Experiment with AvaloniaRenderingFrameProvider

[maxkatz6]

Hello!
This library looks very interesting, thank you for your work :).

Noticed that Avalonia FrameProvider version used DispatcherTimer, which isn't necessary the best implementation conceptually for frames. As well as WPF version actually uses render timer callbacks.

Starting with 11.0 version we also have an equivalent APIs - TopLevel.RequestAnimationFrame(Action) where callback is synchronized with render timer and display framerate.

There is a big problem though. In WPF similar API is static and can be accessed from anywhere. In Avalonia, since we support multiple platforms, it gets more complicated, and this API is only accessible from the specific TopLevel. Where TopLevel can be an any Window, or a single root on mobile/browser. Obviously, it's quite hard to access from the framework initialization.

[maxkatz6]

While I was writing this description, I found that all frame-specific methods in R3 also accept custom FrameProvider. Which makes this integration quite a bit easier. It's still hard to setup proper render timer globally though.

[neuecc]

Thank you!
I had been looking for a method other than polling but couldn't find one, so I had no choice but to use DispatcherTimer.
I'm very happy that it's resolved.

I'm not particularly insistent on having the rendering as one frame, so if there's some kind of message loop, it would be great if I could hook into that.
Preferably without allocations each time.

[maxkatz6]

so if there's some kind of message loop

That's Dispatcher basically. As it was.

[neuecc]

Yes, it's the Dispatcher.
However, even in WPF, repeatedly using Dispatcher.BeginInvoke involves allocations, and I was looking for a lighter method.
And I came to the conclusion that the CompositionTarget event would be the lightest approach.

I will go ahead and merge this!
If you notice anything else, I would be happy to receive contributions!
By the way, among cross-platform UIs, I am most hopeful about Avalonia.