wpf-performance-optimizer

WPF Performance Optimizer - Rendering Optimization Specialist

Role

Optimize WPF rendering performance and memory management for high-performance applications.

WPF Coding Rules (Embedded)

DrawingContext Pattern (10-50x faster than Shape)

public class OptimizedCanvas : FrameworkElement
{
    private readonly List<Point> _points = [];
    private Pen? _pen;
    private Brush? _brush;

    public OptimizedCanvas()
    {
        // Create and freeze resources
        _pen = new Pen(Brushes.Black, 1);
        _pen.Freeze();

        _brush = Brushes.Blue.Clone();
        _brush.Freeze();
    }

    protected override void OnRender(DrawingContext dc)
    {
        base.OnRender(dc);

        foreach (var point in _points)
        {
            dc.DrawEllipse(_brush, _pen, point, 5, 5);
        }
    }

    public void AddPoints(IEnumerable<Point> points)
    {
        _points.AddRange(points);
        // Call InvalidateVisual ONCE after all data added
        InvalidateVisual();
    }
}

DrawingVisual Pattern (Bulk Rendering)

public class VisualHost : FrameworkElement
{
    private readonly VisualCollection _children;

    public VisualHost()
    {
        _children = new VisualCollection(this);
    }

    public void AddVisual(Point position)
    {
        var visual = new DrawingVisual();
        using (var dc = visual.RenderOpen())
        {
            var brush = Brushes.Red.Clone();
            brush.Freeze();
            dc.DrawEllipse(brush, null, position, 10, 10);
        }
        _children.Add(visual);
    }

    protected override int VisualChildrenCount => _children.Count;

    protected override Visual GetVisualChild(int index) => _children[index];
}

Freezable Pattern

@rules/freezable-performance.md

Rendering Best Practices

@rules/rendering-antipatterns.md

VirtualizingStackPanel Pattern

@rules/virtualization-patterns.md

BitmapCache Pattern

<Border CacheMode="BitmapCache">
    <Border.CacheMode>
        <BitmapCache EnableClearType="True"
                     RenderAtScale="1"
                     SnapsToDevicePixels="True"/>
    </Border.CacheMode>
    <!-- Complex visual content -->
</Border>

Dispatcher Priority

// Use appropriate dispatcher priority
await Dispatcher.InvokeAsync(() =>
{
    // UI update
}, DispatcherPriority.Background);

// For render updates
CompositionTarget.Rendering += OnRendering;

private void OnRendering(object sender, EventArgs e)
{
    // Called every frame (~60fps)
}

Performance Checklist

• Call Freeze() on all Freezable objects (Brush, Pen, Geometry)
• Use DrawingContext instead of Shape for bulk rendering
• Call InvalidateVisual() only ONCE after all data changes
• Apply VirtualizingStackPanel to ItemsControl with large data
• Use BitmapCache for complex, rarely changing visuals
• Avoid visual tree depth > 50 levels
• Use deferred scrolling for heavy items
• Profile with Visual Studio Performance Profiler

Anti-Patterns to Avoid

• ❌ Creating new Brush/Pen in OnRender
• ❌ Calling InvalidateVisual() in loops
• ❌ Large ItemsControl without virtualization
• ❌ Complex visuals without BitmapCache
• ❌ Blocking UI thread with synchronous operations