Feature Request: Add support to ObserveOn WinUI 3's DispatcherQueue.

[kmgallahan]

Feature request

Which next library version (i.e., patch, minor or major)?

Rx.NET v5.?.?

What are the platform(s), environment(s) and related component version(s)?

Windows / WinUI 3

How commonly is this feature needed (one project, several projects, company-wide, global)?

Anyone using Rx with WinUI 3 would likely find this useful this at some point.

Please describe the feature.

This is a request to add ObserveOn extension method(s) to accept WinUI 3's Microsoft.UI.Dispatching.DispatcherQueue for scheduling.

Might be pertinent to start by introducing a new HAS_WINUI conditional compilation symbol. The Target framework wouldn't work as a differentiator, but every project file must contain <UseWinUI>true</UseWinUI>, so that could work.

[djonasdev]

+1

microsoft/microsoft-ui-xaml#4219

[kmgallahan]

@dojo90 FYI ReactiveUI has a Scheduler implementation for DispatcherQueue now.

https://github.com/reactiveui/ReactiveUI/tree/main/src/ReactiveUI.WinUI

[andrensairr]

It's nearing the end of 2023 now and all the reading I've done between documentation and GitHub issues for Reactive Extensions, MS.UI.Xaml repo, Windows Runtime SDK does not help me figure out how to observe on my app's dispatcher thread. Trying ObserveOnCoreDispatcher in my WinUI 3 desktop app I encounter the InvalidOperationException "No current Window object found to obtain a CoreDispatcher from." I can't find a scheduler specifically for the DispatcherQueue. Can somebody please explain if this present issue is intended to add support for my use case, and that it is still incomplete? Some improved documentation on all of the relevant technologies here would be immensely helpful but there seems to be a lot of finger pointing between teams.

[kmgallahan]

@andrensairr Just copy+paste this if you aren't using ReactiveUI

https://github.com/reactiveui/ReactiveUI/blob/main/src/ReactiveUI.Maui/WinUI/DispatcherQueueScheduler.cs

[andrensairr]

Thank you @kmgallahan, that seems to do the trick just fine. Not using ReactiveUI just yet, I've a fair bit of work to do before sorting the finer points of my UI and I wasn't sure how complete the WinUI 3 support in ReactiveUI was just yet.

[kmgallahan]

@andrensairr I recently decided to stop using ReactiveUI in favor of just System.Reactive & DynamicData. If you aren't developing a cross-plat app, which I was not, then I found the prescriptive nature to be restrictive. I just extracted the most useful bits I was using (DispatcherQueueScheduler, DisposeWith), and switched from WhenAnyValue to the change notifications offered by DynamicData.