[glennawatson]

Summary

Sequencers that run work on a UI thread can now say whether the calling thread owns them, and hand back one shared sequencer per UI owner.

• IThreadAffineSequencer.CheckAccess() in ReactiveUI.Primitives.Core reports whether the calling thread owns a sequencer. The Avalonia, WPF, WinForms, MAUI, WinUI, Android and Apple sequencers implement it in both flavours.
• For(owner) on AvaloniaScheduler, DispatcherSequencer, ControlSequencer, MauiDispatcherSequencer, DispatcherQueueSequencer and HandlerSequencer returns one cached sequencer per dispatcher, control, dispatcher queue or looper, and returns the shared instance for its own owner.
• WitnessOnOwner(sequencer) and a new WitnessOnSignal<T> constructor deliver a notification inline when the caller owns the sequencer and nothing is waiting; anything raised later queues behind what is already waiting.
• Updates PublicApiSharp.Analyzers to 2.1.0, TUnit to 1.70.1 and Microsoft.Maui.Core to 10.0.110 for the net10 heads.

Why

ReactiveUI.Binding routes every view write onto the thread that owns the view. Each platform currently does that through its own dispatcher code, because no sequencer can say which thread owns it. With CheckAccess and For, the binding platform packages route through these sequencers instead, starting with a new Avalonia package for reactiveui/ReactiveUI.Avalonia#216.

Breaking changes

None. Every change adds API; existing constructors, Main, Current and Instance behave as before.

How this was verified

Tests cover the new operator path and the Avalonia and MAUI sequencers' CheckAccess and For. The WPF, WinForms, WinUI, Android and Apple sequencer changes compile here but their tests only run on Windows or a device, so CI is their first run. The Apple PublicAPI baselines were edited by hand because Apple heads do not build on Linux.

Notes for the reviewer

Start with WitnessOnSignal{T}.cs: the inline path only runs when an owner is passed, so the existing constructor is unchanged. The For lookups hold sequencers in a ConditionalWeakTable keyed by the owner. Blazor and Wasm do not implement IThreadAffineSequencer: the Blazor sequencer has no dispatcher to ask, and Wasm has no owning thread. Some PublicAPI baselines were re-sorted by the regeneration tool without API changes.

Checklist

• I have read the Contribute guide
• The PR title follows Conventional Commits
• Tests cover this change, or the summary says why they do not
• New or changed public API has XML documentation

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
93.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.78%. Comparing base (f68fe17) to head (155d187).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #227   +/-   ##
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  Coverage   99.78%   99.78%           
=======================================
  Files         785      785           
  Lines       24850    24923   +73     
  Branches     2946     2957   +11     
=======================================
+ Hits        24796    24869   +73     
  Misses         54       54           

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[github-actions]

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