Copilot instructions

1---
2applyTo:
3  - "**/*.Android.cs"
4  - "**/*.android.cs"
5  - "**/*.iOS.cs"
6  - "**/*.ios.cs"
7  - "**/*.Windows.cs"
8  - "**/*.windows.cs"
9  - "**/Platform/**"
10  - "**/Platforms/**"
11---
12# Threading and Async Patterns
13 
14## UI Thread Dispatch
15- Platform view modifications MUST happen on the UI thread
16- **Android**: `platformView.Post(() => { })` or `Looper.MainLooper` for thread checks
17- **iOS/MacCatalyst**: `MainThread.BeginInvokeOnMainThread()` or `DispatchQueue.MainQueue`
18- **Windows**: `DispatcherQueue.TryEnqueue()` — be aware of COM threading apartment model
19 
20## Async Handler Operations
21- Use `.FireAndForget(handler)` for async work in mapper methods — never bare `async void`
22- After `await`, verify the handler is still connected (`VirtualView != null`) before applying results
23- Thread `CancellationToken` through long-running operations and check at appropriate yield points
24 
25## Race Condition Prevention
26- Concurrent access to shared state must use `lock`, `Interlocked`, or immutable patterns
27- Image loading and other async pipelines must cancel in-flight operations when the source changes
28- Guard against stale callbacks — platform callbacks may fire after `DisconnectHandler`
29 
30## Platform-Specific Patterns
31- **Android**: API-level checks use `Build.VERSION.SdkInt` comparison, not version string parsing
32- **iOS**: Use `System.OperatingSystem.IsIOSVersionAtLeast()` for linker-friendly runtime checks
33- **Windows**: WinUI version checks may be needed for features in specific Windows App SDK versions
34- Use `System.OperatingSystem` APIs over `RuntimeInformation` — they are trimmer/AOT-friendly
35