Avalonia is a mature, cross-platform UI framework for .NET, enabling developers to build desktop, mobile, and web applications with a single codebase. It provides a rich set of controls, a powerful styling system, data binding, animations, and platform-specific backends (Windows, Linux, macOS, Android, iOS, Browser). The architecture is modular: core libraries (Avalonia.Base, Avalonia.Controls) define the property system, layout, input, and rendering, while platform backends implement windowing, graphics (Skia, Vulkan, OpenGL), and accessibility. The framework includes a XAML compiler, source generators, and extensive testing infrastructure. It is actively maintained with a large community and is used in production applications.
Semi.Avalonia is a comprehensive Avalonia UI theme library inspired by Semi Design, delivered as multiple NuGet packages. It provides a complete set of styled controls (buttons, text boxes, data grids, color pickers, etc.) with Light, Dark, and High Contrast themes, plus localization in 16 languages. The architecture follows Avalonia's resource dictionary and control theme patterns: each control has shared, light, dark, and high contrast XAML files that define visual states, triggers, and animations. A central `SemiTheme` class orchestrates theme swapping and locale selection via merged resource dictionaries. The repository also includes a demo application for desktop, Web, Android, and Lixux DRM platforms. The theming system is built on a well-structured token system using `Variables.axaml` and color palette files (e.g., `Light.axaml`, `Dark.axaml`) that define design tokens like spacing, border radii, and semantic colors. Control themes extensively use `DynamicResource` references, enabling runtime theme switching. The color picker extension (`Semi.Avalonia.ColorPicker`) is a notable sub-system with spectrum, palette, and component tabs supporting RGBA and HSVA models. Animations (e.g., `SemiPopupAnimations`) and custom converters (e.g., `PositionToAngleConverter`) add polish. The demo application is an MVVM-based showcase that exercises all controls and provides installation instructions. The CI/CD pipeline builds and publishes NuGet packages and cross-platform demos. Overall, this is a production-quality theming library with good mainainability, though some duplication between variant themes and a large icon file present potential maintenance costs.
This repository is a comprehensive XAML Behaviors library for Avalonia UI, porting the Microsoft.Xaml.Behaviors pattern to the Avalonia framework. It provides a declarative, XAML-friendly way to attach interactive logic (behaviors, triggers, actions) to UI controls without code-behind, covering common patterns such as event handling, data-driven triggers, command invocation, property changes, drag-and-drop, animations, validation, focus management, and more. The library is split into multiple NuGet packages: core interactivity (base classes), interactions (ready-to-use triggers/actions), custom interactions (control-specific behaviors), drag-and-drop, draggable elements, events, animations, responsive layout, scripting, and ReactiveUI integration. A key innovation is the use of Roslyn source generators to produce strongly-typed, reflection-free versions of actions and triggers, improving AOT compatibility and compile-time safety. The architecture follows a layered design: the foundation is the `Avalonia.Xaml.Interactivity` namespace with `Behavior`, `Trigger`, `Action` base classes and the `Interaction` static class for attaching behaviors. On top of that, `Avalonia.Xaml.Interactions.Core` provides common triggers/actions like `EventTriggerBehavior`, `InvokeCommandAction`, `ChangePropertyAction`, and `DataTriggerBehavior`. The `Custom` package adds hundreds of specialized behaviors for controls (e.g., `AutoCompleteBoxOpenDropDownOnFocusBehavior`, `SplitViewStateBehavior`, `FocusTrapBehavior`). Drag-and-drop is handled by a dedicated framework with `DropHandlerBase`, `ManagedDragDropService`, and behaviors like `PanelDragBehavior`. Animations are built using Avalonia's composition API, with helpers like `AnimationFactory` and `FluidMoveAnimation`. The source generators in `Xaml.Behaviors.SourceGenerators` produce typed wrappers from attributes like `[GenerateTypedAction]` and `[GenerateTypedTrigger]`, reducing boilerplate and runtime reflection. Key entry points for consumers are the `Interaction.Behaviors` attached property in XAML, the `Interaction.ExecuteActions` method, and the various behavior/trigger/action classes. The library depends on Avalonia UI (StyledElement, Control, Visual, TopLevel, etc.) and optionally on ReactiveUI. It includes extensive documentation via DocFX, sample applications demonstrating all features, and unit tests using Avalonia's headless testing infrastructure. The codebase is well-structured with clean abstractions, though its large surface area and reliance on internal Avalonia APIs present some maintenance risks.
Watt Toolkit (Steam++) is a cross-platform desktop application that serves as a multi-functional game toolbox primarily for Steam users. The system provides network acceleration via a local reverse proxy (YARP-based) with HTTPS interception, DNS analysis, and multiple proxy modes (Hosts, System, PAC, VPN, DNS intercept). It includes plugins for Steam account switching, two-factor authenticator management (import/export/recovery), game library management, ArchiSteamFarm integration for card farming, and game tools. The architecture is a modular plugin system built with Avalonia UI, .NET, and ReactiveUI, using a multi-process IPC model for privilege separation. External dependencies include WinDivert for Windows packet interception, XunYou SDK for game acceleration, and ArchiSteamFarm for automated Steam actions. The codebase demonstrates a complex but functional architecture with significant platform-specific code and some areas of technical debt.