NativeChannels.Uno 0.3.0-preview.1

Uno host

NativeChannels.Uno is an optional host for Uno's Skia renderer, pinned to Uno 6.7.135. It adds application registration, per-window sessions, UI dispatch, and an experimental native-view lifecycle surface. It references Core, Uno.WinUI, and dependency injection; it does not require MAUI, Avalonia, Uno navigation, or Uno application architecture packages. Register a compatible transport separately.

Startup and shutdown

After creating your Uno application and window, on the window's UI thread:

var host = app.UseNativeChannels(services => services.AddNativeChannels(options =>
{
    // Register the application's native modules here.
}));
var session = host.CreateSession(window);
var channels = session.Channels;

Each CreateSession(window) creates an independent service provider. Singleton factories run per session; do not register a shared IChannelService instance. Registration is snapshotted. A window's dispatcher is captured explicitly, so multiple windows do not rely on a process-wide UI queue. Resolve channel services initially on that queue.

Use session.Dispatcher.DispatchAsync as a channel handler dispatcher. It queues asynchronous handler starts, propagates exceptions and cancellation, and reports rejected queue submissions. Cancellation before execution prevents the handler from starting; cancellation after execution starts cannot undo its side effects.

Await view disposal, then session.DisposeAsync(), before closing its window. Await host.DisposeAsync() before terminating the application. Shutdown prevents new sessions, cancels each session's Stopping token, and awaits owned services. Repeated disposal shares the same completion. Failures in one session do not skip other sessions. The host cannot guarantee UI cleanup after a dispatcher has stopped. It deliberately does not launch unawaited shutdown from a synchronous Closed event.

Experimental native views

UnoChannelView accepts a factory returning an IUnoNativeView. The factory owns the native object and a distinct method channel for each instance. NativeElement must be a public native wrapper supported by the selected Uno backend. The control invalidates the old channel before destroying resources, supports reconnect, and awaits asynchronous disposal. Explicit disconnect suppresses automatic reattachment until Reconnect is called. Dispose views before their session.

Connected reports assignment to Uno's presenter, not verified native parenting, visibility, input, or focus. The Windows adapter must supply child-window styles before Uno reparents its HWND; see the corrected Windows probe. The host enables WS_CLIPCHILDREN on the attached HWND's actual parent and invalidates the child once so software presentation cannot erase it. This flag remains for the parent window lifetime and is shared by sibling native views. For Windows root HWNDs, the host synchronizes native focus with the managed tab position and routes Tab/Shift+Tab through Uno's focus manager. Reconnect restores focus after the replacement child is shown; removing a focused view advances focus before destroying the HWND. Each root HWND is one tab stop. Compound native controls must manage traversal within their own child HWND trees; that case is not covered by this bridge. This does not provide PDF document accessibility. Native parenting, layout, focus and direct input-message checks pass on Windows. Desktop-tool visual review confirms buttons and PDF content remain visible; broader physical input and accessibility coverage remain outstanding.

macOS uses MacOSNativeView, an adapter-owned AppKit container around Uno 6.7.135's internal native element. Reflection and native lifetime compatibility are isolated in the optional Uno package. The shared Swift view factories remain unchanged. TODO: replace this bridge when Uno #25639 provides public NSView hosting. Consumers do not need a patched Uno build or their own reflection code. This compatibility path is verified against the pinned release in untrimmed desktop builds; trimming/AOT and other Uno versions are not validated. Dispose on the UI thread after detaching the presenter, before releasing the borrowed NSView. The wrapper retains the view while hosted and does not own its plugin callbacks.

This package does not establish six-platform Uno support. See the feasibility matrix for the remaining acceptance work.

Verification

On Windows, run pwsh -File eng/verify-uno-feasibility.ps1 -HostProbe. The consumer uses local NuGet packages and the real Uno UI event loop. It tests registration, independent window sessions, asynchronous and reentrant dispatch, queued cancellation, handler exceptions, view lifetime, and shutdown with a pending call and active subscription. The view fixture uses a managed element; it does not test native parenting. -ReuseCache artifacts/uno-feasibility/cache is available for diagnostic reruns and is recorded as reused-cache evidence. No UI host runtime result on other platforms is implied by this Windows test.

For macOS Interop and PDF parity, run python3 eng/verify-uno-macos-views.py on the Mac with DOTNET_HOST_PATH set to the pinned SDK. It builds ARM64/x64 native libraries, packs the adapters, and runs the existing MAUI/Avalonia verifiers on the host architecture. --reuse-cache <directory> hard-links external packages only; local packages are restored fresh. Evidence, package hashes and released-Uno runtime checks are retained under artifacts/uno-macos-views/<run>/. Physical input and visual acceptance remain separate.