Fixed incorrect timed keyframe expression

[Sergio0694]

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

The TimedKeyFrame APIs are using an incorrect expression, resulting in the animation not playing.

What is the new behavior?

Fixed the expression to calculate the normalized timestamp of timed keyframes, so they work fine now 😄

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Pull Request has been submitted to the documentation repository instructions. Link:
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

[ghost]

Thanks Sergio0694 for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

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[michael-hawker]

@Sergio0694 @JustinXinLiu seems like something serious enough we may want to patch? Thoughts?

[michael-hawker]

@Sergio0694 was this exposed in one of the samples? Is there a way we can visually validate the fix for comparison?

[Sergio0694]

"seems like something serious enough we may want to patch"

Yes, if it was possible to do a hotfix release before 7.1 I'd say this should probably be included.
Right now keyframe animations with timed keyframes are essentially not working otherwise 😅

Granted, it's a pretty niche scenario since you need to:

1. Be using AnimationBuilder manually in code behind
2. Be using custom keyframe animations
3. Be specifically using timed keyframes on top of it

Which I guess also explain why we didn't notice it before.
But yeah, the sooner this fix is out the better 😄

"was this exposed in one of the samples?"

It wasn't, as these APIs are not available from XAML (it only supports normalized keyframes, which are the default).

"Is there a way we can visually validate the fix for comparison?"

It's not much about a visual difference, it's more that without this fix the animation wasn't playing at all 😅
I'll see if I can also add some unit tests. Not the easiest scenario to test there since we need to validate "while an animation plays" to ensure it's going as we want it to (as opposed to other tests that just await for it and then check final values), but I can try out a few things with a timer I guess. It could definitely help with regression testing at least.

[michael-hawker]

Thanks @Sergio0694 let's merge this in to get the fix so things work, and think about general animation testbed for checking things 'in-flight' for the future.