Architecture

Layers

• UI: Avalonia Views and XAML layouts only
• Presentation: ViewModels with state, commands, and reactive composition
• Domain: document models, layout, rendering, parsing, validation
• Infrastructure: file system, persistence, external integrations

MVVM and ReactiveUI

• Views are passive and contain no code-behind logic beyond InitializeComponent()
• All inputs flow through bindings, commands, and behaviors
• ViewModels inherit from ReactiveObject
• Commands use ReactiveCommand
• Derived state uses WhenAnyValue and ObservableAsPropertyHelper
• Dialogs and user flows use Interaction<TIn, TOut>

Avalonia Practices

• XAML for visuals and layout
• Compiled bindings only with explicit x:DataType
• Use DataTemplate or a custom ViewLocator for view lookup
• Prefer DirectProperty unless styling requires StyledProperty

Performance Guidelines

• Prefer allocation-free APIs like Span<T>, ReadOnlySpan<T>, and ArrayPool<T>
• Avoid LINQ in hot paths
• Profile before and after performance changes

Next: Build and Test