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WPF Layout Panels, Measure/Arrange, and DPI to Avalonia

Table of Contents

1. Scope and APIs
2. Layout Mapping
3. Measure/Arrange Authoring
4. Conversion Example
5. Avalonia C# Equivalent
6. Troubleshooting

Scope and APIs

Primary WPF APIs:

• Grid, StackPanel, DockPanel, WrapPanel, Canvas
• MeasureOverride, ArrangeOverride
• DPI-aware sizing assumptions

Primary Avalonia APIs:

• same panel family (Grid, StackPanel, DockPanel, WrapPanel, Canvas)
• MeasureOverride, ArrangeOverride
• TopLevel.RenderScaling and logical-unit layout

Layout Mapping

WPF	Avalonia
Grid.RowDefinitions/ColumnDefinitions	same concept and syntax
DockPanel.Dock	same concept
HorizontalAlignment/VerticalAlignment	same concept
UseLayoutRounding tuning	rely on logical units, tune rendering only where needed

Measure/Arrange Authoring

WPF custom panel logic generally ports 1:1 conceptually:

• measure children with constraints,
• arrange children in final bounds,
• invalidate measure/arrange explicitly only when required.

Conversion Example

WPF XAML:

<Grid Margin="12" RowDefinitions="Auto,*" ColumnDefinitions="200,*">
  <TextBlock Grid.Row="0" Grid.Column="0" Text="Name" />
  <TextBox Grid.Row="0" Grid.Column="1" />
</Grid>

Avalonia XAML:

<Grid Margin="12" RowDefinitions="Auto,*" ColumnDefinitions="200,*">
  <TextBlock Grid.Row="0" Grid.Column="0" Text="Name" />
  <TextBox Grid.Row="0" Grid.Column="1" />
</Grid>

Avalonia C# Equivalent

using Avalonia.Controls;

var form = new Grid
{
    Margin = new Avalonia.Thickness(12),
    RowDefinitions = RowDefinitions.Parse("Auto,*"),
    ColumnDefinitions = ColumnDefinitions.Parse("200,*")
};

form.Children.Add(new TextBlock { Text = "Name" });
var name = new TextBox();
Grid.SetColumn(name, 1);
form.Children.Add(name);

Troubleshooting

1. Ported layout uses too many absolute sizes.
   • replace with star sizing and alignment where possible.
2. custom panel ports remeasure excessively.
   • control invalidation discipline (InvalidateMeasure/InvalidateArrange).
3. DPI behavior differs from WPF assumptions.
   • avoid pixel arithmetic in layout; use logical units and inspect RenderScaling only when needed.

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