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September 2020 - Code Heath, Animation Timelines, Smoothness Metrics, Animation event handlers and more!

September 2020 Chrome Interactions Highlights Archives: go/interactions-team-highlights
<td><td>In this sprint we closed a lot of bugs, but more were opened than

<td><td>We now have breakdowns by priority. Nice to see that we did not lose
ground on P0s or P1s.</td></td>
<td><td>setTimeout can easily cause flakiness, especially on debug

<td><td>Animations are driven by animation frames, using rAF leads to more
robust tests.</td></td>
<td><td>The demo illustrates updating the animation timeline via the
web-animation API.</td></td>

<td><td>Presently it is behind the scroll-timeline feature flag.</td></td>
<td><td>The fps meter will reset itself at first contentful paint (which is
regarded as loading completed).</td></td>

<td><td>The stats before first contentful paint will be discarded when we
report to UMA.</td></td>
<td><td>Previously, we compared zoomed values when starting transitions,
then transitionend based on computed value.</td></td>

<td><td>Now we calculate and compare computed values (as per spec) if zoom
Code health image kevers@ presented a graph to show the progress of bug fixing. xidachen@ removed the usage of setTimeout in animations layout test, and replaced them with rAF. image Mutable timelines kevers@ has been working on scroll timelines and the above demo showcases mutable timelines, which are required for supporting css animation-timeline. kevers@ showed another fun demo for scroll timelines, which uses scroll position to drive a paint worklet animation.. image
Smoothness metrics image xidachen@ improved fps meter by making it account for page loading. Animation event handlers gtsteel@ landed the implementation for ontrasition\* event handler properties. Along with that, gtsteel@ also fixed animationcancel event so that it doesn’t fire after animationend. Zooming no longer breaks transitions gtsteel@ fixed a bug where zooming would cause transition event listeners to fire.
Web tests ⇒ WPT liviutinta@ shared a sheet that lists input related layout tests that we would like to move to wpt/. The spreadsheet also tracks the progress. WebDriver Actions API Spec lanwei@ has landed spec change that adds wheel input to the webdriver action API.
Chrome Interactions Highlights | September 2020 go/interactions-team