WPF Rendering Architecture

Name: rendering-wpf-architecture
Rating: 92
Author: christian289

Rendering Pipeline Overview

code

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(DrawingContext dc)
{
    dc.DrawRectangle(Background, null, new Rect(RenderSize));
}

2. Hardware Acceleration

Rendering Tiers

Tier	GPU Memory	Features
0	< 30MB	Software rendering
1	30-120MB	Partial hardware (no PS 2.0)
2	≥ 120MB	Full hardware acceleration

csharp

int tier = RenderCapability.Tier >> 16;
// 0 = Software, 1 = Partial, 2 = Full GPU

Software Fallback Conditions

WPF falls back to software rendering when:

•GPU memory insufficient
•Texture > 8192px
•Remote Desktop (RDP) session
•AllowsTransparency="True" on Window
•Legacy BitmapEffect used

RenderOptions Optimization

csharp

// For images that will be scaled
RenderOptions.SetBitmapScalingMode(image, BitmapScalingMode.LowQuality);

// For pixel-perfect lines
RenderOptions.SetEdgeMode(element, EdgeMode.Aliased);

// For tiled brushes
RenderOptions.SetCachingHint(brush, CachingHint.Cache);
RenderOptions.SetCacheInvalidationThresholdMinimum(brush, 0.5);
RenderOptions.SetCacheInvalidationThresholdMaximum(brush, 2.0);

3. Performance Optimization

Batch Updates Pattern

csharp

// Bad: Multiple layout passes
for (int i = 0; i < 100; i++)
{
    items[i].Width = newWidths[i]; // Each triggers layout
}

// Good: Single layout pass
using (Dispatcher.DisableProcessing())
{
    for (int i = 0; i < 100; i++)
    {
        items[i].Width = newWidths[i];
    }
} // Layout happens once here

Common Performance Issues

Problem	Cause	Solution
Slow scrolling	Deep Visual Tree	Virtualization
Layout thrashing	Frequent InvalidateMeasure	Batch updates
Slow startup	Complex Grid	Simplify layout
Memory growth	BitmapEffect	Use Effect class

4. Tier-Adaptive Rendering

csharp

public void ConfigureForTier()
{
    int tier = RenderCapability.Tier >> 16;

    if (tier < 2)
    {
        // Disable expensive effects
        DisableDropShadows();
        DisableAnimations();
        UseSimplifiedVisuals();
    }
}