plugins

The `Plugins/Experimental` directory contains optional features:

| Plugin | Purpose |
|--------|---------|
| Part Sheet | Part information sheets |
| Custom experimental features | Beta functionality |

### Design Rationale

**Delegate Pattern**: Using function delegates instead of interfaces:
- Simplifies optional feature implementation
- No assembly scanning required
- Runtime flexibility

**Static Data Customization**: File-based OEM configuration:
- No code changes needed
- Easy deployment
- Clear separation of concerns

**Registration Patterns**: Factory/registration for extensions:
- Type-safe
- Discovery at startup
- Controlled lifecycle

## Reference

### Core Classes

| Class | Location | Description |
|-------|----------|-------------|
| `ApplicationController` | [ApplicationView/ApplicationController.cs](MatterControlLib/ApplicationView/ApplicationController.cs) | Plugin delegates |
| `EditorExtensionsConfig` | [DesignTools/EditorExtensionsConfig.cs](MatterControlLib/DesignTools/EditorExtensionsConfig.cs) | Editor registry |
| `SceneOperations` | [ApplicationView/SceneOperations.cs](MatterControlLib/ApplicationView/SceneOperations.cs) | Operations registry |
| `OemSettings` | [SettingsManagement/OemSettings.cs](MatterControlLib/SettingsManagement/OemSettings.cs) | OEM configuration |

### Interfaces

| Interface | Purpose |
|-----------|---------|
| `IObject3DEditor` | Custom object editor |
| `IContentProvider` | File format handler |
| `INativePlatformFeatures` | Platform features |

### Extension Directories

| Directory | Purpose |
|-----------|---------|
| `Plugins/Experimental/` | Beta features |
| `StaticData/OEMSettings/` | OEM configuration |
| `StaticData/Themes/` | Custom themes |