Skip to content

Snapshot post-layout for all but scroll-timelines #58613

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
chromium-wpt-export-bot merged 2 commits into from
Apr 3, 2026
+14 −9
Merged

Snapshot post-layout for all but scroll-timelines #58613

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e3efa9e
Snapshot post-layout for all but scroll-timelines
lilles Mar 19, 2026
8377e06
Capture uncaught error causing harness flakiness
jonathan-j-lee Apr 3, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 14 additions & 9 deletions scroll-animations/css/scroll-timeline-multi-pass.tentative.html
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
<!DOCTYPE html>
<title>ScrollTimelines may trigger multiple style/layout passes</title>
<link rel="help" src="https://github.com/w3c/csswg-drafts/issues/5261">
<link rel="help" src="https://github.com/whatwg/html/pull/11613">
<link rel="help" src="https://drafts.csswg.org/scroll-animations-1/#avoiding-cycles">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
Expand Down Expand Up @@ -55,7 +56,7 @@
main.insertBefore(scroller, element1);
}

promise_test(async () => {
promise_test(async (t) => {
await waitForNextFrame();

let events1 = [];
Expand All @@ -67,11 +68,11 @@
//
// https://drafts.csswg.org/scroll-animations-1/#avoiding-cycles
assert_equals(getComputedStyle(element1).width, '1px');
(new ResizeObserver(entries => {
(new ResizeObserver(entries => t.step_func(() => {
events1.push(entries);
insertScroller('--timeline2');
assert_equals(getComputedStyle(element2).height, '1px');
})).observe(element1);
}))).observe(element1);

(new ResizeObserver(entries => {
events2.push(entries);
Expand All @@ -96,17 +97,21 @@
assert_equals(events1[0][0].contentBoxSize.length, 1);
assert_equals(events1[0][0].contentBoxSize[0].inlineSize, 100);

// ScrollTimelines created during the ResizeObserver should remain
// inactive during the frame they're created, so the ResizeObserver
// event should not reflect the animated value.
assert_equals(events2.length, 1);
// The HTML PR[3] that uses the 'run snapshot post-layout state steps',
// would try to create new scroll-timelines for each iteration of the
// resize observer loop, so the ResizeObserver event should reflect the
// animated value for the second observation.
//
// [3] https://github.com/whatwg/html/pull/11613/
assert_equals(events2.length, 2);
assert_equals(events2[0].length, 1);
assert_equals(events2[0][0].contentBoxSize.length, 1);
assert_equals(events2[0][0].contentBoxSize[0].blockSize, 1);
assert_equals(events2[1].length, 1);
assert_equals(events2[1][0].contentBoxSize.length, 1);
assert_equals(events2[1][0].contentBoxSize[0].blockSize, 100);

assert_equals(getComputedStyle(element1).width, '100px');

await waitForNextFrame();
assert_equals(getComputedStyle(element2).height, '100px');
}, 'Multiple style/layout passes occur when necessary');
</script>
Loading