Storyboard animation is preventing a bounded prop to be changed until manually stopped

[FrozDark]

Current behavior

When you start a storyboard animation the Completed event fires but the state of animation doesn't change and it blocks the property it bind to from changing until you manually call Stop on storyboard

        someStoryboard.Completed += Animation_Completed;

        private void Animation_Completed(object sender, object e)
        {
            System.Diagnostics.Debug.WriteLine($"Animation_Completed");
            if (someStoryboard.GetCurrentState() != ClockState.Stopped)
            {
                someStoryboard.Stop();
                System.Diagnostics.Debug.WriteLine($"Manual stop animation");
            }
        }

Results in "Animation_Completed", "Manual stop animation" in the debug output

Expected behavior

Really stopped animation

How to reproduce it (as minimally and precisely as possible)

1. Create storyboard animation
2. Run
3. Check out the state in the Completed event

Workaround

Call Stop() on completed event

Works on UWP/WinUI

Yes

Environment

Uno.WinUI / Uno.WinUI.WebAssembly / Uno.WinUI.Skia

NuGet package version(s)

Tested on 4.6.0-dev.576

Affected platforms

Skia (GTK on Linux/macOS/Windows)

IDE

Visual Studio 2022

IDE version

No response

Relevant plugins

No response

Anything else we need to know?

Tested on GTK, But I think it's affected on all Uno platforms

[FrozDark]

Seems like it works the same way as in WinUI (state is not stopped at completed event). But in uno if I don't manually call Stop on storyboard I can not change the property of an element it references to it just blocks it from changing

[Xiaoy312]

It is normal that the Storyboard::GetCurrentState() is not ClockState.Stopped when Timeline::Completed occurs. Because by default the Timeline::FillBehavior is HoldEnd, which allow the animated value to "stay" after the animation is completed and the timeline will be in a ClockState.Filling state on completion.
This is exactly the behavior we are getting from windows, so there is nothing to change here.

Now onto the 2nd part:
> When you start a storyboard animation the Completed event fires [...] and it blocks the property it bind to from changing [...]
Yes, this was an old issue in uno:
#631 We cannot change the value of a DependencyProperty which has been animated
which was fixed recently.