rendering-wpf-architecture

# WPF Rendering Architecture

## Rendering Pipeline Overview
```
User Input → Property Change → InvalidateXxx()
                ↓
        ┌───────────────┐
        │ Measure Pass  │ → Determines DesiredSize
        ├───────────────┤
        │ Arrange Pass  │ → Determines ActualSize/Position
        ├───────────────┤
        │ Render Pass   │ → OnRender() / DrawingContext
        └───────────────┘
                ↓
    Composition Tree → MILCore → DirectX → GPU
```

## 1. Layout Passes

### Invalidation Methods

| Method | Triggers | Use When |
|--------|----------|----------|
| `InvalidateMeasure()` | Measure + Arrange + Render | Size might change |
| `InvalidateArrange()` | Arrange + Render | Position might change |
| `InvalidateVisual()` | Render only | Visual appearance change |

### FrameworkPropertyMetadata Flags
```csharp
public static readonly DependencyProperty RadiusProperty =
    DependencyProperty.Register("Radius", typeof(double), typeof(MyControl),
        new FrameworkPropertyMetadata(10.0,
            FrameworkPropertyMetadataOptions.AffectsRender |
            FrameworkPropertyMetadataOptions.AffectsMeasure));
```

| Flag | Effect |
|------|--------|
| `AffectsMeasure` | Triggers Measure pass |
| `AffectsArrange` | Triggers Arrange pass |
| `AffectsRender` | Triggers Render pass |
| `AffectsParentMeasure` | Parent re-measures |
| `AffectsParentArrange` | Parent re-arranges |

### Custom Control Layout
```csharp
protected override Size MeasureOverride(Size availableSize)
{
    // Calculate desired size based on content
    double width = Math.Min(200, availableSize.Width);
    double height = Math.Min(100, availableSize.Height);
    return new Size(width, height);
}

protected override Size ArrangeOverride(Size finalSize)
{
    // Position children within finalSize
    foreach (UIElement child in Children)
    {
        child.Arrange(new Rect(0, 0, finalSize.Width, finalSize.Height));
    }
    return finalSize;
}

protected override void OnRender(Dra