Avalonia performance

Measure UI performance with a reproducible window size, navigation path, data set, and renderer. Headless tests verify structure and state; they do not measure native compositor frame rate

Layout and collections

Constrain long lists in a Grid and use a virtualizing panel. A StackPanel on the scrolling axis gives an infinite size constraint and can defeat virtualization

<Grid RowDefinitions="Auto,*">
  <TextBlock Text="Items" />
  <ListBox Grid.Row="1" ItemsSource="{Binding Items}">
    <ListBox.ItemsPanel>
      <ItemsPanelTemplate>
        <VirtualizingStackPanel />
      </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
  </ListBox>
</Grid>

This layout fragment assumes a view model exposing Items. Use ItemsControl for small bounded groups, batch collection replacements, and avoid per-item dispatcher posts

Hidden content should use IsVisible="False" when it must leave layout and hit testing. Transparent content can still participate in both

Startup and background work

DeferredContentControl delays view creation and retains it after realization. Production startup can warm deferred sections while the loading screen covers the shell. The initial-tree test measures the uninitialized window, not the final warmed application

Prepare network data and expensive transformations off the dispatcher. Coalesce high-frequency progress so only the latest value is pending, and release decoded article images when the reader closes

Animation and rendering

Reuse shared controls and MotionDurations. Custom continuous animation uses TopLevel.RequestAnimationFrame, stops when hidden or detached, and follows elapsed time rather than assuming a fixed refresh rate

Desktop caps the Skia GPU resource cache at 256 MiB and uses sustained-low-latency garbage collection. The launcher does not force a discrete graphics adapter and leaves adapter selection to the system. These launcher-rendering choices are separate from the user's game GPU selection

To compare a Windows composition backend in PowerShell

$env:HYPRISM_WIN32_COMPOSITION = 'winui'
dotnet run --project Sources/Hyprism.Desktop/Hyprism.Desktop.csproj

Supported values are dxgi (default), winui, and dcomp. Remove the variable after diagnosis

Remove-Item Env:HYPRISM_WIN32_COMPOSITION

Regression workflow

1. Reproduce startup, navigation, scrolling, or download progress separately
2. Record UI-thread time, allocations, visual count, and native frame behavior
3. Change one cause and repeat with the same data
4. Add a focused regression check when the change fixes measurable behavior

Run the existing Desktop suite

dotnet test Tests/Hyprism.Desktop.Tests/Hyprism.Desktop.Tests.csproj

AvaloniaPerformanceTests checks initial visual count, deferred realization, virtualization, and batched collection notifications. Render tests wait for observable final state instead of relying on an assumed animation duration