rendering-with-drawingcontext

# WPF DrawingContext High-Performance Rendering

A pattern for achieving 10-50x performance improvement over Shape objects when rendering large numbers of shapes in WPF using DrawingContext.

## 1. Core Concepts

### Shape vs DrawingContext Approach

| Item | Shape (Polygon, Rectangle, etc.) | DrawingContext |
|------|----------------------------------|----------------|
| **Inheritance** | Canvas | FrameworkElement |
| **Visual count** | One per shape (n) | 1 |
| **Layout calculation** | O(n) Measure/Arrange | O(1) |
| **Memory usage** | Very high (WPF object overhead) | Very low (data only) |
| **Performance** | Baseline | **10-50x faster** |
| **Suitable for** | Few interactive shapes (tens to hundreds) | Large static shapes (thousands to tens of thousands) |

### Why is DrawingContext Fast?

1. **Single Visual**: Only 1 FrameworkElement registered in Visual Tree
2. **Layout bypass**: No Measure/Arrange calculations needed
3. **Batch rendering**: Sent to GPU as single batch
4. **Memory efficiency**: Only stores shape metadata

---

## 2. Basic Implementation Pattern

### 2.1 DrawingContext-Based Custom Control

```csharp
namespace MyApp.Controls;

using System.Windows;
using System.Windows.Media;

public sealed class HighPerformanceCanvas : FrameworkElement
{
    // 1. Struct for storing shape data (lightweight)
    private readonly record struct ShapeData(
        Point Position,
        double Width,
        double Height,
        Brush Fill);

    // 2. Only rendering data stored in memory
    private readonly List<ShapeData> _shapes = [];

    // 3. Optimized Pen (Freeze applied)
    private readonly Pen _pen = new(Brushes.Black, 1);

    public HighPerformanceCanvas()
    {
        // Freeze Pen for performance optimization
        _pen.Freeze();
    }

    // 4. Shape addition method
    public void AddShape(Point position, double width, double height, Color color)
    {
        var brush = new SolidColorBrush(color);
        brush.Freeze();  // Freeze for p