Implement GodotSynchronizationContext

[paulloz]

As we discussed earlier, this is a basic synchronization context using the engine work at godotengine/godot#106030.

Let me know if you think this should be more elaborate. But for now I've been able to work with this on my personal project without issue.

[raulsntos]

Looks generally good. Most of my comments are just questions that came up as I was comparing it with the current implementation in GodotSharp and doesn't necessarily mean a change needs to be made, but if there's no specific reason to differ from the GodotSharp implementation I tend to prefer to keep the status quo.

[raulsntos]

This check doesn't seem to be in GodotSharp. I guess it's a bit of an edge case anyway.

[raulsntos]

Looks good!

[raulsntos]

Thanks!

[scgm0]

An issue has been identified: in GodotSharp, GodotSynchronizationContext is public and can be accessed via Dispatcher.SynchronizationContext to manually invoke GodotSynchronizationContext.Post and GodotSynchronizationContext.Send for executing methods on the main thread. However, this PR only adds GodotSynchronizationContext and marks it as internal. Can we still manually call GodotSynchronizationContext.Post and GodotSynchronizationContext.Send?

[Delsin-Yu]

@scgm0

Can we still manually call GodotSynchronizationContext.Post and GodotSynchronizationContext.Send?

I think you can still get this sync ctx via SynchronizationContext.Current and use Post & Send as usual, as we usually do in C#.

[scgm0]

@scgm0

Can we still manually call GodotSynchronizationContext.Post and GodotSynchronizationContext.Send?

I think you can still get this sync ctx via SynchronizationContext.Current and use Post & Send as usual, as we usually do in C#.

I know about SynchronizationContext.Current, but I recall it's not usable in GodotSharp; you have to use Dispatcher.SynchronizationContext instead. However, I might be mistaken. I'll test later to see if SynchronizationContext.Current works in GodotDotnet.

[scgm0]

I think you can still get this sync ctx via SynchronizationContext.Current and use Post & Send as usual, as we usually do in C#.

It does seem possible to use SynchronizationContext.Current, but it holds different values in different threads, meaning users need to first obtain and store SynchronizationContext.Current in the main thread before they can use it in a child thread.

This isn't a problem per se, but it's less convenient compared to GodotSharp. It would be better if an API similar to Dispatcher.SynchronizationContext could be provided.

[raulsntos]

I don't think we want to expose this API, can you provide more details about your use case? I'd recommend opening a new issue describing what you are trying to do, why you need the GodotSynchronizationContext type to do it, and why alternative solutions fall short. Ideally with an MRP that shows the problem.

If all you need is to run some code in the main thread, I believe CallDeferred should work.

[scgm0]

If all you need is to run some code in the main thread, I believe CallDeferred should work.

CallDeferred works, but in my project, most of what needs to be pushed to the main thread are lambda functions. Since we already have GodotSynchronizationContext, there's no need to use Callable.From to create a wrapper for the lambda.