animations: Finish support for fractional iteration counts
This change also improves support for creating animations with negative
delays, as that is necessary to test support for fractional iteration
lengths.
Fixes: #14858
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This change also improves support for creating animations with negative
delays, as that is necessary to test support for fractional iteration
lengths.
This change also adjusts existing Servo animation tests which assumed
that advancing to the exact moment of the end of the animation would be
considered "before the end." With this change, this moment is "after the
end."
Fixes: #14858
Add support for canceling CSS transitions
This change adds support for canceling CSS transitions when a property is
no longer transitionable. Support for canceling and replacing CSS
transitions when the end value changes is still pending. This change
also takes advantage of updating the constellation message to fix a bug
where transition events could be sent for closed pipelines.
Fixes#15079.
<!-- Please describe your changes on the following line: -->
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#15079.
<!-- Either: -->
- [x] There are tests for these changes OR
- [ ] These changes do not require tests because ___
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