FadeAnimation takes twice as long as expected

[bijington]

While converting the rest of the Animations from XCT I spotted that our use of the Length (MCT) / Duration (XCT) properties do not behave as I expected. Let's just look at the FadeAnimation example for now...

Currently if I create a FadeAnimation with a Length of 300 I expect it to complete it's animation after 300ms however looking at the code it will take twice as long:

public override async Task Animate(VisualElement view)
{
    ArgumentNullException.ThrowIfNull(view);

    var originalOpacity = view.Opacity;

    await view.FadeTo(Opacity, Length, Easing);
    await view.FadeTo(originalOpacity, Length, Easing);
}

I believe the code should read:

    await view.FadeTo(Opacity, Length / 2, Easing);
    await view.FadeTo(originalOpacity, Length / 2, Easing);

If we do decide this is a bug then it is a breaking change to fix it because we would be doubling the speed of everyones fade animations. I assume this is a fairly underused feature of the toolkit given we only have 1 animation in so far and people haven't asked for more.

What are peoples thoughts on this?

[TheCodeTraveler]

Oooh! I totally agree. As a user, if I specified that the Length is 500ms, but then the animation takes 1000ms, I would be perplexed. Yea, We should fix this. This would certainly be a breaking change, but we could queue up CommunityToolkit.Maui v6.0.0 to also include Vlad's breaking change to Popup on Windows #1086.

The option for implementing breaking changes would be when we bump to .NET 8.0, but that won't be until November.

[TheCodeTraveler]

Could you also double-check the Unit Tests, and if we don't have one already, let's make sure to make a BaseAnimationUnitTests.cs class that every current + future Animation will inherit from where it automatically tests + verifies the length of the Animation. Otherwise, I can foresee future Animation PRs also missing this nuance too.

[bijington]

I have added this although it is somewhat flaky right now. I will keep playing around to determine why and what the best approach is:

https://github.com/CommunityToolkit/Maui/blob/163ed96dc040d67c20c0686227b17696840d3540/src/CommunityToolkit.Maui.UnitTests/Animations/BaseAnimationTests.cs

[CliffAgius]

Closed as per the Community Stand-up discussion here: https://youtu.be/N9wMcBP4jtg?t=2889